A Common-Factor Approach for Multivariate Data Cleaning with an Application to Mars Phoenix Mission Data

Data quality is fundamentally important to ensure the reliability of data for stakeholders to make decisions. In real world applications, such as scientific exploration of extreme environments, it is unrealistic to require raw data collected to be perfect. As data miners, when it is infeasible to physically know the why and the how in order to clean up the data, we propose to seek the intrinsic structure of the signal to identify the common factors of multivariate data. Using our new data driven learning method, the common-factor data cleaning approach, we address an interdisciplinary challenge on multivariate data cleaning when complex external impacts appear to interfere with multiple data measurements. Existing data analyses typically process one signal measurement at a time without considering the associations among all signals. We analyze all signal measurements simultaneously to find the hidden common factors that drive all measurements to vary together, but not as a result of the true data measurements. We use common factors to reduce the variations in the data without changing the base mean level of the data to avoid altering the physical meaning.Comment: 12 pages, 10 figures, 1 tabl

A Note on Chiral Symmetry Breaking from Intersecting Branes

In this paper, we will consider the chiral symmetry breaking in the holographic model constructed from the intersecting brane configuration, and investigate the Nambu-Goldstone bosons associated with this symmetry breaking.Comment: 16 pp, minor changes, to appear PR

Signal-Jamming in a Sequential Auction

In a recurring auction early bids may reveal bidders’ types, which in turn affects bidding in later auctions. Bidders take this into account and may bid in a way that conceals their private information until the last auction is played. The present paper analyzes the equilibrium of a sequence of ?rst-price auctions assuming bidders have stable private values. We show that signal-jamming occurs and explore the dynamics of equilibrium prices

P-wave dispersion and attenuation due to scattering by aligned fluid saturated fractures with finite thickness: Theory and experiment

Fractures often play an important role in controlling the fluid flow in hydrocarbon reservoirs. When the seismic wave propagates through media containing fracture corridors, significant scattering dispersion and attenuation can occur. In this work, we study the P-wave dispersion and attenuation due to the scattering caused by 2-D fluid-saturated aligned fractures with finite thickness, which are embedded in an isotropic elastic background medium. Using the Foldy approximation and the representation theorem, the P-wave dispersion and attenuation are related to the displacement discontinuities across the fractures. These fracture displacement discontinuities are obtained from the boundary conditions and the P-wave dispersion and attenuation can thus be calculated. A numerical example shows that the fracture thickness has significant influence on the dispersion and attenuation, especially in the low-frequency regime when the fracture size is smaller than the seismic wavelength. The effects of the fluid bulk modulus are also significant,which are opposite to those of the fracture thickness. However, the effect of the fluid viscosity is found to be negligible for the studied configurations. To validate the proposed model, the theoretical predictions are compared with ultrasonic measurements on fractured samples. The comparison shows overall good agreement between theory and experiment. This work reveals the important influence of fracture thickness and saturating fluid properties on the P-wave scattering dispersion and attenuation. Hence, it shows a potential to extract these parameters from seismic data

Magnetic coupling of a rotating black hole with its surrounding accretion disk

Effects of magnetic coupling (MC) of a rotating black hole (BH) with its surrounding accretion disk are discussed in detail in the following aspects: (i) The mapping relation between the angular coordinate on the BH horizon and the radial coordinate on the disk is modified based on a more reasonable configuration of magnetic field, and a condition for coexistence of the Blandford-Znajek (BZ) and the MC process is derived. (ii) The transfer direction of energy and angular momentum in MC process is described equivalently by the co-rotation radius and by the flow of electromagnetic angular momentum and redshifted energy, where the latter is based on an assumption that the theory of BH magnetosphere is applicable to both the BZ and MC processes. (iii) The profile of the current on the BH horizon and that of the current density flowing from the magnetosphere onto the horizon are given in terms of the angular coordinate of the horizon. It is shown that the current on the BH horizon varies with the latitude of the horizon and is not continuous at the angular boundary between the open and closed magnetic field lines. (iv) The MC effects on disk radiation are discussed, and a very steep emissivity is produced by MC process, which is consistent with the recent XMM-Newton observation of the nearby bright Seyfert 1 galaxy MCG-6-30-15 by a variety of parameters of the BH-disk system.Comment: 24 pages, 19 figures. Accepted by Ap

Pairing Symmetry in Iron-Pnictide Superconductor KFe2_2As2_2

The pairing symmetry is one of the major issues in the study of iron-based superconductors. We adopt a low-energy effective kinetic model based on the first-principles band structure calculations combined with the $J_1$-$J_2$ model for KFe$_2$As$_2$, the phase diagram of pairing symmetries is constructed. Putting the values of $J_1$ and $J_2$ of the $J_1$-$J_2$ model obtained by the first-principles calculations into this phase diagram, we find that the pairing symmetry for KFe$_2$As$_2$ is a nodal $d_{xy}$-wave in the folded Brillouin zone with two iron atoms per unit cell. This is in good agreement with experiments observed a nodal order parameter.Comment: 5 pages, 4 figures (The pairing symmetry is dependent on choosing an effective tight-binding model. In the publication version, we adopt a ten-orbital model by using the maximally localized Wannier functions based on the first-principles band structure calculations, and give an s-wave pairing for KFe$_2$As$_2$

Synthetic Polypeptide Derived from Viral Macrophage Inflammatory Protein II Inhibit VEGF Production of Human Glioma U87 Cells through SDF-1α/CXCR4-Mediated AKT Signaling Pathway

Purpose: To evaluate the effect of synthetic polypeptide (N15P) derived from viral macrophage inflammatory protein II (vMIP-II) on the secretion of vascular endothelial growth factor (VEGF) as well as investigate the signaling pathways involved in stromal cell-derived factor-1α(SDF-1α)/CXC Chemokin Receptor 4 (CXCR4) axis-induced VEGF in glioblastoma U87 cells.Methods: Glioblastoma U87 cells were exposed to SDF-1á, N15P with various concentrations. The expression of CXCR4, SDF-1α and VEGF mRNA were assessed by RT-PCR, while expression level of VEGF was tested by ELISA and protein kinase B (Akt) phosphorylation detected by Western blot.Results: The results showed that CXCR4, SDF-1α, VEGF are expressed in human glioblastoma U87 cell lines. SDF-1α caused a dose-dependent sensitivity of cell proliferation with a maximum effect at 15 µmole/ml, while N15P decreased cell viability in U87 cells in a dose-dependent manner. SDF-1α stimulated the activation of VEGF, and N15P inhibited the activation of VEGF with or without SDF-1α stimulation. VEGF production in U87 cells was associated with Akt pathway. These changes in intracellular processes were blocked by N15P in a dose-dependent manner.Conclusion: The results suggest that N15P suppress SDF-1α/CXCR4  Mediated VEGF production through Akt signaling pathway and this may be a potent therapeutic strategy in glioblastoma.Keywords: Viral macrophage, Inflammatory protein II, Glioblastoma, CXC chemokin receptor 4, Stromal cell-derived factor-1α, Protein kinase

A Molecular Mechanism for Adrenergic-Induced Long QT Syndrome

ObjectivesThis study sought to explore molecular mechanisms underlying the adrenergic-induced QT prolongation associated with KCNQ1 mutations.BackgroundThe most frequent type of congenital long QT syndrome is LQT1, which is caused by mutations in the gene (KCNQ1) that encodes the alpha subunit of the slow component of delayed rectifier K+ current (IKs) channel. We identified 11 patients from 4 unrelated families that are heterozygous for KCNQ1-G269S. Most patients remained asymptomatic, and their resting corrected QT intervals ranged from normal to borderline but were prolonged significantly during exercise.MethodsWild-type (WT) KCNQ1 and/or KCNQ1-G269S (G269S) were expressed in mammalian cells with KCNE1. IKs-like currents were measured in control conditions or after isoproterenol or protein kinase A (PKA) stimulation using the patch-clamp technique. Additionally, experiments that incorporated the phosphomimetic KCNQ1 substitution, S27D, in WT or KCNQ1-G269S were also performed.ResultsThe coexpression of WT-KCNQ1 with varying amounts of G269S decreased IKs, shifted the current-voltage I-V relation of IKs to more positive potentials, and accelerated the IKs deactivation rates in a concentration-dependent manner. In addition, the coexpression of G269S and WT blunted the activation of IKs in response to isoproterenol or PKA stimulation. Lastly, a phosphomimetic substitution in G269S did not show an increased IKs.ConclusionsG269S modestly affected IKs in control conditions, but it almost completely blunted IKs responsiveness in conditions that simulate or mimic PKA phosphorylation of KCNQ1. This insensitivity to PKA stimulation may explain why patients with G269S mutation showed an excessive prolongation of QT intervals on exercise

GeauxDock: A novel approach for mixed-resolution ligand docking using a descriptor-based force field

© 2015 Wiley Periodicals, Inc. Molecular docking is an important component of computer-aided drug discovery. In this communication, we describe GeauxDock, a new docking approach that builds on the ideas of ligand homology modeling. GeauxDock features a descriptor-based scoring function integrating evolutionary constraints with physics-based energy terms, a mixed-resolution molecular representation of protein-ligand complexes, and an efficient Monte Carlo sampling protocol. To drive docking simulations toward experimental conformations, the scoring function was carefully optimized to produce a correlation between the total pseudoenergy and the native-likeness of binding poses. Indeed, benchmarking calculations demonstrate that GeauxDock has a strong capacity to identify near-native conformations across docking trajectories with the area under receiver operating characteristics of 0.85. By excluding closely related templates, we show that GeauxDock maintains its accuracy at lower levels of homology through the increased contribution from physics-based energy terms compensating for weak evolutionary constraints. GeauxDock is available at http://www.institute.Loni.org/lasigma/package/dock/