6,073 research outputs found
Theory of the quasiparticle excitation in high T cuprates: quasiparticle charge and nodal-antinodal dichotomy
A variational theory is proposed for the quasiparticle excitation in high
T cuprates. The theory goes beyond the usual Gutzwiller projected mean
field state description by including the spin-charge recombination effect in
the RVB background. The spin-charge recombination effect is found to
qualitatively alter the behavior of the quasiparticle charge as a function of
doping and cause considerable anisotropy in quasiparticle weight on the Fermi
surface.Comment: 10 page
Manifold Elastic Net: A Unified Framework for Sparse Dimension Reduction
It is difficult to find the optimal sparse solution of a manifold learning
based dimensionality reduction algorithm. The lasso or the elastic net
penalized manifold learning based dimensionality reduction is not directly a
lasso penalized least square problem and thus the least angle regression (LARS)
(Efron et al. \cite{LARS}), one of the most popular algorithms in sparse
learning, cannot be applied. Therefore, most current approaches take indirect
ways or have strict settings, which can be inconvenient for applications. In
this paper, we proposed the manifold elastic net or MEN for short. MEN
incorporates the merits of both the manifold learning based dimensionality
reduction and the sparse learning based dimensionality reduction. By using a
series of equivalent transformations, we show MEN is equivalent to the lasso
penalized least square problem and thus LARS is adopted to obtain the optimal
sparse solution of MEN. In particular, MEN has the following advantages for
subsequent classification: 1) the local geometry of samples is well preserved
for low dimensional data representation, 2) both the margin maximization and
the classification error minimization are considered for sparse projection
calculation, 3) the projection matrix of MEN improves the parsimony in
computation, 4) the elastic net penalty reduces the over-fitting problem, and
5) the projection matrix of MEN can be interpreted psychologically and
physiologically. Experimental evidence on face recognition over various popular
datasets suggests that MEN is superior to top level dimensionality reduction
algorithms.Comment: 33 pages, 12 figure
Optical Monitoring of 3C 390.3 from 1995 to 2004 and Possible Periodicities in the Historical Light Curve
We report V, R, and I band CCD photometry of the radio galaxy 3C 390.3
obtained with the 1.56-m telescope of the Shanghai Astronomical Observatory
from March 1995 to August 2004. Combining these data with data from the
literature, we have constructed a historical light curve from 1894 to 2004 and
searched for periodicities using the CLEANest program. We find possible periods
of 8.30+-1.17, 5.37+-0.49, 3.51+-0.21, and 2.13+-0.08 years.Comment: Accepted by AJ, 34 pages, 11 figure
Mitochondrial calpain-1 disrupts ATP synthase and induces superoxide generation in type 1 diabetic hearts: A novel mechanism contributing to diabetic cardiomyopathy
Calpain plays a critical role in cardiomyopathic changes in type 1 diabetes (T1D). This study investigated how calpain regulates mitochondrial reactive oxygen species (ROS) generation in the development of diabetic cardiomyopathy. T1D was induced in transgenic mice overexpressing calpastatin, in mice with cardiomyocyte-specific capn4 deletion, or in their wild-type littermates by injection of streptozotocin. Calpain-1 protein and activity in mitochondria were elevated in diabetic mouse hearts. The increased mitochondrial calpain-1 was associated with an increase in mitochondrial ROS generation and oxidative damage and a reduction in ATP synthase-α (ATP5A1) protein and ATP synthase activity. Genetic inhibition of calpain or upregulation of ATP5A1 increased ATP5A1 and ATP synthase activity, preventedmitochondrial ROS generation and oxidative damage, and reduced cardiomyopathic changes in diabetic mice. High glucose concentration induced ATP synthase disruption, mitochondrial superoxide generation, and cell death in cardiomyocytes, all of which were prevented by overexpression of mitochondria-targeted calpastatin or ATP5A1. Moreover, upregulation of calpain-1 specifically in mitochondria induced the cleavage of ATP5A1, superoxide generation, and apoptosis in cardiomyocytes. In summary, calpain-1 accumulation in mitochondria disrupts ATP synthase and induces ROS generation, which promotes diabetic cardiomyopathy. These findings suggest a novel mechanism for and may have significant implications in diabetic cardiac complications
Non-relativistic effective theory of dark matter direct detection
Dark matter direct detection searches for signals coming from dark matter
scattering against nuclei at a very low recoil energy scale ~ 10 keV. In this
paper, a simple non-relativistic effective theory is constructed to describe
interactions between dark matter and nuclei without referring to any underlying
high energy models. It contains the minimal set of operators that will be
tested by direct detection. The effective theory approach highlights the set of
distinguishable recoil spectra that could arise from different theoretical
models. If dark matter is discovered in the near future in direct detection
experiments, a measurement of the shape of the recoil spectrum will provide
valuable information on the underlying dynamics. We bound the coefficients of
the operators in our non-relativistic effective theory by the null results of
current dark matter direct detection experiments. We also discuss the mapping
between the non-relativistic effective theory and field theory models or
operators, including aspects of the matching of quark and gluon operators to
nuclear form factors.Comment: 35 pages, 3 figures, Appendix C.3 revised, acknowledgments and
references adde
The Discovery of A Luminous Broad Absorption Line Quasar at A Redshift of 7.02
Despite extensive efforts, only two quasars have been found at to date
due to a combination of low spatial density and high contamination from more
ubiquitous Galactic cool dwarfs in quasar selection. This limits our current
knowledge of the super-massive black hole (SMBH) growth mechanism and
reionization history. In this letter, we report the discovery of a luminous
quasar at , DELS J003836.10152723.6 (hereafter J00381527),
selected using photometric data from DESI Legacy imaging Survey (DELS),
Pan-STARRS1 (PS1) imaging Survey, as well as Wide-field Infrared Survey Explore
() mid-infrared all-sky survey. With an absolute magnitude of
=27.1 and bolometric luminosity of =5.610 , J00381527 is the most luminous quasar
known at . Deep optical to near infrared spectroscopic observations
suggest that J0038-1527 hosts a 1.3 billion solar mass BH accreting at the
Eddington limit, with an Eddington ratio of 1.250.19. The CIV broad
emission line of J00381527 is blue-shifted by more than 3000 km s to
the systemic redshift. More detailed investigations of the high quality spectra
reveal three extremely high velocity CIV broad absorption lines (BALs) with
velocity from 0.08 to 0.14 times the speed of light and total balnicity index
of more than 5000 km s, suggesting the presence of relativistic
outflows. J00381527 is the first quasar found at the epoch of reionization
(EoR) with such strong outflows and provides a unique laboratory to investigate
AGN feedback on the formation and growth of the most massive galaxies in the
early universe.Comment: ApJL in pres
Optical Photometrical Observations and Variability for Quasar 4C 29.45
We reported the result of long term optical variability of the blazar 4C
29.45 (QSO 1156+295, Ton 599), carried out optical photometric observations in
Johnson V, Cousins RI passbands during April 1997 to March 2002 using the 1.56
meter telescope of the Shanghai Astronomical Observatory (SHAO) at Sheshan,
China, compiled the post-1974 optical photometric data of the blazar by
combining our new observations with the published optical data, and found
maximum variations in different passbands: U = 4.41 mag, B =
5.55 mag, V = 4.53 mag, R = 5.80 mag, and I = 5.34 mag.
The average color indices are: UB = 0.18 mag, BV =
0.560.21 mag, BR = 0.930.18 mag, BI = 1.510.24 mag, VR
= 0.440.15 mag and VI = 1.030.23 mag. The post-1974 data give us
an excellent opportunity to search for the existence of possible periodicity in
the light curve. In search for periodicity in the R passband light curve, we
performed Jurkevich test and power spectral (Fourier) analysis methods, and
CLEANest algorithms to remove false signals. We found possible periods of 3.55
and 1.58 years. The possible mechanism for the periodic variability was
discussed.Comment: 12 pages, 9 figures, 5 tables; PASJ in pres
A compact core-jet structure in the changing-look Seyfert NGC 2617
The nearby face-on spiral galaxy NGC 2617 underwent an unambiguous
'inside-out' multi-wavelength outburst in Spring 2013, and a dramatic Seyfert
type change probably between 2010 and 2012, with the emergence of broad optical
emission lines. To search for the jet activity associated with this variable
accretion activity, we carried out multi-resolution and multi-wavelength radio
observations. Using the very long baseline interferometric (VLBI) observations
with the European VLBI Network (EVN) at 1.7 and 5.0 GHz, we find that NGC 2617
shows a partially synchrotron self-absorbed compact radio core with a
significant core shift, and an optically thin steep-spectrum jet extending
towards the north up to about two parsecs in projection. We also observed NGC
2617 with the electronic Multi-Element Remotely Linked Interferometer Network
(e-MERLIN) at 1.5 and 5.5 GHz, and revisited the archival data of the Very
Large Array (VLA) and the Very Long Baseline Array (VLBA). The radio core had a
stable flux density of about 1.4 mJy at 5.0 GHz between 2013 June and 2014
January, in agreement with the expectation of a supermassive black hole in the
low accretion rate state. The northern jet component is unlikely to be
associated with the 'inside-out' outburst of 2013. Moreover, we report that
most optically selected changing-look AGN at z<0.83 are sub-mJy radio sources
in the existing VLA surveys at 1.4 GHz, and it is unlikely that they are more
active than normal AGN at radio frequencies.Comment: 10 pages, 7 figures, accepted for publication in MNRA
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