On the Radio Polarization Signature of Efficient and Inefficient Particle Acceleration in Supernova Remnant SN 1006

We present a radio polarization study of SN 1006, based on combined VLA and ATCA observations at 20 cm that resulted in sensitive images with an angular resolution of 10 arcsec. The fractional polarization in the two bright radio and X-ray lobes of the SNR is measured to be 0.17, while in the southeastern sector, where the radio and non-thermal X-ray emission are much weaker, the polarization fraction reaches a value of 0.6 +- 0.2, close to the theoretical limit of 0.7. We interpret this result as evidence of a disordered, turbulent magnetic field in the lobes, where particle acceleration is believed to be efficient, and a highly ordered field in the southeast, where the acceleration efficiency has been shown to be very low. Utilizing the frequency coverage of our observations, an average rotation measure of ~12 rad/m2 is determined from the combined data set, which is then used to obtain the intrinsic direction of the magnetic field vectors. While the orientation of magnetic field vectors across the SNR shell appear radial, a large fraction of the magnetic vectors lie parallel to the Galactic Plane. Along the highly polarized southeastern rim, the field is aligned tangent to the shock, and therefore also nearly parallel to the Galactic Plane. These results strongly suggest that the ambient field surrounding SN 1006 is aligned with this direction (i.e., from northeast to southwest) and that the bright lobes are due to a polar cap geometry. Our study establishes that the most efficient particle acceleration and generation of magnetic turbulence in SN 1006 is attained for shocks in which the magnetic field direction and shock normal are quasi-parallel, while inefficient acceleration and little to no generation of magnetic turbulence obtains for the quasi-perpendicular case.Comment: Accepted for publication in Astronomical Journa

Measuring Affective Responses to Different Types of Nature Exposure

Natural environments provide many physical and physiological benefits for an individual. Examples may include decreased stress levels, increased intrinsic motivations and prosocial behavior, and more. Fueled by the curiosity of the extent to which nature provides these benefits, this study investigated whether pre-existing preference for either waterscape scenes or mountainous scenes, as well as self-reported affective and associative responses to those environmental exposures are possible explanations for the experience of wellbeing when one is exposed to nature. Measures included the Nature Relatedness Scale, State Vitality Scale, Positive and Negative Affect Scale, and a nature preference scale (mountainous vs. waterscape). Nature relatedness was a significant predictor for state vitality and positive affect, as participants who scored higher on the nature relatedness scale prior to the study rated themselves as happier and more energized after viewing nature scenes. More participants in the water condition cognitively associated themselves interacting with the environment, recounting specific memories of their own, as well as reporting more calm cognitive associations. Also, people who preferred waterscape scenes reported more calm cognitive associations in both conditions. The interaction between picture type and nature preference for the restorative element of fascination showed that individuals who preferred a specific type of nature scene were in turn more fascinated when viewing the scene they preferred. Implications for these results suggest that people who are more closely related to nature experience higher levels of positive affect and state vitality when exposed to natural environments. In addition, one’s own nature preferences result in higher levels of fascination when viewing environments that you like to see

Brightness Distribution in Discrete Radio Sources III. The Structure of the Sources

The visibility functions of 195 radio sources are interpreted in terms of the structure of these sources. Of the 195 sources, 174 are known or presumed to be extragalactic. Seventy-five of these extragalactic sources are resolved with the interferometer spacings used, and complex structure is found in all but 13. In the sources showing complex structure, two similar components with nearly equal intensities are found in 15, 40 show two or more components of unequal intensities, while 7 appear to be a bright core surrounded by a halo. It is suggested that the majority of all extragalactic sources have complex structure. Data are also given on the brightness distributions in the 21 galactic sources observed. In contrast to the extragalactic sources, emission from the galactic sources is typically confined to a single region

Making Room for Innovation: Using Systematic Random Sampling to Quickly and Efficiently Obtain Shelf Occupancy Data

This poster was peer-reviewed for inclusion at the Association of College and Research Libraries' 2015 Conference in Portland, Oregon. Date of presentation is March 26, 2015.Are you preparing to renovate space currently occupied by the stacks to construct a new cafe? A collaborative learning space? A technology-rich environment? If so, data is needed about the collection. How much shelf space is currently occupied by monographs? By serials? How much is empty? How much space would be available if serials were relocated or withdrawn? Find out how to use systematic random sampling to quickly and efficiently obtain shelf occupancy data

On the Radio Polarization Signature of Efficient and Inefficient Particle Acceleration in Supernova Remnant SN 1006

Radio polarization observations provide essential information on the degree of order and orientation of magnetic fields, which themselves play a key role in the particle acceleration processes that take place in supernova remnants (SNRs). Here we present a radio polarization study of SN 1006, based on combined Very Large Array and Australia Telescope Compact Array observations at 20 cm that resulted in sensitive images with an angular resolution of 10 arcsec. The fractional polarization in the two bright radio and X-ray lobes of the SNR is measured to be 0.17, while in the southeastern sector, where the radio and non-thermal X-ray emission are much weaker, the polarization fraction reaches a value of 0.6 ± 0.2, close to the theoretical limit of 0.7. We interpret this result as evidence of a disordered, turbulent magnetic field in the lobes, where particle acceleration is believed to be efficient, and a highly ordered field in the southeast, where the acceleration efficiency has been shown to be very low. Utilizing the frequency coverage of our observations, an average rotation measure of ~12 rad m-2 is determined from the combined data set, which is then used to obtain the intrinsic direction of the magnetic field vectors. While the orientation of magnetic field vectors across the SNR shell appear to be radial, a large fraction of the magnetic vectors lie parallel to the Galactic plane. Along the highly polarized southeastern rim, the field is aligned tangent to the shock, and therefore also nearly parallel to the Galactic plane. These results strongly suggest that the ambient field surrounding SN 1006 is aligned with this direction (i.e., from northeast to southwest) and that the bright lobes are due to a polar cap geometry. Our study establishes that the most efficient particle acceleration and generation of magnetic turbulence in SN 1006 is attained for shocks in which the magnetic field direction and shock normal are quasi-parallel, while inefficient acceleration and little to no generation of magnetic turbulence are obtained for the quasi-perpendicular case.Fil: Reynoso, Estela Marta. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Hughes, John P.. Rutgers University; Estados UnidosFil: Moffett, David A.. Furman University; Estados Unido

Correlation between X-ray Lightcurve Shape and Radio Arrival Time in the Vela Pulsar

We report the results of simultaneous observations of the Vela pulsar in X-rays and radio from the RXTE satellite and the Mount Pleasant Radio Observatory in Tasmania. We sought correlations between the Vela's X-ray emission and radio arrival times on a pulse by pulse basis. At a confidence level of 99.8% we have found significantly higher flux density in Vela's main X-ray peak during radio pulses that arrived early. This excess flux shifts to the 'trough' following the 2nd X-ray peak during radio pulses that arrive later. Our results suggest that the mechanism producing the radio pulses is intimately connected to the mechanism producing X-rays. Current models using resonant absorption of radio emission in the outer magnetosphere as a cause of the X-ray emission are explored as a possible explanation for the correlation.Comment: 6 pages, 5 figures, accepted by Ap

A Broadband Study of the Emission from the Composite Supernova Remnant MSH 11-62

MSH 11-62 (G291.1-0.9) is a composite supernova remnant for which radio and X-ray observations have identified the remnant shell as well as its central pulsar wind nebula. The observations suggest a relatively young system expanding into a low density region. Here we present a study of MSH 11-62 using observations with the Chandra, XMM-Newton, and Fermi observatories, along with radio observations from the Australia Telescope Compact Array (ATCA). We identify a compact X-ray source that appears to be the putative pulsar that powers the nebula, and show that the X-ray spectrum of the nebula bears the signature of synchrotron losses as particles diffuse into the outer nebula. Using data from the Fermi LAT, we identify gamma-ray emission originating from MSH 11-62. With density constraints from the new X-ray measurements of the remnant, we model the evolution of the composite system in order to constrain the properties of the underlying pulsar and the origin of the gamma-ray emission.Comment: 12 Pages, 12 figures. Accepted for publication in the Astrophysical Journa

Microbiology and atmospheric processes: Biological, physical and chemical characterization of aerosol particles

The interest in bioaerosols has traditionally been linked to health hazards for humans, animals and plants. However, several components of bioaerosols exhibit physical properties of great significance for cloud processes, such as ice nucleation and cloud condensation. To gain a better understanding of their influence on climate, it is therefore important to determine the composition, concentration, seasonal fluctuation, regional diversity and evolution of bioaerosols. In this paper, we will review briefly the existing techniques for detection, quantification, physical and chemical analysis of biological particles, attempting to bridge physical, chemical and biological methods for analysis of biological particles and integrate them with aerosol sampling techniques. We will also explore some emerging spectroscopy techniques for bulk and single-particle analysis that have potential for in-situ physical and chemical analysis. Lastly, we will outline open questions and further desired capabilities (e. g., in-situ, sensitive, both broad and selective, on-line, time-resolved, rapid, versatile, cost-effective techniques) required prior to comprehensive understanding of chemical and physical characterization of bioaerosols