25,170 research outputs found
Corrigendum to "Knot Floer homology detects fibred knots"
We correct a mistake on the citation of JSJ theory in \cite{Ni}. Some
arguments in \cite{Ni} are also slightly modified accordingly.Comment: 3 page
Modelling the multi-wavelength emissions from PSR B1259-63/LS 2883: the effects of the stellar disc on shock radiations
PSR B1259-63/LS 2883 is an elliptical pulsar/Be star binary and emits
broadband emissions from radio to TeV -rays. The massive star possesses
an equatorial disc, which is inclined with the orbital plane of the pulsar. The
non-thermal emission from the system is believed to be produced by the pulsar
wind shock and the double-peak profiles in the X-ray and TeV -ray light
curves are related to the phases of the pulsar passing through the disc region
of the star. In this paper, we investigate the interactions between the pulsar
wind and stellar outflows, especially with the presence of the disc, and
present a multi-wavelength modelling of the emission from this system. We show
that the double-peak profiles of X-ray and TeV -ray light curves are
caused by the enhancements of the magnetic field and the soft photons at the
shock during the disc passages. As the pulsar is passing through the equatorial
disc, the additional pressure of the disc pushes the shock surface closer to
the pulsar, which causes the enhancement of magnetic field in the shock, and
thus increases the synchrotron luminosity. The TeV -rays due to the
inverse-Compton (IC) scattering of shocked electrons with seed photons from the
star is expected to peak around periastron which is inconsistent with
observations. However, the shock heating of the stellar disc could provide
additional seed photons for IC scattering during the disc passages, and thus
produces the double-peak profiles as observed in the TeV -ray light
curve. Our model can possibly be examined and applied to other similar
gamma-ray binaries, such as PSR J2032+4127/MT91 213, HESS J0632+057, and LS
I+61303.Comment: 14 pages, 6 figure
Modeling pulsar time noise with long term power law decay modulated by short term oscillations of the magnetic fields of neutron stars
We model the evolution of the magnetic fields of neutron stars as consisting
of a long term power-law decay modulated by short term small amplitude
oscillations. Our model predictions on the timing noise of neutron
stars agree well with the observed statistical properties and correlations of
normal radio pulsars. Fitting the model predictions to the observed data, we
found that their initial parameter implies their initial surface magnetic
dipole magnetic field strength ~ 5E14 G at ~0.4 year old and that the
oscillations have amplitude between E-8 to E-5 and period on the order of
years. For individual pulsars our model can effectively reduce their timing
residuals, thus offering the potential of more sensitive detections of
gravitational waves with pulsar timing arrays. Finally our model can also
re-produce their observed correlation and oscillations of the second derivative
of spin frequency, as well as the "slow glitch" phenomenon.Comment: 10 pages, 6 figures, submitted to IJMPD, invited talk in the 3rd
Galileo-XuGuangqi Meeting}, Beijing, China, 12-16 October 201
Concurrence of superposition
The bounds on concurrence of the superposition state in terms of those of the
states being superposed are studied in this paper. The bounds on concurrence
are quite different from those on the entanglement measure based on von Neumann
entropy (Phys. Rev. Lett. 97, 100502 (2006)). In particular, a nonzero lower
bound can be provided if the states being superposed are properly constrained.Comment: 4 page
Heat Conduction Process on Community Networks as a Recommendation Model
Using heat conduction mechanism on a social network we develop a systematic
method to predict missing values as recommendations. This method can treat very
large matrices that are typical of internet communities. In particular, with an
innovative, exact formulation that accommodates arbitrary boundary condition,
our method is easy to use in real applications. The performance is assessed by
comparing with traditional recommendation methods using real data.Comment: 4 pages, 2 figure
Whole-genome sequencing analysis of quorumsensing Aeromonas hydrophila strain M023 from freshwater
YesAeromonas hydrophila is a well-known waterborne pathogen that recently was found to infect humans. Here, we report the draft genome of a freshwater isolate from a Malaysian waterfall, A. hydrophila strain M023, which portrays N-acylhomoserine lactone-dependent quorum sensing.University of Malaya via High Impact Research Grants (UM C/625/1/HIR/MOHE/CHAN/01, A-000001-50001, and UM C/625/1/HIR/MOHE/CHAN/14/1, H-50001-A000027
Understanding the quorum-sensing bacterium Pantoea stewartii strain M009 with whole-genome sequencing analysis
YesPantoea stewartii is known to be the causative agent of Stewart's wilt, which usually affects sweet corn (Zea mays) with the corn flea beetle as the transmission vector. In this work, we present the whole-genome sequence of Pantoea stewartii strain M009, isolated from a Malaysian tropical rainforest waterfall.University of Malaya via High Impact Research Grants (UM C/625/1/HIR/MOHE/CHAN/01 no. A-000001- 50001 and UM C/625/1/HIR/MOHE/CHAN/14/1 no. H-50001-A000027
Better age estimations using UV-optical colours: breaking the age-metallicity degeneracy
We demonstrate that the combination of GALEX UV photometry in the FUV (~1530
angstroms) and NUV (~2310 angstroms) passbands with optical photometry in the
standard U,B,V,R,I filters can efficiently break the age-metallicity
degeneracy. We estimate well-constrained ages, metallicities and their
associated errors for 42 GCs in M31, and show that the full set of
FUV,NUV,U,B,V,R,I photometry produces age estimates that are ~90 percent more
constrained and metallicity estimates that are ~60 percent more constrained
than those produced by using optical filters alone. The quality of the age
constraints is comparable or marginally better than those achieved using a
large number of spectrscopic indices.Comment: Published in MNRAS (2007), 381, L74 (doi:
10.1111/j.1745-3933.2007.00370.x
Draft genome sequence of a quorum-sensing bacterium, Dickeya sp. strain 2B12, isolated from a freshwater lake
YesDickeya sp. strain 2B12 was isolated from a freshwater lake in Malaysia. Here, we report the draft genome sequence of Dickeya sp. 2B12 sequenced by the Illumina MiSeq platform. With the genome sequence available, this genome sequence will be useful for the study of quorum-sensing activity in this isolate.University of Malaya High-Impact Research( HIR)grants(UMC/625/1/HIR/MOHE/CHAN/01[no.A-000001- 50001] and UM-MOHE HIR UM C/625/1/HIR/MOHE/CHAN/14/1 [no. H-50001-A000027]
Conditioning of BPM pickup signals for operations of the Duke storage ring with a wide range of single-bunch current
The Duke storage ring is a dedicated driver for the storage ring based
oscillator free-electron lasers (FELs), and the High Intensity Gamma-ray Source
(HIGS). It is operated with a beam current ranging from about 1 mA to 100 mA
per bunch for various operations and accelerator physics studies. High
performance operations of the FEL and gamma-ray source require a stable
electron beam orbit, which has been realized by the global orbit feedback
system. As a critical part of the orbit feedback system, the electron beam
position monitors (BPMs) are required to be able to precisely measure the
electron beam orbit in a wide range of the single-bunch current. However, the
high peak voltage of the BPM pickups associated with high single-bunch current
degrades the performance of the BPM electronics, and can potentially damage the
BPM electronics. A signal conditioning method using low pass filters is
developed to reduce the peak voltage to protect the BPM electronics, and to
make the BPMs capable of working with a wide range of single-bunch current.
Simulations and electron beam based tests are performed. The results show that
the Duke storage ring BPM system is capable of providing precise orbit
measurements to ensure highly stable FEL and HIGS operations
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