129,939 research outputs found
Pulsar slow glitches in a solid quark star model
A series of five unusual slow glitches of the radio pulsar B1822-09 (PSR
J1825-0935) were observed over the 1995-2005 interval. This phenomenon is
understood in a solid quark star model, where the reasonable parameters for
slow glitches are presented in the paper. It is proposed that, because of
increasing shear stress as a pulsar spins down, a slow glitch may occur,
beginning with a collapse of a superficial layer of the quark star. This layer
of material turns equivalently to viscous fluid at first, the viscosity of
which helps deplete the energy released from both the accumulated elastic
energy and the gravitation potential. This performs then a process of slow
glitch. Numerical calculations show that the observed slow glitches could be
reproduced if the effective coefficient of viscosity is ~10^2 cm^{2}/s and the
initial velocity of the superficial layer is order of 10^{-10} cm/s in the
coordinate rotating frame of the star.Comment: 5 pages, 5 figures, accepted for publication in MNRAS (Main Journal
The role of phosphorylation and dephosphorylation of shell matrix proteins in shell formation : an in vivo and in vitro study
Protein phosphorylation is a fundamental mechanism regulating many aspects of cellular processes. Shell matrix proteins (SMPs) control crystal nucleation, polymorphism, morphology, and organization of calcium carbonate crystallites during shell formation. SMPs phosphorylation is suggested to be important in shell formation but the mechanism is largely unknown. Here, to investigate the mechanism of phosphorylation of SMPs in biomineralization, we performed in vivo and in vitro experiment. By injection of antibody against the anti-phosphoserine/threonine /tyrosine into the extrapallial fluid of the pearl oyster Pinctada fucata, phosphorylation of matrix proteins were significantly reduced after 6 days. Newly formed prismatic layers and nacre tablet were found to grow abnormally with reduced crystallinity and possibly changed crystal orientation shown by Raman spectroscopy. In addition, regeneration of shells is also inhibited in vivo. Then, protein phosphatase was used to dephosphorylate SMPs extracted from the shells. After dephosphorylation, the ability of SMPs to inhibiting calcium carbonate formation have been reduced. Surprisingly, the ability of SMPs to modulate crystal morphology have been largely compromised although phosphorylation extent remained to be at least half of the control. Furthermore, dephosphorylation of SMPs changed the distribution of protein occlusions and decreased the amount of protein occlusions inside crystals shown by confocal imaging, indicating interaction between phosphorylated SMPs and crystals. Taken together, this study provides insight into the mechanism of phosphorylation of SMPs during shell formation
Dynamic Topology Adaptation Based on Adaptive Link Selection Algorithms for Distributed Estimation
This paper presents adaptive link selection algorithms for distributed
estimation and considers their application to wireless sensor networks and
smart grids. In particular, exhaustive search--based
least--mean--squares(LMS)/recursive least squares(RLS) link selection
algorithms and sparsity--inspired LMS/RLS link selection algorithms that can
exploit the topology of networks with poor--quality links are considered. The
proposed link selection algorithms are then analyzed in terms of their
stability, steady--state and tracking performance, and computational
complexity. In comparison with existing centralized or distributed estimation
strategies, key features of the proposed algorithms are: 1) more accurate
estimates and faster convergence speed can be obtained; and 2) the network is
equipped with the ability of link selection that can circumvent link failures
and improve the estimation performance. The performance of the proposed
algorithms for distributed estimation is illustrated via simulations in
applications of wireless sensor networks and smart grids.Comment: 14 figure
Evolution of Surface Deformations of Weakly-Bound Nuclei in the Continuum
We study weakly-bound deformed nuclei based on the coordinate-space Skyrme
Hartree-Fock-Bogoliubov approach, in which a large box is employed for treating
the continuum and surface diffuseness. Approaching the limit of core-halo
deformation decoupling, calculations found an exotic "egg"-like structure
consisting of a spherical core plus a prolate halo in Ne, in which the
resonant continuum plays an essential role. Generally the halo probability and
the decoupling effect in heavy nuclei are reduced compared to light nuclei, due
to denser level densities around Fermi surfaces. However, deformed halos in
medium-mass nuclei are possible with sparse levels of negative parity, for
example, in Ge. The surface deformations of pairing density
distributions are also influenced by the decoupling effect and are sensitive to
the effective pairing Hamiltonian.Comment: 5 pages and 5 figure
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