Alternative Sources of Accurate Agriculture Topography

The goal is to measure the relative accuracy of alternate methods to create topographic data of agriculture fields for water flow and related analyses

Efficient Receipt-Free Ballot Casting Resistant to Covert Channels

We present an efficient, covert-channel-resistant, receipt-free ballot casting scheme that can be used by humans without trusted hardware. In comparison to the recent Moran-Naor proposal, our scheme produces a significantly shorter ballot, prevents covert channels in the ballot, and opts for statistical soundness rather than everlasting privacy (achieving both seems impossible). The human interface remains the same, based on Neff\u27s MarkPledge scheme, and requires of the voter only short-string operations

Ultraviolet Imaging of the Globular Cluster 47 Tucanae

We have used the Ultraviolet Imaging Telescope to obtain deep far-UV (1620 Angstrom), 40' diameter images of the prototypical metal-rich globular cluster 47 Tucanae. We find a population of about 20 hot (Teff > 9000 K) objects near or above the predicted UV luminosity of the hot horizontal branch (HB) and lying within two half-light radii of the cluster center. We believe these are normal hot HB or post-HB objects rather than interacting binaries or blue stragglers. IUE spectra of two are consistent with post-HB phases. These observations, and recent HST photometry of two other metal-rich clusters, demonstrate that populations with rich, cool HB's can nonetheless produce hot HB and post-HB stars. The cluster center also contains an unusual diffuse far-UV source which is more extended than its V-band light. It is possible that this is associated with an intracluster medium, for which there was earlier infrared and X-ray evidence, and is produced by C IV emission or scattered light from grains.Comment: 13 pages AASLaTeX including one postscript figure and one bitmapped image, JPEG format. Submitted to the Astronomical Jorunal. Full Postscript version available at http://www.astro.virginia.edu/~bd4r

Separating the Influences of Diagenesis, Productivity and Anthropogenic Nitrogen Deposition on Sedimentary δ15N Variations

The stable isotopic composition of nitrogen (δ15N) in organic lake sediments is frequently used to infer changes in the source or cycling of N prior to sedimentation. However, diagenetic processes that occur after sedimentation can systematically alter the primary isotopic signal recorded in sedimentary organic matter and must be accounted for in order to detect changes in the δ15N of nitrogen inputs to the sediment surface. Here we present a null model that estimates the diagenetic effect on sedimentary lake δ15N records. The model was tested using lake sediment cores from relatively pristine alpine lakes in the Wind River and Teton Ranges of Wyoming, USA. Model-inferred increases in productivity were tested against independent productivity proxies (diatom accumulation rates and the planktonic to benthic ratio), and inferred changes in anthropogenic nitrogen contribution were validated with records of atmospheric nitrogen deposition from the nearby Fremont Glacier, Wyoming. Diagenetic overprinting significantly altered sediment δ15N profiles, and the degree of alteration was not constant through time. Of the cores analyzed, ∼30–70% of the variability can be explained by diagenesis alone, with the remainder explained by either a change in productivity or a change in the isotopic composition of the source material. Our null model of isotopic fractionation proved to be successful at separating the diagenetic overprinting from other causes of isotopic shifts, thereby providing environmental scientists with an analytical tool to partition the effects of diagenesis and environmental change on sedimentary δ15N values

Alternative Sources of Accurate Agricultural Topography

Bob Recker started Cedar Valley Innovation, CVI, in 2004 following his retirement from John Deere after 41 years. CVI works on many small-scale experiments to test if they can be applied in large-scale settings. CVI is a small business hoping to make a big impact on agriculture. On this project specifically, our client’s goal is to study the relative accuracy of alternative methods of data collection to create topographical data of agricultural fields for purpose of water flow and related field analysis.Our group understands the possible solutions for the problem of analyzing water flow are tractor-based ground units, drones, and satellite imagery. We also know relative costs for each system or method. CVI is seeking a definitive answer on which method is best and which method would be easiest for farmers to replicate. If our group tells people how we analyzed field A, would they be able to go analyze field B on their own? Our group has not been able to find specific examples of other companies working on analyzing the pros and cons amongst all three methods. There are plenty of companies working on improving, or trying to sell one method, but very few are attempting to determine which one of the three is the best. While determining which method is best for topographical data for water flow analysis, we will also be able to determine other areas farmers could use the topographical data. Mapping fields, scouting crop health, monitoring weeds or need for fertilizer could all be solved with some of the same methods (Darr, 2018)

UIT Detection of Hot Stars in the Globular Cluster NGC362

We used the Ultraviolet Imaging Telescope during the March 1995 Astro-2 mission to obtain a deep far-UV image of the globular cluster NGC 362, which was formerly thought to have an almost entirely red horizontal branch (HB). 84 hot (T_eff > 8500 K) stars were detected within a radius of 8'.25 of the cluster center. Of these, 43 have FUV magnitudes consistent with HB stars in NGC 362, and at least 34 are cluster members. The number of cluster members is made uncertain by background contamination from blue stars in the Small Magellanic Cloud (SMC). There are six candidate supra-HB stars which have probably evolved from the HB. We discuss the implications of these results for the production of hot blue stars in stellar populations.Comment: 10 pages AASLaTeX including one postscript figure and one compressed bitmap, .jpg format. To appear in Ap. J. Letters. Postscript version also available at http://www.astro.virginia.edu/~bd4r

Bond-rearrangement and ionization mechanisms in the photo-double-ionization of simple hydrocarbons (C2H4, C2H3F, and 1,1-C2H2F2) near and above threshold

Citation: Gaire, B., Gatton, A., Wiegandt, F., Neff, J., Janke, C., Zeller, S., . . . Weber, T. (2016). Bond-rearrangement and ionization mechanisms in the photo-double-ionization of simple hydrocarbons (C2H4, C2H3F, and 1,1-C2H2F2) near and above threshold. Physical Review A, 94(3), 8. doi:10.1103/PhysRevA.94.033412We investigate bond-rearrangement driven by photo-double-ionization (PDI) near and above the double-ionization threshold in a sequence of carbon-carbon double-bonded hydrocarbon molecules: ethylene, fluoroethylene, and 1,1-difluoroethylene. We employ the kinematically complete cold target recoil ion momentum spectroscopy method to resolve all photo-double-ionization events leading to two-ion fragments. We observe changes in the branching ratios of different dissociative ionization channels depending on the presence of no, one, or two fluorine atoms. The role of the fluorine atom in the bond-rearrangement channels is intriguing, as evident by the reordering of the threshold energies of the PDI in the fluorinated molecules. These effects offer a compelling argument that the electronegativity of the fluorine (or the polarity of the molecule) strongly influences the potential energy surfaces of the molecules and drives bond rearrangement during the dissociation process. The energy sharing and the relative angle between the three-dimensional momentum vectors of the two electrons enable us to distinguish between knockout and other ionization mechanisms of the PDI processes

Extinction Corrected Star Formation Rates Empirically Derived from Ultraviolet-Optical Colors

Using a sample of galaxies from the Sloan Digital Sky Survey spectroscopic catalog with measured star-formation rates (SFRs) and ultraviolet (UV) photometry from the GALEX Medium Imaging Survey, we derived empirical linear correlations between the SFR to UV luminosity ratio and the UV-optical colors of blue sequence galaxies. The relations provide a simple prescription to correct UV data for dust attenuation that best reconciles the SFRs derived from UV and emission line data. The method breaks down for the red sequence population as well as for very blue galaxies such as the local ``supercompact'' UV luminous galaxies and the majority of high redshift Lyman Break Galaxies which form a low attenuation sequence of their own.Comment: 20 pages, 11 figures, accepted for publication in the ApJS GALEX special issu

Observation of enhanced chiral asymmetries in the inner-shell photoionization of uniaxially oriented methyloxirane enantiomers

Most large molecules are chiral in their structure: they exist as two enantiomers, which are mirror images of each other. Whereas the rovibronic sublevels of two enantiomers are almost identical, it turns out that the photoelectric effect is sensitive to the absolute configuration of the ionized enantiomer - an effect termed Photoelectron Circular Dichroism (PECD). Our comprehensive study demonstrates that the origin of PECD can be found in the molecular frame electron emission pattern connecting PECD to other fundamental photophysical effects as the circular dichroism in angular distributions (CDAD). Accordingly, orienting a chiral molecule in space enhances the PECD by a factor of about 10