33,745 research outputs found
Thermoelectrically Controlled Spin-Switch
The search for novel spintronic devices brings about new ways to control
switching in magnetic thin-films. In this work we experimentally demonstrate a
device based on thermoelectrically controlled exchange coupling. The read out
signal from a giant magnetoresistance element is controlled by exchange
coupling through a weakly ferromagnetic Ni-Cu alloy. This exchange coupling is
shown to vary strongly with changes in temperature, and both internal Joule
heating and external heating is used to demonstrate magnetic switching. The
device shows no degradation upon thermal cycling. Ways to further optimize the
device performance are discussed. Our experimental results show a new way to
thermoelectrically control magnetic switching in multilayers.Comment: 4 pages, 4 figure
Exchange coupling and magnetoresistance in CoFe/NiCu/CoFe spin-valves near the Curie point of the spacer
Thermal control of exchange coupling between two strongly ferromagnetic
layers through a weakly ferromagnetic Ni-Cu spacer and the associated
magnetoresistance is investigated. The spacer, having a Curie point slightly
above room temperature, can be cycled between its paramagnetic and
ferromagnetic states by varying the temperature externally or using joule
heating. It is shown that the giant magnetoresistance vanishes due to a strong
reduction of the mean free path in the spacer at above ~30 % Ni concentration
-- before the onset of ferromagnetism. Finally, a device is proposed and
demonstrated which combines thermally controlled exchange coupling and large
magnetoresistance by separating the switching and the read out elements.Comment: 4 pages, 4 figure
Cross-shaped and Degenerate Singularities in an Unstable Elliptic Free Boundary Problem
We investigate singular and degenerate behavior of solutions of the unstable
free boundary problem First, we construct a
solution that is not of class and whose free boundary consists of
four arcs meeting in a {\em cross}-shaped singularity. This solution is
completely unstable/repulsive from above and below which would make it hard to
get by the usual methods, and even numerics is non-trivial. We also show
existence of a degenerate solution. This answers two of the open questions in a
recent paper by R. Monneau-G.S. Weiss
BRUCE: a program for the detection of transfer-messenger RNA genes in nucleotide sequences
A computer program, BRUCE, was developed for the identification of transfer‐messenger RNA (tmRNA) genes. The program employs heuristic algorithms to search for a tRNAAla‐like secondary structure surrounding a short sequence encoding the tag peptide. In the 57 completely sequenced bacterial genomes where tmRNA genes have been reported previously, BRUCE identified all with no false positives. In addition, BRUCE found 99 of the 100 tmRNAs identified previously in other bacteria, red chloroplasts and cyanelles. The output of the program reports the proposed tRNA secondary structure, the tmRNA gene sequence and the tag peptide
The time evolution of marginally trapped surfaces
In previous work we have shown the existence of a dynamical horizon or
marginally trapped tube (MOTT) containing a given strictly stable marginally
outer trapped surface (MOTS). In this paper we show some results on the global
behavior of MOTTs assuming the null energy condition. In particular we show
that MOTSs persist in the sense that every Cauchy surface in the future of a
given Cauchy surface containing a MOTS also must contain a MOTS. We describe a
situation where the evolving outermost MOTS must jump during the coalescence of
two seperate MOTSs. We furthermore characterize the behavior of MOTSs in the
case that the principal eigenvalue vanishes under a genericity assumption. This
leads to a regularity result for the tube of outermost MOTSs under the
genericity assumption. This tube is then smooth up to finitely many jump times.
Finally we discuss the relation of MOTSs to singularities of a space-time.Comment: 21 pages. This revision corrects some typos and contains more
detailed proofs than the original versio
Relativistic Two-stream Instability
We study the (local) propagation of plane waves in a relativistic,
non-dissipative, two-fluid system, allowing for a relative velocity in the
"background" configuration. The main aim is to analyze relativistic two-stream
instability. This instability requires a relative flow -- either across an
interface or when two or more fluids interpenetrate -- and can be triggered,
for example, when one-dimensional plane-waves appear to be left-moving with
respect to one fluid, but right-moving with respect to another. The dispersion
relation of the two-fluid system is studied for different two-fluid equations
of state: (i) the "free" (where there is no direct coupling between the fluid
densities), (ii) coupled, and (iii) entrained (where the fluid momenta are
linear combinations of the velocities) cases are considered in a
frame-independent fashion (eg. no restriction to the rest-frame of either
fluid). As a by-product of our analysis we determine the necessary conditions
for a two-fluid system to be causal and absolutely stable and establish a new
constraint on the entrainment.Comment: 15 pages, 2 eps-figure
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