To help allies, send security guarantees, not nuclear bombs

Despite the end of the Cold War more than two decades ago, the U.S. still deploys nuclear weapons in several countries. But does deploying these weapons act as a deterrent to conflict, making these countries safer? In new research which analyses the effects of such nuclear deployments, Matthew Fuhrmann and Todd S. Sechser find that their presence does little, when compared with alliance guarantees. They write that having an alliance with a nuclear armed ally is actually more effective in preventing armed conflicts than the local deployment of the weapons themselves

Investigating GNSS multipath effects induced by co-located Radar Corner Reflectors

Abstract Radar Corner Reflectors (CR) are increasingly used as reference targets for land surface deformation measurements with the Interferometric Synthetic Aperture Radar (InSAR) technique. When co-located with ground-based Global Navigation Satellite Systems (GNSS) infrastructure, InSAR observations at CR can be used to integrate relative measurements of surface deformation into absolute reference frames defined by GNSS. However, CR are also a potential source of GNSS multipath effects and may therefore have a detrimental effect on the GNSS observations. In this study, we compare daily GNSS coordinate time series and 30-second signal-to-noise ratio (SNR) observations for periods before and after CR deployment at a GNSS site. We find that neither the site coordinates nor the SNR values are significantly affected by the CR deployment, with average changes being within 0.1 mm for site coordinates and within 1 % for SNR values. Furthermore, we generate empirical site models by spatially stacking GNSS observation residuals to visualise and compare the spatial pattern in the surroundings of GNSS sites. The resulting stacking maps indicate oscillating patterns at elevation angles above 60 degrees which can be attributed to the CR deployed at the analysed sites. The effect depends on the GNSS antenna used at a site with the magnitude of multipath patterns being around three times smaller for a high-quality choke ring antenna compared to a ground plane antenna without choke rings. In general, the CR-induced multipath is small compared to multipath effects at other GNSS sites located in a different environment (e. g. mounted on a building)

Combination of GNSS and InSAR measured at co-located geodetic monitoring sites

Global Navigation Satellite Systems (GNSS) can provide a temporally dense set of geodetic coordinate observations in three dimensions at a limited number of discrete measurement points on the ground. Compared to this, the Interferometric Synthetic Aperture Radar (InSAR) technique gives a spatially dense set of geodetic observations of ground surface movement in the viewing geometry of the satellite platform, but with a temporal sampling limited to the orbital revisit of the satellite. Using both of these methods together can leverage the advantages of each to derive more accurate, validated surface displacement estimates with both high temporal and spatial resolution. In this paper, we discuss the properties of both techniques with a view to combined usage for improving future national datums. We apply differential GNSS processing to data observed at a local geodetic network in the Sydney region as well as time series InSAR analysis of Radarsat-2 data. We compare and validate surface displacements resulting from the two techniques at 21 geodetic monitoring sites equipped with GNSS and radar corner reflectors (CRs). The resulting GNSS/InSAR displacement time series agree at the level of 5 to 10 mm. This case study shows that co-located GNSS/CR sites are well-suited to compare and combine GNSS and InSAR measurements. An investigation of potential multipath effects introduced by the CRs attached directly to GNSS monumentation found that daily site coordinates are affected at a level below 0.1 mm. The GNSS/CR sites may hence serve as a local tie for future incorporation of InSAR into national datums. This will allow frequent updates of national geodetic networks and corresponding datums by using the large-scale and spatially dense information on surface displacements resulting from InSAR analyses

Demo: A Low-Cost Fleet Monitoring System

Organizations use fleet monitoring systems for e.g., vehicle tracking, driver behavior analysis, and efficient fleet management. Current systems are designed for commercial use and are of high cost. We present a prototype of a low-cost fleet monitoring system that could be used for non-commercial applications. The system is composed of a device, a service application, and a Web application. The device reads data such as speed and fuel from the internal network of the connected vehicle and the location of the vehicle and sends them to a remote service. The remote service processes and stores the data. The users use a Web application to view the data about their vehicles in real-time

An Exceptional Radio Flare in Markarian 421

In September 2012, the high-synchrotron-peaked (HSP) blazar Markarian 421 underwent a rapid wideband radio flare, reaching nearly twice the brightest level observed in the centimeter band in over three decades of monitoring. In response to this event we carried out a five epoch centimeter- to millimeter-band multifrequency Very Long Baseline Array (VLBA) campaign to investigate the aftermath of this emission event. Rapid radio variations are unprecedented in this object and are surprising in an HSP BL Lac object. In this flare, the 15 GHz flux density increased with an exponential doubling time of about 9 days, then faded to its prior level at a similar rate. This is comparable with the fastest large-amplitude centimeter-band radio variability observed in any blazar. Similar flux density increases were detected up to millimeter bands. This radio flare followed about two months after a similarly unprecedented GeV gamma-ray flare (reaching a daily E>100 MeV flux of (1.2 +/- 0.7)x10^(-6) ph cm^(-2) s^(-1)) reported by the Fermi Large Area Telescope (LAT) collaboration, with a simultaneous tentative TeV detection by ARGO-YBJ. A cross-correlation analysis of long-term 15 GHz and LAT gamma-ray light curves finds a statistically significant correlation with the radio lagging ~40 days behind, suggesting that the gamma-ray emission originates upstream of the radio emission. Preliminary results from our VLBA observations show brightening in the unresolved core region and no evidence for apparent superluminal motions or substantial flux variations downstream.Comment: 5 pages, 8 figures. Contributed talk at the meeting "The Innermost Regions of Relativistic Jets and Their Magnetic Fields", Granada, Spain. Updated to correct author list and reference

RPR Review of Policy Research Preferences, Knowledge, and Citizen Probability Assessments of the Terrorism Risk of Nuclear Powerr opr_552 207..227

Abstract How does the American public assess risk when it comes to national security issues? This paper addresses this question by analyzing variation in citizen probabilit

Preferences, Knowledge, and Citizen Probability Assessments of the Terrorism Risk of Nuclear Power

The definitive version is available at www.interscience.wiley.com.How does the American public assess risk when it comes to national security issues? This paper addresses this question by analyzing variation in citizen probability assessments of the terrorism risk of nuclear power plants. Drawing on the literature on how motivated reasoning, selective information processing, and domain specific knowledge influence public opinion, we argue that heterogeneous issue preferences and knowledge of nuclear energy and homeland security have important explanatory power. Using original data from a unique 2009 national survey in the United States, we show that Americans are divided in their probability assessments of the terrorism risk of nuclear power plants. Consistent with our theoretical expectations, individuals who support using nuclear power to meet rising energy demands, who are generally less concerned with terrorism, or who are more knowledgeable about terrorism and nuclear security tend to provide lower assessments of the likelihood that nuclear power plants increase terrorist attacks, and vice versa. The findings have implications for the literature on public opinion, risk assessment, energy policy and planning, and homeland security.This material is based upon work supported by the U.S. Department of Homeland Security under Grant Award Number 2008-DN-077-ARI018-03. The views and conclusions in the paper are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security

Blazars in the Fermi Era: The OVRO 40-m Telescope Monitoring Program

The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15 GHz radio monitoring program with the 40-m telescope at the Owens Valley Radio Observatory (OVRO). This program began with the 1158 northern (declination>-20 deg) sources from the Candidate Gamma-ray Blazar Survey (CGRaBS) and now encompasses over 1500 sources, each observed twice per week with a ~4 mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample. We demonstrate that, with high significance (7-sigma), gamma-ray-loud blazars detected by the LAT during its first 11 months of operation vary with about a factor of two greater amplitude than do the gamma-ray-quiet blazars in our sample. We also find a significant (3-sigma) difference between variability amplitude in BL Lacertae objects and flat-spectrum radio quasars (FSRQs), with the former exhibiting larger variability amplitudes. Finally, low-redshift (z<1) FSRQs are found to vary more strongly than high-redshift FSRQs, with 3-sigma significance. These findings represent an important step toward understanding why some blazars emit gamma-rays while others, with apparently similar properties, remain silent.Comment: 23 pages, 24 figures. Submitted to ApJ

A Climatology of Cold-Season Nonconvective Wind Events in the Great Lakes Region

A 44-yr climatology of nonconvective wind events (NCWEs) for the Great Lakes region has been created using hourly wind data for 38 first-order weather stations during the months of November through April. The data were analyzed in terms of the two National Weather Service (NWS) criteria for a high-wind watch or warning: sustained winds of at least 18 m s-1for at least 1 h or a wind gust of at least 26 m s-1for any duration. The results indicate a pronounced southwest quadrant directional preference for nonconvective high winds in this region. Between 70% and 76% of all occurrences that satisfied the NWS criteria for NCWEs were associated with wind directions from 180° through 270°. Within the southwest quadrant, the west-southwest direction is preferred, with 14%-35% of all NCWEs coming from this particular compass heading. This directional preference is borne out in five out of six stations with high occurrences of cold-season NCWEs (Buffalo, New York; Dayton, Ohio; Lansing, Michigan; Moline, Illinois; Springfield, Illinois). Given the geographic spread of these stations, a nontopographic cause for the directional preference of cold-season NCWEs is indicated. The connection between NCWEs and low pressure systems found in this climatology and in case studies suggests that midlatitude cyclone dynamics may be a possible cause of the directional preference