325 research outputs found
Observation of Multiple-Gap Structure in Hidden Order State of URu2Si2 from Optical Conductivity
We have measured the far infrared reflectance of the heavy fermion compound
URuSi through the phase transition at T=17.5 K dubbed 'hidden
order' with light polarized along both the a- and c-axes of the tetragonal
structure. The optical conductivity allows the formation of the hidden order
gap to be investigated in detail. We find that both the conductivity and the
gap structure are anisotropic, and that the c-axis conductivity shows evidence
for a double gap structure, with meV and
meV respectively at 4 K, while the gap seen in the a-axis conductivity has a
value of meV at 4 K. The opening of the gaps does not follow the
behaviour expected from mean field theory in the vicinity of the transition.Comment: 6 pages, 5 figure
Soybean Variety Trial Archive
This report features the available soybean variety trial data from 2003-2017. Crop performance testing results are released annually through the activities of SDSU Extension and the South Dakota Agricultural Experiment Station at SDSU
Corn Hybrid Trial Archive
This report features the available corn data from 2003-2017. Crop performance testing results are released annually through the activities of SDSU Extension and the South Dakota Agricultural Experiment Station at SDSU
Temperature-Dependent Gentamicin Resistance of Francisella tularensis is Mediated by Uptake Modulation
Gentamicin (Gm) is an aminoglycoside commonly used to treat bacterial infections such as tularemia - the disease caused by Francisella tularensis. In addition to being pathogenic, F. tularensis is found in environmental niches such as soil where this bacterium likely encounters Gm producers (Micromonospora sp.). Here we show that F. tularensis exhibits increased resistance to Gm at ambient temperature (26°C) compared to mammalian body temperature (37°C). To evaluate whether F. tularensis was less permeable to Gm at 26°C, a fluorescent marker [Texas Red (Tr)] was conjugated with Gm, yielding Tr-Gm. Bacteria incubated at 26°C showed reduced fluorescence compared to those at 37°C when exposed to Tr-Gm suggesting that uptake of Gm was reduced at 26°C. Unconjugated Gm competitively inhibited uptake of Tr-Gm, demonstrating that this fluorescent compound was taken up similarly to unconjugated Gm. Lysates of F. tularensis bacteria incubated with Gm at 37°C inhibited the growth of Escherichia coli significantly more than lysates from bacteria incubated at 26°C, further indicating reduced uptake at this lower temperature. Other facultative pathogens (Listeria monocytogenes and Klebsiella pneumoniae) exhibited increased resistance to Gm at 26°C suggesting that the results generated using F. tularensis may be generalizable to diverse bacteria. Regulation of the uptake of antibiotics provides a mechanism by which facultative pathogens survive alongside antibiotic-producing microbes in nature
Spring Wheat Variety Trial Archive
Crop performance testing results are released annually through the activities of SDSU Extension and the South Dakota Agricultural Experiment Station at SDSU
Chandra X-Ray Observations of Two Unusual BAL Quasars
We report sensitive Chandra X-ray non-detections of two unusual, luminous
Iron Low-Ionization Broad Absorption Line Quasars (FeLoBALs). The observations
do detect a non-BAL, wide-binary companion quasar to one of the FeLoBAL
quasars. We combine X-ray-derived column density lower limits (assuming solar
metallicity) with column densities measured from ultraviolet spectra and CLOUDY
photoionization simulations to explore whether constant density slabs at broad
line region densities can match the physical parameters of these two BAL
outflows, and find that they cannot. In the "overlapping-trough" object SDSS
J0300+0048, we measure the column density of the X-ray absorbing gas to be N_H
>= 1.8 x 1024 cm-2. From the presence of Fe II UV78 absorption but lack of Fe
II UV195/UV196 absorption, we infer the density in that part of the absorbing
region to be n_e ~ 106 cm-3. We do find that a slab of gas at that density
might be able to explain this object's absorption. In the Fe III-dominant
object SDSS J2215-0045, the X-ray absorbing column density of N_H >= 3.4 x 1024
cm-2 is consistent with the Fe III-derived N_H >= 2 x 1022 cm-2 provided the
ionization parameter is log U > 1.0 for both the n_e = 1011 cm-3 and n_e = 1012
cm-3 scenarios considered (such densities are required to produce Fe III
absorption without Fe II absorption). However, the velocity width of the
absorption rules out its being concentrated in a single slab at these
densities. Instead, this object's spectrum can be explained by a low density,
high ionization and high temperature disk wind that encounters and ablates
higher density, lower ionization Fe III-emitting clumps.Comment: 18 pages, 6 figure
Oats Variety Trial Archive
This report features the available oats data from 2003-2017. Crop performance testing results are released annually through the activities of SDSU Extension and the South Dakota Agricultural Experiment Station at SDSU
Emergence and Variability of Broad Absorption Line Quasar Outflows
We isolate a set of quasars that exhibit emergent C iv broad absorption lines
(BALs) in their spectra by comparing spectra in the SDSS Data Release 7 and the
SDSS/BOSS Data Releases 9 and 10. After visually defining a set of emergent
BALs, follow-up observations were obtained with the Gemini Observatory for 105
quasars. We find an emergence rate consistent with the previously reported
disappearance rate of BAL quasars given the relative numbers of non-BAL and BAL
quasars in the SDSS. We find candidate newly emerged BALs are preferentially
drawn from among BALs with smaller balnicity indices, shallower depths, larger
velocities, and smaller widths. Within two rest-frame years (average) after a
BAL has emerged, we find it equally likely to continue increasing in equivalent
width in an observation six months later (average) as it is to start
decreasing. From the time separations between our observations, we conclude the
coherence time-scale of BALs is less than 100 rest-frame days. We observe
coordinated variability among pairs of troughs in the same quasar, likely due
to clouds at different velocities responding to the same changes in ionizing
flux; and the coordination is stronger if the velocity separation between the
two troughs is smaller. We speculate the latter effect may be due to clouds
having on average lower densities at higher velocities due to mass conservation
in an accelerating flow, causing the absorbing gas in those clouds to respond
on different timescales to the same ionizing flux variations.Comment: 37 pages, 25 figure
Field Pea Variety Trial Archive
This report features the available pea data from 2003-2017. Crop performance testing results are released annually through the activities of SDSU Extension and the South Dakota Agricultural Experiment Station at SDSU
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