1,163 research outputs found
New Distributional Records of the Ohio Shrimp, Macrobrachium ohione Smith (Decapoda: Palaemonidae) in Arkansas
The Ohio shrimp (Macrobrachium ohione) is a migratory (amphidromous) river shrimp that occurs in some Arkansas rivers. It is known from the Upper Missouri River from its mouth downstream to the Gulf of Mexico, but shrimp abundance has declined, particularly upstream of Louisiana. Ohio Shrimp has also been collected in the lower reach of the Missouri River not far from the confluence of the Mississippi River in St. Louis County. Dams and alterations in channel flow are hypothesized to have impacted upriver migrations of shrimp. Current range, abundance, and life history of Ohio shrimp is relatively unknown in the Mississippi River basin in reaches distant from sea water. Here, we report recent collections of Ohio shrimp in Arkansas rivers that were notably greater than 800 km from the Gulf of Mexico
What it takes to measure a fundamental difference between dark matter and baryons: the halo velocity anisotropy
Numerous ongoing experiments aim at detecting WIMP dark matter particles from
the galactic halo directly through WIMP-nucleon interactions. Once such a
detection is established a confirmation of the galactic origin of the signal is
needed. This requires a direction-sensitive detector. We show that such a
detector can measure the velocity anisotropy beta of the galactic halo.
Cosmological N-body simulations predict the dark matter anisotropy to be
nonzero, beta~0.2. Baryonic matter has beta=0 and therefore a detection of a
nonzero beta would be strong proof of the fundamental difference between dark
and baryonic matter. We estimate the sensitivity for various detector
configurations using Monte Carlo methods and we show that the strongest signal
is found in the relatively few high recoil energy events. Measuring beta to the
precision of ~0.03 will require detecting more than 10^4 WIMP events with
nuclear recoil energies greater than 100 keV for a WIMP mass of 100 GeV and a
32S target. This number corresponds to ~10^6 events at all energies. We discuss
variations with respect to input parameters and we show that our method is
robust to the presence of backgrounds and discuss the possible improved
sensitivity for an energy-sensitive detector.Comment: 15 pages, 8 figures, accepted by JCAP. Matches accepted versio
Extruded single ring hollow core optical fibers for Raman sensing
Abstract not availableG. Tsiminis, K. J. Rowland, H. Ebendorff-Heidepriem, N. A. Spooner and T. M. Monr
Lowering the energy threshold in COSINE-100 dark matter searches
COSINE-100 is a dark matter detection experiment that uses NaI(Tl) crystal
detectors operating at the Yangyang underground laboratory in Korea since
September 2016. Its main goal is to test the annual modulation observed by the
DAMA/LIBRA experiment with the same target medium. Recently DAMA/LIBRA has
released data with an energy threshold lowered to 1 keV, and the persistent
annual modulation behavior is still observed at 9.5. By lowering the
energy threshold for electron recoils to 1 keV, COSINE-100 annual modulation
results can be compared to those of DAMA/LIBRA in a model-independent way.
Additionally, the event selection methods provide an access to a few to sub-GeV
dark matter particles using constant rate studies. In this article, we discuss
the COSINE-100 event selection algorithm, its validation, and efficiencies near
the threshold
Heat flow of the Earth and resonant capture of solar 57-Fe axions
In a very conservative approach, supposing that total heat flow of the Earth
is exclusively due to resonant capture inside the Earth of axions, emitted by
57-Fe nuclei on Sun, we obtain limit on mass of hadronic axion: m_a<1.8 keV.
Taking into account release of heat from decays of 40-K, 232-Th, 238-U inside
the Earth, this estimation could be improved to the value: m_a<1.6 keV. Both
the values are less restrictive than limits set in devoted experiments to
search for 57-Fe axions (m_a<216-745 eV), but are much better than limits
obtained in experiments with 83-Kr (m_a<5.5 keV) and 7-Li (m_a<13.9-32 keV).Comment: 8 page
Direct Detection of Dark Matter in Supersymmetric Models
We evaluate neutralino-nucleon scattering rates in several well-motivated
supersymmetric models, and compare against constraints on the neutralino relic
density, BF( b\to s\gamma ) as well as the muon anomalous magnetic moment a_\mu
. In the mSUGRA model, the indirect constraints favor the hyperbolic
branch/focus point (HB/FP) region of parameter space, and in fact this region
is just where neutralino-nucleon scattering rates are high enough to be
detected in direct dark matter search experiments! In Yukawa unified SUSY
SO(10) models with scalar mass non-universality, the relic density of
neutralinos is almost always above experimental bounds, while the corresponding
direct detection rates are below experimental levels. Conversely, in five
dimensional SO(10) models where gauge symmetry breaking is the result of
compactification of the extra dimension, and supersymmetry breaking is
communicated via gaugino mediation, the relic density is quite low, while
direct detection rates can be substantial.Comment: 25 page latex file including 18 EPS figures; revised version with
references added and cross sections rescaled; figures changed. A copy of the
paper with better resolution figures can be found at
http://www.hep.fsu.edu/~belyaev/projects/directz1
Performance Comparison between Consequent-Pole and Inset Modular Permanent Magnet Machines
This paper proposes some consequent-pole modular
permanent magnet machines with different flux gap widths
and slot/pole number combinations. The corresponding inset
modular permanent magnet machines having the same
magnet volume are also presented for comparison. It has been
demonstrated that the output torques of the consequent pole
modular machines are always higher than those of the inset
modular machines regardless of flux gap widths and slot/pole
number combinations. Other electromagnetic performances
such as back-EMF, cogging torque, and iron losses, etc. are
calculated by 2D FEA software and compared as well. The
advantages and disadvantages of consequent and inset
modular permanent magnet machines are summarized in this
paper
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