175 research outputs found
Sampling expansions associated with quaternion difference equations
Starting with a quaternion difference equation with boundary conditions, a
parameterized sequence which is complete in finite dimensional quaternion
Hilbert space is derived. By employing the parameterized sequence as the kernel
of discrete transform, we form a quaternion function space whose elements have
sampling expansions. Moreover, through formulating boundary-value problems, we
make a connection between a class of tridiagonal quaternion matrices and
polynomials with quaternion coefficients. We show that for a tridiagonal
symmetric quaternion matrix, one can always associate a quaternion
characteristic polynomial whose roots are eigenvalues of the matrix. Several
examples are given to illustrate the results
MS imaging of small metabolites in fruits
MS Imaging of large molecules, e.g. proteins and lipids, have been reported with MALDI. On the other hand, few works have been done on mapping the small molecules by MALDI imaging. This is mainly due to the high chemical noise background interference in the low mass region caused by chemical matrices. DESI Imaging, however, could be complementary to MALDI in that sample can be analyzed directly without matrices.
A large group of small metabolites are of considerable physiological and morphological importance in plants, e.g. flavonols involve in plant defense against environmental stresses and organic acids are one of important factors for fruit quality, but knowledge of their precise functions is limited due to insufficient characterization of their spatial responses.
In this communication we will discuss methodological details about MS imaging of small metabolites in apple and grape in terms of sample preparation, imaging methods, and other experimental concerns by using MALDI [1] and DESI source coupled with a high resolution/accurate LTQ-Orbitrap mass spectrometer. Finally, we will describe the spatial distributions of flavonols and organic acids in apple and grape, respectively
Downregulation of FABP4 promotes osteoclast formation and function by acting PPAR-γ signaling
LAMOST observations in the Kepler field. Analysis of the stellar parameters measured with the LASP based on the low-resolution spectra
All of the 14 subfields of the Kepler field have been observed at least once
with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST,
Xinglong Observatory, China) during the 2012-2014 observation seasons. There
are 88,628 reduced spectra with SNR (signal-to-noise ratio in g band)
6 after the first round (2012-2014) of observations for the
LAMOST-Kepler project (LK-project). By adopting the upgraded version of the
LAMOST Stellar Parameter pipeline (LASP), we have determined the atmospheric
parameters ( , , and ) and heliocentric radial
velocity for 51,406 stars with 61,226 spectra. Compared with
atmospheric parameters derived from both high-resolution spectroscopy and
asteroseismology method for common stars in Huber et al. (2014), an external
calibration of LASP atmospheric parameters was made, leading to the
determination of external errors for the giants and dwarfs, respectively.
Multiple spectroscopic observations for the same objects of the LK-project were
used to estimate the internal uncertainties of the atmospheric parameters as a
function of SNR with the unbiased estimation method. The LASP atmospheric
parameters were calibrated based on both the external and internal
uncertainties for the giants and dwarfs, respectively. A general statistical
analysis of the stellar parameters leads to discovery of 106 candidate
metal-poor stars, 9 candidate very metal-poor stars, and 18 candidate
high-velocity stars. Fitting formulae were obtained segmentally for both the
calibrated atmospheric parameters of the LK-project and the KIC parameters with
the common stars. The calibrated atmospheric parameters and radial velocities
of the LK-project will be useful for studying stars in the Kepler field.Comment: 53 pages, 21 figures, 5 tables, Accepted for publication by ApJ
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