Non-negative matrix factorization for self-calibration of photometric redshift scatter in weak lensing surveys

Photo-z error is one of the major sources of systematics degrading the accuracy of weak lensing cosmological inferences. Zhang et al. (2010) proposed a self-calibration method combining galaxy-galaxy correlations and galaxy-shear correlations between different photo-z bins. Fisher matrix analysis shows that it can determine the rate of photo-z outliers at a level of 0.01-1% merely using photometric data and do not rely on any prior knowledge. In this paper, we develop a new algorithm to implement this method by solving a constrained nonlinear optimization problem arising in the self-calibration process. Based on the techniques of fixed-point iteration and non-negative matrix factorization, the proposed algorithm can efficiently and robustly reconstruct the scattering probabilities between the true-z and photo-z bins. The algorithm has been tested extensively by applying it to mock data from simulated stage IV weak lensing projects. We find that the algorithm provides a successful recovery of the scatter rates at the level of 0.01-1%, and the true mean redshifts of photo-z bins at the level of 0.001, which may satisfy the requirements in future lensing surveys.Comment: 12 pages, 6 figures. Accepted for publication in ApJ. Updated to match the published versio

PKCα and CPI-17 expression and spatial-temporal distribution with activation in pig stomach antrum and fundus

Smooth muscle contraction is a complicated process coordinated by contractile, regulatory and cytoskeletal proteins. The force generation depends on the phosphorylation of Myosin Regulatory Light Chain (MLC20). Myosin Light Chain Kinase (MLCK) and Myosin Light Chain Phosphatase (MLCP) are the two main regulators of the MLC20 phosphorylation level. MLCP is further controlled by two known pathways including the G protein coupled receptors (GPCRs)/ phospholipase C (PLC)/ diacylglycerol (DAG)/ protein kinase C (PKC)/ PKC-potentiated inhibitory protein for heterotrimeric myosin light chain phosphatase of 17 kDa (CPI-17) pathway. While messengers involved in this pathway have been proposed, studies on the details of the pathway are still controversial. This study explored the spatial-temporal regulation and distribution of PKCα and CPI-17 in intact animal tissues. Immunohistochemical results show that the distribution of PKCα in the longitudinal and circular layers of the fundus and antrum under relaxed conditions was predominantly localized at or near the periphery of the smooth muscle cell. Stimulation of the tissues with 1μM phorbol 12,13-dibutyrate (PDBu) for 10 or 30 minutes or 1μM carbachol (CCh) for 3 minutes does not alter the distribution pattern of PKCα. Different from PKCα, CPI-17 appeared to be uniformly distributed throughout the smooth muscle cells under relaxed conditions. Stimulation of the tissues with 1μM PDBu or 1μM CCh for 30 minutes led to a significant distribution shift of CPI-17 from throughout the cytosol to primarily at the cell periphery. Results from double labeling of PKCα and vinculin/talin under relaxed condition or CPI-17 and vinculin/talin under stimulated condition suggested that PKCα and CPI-17 were not associated with the adherens junction. It is likely that PKCα and CPI-17 are localized at the caveolae on the plasma membrane. This study also revealed that the force generated in tonic fundus smooth muscle is much greater than that in phasic antrum tissue upon PDBu stimulation. Immunoblot analyses demonstrated that this difference was not caused by a difference in the expression of PKCα or CPI-17 between these two tissues

The NLO electroweak effects on the Higgs production in association with bottom quark pair at the LHC

The dominant contribution to the Higgs production in association with bottom quark pair at the LHC is gluon-gluon fusion parton subprocess. We present a complete calculation of the next-to-leading order (NLO) electroweak (EW) corrections to this channel. The other small contributions with quarks in the initial state are calculated at tree level. We find that the NLO EW corrections can suppress the leading order (LO) contributions significantly.Comment: 12 pages, 7 figures. Version accepted by Phys.Rev.

Large deviations in the reinforced random walk model on trees

In this paper, we consider the linearly reinforced and the once-reinforced random walk models in the transient phase on trees. We show the large deviations for the upper tails for both models. We also show the exponential decay for the lower tail in the once-reinforced random walk model. On the other hand, the lower tail is in polynomial decay for the linearly reinforced random walk model.Comment: 20 page

Weak lensing power spectrum reconstruction by counting galaxies.-- I: the ABS method

We propose an Analytical method of Blind Separation (ABS) of cosmic magnification from the intrinsic fluctuations of galaxy number density in the observed galaxy number density distribution. The ABS method utilizes the different dependences of the signal (cosmic magnification) and contamination (galaxy intrinsic clustering) on galaxy flux, to separate the two. It works directly on the measured cross galaxy angular power spectra between different flux bins. It determines/reconstructs the lensing power spectrum analytically, without assumptions of galaxy intrinsic clustering and cosmology. It is unbiased in the limit of infinite number of galaxies. In reality the lensing reconstruction accuracy depends on survey configurations, galaxy biases, and other complexities, due to finite number of galaxies and the resulting shot noise fluctuations in the cross galaxy power spectra. We estimate its performance (systematic and statistical errors) in various cases. We find that, stage IV dark energy surveys such as SKA and LSST are capable of reconstructing the lensing power spectrum at $z\simeq 1$ and \ell\la 5000 accurately. This lensing reconstruction only requires counting galaxies, and is therefore highly complementary to the cosmic shear measurement by the same surveys.Comment: v1: 13 pages, 10 figures. v2: minor revisions. ApJ in pres