645 research outputs found
Monte Carlo Neutrino Oscillations
We demonstrate that the effects of matter upon neutrino propagation may be
recast as the scattering of the initial neutrino wavefunction. Exchanging the
differential, Schrodinger equation for an integral equation for the scattering
matrix S permits a Monte Carlo method for the computation of S that removes
many of the numerical difficulties associated with direct integration
techniques
Interpreting syndepositional sediment remobilization and deformation beneath submarine gravity flows; a kinematic boundary layer approach
Turbidite sandstones and related deposits commonly contain deformation structures and remobilized sediment that might have resulted from post-depositional modification such as downslope creep (e.g. slumping) or density-driven loading by overlying deposits. However, we consider that deformation can occur during the passage of turbidity currents that exerted shear stress on their substrates (whether entirely pre-existing strata, sediment deposited by earlier parts of the flow itself or some combination of these). Criteria are outlined here, to avoid confusion with products of other mechanisms (e.g. slumping or later tectonics), which establish the synchronicity between the passage of overriding flows and deformation of their substrates. This underpins a new analytical framework for tracking the relationship between deformation, deposition and the transit of the causal turbidity current, through the concept of kinematic boundary layers. Case study examples are drawn from outcrop (Miocene of New Zealand, and Apennines of Italy) and subsurface examples (Britannia Sandstone, Cretaceous, UK Continental Shelf). Example structures include asymmetric flame structures, convolute lamination, some debritic units and injection complexes, together with slurry and mixed slurry facies. These structures may provide insight into the rheology and dynamics of submarine flows and their substrates, and have implications for the development of subsurface turbidite reservoirs
Invalidation of the Kelvin Force in Ferrofluids
Direct and unambiguous experimental evidence for the magnetic force density
being of the form in a certain geometry - rather than being the
Kelvin force - is provided for the first time. (M is the
magnetization, H the field, and B the flux density.)Comment: 4 pages, 4 figure
Diffusion and jump-length distribution in liquid and amorphous CuZr
Using molecular dynamics simulation, we calculate the distribution of atomic
jum ps in CuZr in the liquid and glassy states. In both states
the distribution of jump lengths can be described by a temperature independent
exponential of the length and an effective activation energy plus a
contribution of elastic displacements at short distances. Upon cooling the
contribution of shorter jumps dominates. No indication of an enhanced
probability to jump over a nearest neighbor distance was found. We find a
smooth transition from flow in the liquid to jumps in the g lass. The
correlation factor of the diffusion constant decreases with decreasing
temperature, causing a drop of diffusion below the Arrhenius value, despite an
apparent Arrhenius law for the jump probability
The Cosmological Evolution of the Average Mass Per Baryon
Subsequent to the early Universe quark-hadron transition the universal baryon
number is carried by nucleons: neutrons and protons. The total number of
nucleons is preserved as the Universe expands, but as it cools lighter protons
are favored over heavier neutrons reducing the average mass per baryon. During
primordial nucleosynthesis free nucleons are transformed into bound nuclides,
primarily helium, and the nuclear binding energies are radiated away, further
reducing the average mass per baryon. In particular, the reduction in the
average mass per baryon resulting from Big Bang Nucleosynthesis (BBN) modifies
the numerical factor relating the baryon (nucleon) mass and number densities.
Here the average mass per baryon, m_B, is tracked from the early Universe to
the present. The result is used to relate the present ratio of baryons to
photons (by number) to the present baryon mass density at a level of accuracy
commensurate with that of recent cosmological data, as well as to estimate the
energy released during post-BBN stellar nucleosynthesis.Comment: 5 pages; no figures; updated references; final version published in
JCAP, 10 (2006) 01
Quantitative Nondestructive Evaluation of Cementite in Steel and White Cast Iron by Ferromagnetic Parameters
The change in the microstructure state (lattice defects, especially dislocations, precipitations and thus the stress fields) with the addition of alloying elements plays an important role for the strength and the toughness of a material. In order to determine these microstructural parameters, up to now the electron microscopy and similar methods are used. X-ray methods are normally used to determine residual stresses
The Effect of Bound Dineutrons upon BBN
We have examined the effects of a bound dineutron, n2, upon big bang
nucleosynthesis (BBN) as a function of its binding energy B_n2. We find a
weakly bound dineutron has little impact but as B_n2 increases its presence
begins to alter the flow of free nucleons to helium-4. Due to this disruption,
and in the absence of changes to other binding energies or fundamental
constants, BBN sets a reliable upper limit of B_n2 <~ 2.5 MeV in order to
maintain the agreement with the observations of the primordial helium-4 mass
fraction and D/H abundance
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