813 research outputs found
Western Massasauga (Sistrurus tergeminus): Species Conservation Assessment
The primary goal in development of at-risk species conservation assessments is to compile biological and ecological information that may assist conservation practitioners in making decisions regarding the conservation of species of interest. The Nebraska Natural Legacy Project recognizes the Western Massasauga (Sistrurus tergeminus) as a Tier I at-risk species. Provided are some general management recommendations regarding Western Massasaugas. Conservation practitioners will need to use professional judgment to make specific management decisions based on objectives, location, and a multitude of variables. This resource was designed to share available knowledge of this at-risk species that will aid in the decision-making process or in identifying research needs to benefit the species. Species conservation assessments will need to be updated as relevant scientific information becomes available and/or conditions change. Though the Nebraska Natural Legacy Project focuses efforts in the state’s Biologically Unique Landscapes, it is recommended that whenever possible, practitioners make considerations for a species throughout its range in order to increase the outcome of successful conservation efforts. And in the case of conservation for massasaugas, it is particularly necessary to take into account the seasonal needs of the species and conserve both wintering and summer foraging habitat.
Criteria for selection as Tier I State listed, G3T3
Trends since 2005 in NE Stable
Range in NE Very southeast portion of state
Habitat Wet mesic tallgrass prairie, wet meadow/marsh/wet prairie, lower-middle tallgrass prairie, cordgrass wet prairie, crayfish burrows
Threats Loss/degradation of tallgrass prairie habitat, woody invasion, tilling for agriculture, prescribed fires, haying, vehicle mortality, persecution by humans
Climate Change Vulnerability Index: Highly Vulnerable (NatureServe 2013)
Research/Inventory Determine size/extent of Colfax County population; conduct surveys to assess distribution and abundance; conduct population monitoring and population viability assessment
Landscapes Lower Platte River, Sandstone Prairies, Southeast Prairie
Valence Instability of YbCuSi through its quantum critical point
We report Resonant inelastic x-ray scattering measurements (RIXS) in
YbCuSi at the Yb L edge under high pressure (up to 22 GPa) and at
low temperatures (down to 7 K) with emphasis on the vicinity of the transition
to a magnetic ordered state. We find a continuous valence change towards the
trivalent state with increasing pressure but with a pronounced change of slope
close to the critical pressure. Even at 22 GPa the Yb state is not fully
achieved. The pressure where this feature is observed decreases as the
temperature is reduced to 9 GPa at 7K, a value close to the critical pressure
(\itshape{p\normalfont{}}\normalfont 7.5 GPa) where magnetic
order occurs. The decrease in the valence with decreasing temperature
previously reported at ambient pressure is confirmed and is found to be
enhanced at higher pressures. We also compare the f electron occupancy between
YbCuSi and its Ce-counterpart, CeCuSi
Non-Commutativity effects in the Dirac equation in crossed electric and magnetic fields
In this paper we present exact solutions of the Dirac equation on the
non-commutative plane in the presence of crossed electric and magnetic fields.
In the standard commutative plane such a system is known to exhibit contraction
of Landau levels when the electric field approaches a critical value. In the
present case we find exact solutions in terms of the non-commutative parameters
(momentum non-commutativity) and (coordinate non-commutativity)
and provide an explicit expression for the Landau levels. We show that
non-commutativity preserves the collapse of the spectrum. We provide a dual
description of the system: (i) one in which at a given electric field the
magnetic field is varied and the other (ii) in which at a given magnetic field
the electric field is varied. In the former case we find that momentum
non-commutativity () splits the critical magnetic field into two critical
fields while coordinates non-commutativity () gives rise to two
additional critical points not at all present in the commutative scenario.Comment: 6 pages, 4 figures, Accepted for publication by EuroPhysics Letters
(EPL
Electric Dipole Moments and Polarizability in the Quark-Diquark Model of the Neutron
For a bound state internal wave function respecting parity symmetry, it can
be rigorously argued that the mean electric dipole moment must be strictly
zero. Thus, both the neutron, viewed as a bound state of three quarks, and the
water molecule, viewed as a bound state of ten electrons two protons and an
oxygen nucleus, both have zero mean electric dipole moments. Yet, the water
molecule is said to have a nonzero dipole moment strength with
. The neutron may also be said to have
an electric dipole moment strength with .
The neutron analysis can be made experimentally consistent, if one employs a
quark-diquark model of neutron structure.Comment: four pages, two figure
Solution of One-dimensional Dirac Equation via Poincare Map
We solve the general one-dimensional Dirac equation using a "Poincare Map"
approach which avoids any approximation to the spacial derivatives and reduces
the problem to a simple recursive relation which is very practical from the
numerical implementation point of view. To test the efficiency and rapid
convergence of this approach we apply it to a vector coupling Woods--Saxon
potential, which is exactly solvable. Comparison with available analytical
results is impressive and hence validates the accuracy and efficiency of this
method.Comment: 8 pages, 6 figures. Version to appear in EP
Scattering of Woods-Saxon Potential in Schrodinger Equation
The scattering solutions of the one-dimensional Schrodinger equation for the
Woods-Saxon potential are obtained within the position-dependent mass
formalism. The wave functions, transmission and reflection coefficients are
calculated in terms of Heun's function. These results are also studied for the
constant mass case in detail.Comment: 14 page
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