An Experimental Study of Persuasive Social Communication

Studies of contextual effects on political behavior are plagued by concerns about internal validity. Perhaps of greatest concern are possible selection mechanisms that appear to present statistical support for contextual influence when social communication has no real effect. This paper presents an experimental framework for testing contextual effects that ameliorates these concerns through exogenous assignment to communication networks. This experiment allows for an analysis of the factors that make discussion partners influential. These factors can be divided into two categories: (1) characteristics of the dyad and its members; (2) characteristics of the residual discussion network. The most robust findings suggest that factors in this latter category play the greatest role in the likelihood that a discussion partner is influential

Dutch Elm Disease Resistant Cultivars for Campus Environmental Sustainability

Dutch Elm Disease Resistant Cultivars for Campus Environmental Sustainability John Dryden, Dept. of Civil Engineering & Construction Management ($3,135.00) 100 Dutch Elm Disease (DED) Resistant elm cultivar seedlings were grown to sapling size, then planted around campus by student groups and GS Landscape Services, and serve as campus landmark trees during Arbor Day plantings. These saplings also serve as propagation ‘parents’, thus ensuring a steady future supply of DED resistant elm trees for GS. As there has been virtually no research into the performance of these cultivars in Georgia, the long-term performance of these cultivars was reported to the National Elm Trial as part of their continuing research

SONTRAC—A low background, large area solar neutron spectrometer

SONTRAC is a scintillating fiber neutron detector designed to measure solar flare neutrons from a balloon or spacecraft platform. The instrument is comprised of alternating orthogonal planes of scintillator fibers viewed by photomultiplier tubes and image intensifier/CCD camera optics. It operates by tracking the paths of recoil protons from the double scatter of 20 to 200 MeV neutrons off hydrogen in the plastic scintillator, thereby providing the necessary information to determine the incident neutron direction and energy. SONTRAC is also capable of detecting and measuring high-energy gamma rays \u3e20 MeV as a “solid-state spark chamber.” The self-triggering and track imaging features of a prototype for tracking in two dimensions have been demonstrated in calibrations with cosmic-ray muons, 14 to ∼65 MeV neutrons and ∼20 MeV protons

Feasible US steps to strengthen NATO deterrence in the Baltics and Poland

With Russia's invasion of Ukraine, a renewed assessment of efforts by the United States and the North Atlantic Treaty Organization (NATO) to deter Russia from taking military action on NATO's eastern flank has become particularly salient. In the coming weeks, NATO leadership will meet to discuss what longer term force posture adjustments are required to create such a deterrent. This paper proposes several modest policy recommendations which will help inform the discussion and ultimately strengthen NATO's conventional deterrence postur

Interim security insights and implications from the first two months of the Russia-Ukraine war

Russia's ongoing struggles during its invasion of Ukraine have led some to suggest that the Russian military lacks the capability to credibly threaten the North Atlantic Treaty Organization (NATO) and its member states. However, narrowly focusing on Russia's tactical and operational struggles, while omitting the flawed Russian strategic decisionmaking which underpinned the invasion, is a dangerous approach. While Russia's significant losses in this war will clearly degrade its ability to conduct large scale offensive operations against NATO in the short term, it is too soon to write off the medium to long-term threat posed by Russia. Therefore, as the Russian invasion enters a new phase, it is useful to determine what lessons should and should not be derived from this conflict. In our subsequent analysis, we analyze these initial insights and provide policy recommendations for NATO to enhance its conventional capability and strengthen its ability to credibly deter future Russian aggression

Optimization of Single-Sided Charge-Sharing Strip Detectors

Simulation of the charge sharing properties of single-sided CZT strip detectors with small anode pads are presented. The effect of initial event size, carrier repulsion, diffusion, drift, trapping and detrapping are considered. These simulations indicate that such a detector with a 150 µm pitch will provide good charge sharing between neighboring pads. This is supported by a comparison of simulations and measurements for a similar detector with a coarser pitch of 225 µm that could not provide sufficient sharing. The performance of such a detector used as a gamma-ray imager is discussed

Further studies of single-sided charge-sharing CZT strip detectors

We report progress in the study of a thick CZT strip detector module designed to perform gamma-ray spectroscopy and 3-D imaging. We report preliminary performance measurements of 7.5 mm thick single-sided charge-sharing strip detector prototype devices. This design features both row and column contacts on the anode surface. This electron-only approach addresses problems associated with poor hole transport in CZT that limit the thickness and energy range of double-sided strip detectors. This work includes laboratory and simulation studies aimed at developing compact, efficient, detector modules for 0.05 to 1 MeV gamma measurements while minimizing the number and complexity of the electronic readout channels. This is particularly important in space-based coded aperture and Compton telescope instruments that require large area, large volume detector arrays. Such arrays will be required for the NASA Black Hole Finder Probe (BHFP)and Advanced Compton Telescope (ACT). This new design requires an anode pattern with contacts whose dimensions and spacing are roughly the size of the ionization charge cloud. The first prototype devices have 125 μm anode contacts on 225 μm pitch. Our results demonstrate the principle of operation but suggest that even finer anode contact feature sizes will be necessary to achieve the desired performance

Continued Studies of Single-Sided Charge-Sharing CZT Strip Detectors

In this paper, we report progress in the study of thick single-sided charge-sharing cadmium zinc telluride (CZT) strip detector modules designed to perform gammaray spectroscopy and 3-D imaging. We report on continuing laboratory and simulation measurements of prototype detectors with 11×11 unit cells (15×15×7.5mm3 ). We report preliminary measurements of the 3-D spatial resolution. Our studies are aimed at developing compact, efficient, detector modules for 0.05 to 1 MeV gamma measurements while minimizing the number and complexity of the electronic readout channels. This is particularly important in space-based coded aperture and Compton telescope instruments that require large area, large volume detector arrays. Such arrays will be required for the NASA’s Black Hole Finder Probe (BHFP) and Advanced Compton Telescope (ACT). This design requires an anode pattern with contacts whose dimensions and spacing are roughly the size of the ionization charge cloud. The first prototype devices have 125µm anode contacts on 225µm pitch. Our studies conclude that finer pitch contacts will be required to improve imaging efficiency

Development and performance of the Fast Neutron Imaging Telescope for SNM detection

FNIT (the Fast Neutron Imaging Telescope), a detector with both imaging and energy measurement capabilities, sensitive to neutrons in the range 0.8-20 MeV, was initially conceived to study solar neutrons as a candidate design for the Inner Heliosphere Sentinel (IHS) spacecraft of NASA\u27s Solar Sentinels program and successively reconfigured to locate fission neutron sources. By accurately identifying the position of the source with imaging techniques and reconstructing the Watt spectrum of fission neutrons, FNIT can detect samples of special nuclear material (SNM), including heavily shielded and masked ones. The detection principle is based on multiple elastic neutron-proton scatterings in organic scintillators. By reconstructing n-p event locations and sequence and measuring the recoil proton energies, the direction and energy spectrum of the primary neutron flux can be determined and neutron sources identified. We describe the design of the FNIT prototype and present its energy reconstruction and imaging performance, assessed by exposing FNIT to a neutron beam and to a Pu fission neutron source