373 research outputs found
V1647 Orionis: Optical Photometric and Spectroscopic Monitoring Through the 2003-2006 Outburst
We present results from an optical imaging and spectroscopic monitoring
campaign on the young, low-mass eruptive variable star V1647 Orionis. The star
and associated nebulosity (McNeil's Nebula) were observed over the period
February 2004 to February 2006 with observations commencing a few months after
the original outburst event occurred. Using the Gemini North telescope, we
obtained multi-band optical imaging photometry and medium-resolution long-slit
spectroscopy of V1647 Ori on an approximately monthly interval. During this
period, V1647 Ori remained at, or close to, peak brightness and then faded by 5
magnitudes to close to its pre-outburst brightness. This implies an outburst
timescale of around 27 months. Spectral features seen in both emission and
absorption varied considerably during the monitoring period. For example, the
Halpha line changed significantly in both intensity and profile. We present and
discuss the observed photometric and spectroscopic changes and consider how
this eruptive event relates to the early formative stages of low-mass stars.Comment: 59 pages, 22 figure
The Hidden Charm Decay of and Final State Interaction Effects
We investigate whether the final state interaction (FSI) effect plays a
significant role in the large hidden charm decay width of X(3872) and Y(3940)
using a model. Our numerical result suggests (1) the FSI contribution to
is tiny; (2) from FSI is around several keV, far
less than Belle's experimental value 7 MeV.Comment: 5 pages, 3 figures, 1 table. Version to appear in Physics Letters
Polarisation-insensitive generation of complex vector modes from a digital micromirror device
In recent time there has been an increasing amount of interest in developing novel techniques for the generation of complex vector light beams. Amongst these, digital holography stands out as one of the most flexible and versatile with almost unlimited freedom in the generation of scalar and complex vector light fields featuring arbitrary polarisation distributions and spatial profiles. In this manuscript we put forward a novel technique, which relies on the polarisation-insensitive attribute of Digital Micromirror Devices (DMDs). In a prior work where we outlined a new detection scheme based on Stokes projections we alluded to this technique. Here we outline the creation process in full, providing all the details for its experimental implementation. In addition, we fully characterise the performance of such technique, providing a quantitative analysis of the generated modes. To this end, we experimentally reconstruct the transverse polarisation distribution of arbitrary vector modes and compare the ellipticity and flatness of the polarisation ellipses with theoretical predictions. Further, we also generate vector modes with arbitrary degrees of non-separability and determine their degree of concurrence comparing this to theoretical predictions
Charmless Decays Based on the six-quark Effective Hamiltonian with Strong Phase Effects II
We provide a systematic study of charmless decays (
and denote pseudoscalar and vector mesons, respectively) based on an
approximate six-quark operator effective Hamiltonian from QCD. The calculation
of the relevant hard-scattering kernels is carried out, the resulting
transition form factors are consistent with the results of QCD sum rule
calculations. By taking into account important classes of power corrections
involving "chirally-enhanced" terms and the vertex corrections as well as weak
annihilation contributions with non-trivial strong phase, we present
predictions for the branching ratios and CP asymmetries of decays into
PP, PV and VV final states, and also for the corresponding polarization
observables in VV final states. It is found that the weak annihilation
contributions with non-trivial strong phase have remarkable effects on the
observables in the color-suppressed and penguin-dominated decay modes. In
addition, we discuss the SU(3) flavor symmetry and show that the symmetry
relations are generally respected
Electric-field-induced local distortion and large electrostrictive effects in lead-free NBT-based relaxor ferroelectrics
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
A novel subset of CD4+ TH2 memory/effector cells that produce inflammatory IL-17 cytokine and promote the exacerbation of chronic allergic asthma
Memory CD4+ T cells that produce both Th2 and Th17 cytokines are increased in the blood of patients with atopic asthma and in the lungs of asthmatic mice, where they contribute to inflammation
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