1,723 research outputs found

    Foreign Policy Views and U.S. Standing in the World

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    What do Americans think about the US role in world affairs and why do they think the way they do? Americans typically do not think about foreign policy most of the time, and, as a consequence, know relatively little about it (Almond 1950, Lippmann 1955, Converse 1964, Erskine 1963, Edwards 1983, Sobel 1993, Holsti 2004, Canes-Wrone 2006, Page and Bouton 2006, Berinsky 2007). While foreign policy issues can become salient when major international events (like 9/11 and the Iraq War) arise or when political candidates focus on foreign policy (Aldrich, Sullivan and Borgida 1989), ceteris paribus, Americans know and care more about domestic politics (Delli-Carpini and Keeter 1996, Holsti 1994, Canes-Wrone 2006, Converse 1964). Consequently, typical Americans are broadly aware of foreign policy, and have some available attitudes about it (Page and Bouton 2006, Aldrich et al. 1989). However, except in the face of political priming by elites or exogenous shocks, such attitudes may not be broadly accessible when making political decisions, like voting.

    H I Structure and Kinematics of the Interstellar Medium in the LITTLE THINGS Galaxies

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    We present a catalog of the neutral atomic hydrogen structures (H I holes) and the analysis of their properties in nearby (≀ 10.3 Mpc) gas-rich dwarf galaxies of the LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes, The H I Nearby Galaxy Survey) group. We used high sensitivity (≀ 1.1 mJy beam-1 channel-1), high velocity resolution (1.3 km s-1 to 2.6 km s-1) and high linear resolution (average ~110 pc; angular resolution ~6”) H I data of 37 dwarf irregulars and four blue compact dwarf galaxies. We cataloged H I holes in the entire sample and studied the of the properties of holes. We also investigated the effect of H I porosity on star formation, and the correlation of the star formation rate (SFR) calculated from H I holes with standard star formation tracers Hα and FUV. We detected 306 H I holes in LITTLE THINGS galaxies. We confirmed 22 kpc-sized holes, the largest and the smallest hole diameters are about 2.3 kpc and 38 pc (resolution limit) respectively. The expansion velocities of the holes range from 5 km s-1 (upper limit) to 30 km s-1, and the rotational velocities range from 6 km s-1 to 77 km s-1. The H I disk radii of the galaxies range from about 0.5 kpc to 6.7 kpc. The kinetic ages of the holes range from about 1 to 127 Myr, and the estimated scale heights are varying from 61 pc to 653 pc. The percentage distribution of the holes outside and inside the V-band break radius is nearly uniform, 49% and 51% respectively. In LITTLE THINGS galaxies, we found no obvious correlation between the surface and volume porosities, and SFR. However, two highest and two lowest porosity galaxies have no star formation at present. The holes are consistent with the SFR estimated from the energy required to create a hole and the star formation rates measured from Hα and FUV, indicating that the holes are consistent with a star formation origin

    Das atmosphÀrische Aerosol-VorlÀufergas SO<sub>2</sub>: Messungen mit einem flugzeuggetragenem Massenspektrometer

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    The present diploma thesis addresses the development, characterization, and successful deployment of a chemical ionization mass spectrometer (CIMS) to precisely determine the atmospheric mixing ratio of sulfur dioxide at altitudes ranging from 0 to 12 km. During the international campaign ITOP (intercontinental transport of pollution) the CIMS instrument was integrated in the research aircraft Falcon of the German Aerospace Center (DLR). First results of the measurements performed during the ITOP campaign are presented in this diploma thesis. The time resolution of the instrument is about 1 s, and the error for a single data point remains within 10 to 17 % for average atmospheric SO2 mixing ratios. Using isotopically labeled sulfur dioxide (34SO2) as calibration gas, a calibration factor was determined which includes the influence of humidity, wall losses, temperature, and pressure on the measured gas concentrations

    High-altitude migration of Heteroptera in Britain

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    Heteroptera caught during day and night sampling at a height of 200 m above ground at Cardington, Bedfordshire, UK, during eight summers (1999, 2000, and 2002-2007) were compared to high-altitude catches made over the UK and North Sea from the 1930s to the 1950s. The height of these captures indicates that individuals were engaged in windborne migration over distances of at least several kilometres and probably tens of kilometres. This conclusion is generally supported by what is known of the species' ecologies, which reflect the view that the level of dispersiveness is associated with the exploitation of temporary habitats or resources. The seasonal timing of the heteropteran migrations is interpreted in terms of the breeding/overwintering cycles of the species concerned

    Determining Protease Substrate Selectivity and Inhibition by Label-Free Supramolecular Tandem Enzyme Assays

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    An analytical method has been developed for the continuous monitoring of protease activity on unlabeled peptides in real time by fluorescence spectroscopy. The assay is enabled by a reporter pair comprising the macrocycle cucurbit[7]uril (CB7) and the fluorescent dye acridine orange (AO). CB7 functions by selectively recognizing N-terminal phenylalanine residues as they are produced during the enzymatic cleavage of enkephalin-type peptides by the metalloendopeptidase thermolysin. The substrate peptides (e.g., Thr-Gly-Ala-Phe-Met-NH2) bind to CB7 with moderately high affinity (K ≈ 104 M–1), while their cleavage products (e.g., Phe-Met-NH2) bind very tightly (K \u3e 106 M–1). AO signals the reaction upon its selective displacement from the macrocycle by the high affinity product of proteolysis. The resulting supramolecular tandem enzyme assay effectively measures the kinetics of thermolysin, including the accurate determination of sequence specificity (Ser and Gly instead of Ala), stereospecificity (d-Ala instead of l-Ala), endo- versus exopeptidase activity (indicated by differences in absolute fluorescence response), and sensitivity to terminal charges (−CONH2 vs −COOH). The capability of the tandem assay to measure protease inhibition constants was demonstrated on phosphoramidon as a known inhibitor to afford an inhibition constant of (17.8 ± 0.4) nM. This robust and label-free approach to the study of protease activity and inhibition should be transferable to other endo- and exopeptidases that afford products with N-terminal aromatic amino acids

    Rapid encoding of task regularities in the human hippocampus guides sensorimotor timing

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    The brain encodes the statistical regularities of the environment in a task-specific yet flexible and generalizable format. Here, we seek to understand this process by bridging two parallel lines of research, one centered on sensorimotor timing, and the other on cognitive mapping in the hippocampal system. By combining functional magnetic resonance imaging (fMRI) with a fast-paced time-to-contact (TTC) estimation task, we found that the hippocampus signaled behavioral feedback received in each trial as well as performance improvements across trials along with reward-processing regions. Critically, it signaled performance improvements independent from the tested intervals, and its activity accounted for the trial-wise regression-to-the-mean biases in TTC estimation. This is in line with the idea that the hippocampus supports the rapid encoding of temporal context even on short time scales in a behavior-dependent manner. Our results emphasize the central role of the hippocampus in statistical learning and position it at the core of a brain-wide network updating sensorimotor representations in real time for flexible behavior
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