1,337 research outputs found
Movement of yellowtail snapper (Ocyurus chrysurus Block 1790) and black grouper (Mycteroperca bonaci Poey 1860) in the northern Florida Keys National Marine Sanctuary as determined by acoustic telemetry
We tagged a total of 14 yellowtail snapper (Ocyurus chrysurus Bloch 1790) and black grouper (Mycteroperca bonaci Poey 1860) inside the Conch Reef Research Only Area (a no-take marine reserve) in the northern Florida Keys National Marine Sanctuary in November 2001. Both species are heavily exploited in the region. Our objective was to characterize site fidelity and movement behavior along the reef tract to the north and south of the release point. Fishes were collected by baited hook and line from the surface, surgically-tagged with coded-acoustic transmitters, and returned to the reef by snorkelers. Tracking of fish movement behavior was conducted by five acoustic receivers deployed on the seafloor from Davis Reef in the south to Pickles Reef in the north. Fishes were tracked for up to eight months. Results indicated that the
majority of signal detections for individual fish from both species were recorded at the two Conch Reef receivers. Limited movement from Conch Reef to Davis Reef was recorded, but no signal detections were recorded at the two sites to the north of Conch Reef. These results suggest
that both species show site fidelity to Conch Reef. Future studies will seek to characterize this site fidelity with increased temporal and spatial resolution at Conch Reef. (PDF contains 25 pages.
X-ray Absorption Near Edge Structure of FePt nanoclusters
X-ray Absorption Near Edge Structure [XANES] of FePt nanoclusters has been
studied using a full multiple scattering, self-consistent field [SCF],
real-space Green`s function approach realized via the powerful ab initio FEFF8
code. One purpose of our study is to determine the sensitivity of Pt L3 edge
with respect to the size and shape of the FePt nanoclusters. We also give the
results of the calculations with respect to the Fe L3 edge. Calculations are
made with and without core-hole for two main reasons, to check and cross-check
the FEFF code and also since in some cases it is known such as Pt clusters that
better results are obtained without the core-hole. This is mainly because the
screening electron will occupy empty d or f states and correspondingly reduce
the white line intensity.Comment: TeX version 3.14159, LaTex2e, 6 pages with 6 figure
Five Low-Cost Ideas to Help Families Save for College
Improvements to the 529 platform could increase the number of low- and moderate-income families saving in 529s and make it easier for these families to build assets for education. These reforms include large initiatives, such as coordinating existing higher education tax credits and financial aid with 529s, as well as small initiatives to increase savings. This document contains several low-cost, simple reforms for 529s at the federal level. These would be important first steps for enabling more low- and moderate-income students to complete higher education
Local Atomic Structure of Martensitic NiMnGa: An EXAFS Study
The local atomic structure of NiMnGa with 0
0.16 alloys was explored using Mn and Ga K-edge Extended X-ray Absorption Fine
Structure (EXAFS) measurement. Inorder to study the atomic re-arrangements that
occur upon martensitic transformation, room temperature and low temperature
EXAFS were recorded. The changes occurring in the L2 unit cell and the bond
lengths obtained from the analysis enables us to determine the modulation
amplitudes over which the constituent atoms move giving rise to shuffling of
the atomic planes in the modulated structure. The EXAFS analysis also suggests
the changes in hybridization of Ga- and Ni- orbitals associated with the
local symmetry breaking upon undergoing martensitic transition.Comment: Accepted for publication in Physical Review
Strengthening VITA to Boost Financial Security at Tax Time and Beyond
At the beginning of every year, the vast majority of American households turn their attention to the ritual of filing their federal and state income tax returns. Some see it as a civic duty, others as a burdensome chore. But for tens of millions of low- and moderate-income families and individuals, tax time represents a springboard to economic opportunity and financial security.Key PointsEvery year, the VITA program helps millions of low- and moderate-income Americans file their taxes for free.The VITA program is driven by thousands of community organizations nationwide, which leverage a modest federal grant matched with significant local investment.VITA tax preparation has the highest accuracy rate of any tax preparation service, and VITA has increased the number of returns filed every year since the program was authorized.There is an overwhelming demand for VITA services, but VITA sites need more flexibility to innovate and respond to local community needs.Congress, the Administration and states should expand VITA and make key reforms to spur local innovation
Reconstruction of deglacial sea surface temperatures in the tropical Pacific from selective analysis of a fossil coral
The Sr/Ca of coral skeletons demonstrates potential as an indicator of sea surface temperatures (SSTs). However, the glacial-interglacial SST ranges predicted from Sr/Ca of fossil corals are usually higher than from other marine proxies. We observed infilling of secondary aragonite, characterised by high Sr/Ca ratios, along intraskeletal pores of a fossil coral from Papua New Guinea that grew during the penultimate deglaciation (130 +/- 2 ka). Selective microanalysis of unaltered areas of the fossil coral indicates that SSTs at similar to 130 ka were <= 1 degrees C cooler than at present in contrast with bulk measurements ( combining infilled and unaltered areas) which indicate a difference of 6-7 degrees C. The analysis of unaltered areas of fossil skeletons by microprobe techniques may offer a route to more accurate reconstruction of past SSTs.</p
XAFS spectroscopy. I. Extracting the fine structure from the absorption spectra
Three independent techniques are used to separate fine structure from the
absorption spectra, the background function in which is approximated by (i)
smoothing spline. We propose a new reliable criterion for determination of
smoothing parameter and the method for raising of stability with respect to
k_min variation; (ii) interpolation spline with the varied knots; (iii) the
line obtained from bayesian smoothing. This methods considers various prior
information and includes a natural way to determine the errors of XAFS
extraction. Particular attention has been given to the estimation of
uncertainties in XAFS data. Experimental noise is shown to be essentially
smaller than the errors of the background approximation, and it is the latter
that determines the variances of structural parameters in subsequent fitting.Comment: 16 pages, 7 figures, for freeware XAFS analysis program, see
http://www.crosswinds.net/~klmn/viper.htm
Structural precursor to the metal-insulator transition in V_2O_3
The temperature dependence of the local structure of V_2O_3 in the vicinity
of the metal to insulator transition (MIT) has been investigated using hard
X-ray absorption spectroscopy. It is shown that the vanadium pair distance
along the hexagonal c-axis changes abruptly at the MIT as expected. However, a
continuous increase of the tilt of these pairs sets in already at higher
temperatures and reaches its maximum value at the onset of the electronic and
magnetic transition. These findings confirm recent theoretical results which
claim that electron-lattice coupling is important for the MIT in V_2O_3. Our
results suggest that interactions in the basal plane play a decisive role for
the MIT and orbital degrees of freedom drive the MIT via changes in
hybridization.Comment: 6 pages, 5 figures, 2 table
Structure Analysis of Natural WangdaodeiteâLiNbOâ-Type FeTiOâ
This paper reports the first structure refinement of natural wangdaodeite, LiNbOâ-type FeTiOâ from the Ries impact structure. Wangdaodeite occurs together with recrystallized ilmenite clasts in shock melt veins which have experienced peak shock pressures of between 17 and 22 GPa. Comparison of natural and synthetic wangdaodeite points toward a correlation between the distortion of ferrate- and titanate-polyhedra and the c/a ratio of the unit cell. The Raman spectrum of wangdaodeite is calculated based on the refined structure. Comparison to the reported spectrum of the type-material shows that the Raman peak at 738â740 cmâ»Âč is indicative for this phase, whereas other features in type-wangdaodeite are tentatively assigned to disordered ilmenite
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