1,198 research outputs found
Transport in the metallic regime of Mn doped III-V Semiconductors
The standard model of Mn doping in GaAs is subjected to a coherent potential
approximation (CPA) treatment. Transport coefficients are evaluated within the
linear response Kubo formalism. Both normal (NHE) and anomalous contributions
(AHE) to the Hall effect are examined. We use a simple model density of states
to describe the undoped valence band. The CPA bandstructure evolves into a spin
split band caused by the exchange scattering with Mn dopants. This gives
rise to a strong magnetoresistance, which decreases sharply with temperature.
The temperature () dependence of the resistance is due to spin disorder
scattering (increasing with ), CPA bandstructure renormalization and charged
impurity scattering (decreasing with ). The calculated transport
coefficients are discussed in relation to experiment, with a view of assessing
the overall trends and deciding whether the model describes the right physics.
This does indeed appear to be case, bearing in mind that the hopping limit
needs to be treated separately, as it cannot be described within the band CPA.Comment: submitted to Phys. Rev.
Neutron Investigations of Novel Magnetic Phases
Recent years have seen a renewed search for Fe based permanent magnets, spurred by the discovery of Nd2Fe14B and interstitially modified rare-earth iron binaries. The insights derived from those compounds have suggested a number of routes to the development of such systems, including selective site substitution and combinations of site substitution and interstitial modification. Neutron diffraction is an essential component of this work, since it provides systematic information about the location of substitutional and interstitial atoms, and about the effects these changes have on the magnetic interactions in the systems of interes
Creating Online Lessons: A Faculty Development Seminar Series
The World Wide Web is being used increasingly to deliver instruction in medical education. Consequently, there is a need to train faculty in developing and implementing online instruction. We developed and implemented a seminar series to teach faculty to create educationally sound, well designed online instruction.
Instruction was delivered to 15 participants via a six session seminar on developing web based lessons, supplemented with web-based instruction. First, the participants learned the basics of instructional design via a web based module. They then completed content outlines for their online lessons prior to the first seminar. Lesson development, web site development and the use of a web based instructional shell to implement the online lessons were each taught in two two hour sessions.
Eight participants developed online lessons and four actually implemented them. Feedback was mostly positive, with suggestions for improvement. All eight participants who completed the series said they would recommend it to their colleagues.
Because a longitudinal workshop type of seminar series requires a large amount of participant time outside of class, a six month seminar series may be too long. It is important at the beginning of the series to help participants select topics suitable for online instruction and to help them narrow their topics. We may change the attendance guidelines so faculty would attend only the session on instructional design and have their staff attend the technical sessions on web site design, HTML editing and online course delivery systems. This would better match the actual practice of faculty designing the instruction and staff developing it
Differential requirement for BMP signaling in atrial and ventricular lineages establishes cardiac chamber proportionality
AbstractThe function of an organ relies upon the proper relative proportions of its individual operational components. For example, effective embryonic circulation requires the appropriate relative sizes of each of the distinct pumps created by the atrial and ventricular cardiac chambers. Although the differences between atrial and ventricular cardiomyocytes are well established, little is known about the mechanisms regulating production of proportional numbers of each cell type. We find that mutation of the zebrafish type I BMP receptor gene alk8 causes reduction of atrial size without affecting the ventricle. Loss of atrial tissue is evident in the lateral mesoderm prior to heart tube formation and results from the inhibition of BMP signaling during cardiac progenitor specification stages. Comparison of the effects of decreased and increased BMP signaling further demonstrates that atrial cardiomyocyte production correlates with levels of BMP signaling while ventricular cardiomyocyte production is less susceptible to manipulation of BMP signaling. Additionally, mosaic analysis provides evidence for a cell-autonomous requirement for BMP signaling during cardiomyocyte formation and chamber fate assignment. Together, our studies uncover a new role for BMP signaling in the regulation of chamber size, supporting a model in which differential reception of cardiac inductive signals establishes chamber proportion
Superparamagnetic-like ac susceptibility behavior in a "partially disordered antiferromagnetic" compound, CaCoRhO
We report the results of dc and ac magnetization measurements as a function
of temperature (1.8 - 300 K) for the spin chain compound, CaCoRhO,
which has been recently reported to exhibit a partially disordered
antiferromagnetic (PDAF) structure in the range 30 - 90 K and spin-glass
freezing below 30 K. We observe an unexpectedly large frequency dependence of
ac susceptibility in the T range 30 - 90 K, typical of superparamagnets. In
addition, we find that there is no difference in the isothermal remanent
magnetization behavior for the two regimes below 90 K. These findings call for
more investigations to understand the magnetism of this compound.Comment: 4 pages, 3 figure
Adapting Navy Medicine for Future Warfighting: Scenario Thinking for Combat Casualty Care
Art Valeri, Jay Yelon, Juanita Hopkins and Seamus Markey are NPS student authors.The article of record as published may be found at https://cimsec.org/scenario-thinking-for-combat-casualty-care
Sublattice Asymmetric Reductions of Spin Values on Stacked Triangular Lattice Antiferromagnet CsCoBr
We study the reductions of spin values of the ground state on a stacked
triangular antiferromagnet using the spin-wave approach. We find that the spin
reductions have sublattice asymmetry due to the cancellation of the molecular
field. The sublattice asymmetry qualitatively analyzes the NMR results of
CsCoBr.Comment: 5pages, 5figure
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