2,321 research outputs found
Douglas Shoal preliminary site assessment report
Document R.1.59918002, Version 1.Report prepared by Cardno Ltd for the Great Barrier Reef Marine Park Authority
Optical matrix elements in tight-binding models with overlap
We investigate the effect of orbital overlap on optical matrix elements in
empirical tight-binding models. Empirical tight-binding models assume an
orthogonal basis of (atomiclike) states and a diagonal coordinate operator
which neglects the intra-atomic part. It is shown that, starting with an atomic
basis which is not orthogonal, the orthogonalization process induces
intra-atomic matrix elements of the coordinate operator and extends the range
of the effective Hamiltonian. We analyze simple tight-binding models and show
that non-orthogonality plays an important role in optical matrix elements. In
addition, the procedure gives formal justification to the nearest-neighbor
spin-orbit interaction introduced by Boykin [Phys. Rev \textbf{B} 57, 1620
(1998)] in order to describe the Dresselahaus term which is neglected in
empirical tight-binding models.Comment: 16 pages 6 figures, to appear in Phys. Rev.
LIDAR DERIVED SALT MARSH TOPOGRAPHY AND BIOMASS: DEFINING ACCURACY AND SPATIAL PATTERNS OF UNCERTAINTY
As valuable and vulnerable blue carbon ecosystems, salt marshes require adaptable and robust monitoring methods that span a range of spatiotemporal scales. The application of unmanned aerial vehicle (UAV) based remote sensing is a key tool in achieving this goal. Due to the particular characteristics of tidal wetlands, however, there are challenges in obtaining research and management relevant data with the requisite level of accuracy. In this study, the spatial patterns in uncertainty stemming from scan angle, binning method, vegetation structure and platform surface morphology are examined in the context of UAV light detection and ranging (LiDAR) derived digital elevation models (DEM). The results demonstrate that overlapping the UAV flight paths sufficiently to avoid sole reliance on LIDAR data with scan angles exceeding 15 degrees is advisable. Furthermore, the spatial arrangement of halophyte species and marsh morphology has a clear influence on DEM accuracy. The largest errors were associated with sudden structural transitions at the marsh channel boundaries. The DEMmean was found to be the most accurate for bare ground, while the DEMmin was the most accurate for channels and the middle to high marsh vegetation (MAEs = −0.01m). For the low to middle vegetation, all the trialled DEMs returned a similar magnitude of mean error (MAE = ± 0.03m). The accuracy difference between the two vegetation associations examined appears to be connected to variations in coverage, height and biomass. Overall, these findings reinforce the link between salt marsh biogeomorphic complexity and the spatial distribution and magnitude of LiDAR DEM erro
Optical injection and terahertz detection of the macroscopic Berry curvature
We propose an experimental scheme to probe the Berry curvature of solids. Our
method is sensitive to arbitrary regions of the Brillouin zone, and employs
only basic optical and terahertz techniques to yield a background free signal.
Using semiconductor quantum wells as a prototypical system, we discuss how to
inject Berry curvature macroscopically, and probe it in a way that provides
information about the underlying microscopic Berry curvature.Comment: 4 pages, accepted in Physical Review Letter
Tissue Damage and Nutritive Value of Warm-Season Grasses Following a Freeze
Bahiagrass (Paspalum notatum Flugge) is a major forage for livestock in the subtropics of the U.S.A. However, it is subject to freeze damage with minimal winter regrowth, and is generally considered a poor grass for stockpiling due to poor quality of the residue. Bahiagrass genotypes have been found showing a range of leaf freezing tolerance in the in the field (-30 C) (Blount et al., 2001). Other C4 grasses have been reported to have genotype-specific tolerances to below-freezing temperatures ranging from -3 to -100 C (Sakai & Larcher, 1987). This research was begun to try to understand the processes that take place following freeze injury to bahiagrass. Three grasses native to the Midwest, big bluestem (Andropogon gerardii Vitman cv Alamo), Indiangrass (Sorghastrum nutans (L.) Nash cv Lometa), and switchgrass (Panicum virgatum L. cv Kaw) and commonly used for stockpiling were used for comparison
Survey of Subterranean Termite (Isoptera: Rhinotermitidae) Utilization of Temperate Forests
Both native and invasive subterranean termites (Isoptera: Rhinotermitidae), including the Formosan subterranean termite, are well known pests of urban areas, but little is known about their distribution or impact in forest ecosystems of the southeastern United States. Recently harvested timber stumps were mechanically inspected for the presence of subterranean termites in multiple locations across southern Mississippi and eastern Louisiana. A systematic line plot cruise with 100 x 200m spacing and1/20thha plots was implemented, and all stumps with a diameter greater than 7.6cm were inspected. In total, 7,413 stumps were inspected for the presence of subterranean termites, and 406 of those contained native subterranean termite (Reticulitermes spp) infestations. Light traps were also placed at 8 sites to detect the presence of subterranean termite alates. While no invasive Formosan subterranean termites were found during mechanical inspection of tree stumps, alates were captured in light traps at three sites. The proportion of stumps infested with subterranean termites was negatively correlated with the number of stumps in each plot. Although 6.27% of pine stumps and 1.86% of hardwood stumps were infested, no correlation was found between subterranean termite presence and type of stump (pine or hardwood). Infestations of stumps by subterranean termites ranged from 0.94% to 14.97% depending on site
SOCIAL MEDIA: CREATING STUDENT AWARENESS OF ITS USE IN THE HIRING PROCESS
As the use of social media permeates our lives, it is important for business educators to promote the effective use of this technology to students for both their role as job seekers as well as potential hiring managers. This article will present current perceptions among business students on using social media in the job search process, primary research from recruiters in an attempt to understand employers’ policies and practices with respect to the use of social media in the hiring process, key laws which students should be aware of with respect to the use of social media by employers, and practical guidance for students throughout their business school experience. In addition, a proposed teaching method will be presented on how to convey this practical guidance to students in a compelling and impactful manner
A priori Wannier functions from modified Hartree-Fock and Kohn-Sham equations
The Hartree-Fock equations are modified to directly yield Wannier functions
following a proposal of Shukla et al. [Chem. Phys. Lett. 262, 213-218 (1996)].
This approach circumvents the a posteriori application of the Wannier
transformation to Bloch functions. I give a novel and rigorous derivation of
the relevant equations by introducing an orthogonalizing potential to ensure
the orthogonality among the resulting functions. The properties of these,
so-called a priori Wannier functions, are analyzed and the relation of the
modified Hartree-Fock equations to the conventional, Bloch-function-based
equations is elucidated. It is pointed out that the modified equations offer a
different route to maximally localized Wannier functions. Their computational
solution is found to involve an effort that is comparable to the effort for the
solution of the conventional equations. Above all, I show how a priori Wannier
functions can be obtained by a modification of the Kohn-Sham equations of
density-functional theory.Comment: 7 pages, RevTeX4, revise
Metamagnetic Quantum Criticality
A renormalization group treatment of metamagnetic quantum criticality in
metals is presented. In clean systems the universality class is found to be of
the overdamped, conserving (dynamical exponent z=3) Ising type. Detailed
results are obtained for the field and temperature dependence of physical
quantities including the differential susceptibility, resistivity and specific
heat near the transition. An application of the theory is made to Sr3Ru2O7,
which appears to exhibit a metamagnetic critical end-point at a very low
temperature and a field of order 5-7T.Comment: 4 pages latex (Revtex 4) and 3 eps figure
Conserved Spin and Orbital Angular Momentum Hall Current in a Two-Dimensional Electron System with Rashba and Dresselhaus Spin-orbit Coupling
We study theoretically the spin and orbital angular momentum (OAM) Hall
effect in a high mobility two-dimensional electron system with Rashba and
Dresselhuas spin-orbit coupling by introducing both the spin and OAM torque
corrections, respectively, to the spin and OAM currents. We find that when both
bands are occupied, the spin Hall conductivity is still a constant (i.e.,
independent of the carrier density) which, however, has an opposite sign to the
previous value. The spin Hall conductivity in general would not be cancelled by
the OAM Hall conductivity. The OAM Hall conductivity is also independent of the
carrier density but depends on the strength ratio of the Rashba to Dresselhaus
spin-orbit coupling, suggesting that one can manipulate the total Hall current
through tuning the Rashba coupling by a gate voltage. We note that in a pure
Rashba system, though the spin Hall conductivity is exactly cancelled by the
OAM Hall conductivity due to the angular momentum conservation, the spin Hall
effect could still manifest itself as nonzero magnetization Hall current and
finite magnetization at the sample edges because the magnetic dipole moment
associated with the spin of an electron is twice as large as that of the OAM.
We also evaluate the electric field-induced OAM and discuss the origin of the
OAM Hall current. Finally, we find that the spin and OAM Hall conductivities
are closely related to the Berry vector (or gauge) potential.Comment: latest revised version; Accepted for publication in Physical Review
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