21,823 research outputs found
The role of voice technology in advanced helicopter cockpits
The status of voice output and voice recognition technology in relation to helicopter cockpit applications is described. The maturing of this technology provides many opportunities for new approaches to crew workload reduction. The helicopter operating environment, potential application areas, and the impact on advanced cockpit design are discussed
Fractional Chern Insulators in Bands with Zero Berry Curvature
Even if a noninteracting system has zero Berry curvature everywhere in the
Brillouin zone, it is possible to introduce interactions that stabilise a
fractional Chern insulator. These interactions necessarily break time-reversal
symmetry (either spontaneously or explicitly) and have the effect of altering
the underlying band structure. We outline a number of ways in which this may be
achieved, and show how similar interactions may also be used to create a
(time-reversal symmetric) fractional topological insulator. While our approach
is rigorous in the limit of long range interactions, we show numerically that
even for short range interactions a fractional Chern insulator can be
stabilised in a band with zero Berry curvature.Comment: 7 pages, 2 figures; Published versio
Perturbative Approach to Flat Chern Bands in the Hofstadter Model
We present a perturbative approach to the study of the Hofstadter model for
when the amount of flux per plaquette is close to a rational fraction. Within
this approximation certain eigenstates of the system are shown to be
multi-component wavefunctions that connect smoothly to the Landau levels of the
continuum. The perturbative corrections to these are higher Landau level
contributions that break rotational invariance and allow the perturbed states
to adopt the symmetry of the lattice. In the presence of interactions, this
approach allows for the calculation of generalised Haldane pseudopotentials,
and in turn, the many-body properties of the system. The method is sufficiently
general that it can apply to a wide variety of lattices, interactions and
magnetic field strengths.Comment: 40 pages, 15 figures; v2 includes minor changes, additional
references and an expanded background sectio
They (Don't) Care About Education: A Counternarrative on Black Male Students' Responses to Inequitable Schooling
Focus group interviews and systematic content analysis of 304 essays written by black male undergraduates refute the dominant message that black men do not care about education. On the contrary, these students aspire to earn doctoral degrees in education despite acute understanding that the education system is stacked against them. The analysis asks what compels that dedication
Far-infrared observations of Sagittarius B2: Reconsideration of source structure
New moderate-angular-resolution far-infrared observations of the Sagittarius B2 star-forming region are presented, discussed, and compared with recent radio molecular and continuum observations of this source. In contrast to previous analyses, its far-infrared spectrum is interpreted as the result of a massive frigid cloud overlying a more-or-less normal infrared source, a natural explanation for the object's previously-noted pecularities. The characteristics derived for the obscuring cloud are similar to those found for the W51 MAIN object. Both sources have high sub-millimeter surface brightness, a high ratio of sub-millimeter to far-infrared flux, and numerous regions of molecular maser emission
How much are senior UK public health professionals taught about mental health?
Directors, consultants and specialists in public mental health play a major role in developing and implementing local and national mental health policy. This study focuses on what academic training they receive about mental health via Master of Public Health (MPH) programmes. If you are a clinical psychologist involved in teaching on a MPH course we would be interested in hearing about your experiences
Fluorine in the solar neighborhood - is it all produced in AGB-stars?
The origin of 'cosmic' fluorine is uncertain, but there are three proposed
production sites/mechanisms: AGB stars, nucleosynthesis in Type II
supernovae, and/or the winds of Wolf-Rayet stars. The relative importance of
these production sites has not been established even for the solar
neighborhood, leading to uncertainties in stellar evolution models of these
stars as well as uncertainties in the chemical evolution models of stellar
populations.
We determine the fluorine and oxygen abundances in seven bright, nearby
giants with well-determined stellar parameters. We use the 2.3 m
vibrational-rotational HF line and explore a pure rotational HF line at 12.2
m. The latter has never been used before for an abundance analysis. To be
able to do this we have calculated a line list for pure rotational HF lines. We
find that the abundances derived from the two diagnostics agree.
Our derived abundances are well reproduced by chemical evolution models only
including fluorine production in AGB-stars and therefore we draw the conclusion
that this might be the main production site of fluorine in the solar
neighborhood. Furthermore, we highlight the advantages of using the 12 m
HF lines to determine the possible contribution of the -process to the
fluorine budget at low metallicities where the difference between models
including and excluding this process is dramatic
Cs-135 - Ba-135: A new cosmochronometric constraint on the origin of the Earth and the astrophysical site of the origin of the solar system
It is argued that if Cs-135 was indeed present in the early solar system at the level inferred from evidence presented here, then two major conclusions follow. (1) A supernova contributed newly synthesized r-process matter into the protosolar reservoir within approx. 5 Ma of the Cs/Ba fractionation recorded in LEW 86010; (2) The strong Cs depletion in the bulk Earth reservoir (Cs-133/Ba-135 approx. 0.1) took place very early in solar system history. If this volatile loss was pre-accretionary, then the accretionary chronology of the Earth is not constrained. However, if it is a consequence of accretion, then the very tight time constraint of approx. less than 5 Ma (rel. to LEW 86010) is obtained for accretion of most of the Earth's mass
Electricity deregulation and the valuation of visibility loss in wilderness areas: A research note.
Visibility in most wilderness areas in the northeastern United States has declined substantially since the 1970s. As noted by Hill et al. (2000), despite the 1977 Clean Air Act and subsequent amendments, human induced smog conditions are becoming increasingly worse. Average visibility in class I airsheds, such as the Great Gulf Wilderness in New Hampshire’s White Mountains, is now about one-third of natural conditions. A particular concern is that deregulation of electricity production could result in further degradation because consumers may switch to lower cost fossil fuel generation (Harper 2000). To the extent that this system reduces electricity costs, it may also affect firm location decisions (Halstead and Deller 1997). Yet, little is known about the extent to which consumers are likely to make tradeoffs between electric bills and reduced visibility in nearby wilderness areas. This applied research uses a contingent valuation approach in an empirical case study of consumers’ tradeoffs between cheaper electric bills and reduced visibility in New Hampshire’s White Mountains. We also examine some of the problems associated with uncertainty with this type of analysis; that is, how confident respondents are in their answers to the valuation questions. Finally, policy implications of decreased visibility due to electricity deregulation are discussed
Constraining the Anomalous Microwave Emission Mechanism in the S140 Star Forming Region with Spectroscopic Observations Between 4 and 8 GHz at the Green Bank Telescope
Anomalous microwave emission (AME) is a category of Galactic signals that
cannot be explained by synchrotron radiation, thermal dust emission, or
optically thin free-free radiation. Spinning dust is one variety of AME that
could be partially polarized and therefore relevant for ongoing and future
cosmic microwave background polarization studies. The Planck satellite mission
identified candidate AME regions in approximately patches that were
found to have spectra generally consistent with spinning dust grain models. The
spectra for one of these regions, G107.2+5.2, was also consistent with
optically thick free-free emission because of a lack of measurements between 2
and 20 GHz. Follow-up observations were needed. Therefore, we used the C-band
receiver (4 to 8 GHz) and the VEGAS spectrometer at the Green Bank Telescope to
constrain the AME mechanism. For the study described in this paper, we produced
three band averaged maps at 4.575, 5.625, and 6.125 GHz and used aperture
photometry to measure the spectral flux density in the region relative to the
background. We found if the spinning dust description is correct, then the
spinning dust signal peaks at GHz, and it explains the excess
emission. The morphology and spectrum together suggest the spinning dust grains
are concentrated near S140, which is a star forming region inside our chosen
photometry aperture. If the AME is sourced by optically thick free-free
radiation, then the region would have to contain HII with an emission measure
of and a physical extent of
. This result suggests the HII
would have to be ultra or hyper compact to remain an AME candidate.Comment: 21 pages, 14 figures. Submitted to Ap
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