565 research outputs found
Unravelling Ritual: Victor Turner and the problems of exegesis
As a pioneer in the interpretation of ritual, Victor Turner showed us how to access other peoplesâ deepest understandings about the nature of life. In the process, he encountered problems of presentation that ethnographers still have to confront. This paper explores Turnerâs solutions to these problems, and how subsequent authors have modified them.
Keywords: ritual, ethnography, Victor Turne
Nonadiabatic electron heat pump
We investigate a mechanism for extracting heat from metallic conductors based
on the energy-selective transmission of electrons through a spatially
asymmetric resonant structure subject to ac driving. This quantum refrigerator
can operate at zero net electronic current as it replaces hot by cold electrons
through two energetically symmetric inelastic channels. We present numerical
results for a specific heterostructure and discuss general trends. We also
explore the conditions under which the cooling rate may approach the ultimate
limit given by the quantum of cooling power.Comment: 4 pages, 3 figures; published version, typos correcte
An Optimal Design for Universal Multiport Interferometers
Universal multiport interferometers, which can be programmed to implement any
linear transformation between multiple channels, are emerging as a powerful
tool for both classical and quantum photonics. These interferometers are
typically composed of a regular mesh of beam splitters and phase shifters,
allowing for straightforward fabrication using integrated photonic
architectures and ready scalability. The current, standard design for universal
multiport interferometers is based on work by Reck et al (Phys. Rev. Lett. 73,
58, 1994). We demonstrate a new design for universal multiport interferometers
based on an alternative arrangement of beam splitters and phase shifters, which
outperforms that by Reck et al. Our design occupies half the physical footprint
of the Reck design and is significantly more robust to optical losses.Comment: 8 pages, 4 figure
Processing Results of western Australian Wool
Despite a perception by some that Western Australian wool \u27processes poorly\u27, this study found that the consignments processed:
1. into longer tops suited for worsted weaving
2. into longer than predicted tops
3. with the same consistency as other Australian consignment
Constraining 3D Magnetic Field Extrapolations Using The Twin Perspectives of STEREO
The 3D magnetic topology of a solar active region (NOAA 10956) was
reconstructed using a linear force-free field extrapolation constrained using
the twin perspectives of \emph{STEREO}. A set of coronal field configurations
was initially generated from extrapolations of the photospheric magnetic field
observed by the Michelson Doppler Imager (MDI) on \emph{SOHO}. Using an EUV
intensity-based cost function, the extrapolated field lines that were most
consistent with 171\AA\ passband images from the Extreme UltraViolet Imager
(EUVI) on \emph{STEREO} were identified. This facilitated quantitative
constraints to be placed on the twist () of the extrapolated field
lines, where . Using the constrained
values of , the evolution in time of twist, connectivity, and magnetic
energy were then studied. A flux emergence event was found to result in
significant changes in the magnetic topology and total magnetic energy of the
region
Tomography of photon-number resolving continuous-output detectors
We report a comprehensive approach to analysing continuous-output photon
detectors. We employ principal component analysis to maximise the information
extracted, followed by a novel noise-tolerant parameterised approach to the
tomography of PNRDs. We further propose a measure for rigorously quantifying a
detector's photon-number-resolving capability. Our approach applies to all
detectors with continuous-output signals. We illustrate our methods by applying
them to experimental data obtained from a transition-edge sensor (TES)
detector.Comment: 5 pages, 3 figures, also includes supplementary informatio
Constant cross section of loops in the solar corona
The corona of the Sun is dominated by emission from loop-like structures.
When observed in X-ray or extreme ultraviolet emission, these million K hot
coronal loops show a more or less constant cross section. In this study we show
how the interplay of heating, radiative cooling, and heat conduction in an
expanding magnetic structure can explain the observed constant cross section.
We employ a three-dimensional magnetohydrodynamics (3D MHD) model of the
corona. The heating of the coronal plasma is the result of braiding of the
magnetic field lines through footpoint motions and subsequent dissipation of
the induced currents. From the model we synthesize the coronal emission, which
is directly comparable to observations from, e.g., the Atmospheric Imaging
Assembly on the Solar Dynamics Observatory (AIA/SDO). We find that the
synthesized observation of a coronal loop seen in the 3D data cube does match
actually observed loops in count rate and that the cross section is roughly
constant, as observed. The magnetic field in the loop is expanding and the
plasma density is concentrated in this expanding loop; however, the temperature
is not constant perpendicular to the plasma loop. The higher temperature in the
upper outer parts of the loop is so high that this part of the loop is outside
the contribution function of the respective emission line(s). In effect, the
upper part of the plasma loop is not bright and thus the loop actually seen in
coronal emission appears to have a constant width. From this we can conclude
that the underlying field-line-braiding heating mechanism provides the proper
spatial and temporal distribution of the energy input into the corona --- at
least on the observable scales.Comment: 8 pages, 9 figures, accepted for publication in A&
- âŠ