50,636 research outputs found
The Benefish consortium 24 month report WP6: productivity modelling of OWI's and welfare intervention measures
In order to accurately model all costs and benefits associated with welfare interventions for farmed fish it is necessary to establish how any welfare actions affect productivity. Productivity modelling within Benefish has been conducted in WP6. WP6 aimed to model relationships between welfare interventions, changes in OWI’s and measures of productivity. It did so focusing only on the effects which were biological in nature: economic costs and benefits attributed to changes in productivity are addressed in WP8
Hall effect in laser ablated Co_2(Mn,Fe)Si thin films
Pulsed laser deposition was employed to grow thin films of the Heusler
compounds Co_2MnSi and Co_2FeSi. Epitaxial growth was realized both directly on
MgO (100) and on a Cr or Fe buffer layer. Structural analysis by x-ray and
electron diffraction shows for both materials the ordered L2_1 structure. Bulk
magnetization was determined with a SQUID magnetometer. The values agree with
the Slater-Pauling rule for half-metallic Heusler compounds. On the films grown
directly on the substrate measurements of the Hall effect have been performed.
The normal Hall effect is nearly temperature independent and points towards a
compensated Fermi surface. The anomalous contribution is found to be dominated
by skew scattering. A remarkable sign change of both normal and anomalous Hall
coefficients is observed on changing the valence electron count from 29 (Mn) to
30 (Fe).Comment: 9 pages, 6 figures submitted to J Phys
Specific protein-protein binding in many-component mixtures of proteins
Proteins must bind to specific other proteins in vivo in order to function.
The proteins must bind only to one or a few other proteins of the of order a
thousand proteins typically present in vivo. Using a simple model of a protein,
specific binding in many component mixtures is studied. It is found to be a
demanding function in the sense that it demands that the binding sites of the
proteins be encoded by long sequences of bits, and the requirement for specific
binding then strongly constrains these sequences. This is quantified by the
capacity of proteins of a given size (sequence length), which is the maximum
number of specific-binding interactions possible in a mixture. This calculation
of the maximum number possible is in the same spirit as the work of Shannon and
others on the maximum rate of communication through noisy channels.Comment: 13 pages, 3 figures (changes for v2 mainly notational - to be more in
line with notation in information theory literature
Large inverse tunneling magnetoresistance in CoCrFeAl/MgO/CoFe magnetic tunnel junctions
Magnetic tunnel junctions with the layer sequence
CoCrFeAl/MgO/CoFe were fabricated by magnetron sputtering
at room temperature (RT). The samples exhibit a large inverse tunneling
magnetoresistance (TMR) effect of up to -66% at RT. The largest value of -84%
at 20 K reflects a rather weak influence of temperature. The dependence on the
voltage drop shows an unusual behavior with two almost symmetric peaks at
mV with large inverse TMR ratios and small positive values around zero
bias
Evolution of shuttle avionics redundancy management/fault tolerance
The challenge of providing redundancy management (RM) and fault tolerance to meet the Shuttle Program requirements of fail operational/fail safe for the avionics systems was complicated by the critical program constraints of weight, cost, and schedule. The basic and sometimes false effectivity of less than pure RM designs is addressed. Evolution of the multiple input selection filter (the heart of the RM function) is discussed with emphasis on the subtle interactions of the flight control system that were found to be potentially catastrophic. Several other general RM development problems are discussed, with particular emphasis on the inertial measurement unit RM, indicative of the complexity of managing that three string system and its critical interfaces with the guidance and control systems
Electronic transport in quantum cascade structures
The transport in complex multiple quantum well heterostructures is
theoretically described. The model is focused on quantum cascade detectors,
which represent an exciting challenge due to the complexity of the structure
containing 7 or 8 quantum wells of different widths. Electronic transport can
be fully described without any adjustable parameter. Diffusion from one subband
to another is calculated with a standard electron-optical phonon hamiltonian,
and the electronic transport results from a parallel flow of electrons using
all the possible paths through the different subbands. Finally, the resistance
of such a complex device is given by a simple expression, with an excellent
agreement with experimental results. This relation involves the sum of
transitions rates between subbands, from one period of the device to the next
one. This relation appears as an Einstein relation adapted to the case of
complex multiple quantum structures.Comment: 6 pages, 5 figures, 1 tabl
Spin Model for Inverse Melting and Inverse Glass Transition
A spin model that displays inverse melting and inverse glass transition is
presented and analyzed. Strong degeneracy of the interacting states of an
individual spin leads to entropic preference of the "ferromagnetic" phase,
while lower energy associated with the non-interacting states yields a
"paramagnetic" phase as temperature decreases. An infinite range model is
solved analytically for constant paramagnetic exchange interaction, while for
its random exchange, analogous results based on the replica symmetric solution
are presented. The qualitative features of this model are shown to resemble a
large class of inverse melting phenomena. First and second order transition
regimes are identified
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