7,424 research outputs found
Landau level spectroscopy of surface states in the topological insulator BiSb via magneto-optics
We have performed broad-band zero-field and magneto-infrared spectroscopy of
the three dimensional topological insulator BiSb. The
zero-field results allow us to measure the value of the direct band gap between
the conducting and valence bands. Under applied field in the
Faraday geometry (\emph{k} \emph{H} C1), we measured the presence of
a multitude of Landau level (LL) transitions, all with frequency dependence
. We discuss the ramification of this observation for
the surface and bulk properties of topological insulators.Comment: 7 pages, 8 figures, March Meeting 2011 Abstract: J35.0000
Johnson Space Center's Solar and Wind-Based Renewable Energy System
The NASA Johnson Space Center (JSC) in Houston, Texas has a Sustainability Partnership team that seeks ways for earth-based sustainability practices to also benefit space exploration research. A renewable energy gathering system was installed in 2007 at the JSC Child Care Center (CCC) which also offers a potential test bed for space exploration power generation and remote monitoring and control concepts. The system comprises: 1) several different types of photovoltaic panels (29 kW), 2) two wind-turbines (3.6 kW total), and 3) one roof-mounted solar thermal water heater and tank. A tie to the JSC local electrical grid was provided to accommodate excess power. The total first year electrical energy production was 53 megawatt-hours. A web-based real-time metering system collects and reports system performance and weather data. Improvements in areas of the CCC that were detected during subsequent energy analyses and some concepts for future efforts are also presented
Electronic Scattering Effects in Europium-Based Iron Pnictides
In a comprehensive study, we investigate the electronic scattering effects in
EuFe(AsP) by using Fourier-transform infrared
spectroscopy. In spite of the fact that Eu local moments order around
\,K, the overall optical response is strikingly similar
to the one of the well-known Ba-122 pnictides. The main difference lies within
the suppression of the lower spin-density-wave gap feature. By analysing our
spectra with a multi-component model, we find that the high-energy feature
around 0.7\,eV -- often associated with Hund's rule coupling -- is highly
sensitive to the spin-density-wave ordering, this further confirms its direct
relationship to the dynamics of itinerant carriers. The same model is also used
to investigate the in-plane anisotropy of magnetically detwinned
EuFeAs in the antiferromagnetically ordered state, yielding a
higher Drude weight and lower scattering rate along the crystallographic
-axis. Finally, we analyse the development of the room temperature spectra
with isovalent phosphor substitution and highlight changes in the scattering
rate of hole-like carriers induced by a Lifshitz transition
Corrections to Sirlin's Theorem in Chiral Perturbation Theory
We present the results of the first two-loop calculation of a form factor in
full Chiral Perturbation Theory. We choose a specific
linear combination of and form factors (the one
appearing in Sirlin's theorem) which does not get contributions from order
operators with unknown constants. For the charge radii, the correction to
the previous one-loop result turns out to be significant, but still there is no
agreement with the present data due to large experimental uncertainties in the
kaon charge radii.Comment: 6 pages, Latex, 2 LaTeX figure
Improving Well-Being in the Basic Course: The Impact of Interpersonal Communication Competence and Public Speaking Anxiety on Loneliness, Belongingness, and Flourishing
This study evaluated whether interpersonal communication competence and public speaking anxiety had an impact on three indicators of student well-being (loneliness, belongingness, and flourishing) as well as evaluated whether the two most popular types of the introductory communication course (public speaking and hybrid/fundamentals) impacted interpersonal communication competence and public speaking anxiety to the same extent. Survey data was collected from 1378 students enrolled in one of these two introductory communication courses. Results showed that interpersonal communication competence was the strongest predictor of all three outcome variables, and the public speaking anxiety predicted some additional variance in loneliness and belongingness, but not flourishing. Both types of courses significantly increased interpersonal communication competence and reduced public speaking anxiety, and there was no difference between the two course types in the extent to which they impacted those outcomes
Weak-coupling superconductivity in a strongly correlated iron pnictide
Iron-based superconductors have been found to exhibit an intimate interplay
of orbital, spin, and lattice degrees of freedom, dramatically affecting their
low-energy electronic properties, including superconductivity. Albeit the
precise pairing mechanism remains unidentified, several candidate interactions
have been suggested to mediate the superconducting pairing, both in the orbital
and in the spin channel. Here, we employ optical spectroscopy (OS),
angle-resolved photoemission spectroscopy (ARPES), ab initio band-structure,
and Eliashberg calculations to show that nearly optimally doped
NaFeCoAs exhibits some of the strongest orbitally selective
electronic correlations in the family of iron pnictides. Unexpectedly, we find
that the mass enhancement of itinerant charge carriers in the strongly
correlated band is dramatically reduced near the point and attribute
this effect to orbital mixing induced by pronounced spin-orbit coupling.
Embracing the true band structure allows us to describe all low-energy
electronic properties obtained in our experiments with remarkable consistency
and demonstrate that superconductivity in this material is rather weak and
mediated by spin fluctuations.Comment: Open access article available online at
http://www.nature.com/articles/srep1862
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Association Between APOL1 Genotypes and Risk of Cardiovascular Disease in MESA (Multi-Ethnic Study of Atherosclerosis).
BACKGROUND:APOL1 genetic variants confer an increased risk for kidney disease. Their associations with cardiovascular disease (CVD) are less certain. We aimed to compare the prevalence of subclinical CVD and incidence of atherosclerotic CVD and heart failure by APOL1 genotypes among self-identified black participants of MESA (Multi-Ethnic Study of Atherosclerosis). METHODS AND RESULTS:Cross-sectional associations of APOL1 genotypes (high-risk=2 alleles; low-risk=0 or 1 allele) with coronary artery calcification, carotid-intimal media thickness, and left ventricular mass were evaluated using logistic and linear regression. Longitudinal associations of APOL1 genotypes with incident myocardial infarction, stroke, coronary heart disease, and congestive heart failure were examined using Cox regression. We adjusted for African ancestry, age, and sex. We also evaluated whether hypertension or kidney function markers explained the observed associations. Among 1746 participants with APOL1 genotyping (mean age 62 years, 55% women, mean cystatin C-based estimated glomerular filtration rate 89 mL/min per 1.73 m2, 12% with albuminuria), 12% had the high-risk genotypes. We found no difference in prevalence or severity of coronary artery calcification, carotid-intimal media thickness, or left ventricular mass by APOL1 genotypes. The APOL1 high-risk group was 82% more likely to develop incident heart failure compared with the low-risk group (95% confidence interval, 1.01-3.28). Adjusting for hypertension (hazard ratio, 1.80; 95% confidence interval, 1.00-3.24) but not markers of kidney function (hazard ratio, 1.86; 95% confidence interval, 1.03-3.35) slightly attenuated this association. The APOL1 high-risk genotypes were not significantly associated with other clinical CVD outcomes. CONCLUSIONS:Among blacks without baseline CVD, the APOL1 high-risk variants may be associated with increased risk for incident heart failure but not subclinical CVD or incident clinical atherosclerotic CVD
Embodied cognition, abstract concepts, and the benefits of new technology for implicit body manipulation
Current approaches on cognition hold that concrete concepts are grounded in concrete experiences. There is no consensus, however, as to whether this is equally true for abstract concepts. In this review we discuss how the body might be involved in understanding abstract concepts through metaphor activation. Substantial research has been conducted on the activation of common orientational metaphors with bodily manipulations, such as "power is up" and "more is up" representations. We will focus on the political metaphor that has a more complex association between the concept and the concrete domain. However, the outcomes of studies on this political metaphor have not always been consistent, possibly because the experimental manipulation was not implicit enough. The inclusion of new technological devices in this area of research, such as the Wii Balance Board, seems promising in order to assess the groundedness of abstract conceptual spatial metaphors in an implicit manner. This may aid further research to effectively demonstrate the interrelatedness between the body and more abstract representations
The Constitutive Relations and the Magnetoelectric Effect for Moving Media
In this paper the constitutive relations for moving media with homogeneous
and isotropic electric and magnetic properties are presented as the connections
between the generalized magnetization-polarization bivector and
the electromagnetic field F. Using the decompositions of F and ,
it is shown how the polarization vector P(x) and the magnetization vector M(x)
depend on E, B and two different velocity vectors, u - the bulk velocity vector
of the medium, and v - the velocity vector of the observers who measure E and B
fields. These constitutive relations with four-dimensional geometric
quantities, which correctly transform under the Lorentz transformations (LT),
are compared with Minkowski's constitutive relations with the 3-vectors and
several essential differences are pointed out. They are caused by the fact
that, contrary to the general opinion, the usual transformations of the
3-vectors , , , , etc. are
not the LT. The physical explanation is presented for the existence of the
magnetoelectric effect in moving media that essentially differs from the
traditional one.Comment: 18 pages, In Ref. [10] here, which corresponds to Ref. [18] in the
published paper in IJMPB, Z. Oziewicz's published paper is added. arXiv admin
note: text overlap with arXiv:1101.329
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