2,016 research outputs found
Starry Messages: Searching for Signatures of Interstellar Archaeology
Searching for signatures of cosmic-scale archaeological artifacts such as
Dyson spheres or Kardashev civilizations is an interesting alternative to
conventional SETI. Uncovering such an artifact does not require the intentional
transmission of a signal on the part of the original civilization. This type of
search is called interstellar archaeology or sometimes cosmic archaeology. The
detection of intelligence elsewhere in the Universe with interstellar
archaeology or SETI would have broad implications for science. For example, the
constraints of the anthropic principle would have to be loosened if a different
type of intelligence was discovered elsewhere. A variety of interstellar
archaeology signatures are discussed including non-natural planetary
atmospheric constituents, stellar doping with isotopes of nuclear wastes, Dyson
spheres, as well as signatures of stellar and galactic-scale engineering. The
concept of a Fermi bubble due to interstellar migration is introduced in the
discussion of galactic signatures. These potential interstellar archaeological
signatures are classified using the Kardashev scale. A modified Drake equation
is used to evaluate the relative challenges of finding various sources. With
few exceptions interstellar archaeological signatures are clouded and beyond
current technological capabilities. However SETI for so-called cultural
transmissions and planetary atmosphere signatures are within reach.Comment: 29 pages including 4 figures and 1 tabl
Negative Particle Planar and Axial Channeling and Channeling Collimation
While information exists on high energy negative particle channeling there
has been little study of the challenges of negative particle bending and
channeling collimation. Partly this is because negative dechanneling lengths
are relatively much shorter. Electrons are not particularly useful for
investigating negative particle channeling effects because their material
interactions are dominated by channeling radiation. Another important factor is
that the current central challenge in channeling collimation is the
proton-proton Large Hadron Collider (LHC) where both beams are positive. On the
other hand in the future the collimation question might reemerge for
electron-positron or muon colliders. Dechanneling lengths increase at higher
energies so that part of the negative particle experimental challenge
diminishes. In the article different approaches to determining negative
dechanneling lengths are reviewed. The more complicated case for axial
channeling is also discussed. Muon channeling as a tool to investigate
dechanneling is also discussed. While it is now possible to study muon
channeling it will probably not illuminate the study of negative dechanneling.Comment: 15 pages, 1 figure, docx fil
No-vent fill pressurization tests using a cryogen simulant
The results are described of an experimental program which studied the performance of various no-vent fill techniques for tank-to-tank liquid transfer. The tests were performed using a cryogen simulant (Freon-114) and a test bed consisting of a multiple tank/plumbing network that enabled studies of a variety of different inlet flow and active mixing regimes. Several results and conclusions were drawn from the 26 transfer experiments comprising the program. Most notable was the significant improvement in fill performance (i.e., minimized fill time and maximized fill fraction) with increased agitation of the liquid surface. Another was the close correlation between measured condensation rates and those predicted by recent theories which express condensation as a function of turbulent eddy effects on the liquid surface. In most cases, test data exhibited strong agreement with an analytical model which accounts for tank heat transfer and thermodynamics in a 1 g environment
Effect of Light Therapy Among Peripheral Neuropathy Patients
This poster was presented at the Great Plains Honors Conference in Siloam Springs, Arkansas.https://scholarworks.uttyler.edu/student_posters/1012/thumbnail.jp
Possible observation of phase separation near a quantum phase transition in doubly connected ultrathin superconducting cylinders of aluminum
The kinetic energy of superconducting electrons in an ultrathin, doubly
connected superconducting cylinder, determined by the applied flux, increases
as the cylinder diameter decreases, leading to a destructive regime around
half-flux quanta and a superconductor to normal metal quantum phase transition
(QPT). Regular step-like features in resistance vs. temperature curves taken at
fixed flux values were observed near the QPT in ultrathin Al cylinders. It is
proposed that these features are most likely resulted from a phase separation
near the QPT in which normal regions nucleate in a homogeneous superconducting
cylinder.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let
A Population of Teraelectronvolt Pulsar Wind Nebulae in the H.E.S.S. Galactic Plane Survey
The most numerous source class that emerged from the H.E.S.S. Galactic Plane
Survey are Pulsar Wind Nebulae (PWNe). The 2013 reanalysis of this survey,
undertaken after almost 10 years of observations, provides us with the most
sensitive and most complete census of gamma-ray PWNe to date. In addition to a
uniform analysis of spectral and morphological parameters, for the first time
also flux upper limits for energetic young pulsars were extracted from the
data. We present a discussion of the correlation between energetic pulsars and
TeV objects, and their respective properties. We will put the results in
context with the current theoretical understanding of PWNe and evaluate the
plausibility of previously non-established PWN candidates.Comment: 4 pages, 5 figures. In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil
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Fundamental channeling questions at ultra relativistic energies
TeV-range bent crystal channeling has interesting advantages for several applications at high energy accelerators. Observations of enhanced deflection over the whole arc of a bent crystal at RHIC and recently at the Tevatron may be due to a process called ''volume reflection''. More investigations of volume reflection and of the complimentary process, volume capture, are needed. So-called quasimosaic bending processes also deserve additional study. Negative particle channeling may be relevant to channeling collimation for electron machines. Electron and positron channeling and channeling radiation are interwoven so that the impact of channeling radiation on applications needs to be better understood. Beams in the 0.1 to 1 GeV range may be useful for some of these investigations. Finally there has been little or no study of positive and negative muon channeling. The current understanding of these topics and the desirability of further work is reviewed
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