20,801 research outputs found
Fiberglass container shells form contamination-free storage units
Interchangeable molded fiberglass shells are locked together to form storage units of various depths. These units can hold components weighing 1500 pounds, are easily transportable, and protect contents from contamination
Prim Drift, CopyBots, and Folk Preservation: Three Copyright Parables about Art in the Digital Age
This paper employs a series of case studies from the domains of
digital arts and creative/experimental new media to elicit tensions and contradictions in the current state of copyright and intellectual property law. I pay particular attention to the role of the "pirate" as preservationist--rather than taint or corrupt, historically we know that piracy has helped guarantee the survival of important works of literature and art. Throughout, I insist that the humanist is not a dabbler or interloper in these matters; humanistic knowledge, particularly semiotics (the study of sign systems) has the potential to lend consistency and coherence to case law that is currently shot through with loopholes, contradictions, and dead ends. To that end, I also outline the potential of a center devoted to intellectual property law and humanities advocacy
The Carbon footprint of B[e] supergiants
We report on the first detection of C enhancement in two B[e]
supergiants in the Large Magellanic Cloud. Stellar evolution models predict the
surface abundance in C to strongly increase during main-sequence and
post-main sequence evolution of massive stars. However, direct identification
of chemically processed material on the surface of B[e] supergiants is hampered
by their dense, disk-forming winds, hiding the stars. Recent theoretical
computations predict the detectability of enhanced C via the molecular
emission in CO arising in the circumstellar disks of B[e] supergiants.
To test this potential method and to unambiguously identify a post-main
sequence B[e]SG by its CO emission, we have obtained high-quality
-band spectra of two known B[e] supergiants in the Large Magellanic Cloud,
using the Very Large Telescope's Spectrograph for INtegral Field Observation in
the Near-Infrared (VLT/SINFONI). Both stars clearly show the CO band
emission, whose strength implies a strong enhancement of C, in agreement
with theoretical predictions. This first ever direct confirmation of the
evolved nature of B[e] supergiants thus paves the way to the first
identification of a Galactic B[e] supergiant.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter
On the hydrogen neutral outflowing disks of B[e] supergiants
(abridged) B[e] supergiants are known to possess geometrically thick dusty
disks. Disk-forming wind models have, however, been found to be insufficient in
reproducing the observed dust emission. This problem arises due to the severe
assumption that, as for classical Be stars, the near-infrared excess emission
originates in the disk. Modeling of the free-free and free-bound emission
therefore results in an upper limit for the disk mass loss rate, hampering dust
condensation in the disk. We propose a revised scenario for the non-spherical
winds of B[e] supergiants: a normal B-type line-driven polar wind and an
outflowing disk-forming wind that is neutral in hydrogen at, or very close to
the stellar surface. We concentrate on the pole-on seen LMC B[e] supergiant
R126 and calculate the line luminosities of the optical [OI] emission lines
with an outflowing disk scenario. In addition, we compute the free-free and
free-bound emission from a line-driven polar wind and model the spectral energy
distribution in the optical and near-infrared. Good fits to the [OI] line
luminosities are achieved for an outflowing disk that is neutral in hydrogen
right from the stellar surface. Neutral thereby means that hydrogen is ionized
by less than 0.1%. Consequently, the free-free and free-bound emission cannot
(dominantly) arise from the disk and cannot limit the disk mass loss rate. The
hydrogen neutral outflowing disk scenario therefore provides an ideal
environment for efficient dust formation. The spectral energy distribution in
the optical and near-infrared range can be well fitted with the stellar
continuum plus free-free and free-bound emission from the polar line-driven
wind. Our modeling further delivers minimum values for \dot{M}(disk) > 2.5d-5
M_sun/yr and for the density contrast between equatorial and polar wind of ~10.Comment: 9 pages, 8 figures, accepted for publication in A&
When a quantum measurement can be implemented locally ... and when it cannot
Local operations on subsystems and classical communication between parties
(LOCC) constitute the most general protocols available on spatially separated
quantum systems. Every LOCC protocol implements a separable generalized
measurement -- a complete measurement for which every outcome corresponds to a
tensor product of operators on individual subsystems -- but it is known that
there exist separable measurements that cannot be implemented by LOCC. A
longstanding problem in quantum information theory is to understand the
difference between LOCC and the full set of separable measurements. In this
paper, we show how to construct an LOCC protocol to implement an arbitrary
separable measurement, except that with those measurements for which no LOCC
protocol exists, the method shows explicitly that this is the case.Comment: 21 pages, 7 figures. Extensively revised to include details of all
arguments, explicitly proving all results in full rigor. Version 3 has
sections reordered and other restructuring, but otherwise contains the same
discussion as version
Experimental scheme for qubit and qutrit symmetric informationally complete positive operator-valued measurements using multiport devices
It is crucial for various quantum information processing tasks that the state
of a quantum system can be determined reliably and efficiently from general
quantum measurements. One important class of measurements for this purpose is
symmetric informationally complete positive operator-valued measurements
(SIC-POVMs). SIC-POVMs have the advantage of providing an unbiased estimator
for the quantum state with the minimal number of outcomes needed for full
tomography. By virtue of Naimark's dilation theorem, any POVM can always be
realized with a suitable coupling between the system and an auxiliary system
and by performing a projective measurement on the joint system. In practice,
finding the appropriate coupling is rather non-trivial. Here we propose an
experimental design for directly implementing SIC-POVMs using multiport devices
and path-encoded qubits and qutrits, the utility of which has recently been
demonstrated by several experimental groups around the world. Furthermore, we
describe how these multiports can be attained in practice with an integrated
photonic system composed of nested linear optical elements.Comment: 7 pages, 5 figures; v2 published versio
Reduction of noise in gyro outputs
Technique is described to reduce extraneous gyro output signals by using relatively inexpensive shrouds which do not increase power comsumption. Shrouds reduce noise by minimizing mass of gas spinning with rotor, reducing Reynolds number near rotor, and inducing laminar flow
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