28,953 research outputs found
Behavior of heuristics and state space structure near SAT/UNSAT transition
We study the behavior of ASAT, a heuristic for solving satisfiability
problems by stochastic local search near the SAT/UNSAT transition. The
heuristic is focused, i.e. only variables in unsatisfied clauses are updated in
each step, and is significantly simpler, while similar to, walksat or Focused
Metropolis Search. We show that ASAT solves instances as large as one million
variables in linear time, on average, up to 4.21 clauses per variable for
random 3SAT. For K higher than 3, ASAT appears to solve instances at the ``FRSB
threshold'' in linear time, up to K=7.Comment: 12 pages, 6 figures, longer version available as MSc thesis of first
author at http://biophys.physics.kth.se/docs/ardelius_thesis.pd
Disruption of a planet spiralling into its host star
The processes leading deformation and destruction of planets spiraling into
the convective envelope of their host stars are described. The planet is
compressed by the ram pressure, and deformed into a flattened shape for which a
quantitative model is developed. Compression increases the planet's density
contrast with the envelope and its gravitational binding energy. This increases
the survivability especially of gas planets. An estimate is given for the depth
of disruption by ram pressure, and for the subsequent fragmentation of the
remnants. We show how the debris of rocky or iron planets, instead of mixing
through the convection zone, sinks below the base of the convection zone. The
time scale of the entire sequence of events is of the order of a few orbital
times of the planet. If spiral-in of (partly) icy, rocky or iron planets has
happened to the pre-main sequence Sun, it could account for the higher opacity
below the base of the convection zone as inferred from helioseismology.Comment: 14 pages, 8 figures, accepted for publication in Ap
Non-Hermitian coherent coupling of nanomagnets by exchange spin waves
Non-Hermitian physics has recently attracted much attention in optics and
photonics. Less explored is non-Hermitian magnonics that provides opportunities
to take advantage of the inevitable dissipation of magnons or spin waves in
magnetic systems. Here we demonstrate non-Hermitian coherent coupling of two
distant nanomagnets by fast spin waves with sub-50 nm wavelengths. Magnons in
two nanomagnets are unidirectionally phase-locked with phase shifts controlled
by magnon spin torque and spin-wave propagation. Our results are attractive for
analog neuromorphic computing that requires unidirectional information
transmission
CD4+ T-cell responses to Epstein-Barr virus nuclear antigen EBNA1 in Chinese populations are highly focused on novel C-terminal domain-derived epitopes
Epstein-Barr virus nuclear antigen EBNA1, the one viral protein uniformly expressed in nasopharyngeal carcinoma (NPC), represents a prime target for T-cell-based immunotherapy. However, little is known about the EBNA1 epitopes, particularly CD4 epitopes, presented by HLA alleles in Chinese people, the group at highest risk for NPC. We analyzed the CD4 T-cell responses to EBNA1 in 78 healthy Chinese donors and found marked focusing on a small number of epitopes in the EBNA1 C-terminal region, including a DP5- restricted epitope that was recognized by almost half of the donors tested and elicited responses able to recognize EBNA1-expressing, DP5-positive target cells
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