8,097 research outputs found
Decision Tree Analysis as a Supplementary Tool to Enhance Histomorphological Differentiation when Distinguishing Human from Non-human Cranial Bone in both Burnt and Unburnt States: A feasibility study
This feasibility study was undertaken to describe and record the histological characteristics of burnt and unburnt cranial bone fragments from human and non-human bones. Reference series of fully mineralised, transverse sections of cranial bone, from all variables and specimen states were prepared by manual cutting and semi-automated grinding and polishing methods. A photomicrograph catalogue reflecting differences in burnt and unburnt bone from human and non-humans was recorded and qualitative analysis was performed using an established classification system based on primary bone characteristics. The histomorphology associated with human and non-human samples was, for the main part, preserved following burning at high temperature. Clearly, fibro-lamellar complex tissue subtypes, such as plexiform or laminar primary bone, were only present in non-human bones. A decision tree analysis based on histological features provided a definitive identification key for distinguishing human from non-human bone, with an accuracy of 100%. The decision tree for samples where burning was unknown was 96% accurate, and multi-step classification to taxon was possible with 100% accuracy. The results of this feasibility study, strongly suggest that histology remains a viable alternative technique if fragments of cranial bone require forensic examination in both burnt and unburnt states. The decision tree analysis may provide an additional, but vital tool to enhance data interpretation. Further studies are needed to assess variation in histomorphology taking into account other cranial bones, ontogeny, species and burning conditions
Catastrophe versus instability for the eruption of a toroidal solar magnetic flux rope
The onset of a solar eruption is formulated here as either a magnetic
catastrophe or as an instability. Both start with the same equation of force
balance governing the underlying equilibria. Using a toroidal flux rope in an
external bipolar or quadrupolar field as a model for the current-carrying flux,
we demonstrate the occurrence of a fold catastrophe by loss of equilibrium for
several representative evolutionary sequences in the stable domain of parameter
space. We verify that this catastrophe and the torus instability occur at the
same point; they are thus equivalent descriptions for the onset condition of
solar eruptions.Comment: V2: update to conform to the published article; new choice for
internal inductance of torus; updated Fig. 2; new Figs. 3, 5, and
Kaon Condensation in a Nambu--Jona-Lasinio (NJL) Model at High Density
We demonstrate a fully self-consistent microscopic realization of a
kaon-condensed colour-flavour locked state (CFLK0) within the context of a
mean-field NJL model at high density. The properties of this state are shown to
be consistent with the QCD low-energy effective theory once the proper gauge
neutrality conditions are satisfied, and a simple matching procedure is used to
compute the pion decay constant, which agrees with the perturbative QCD result.
The NJL model is used to compare the energies of the CFLK0 state to the parity
even CFL state, and to determine locations of the metal/insulator transition to
a phase with gapless fermionic excitations in the presence of a non-zero
hypercharge chemical potential and a non-zero strange quark mass. The
transition points are compared with results derived previously via effective
theories and with partially self-consistent NJL calculations. We find that the
qualitative physics does not change, but that the transitions are slightly
lower.Comment: 21 pages, ReVTeX4. Clarified discussion and minor change
Simulated Gas Turbine Casing Response to Rotor Blade Pressure Excitation
Non-intrusive measurement of blade condition within gas turbines is of major interest within all areas of their use. It is proposed that the measurement of the casing vibration, due to the aerodynamic-structural interaction within the turbine, could provide a means of blade condition monitoring and modal parameter estimation. In order to understand the complex relationship between blade vibrations and casing response, an analytical model of the casing and simulated pressure signal associated with the rotor blades is presented. A mathematical formulation is undertaken of the internal pressure signal due to both the rotating bladed disk as well as individual blade vibrations and the solution of the casing response is formulated. Excitation by the stator blades and their contribution to the casing response is also investigated. Some verification of the presented analytical model is provided by comparison with Finite Element Analysis results for various rotor rotational speeds
Processing 'Large' Data Sets From 100% Bottom Coverage 'Shallow' Water Sweep Surveys A New Challenge for the Canadian Hydrographic Service
Vibration effects on heat transfer in cryogenic systems Quarterly progress report, Jul. 1 - Sep. 30, 1967
Water test apparatus used to determine vibration effects on heat transfer in cryogenic system
Distinguishing Solar Flare Types by Differences in Reconnection Regions
Observations show that magnetic reconnection and its slow shocks occur in
solar flares. The basic magnetic structures are similar for long duration event
(LDE) flares and faster compact impulsive (CI) flares, but the former require
less non-thermal electrons than the latter. Slow shocks can produce the
required non-thermal electron spectrum for CI flares by Fermi acceleration if
electrons are injected with large enough energies to resonate with scattering
waves. The dissipation region may provide the injection electrons, so the
overall number of non-thermal electrons reaching the footpoints would depend on
the size of the dissipation region and its distance from the chromosphere. In
this picture, the LDE flares have converging inflows toward a dissipation
region that spans a smaller overall length fraction than for CI flares. Bright
loop-top X-ray spots in some CI flares can be attributed to particle trapping
at fast shocks in the downstream flow, the presence of which is determined by
the angle of the inflow field and velocity to the slow shocks.Comment: 15 pages TeX and 2 .eps figures, accepted to Ap.J.Let
Non-existence of Skyrmion-Skyrmion and Skyrmion-anti-Skyrmion static equilibria
We consider classical static Skyrmion-anti-Skyrmion and Skyrmion-Skyrmion
configurations, symmetric with respect to a reflection plane, or symmetric up
to a -parity transformation respectively. We show that the stress tensor
component completely normal to the reflection plane, and hence its integral
over the plane, is negative definite or positive definite respectively.
Classical Skyrmions always repel classical Skyrmions and classical Skyrmions
always attract classical anti-Skyrmions and thus no static equilibrium, whether
stable or unstable, is possible in either case. No other symmetry assumption is
made and so our results also apply to multi-Skyrmion configurations. Our
results are consistent with existing analyses of Skyrmion forces at large
separation, and with numerical results on Skymion-anti-Skyrmion configurations
in the literature which admit a different reflection symmetry. They also hold
for the massive Skyrme model. We also point out that reflection symmetric
self-gravitating Skyrmions or black holes with Skyrmion hair cannot rest in
symmetric equilibrium with self-gravitating anti-Skyrmions.Comment: v2 Typos corrected, refs added. v3 Journal versio
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