Gaussian Process Modelling for Improved Resolution in Faraday Depth Reconstruction

The incomplete sampling of data in complex polarization measurements from radio telescopes negatively affects both the rotation measure (RM) transfer function and the Faraday depth spectra derived from these data. Such gaps in polarization data are mostly caused by flagging of radio frequency interference and their effects worsen as the percentage of missing data increases. In this paper we present a novel method for inferring missing polarization data based on Gaussian processes (GPs). Gaussian processes are stochastic processes that enable us to encode prior knowledge in our models. They also provide a comprehensive way of incorporating and quantifying uncertainties in regression modelling. In addition to providing non-parametric model estimates for missing values, we also demonstrate that Gaussian process modelling can be used for recovering rotation measure values directly from complex polarization data, and that inferring missing polarization data using this probabilistic method improves the resolution of reconstructed Faraday depth spectra.Comment: 16 pages, 10 figures, submitted to MNRA

Astrocyte Ca2+-evoked ATP release regulates myelinated axon excitability and conduction speed*

INTRODUCTION: Astrocytes support neuronal function throughout the central nervous system. In the gray matter, they regulate synapse number during development, remove synaptically released neurotransmitters to terminate their action and prevent excitotoxicity, control the extracellular potassium concentration to prevent hyperexcitability, regulate blood flow to ensure an adequate energy supply, provide lactate to neurons for energy, and respond to rises of intracellular calcium concentration ([Ca2+]i) by releasing adenosine triphosphate (ATP) and other gliotransmitters that act on neuronal receptors to modulate information processing. However, their role is unclear in the white matter, which transmits information rapidly between gray matter areas using axons wrapped with capacitance-reducing myelin (although they have been suggested to regulate myelination during development and during normal function). RATIONALE: Recently, it has been suggested that learning and memory may reflect not only changes in synaptic function in the gray matter, but also changes in white matter function. In particular, neural circuit function might be regulated by changes in the conduction speed of myelinated axons that result in an altered arrival time of action potentials at a distant neuron. These speed changes might be brought about by alterations of the properties of the passively conducting myelinated internodes or of the intervening excitable nodes of Ranvier, where the action potential is generated. We applied immunohistochemistry to assess how astrocytes interact with myelinated axons, neuronal stimulation and light-evoked calcium uncaging in astrocytes to evoke Ca2+-dependent release of gliotransmitters, and electrophysiology and pharmacology to characterize how astrocyte-released substances might affect the axon initial segment (AIS) and nodes of Ranvier of myelinated neurons. Measurements of conduction velocity and computer modeling allowed us to interpret the results. RESULTS: Astrocytes closely approach the axons of myelinated neurons in layer V of the cerebral cortex that enter the corpus callosum. Uncaging Ca2+ within astrocytes or stimulating spike trains in neurons evoked a rise of astrocyte [Ca2+]i that triggered the release of ATP-containing vesicles from these cells. This evoked an inward current in the AIS and nodes of Ranvier of the pyramidal neurons. Pharmacology showed that this was mediated by the activation of Gs-linked adenosine A2a receptors (A2aRs), implying that the released ATP was converted to adenosine by extracellular enzymes. The A2aRs raise the intracellular concentration of cyclic AMP, which activates hyperpolarization-activated cyclic nucleotide–gated (HCN) channels mediating the inward hyperpolarization-activated current (Ih) and thus depolarizes the cell. In the AIS, the activation of A2aRs alters excitability and hence action potential generation, whereas in the nodes of Ranvier, it decreases the conduction speed of the action potential along the axon. CONCLUSION: As in the gray matter, astrocyte [Ca2+]i regulates the release of ATP into the extracellular space in the white matter. After conversion to adenosine, this regulates the excitability and conduction speed of myelinated axons. The changes in excitability at the AIS will lead to changes in the relationship between the synaptic input and action potential output of the cell. The altered conduction speed of the myelinated axon may change neural circuit function by changing the action potential arrival time at the cell’s output synapses, thus altering the integration of signals in postsynaptic neurons. Variations in astrocyte-derived adenosine level can occur between wake and sleep states, and the extracellular adenosine concentration rises during energy deprivation conditions. These changes in adenosine level could thus control white matter information flow and neural circuit function

On the effect of resonances in composite Higgs phenomenology

We consider a generic composite Higgs model based on the coset SO(5)/SO(4) and study its phenomenology beyond the leading low-energy effective lagrangian approximation. Our basic goal is to introduce in a controllable and simple way the lowest-lying, possibly narrow, resonances that may exist is such models. We do so by proposing a criterion that we call partial UV completion. We characterize the simplest cases, corresponding respectively to a scalar in either singlet or tensor representation of SO(4) and to vectors in the adjoint of SO(4). We study the impact of these resonances on the signals associated to high-energy vector boson scattering, pointing out for each resonance the characteristic patterns of depletion and enhancement with respect to the leading-order chiral lagrangian. En route we derive the O(p^4) general chiral lagrangian and discuss its peculiar accidental and approximate symmetries.Comment: v3: a few typos corrected. Conclusions unchange

The Landau Pole and Z′Z^{\prime} decays in the 331 bilepton model

We calculate the decay widths and branching ratios of the extra neutral boson $Z^{\prime}$ predicted by the 331 bilepton model in the framework of two different particle contents. These calculations are performed taken into account oblique radiative corrections, and Flavor Changing Neutral Currents (FCNC) under the ansatz of Matsuda as a texture for the quark mass matrices. Contributions of the order of $10^{-1}-10^{-2}$ are obtained in the branching ratios, and partial widths about one order of magnitude bigger in relation with other non- and bilepton models are also obtained. A Landau-like pole arise at 3.5 TeV considering the full particle content of the minimal model (MM), where the exotic sector is considered as a degenerated spectrum at 3 TeV scale. The Landau pole problem can be avoid at the TeV scales if a new leptonic content running below the threshold at $$ TeV is implemented as suggested by other authors.Comment: 20 pages, 5 figures, LaTeX2

Quantitative, Architectural Analysis of Immune Cell Subsets in Tumor-Draining Lymph Nodes from Breast Cancer Patients and Healthy Lymph Nodes

Background: To date, pathological examination of specimens remains largely qualitative. Quantitative measures of tissue spatial features are generally not captured. To gain additional mechanistic and prognostic insights, a need for quantitative architectural analysis arises in studying immune cell-cancer interactions within the tumor microenvironment and tumor-draining lymph nodes (TDLNs). Methodology/Principal Findings: We present a novel, quantitative image analysis approach incorporating 1) multi-color tissue staining, 2) high-resolution, automated whole-section imaging, 3) custom image analysis software that identifies cell types and locations, and 4) spatial statistical analysis. As a proof of concept, we applied this approach to study the architectural patterns of T and B cells within tumor-draining lymph nodes from breast cancer patients versus healthy lymph nodes. We found that the spatial grouping patterns of T and B cells differed between healthy and breast cancer lymph nodes, and this could be attributed to the lack of B cell localization in the extrafollicular region of the TDLNs. Conclusions/Significance: Our integrative approach has made quantitative analysis of complex visual data possible. Our results highlight spatial alterations of immune cells within lymph nodes from breast cancer patients as an independent variable from numerical changes. This opens up new areas of investigations in research and medicine. Future application of this approach will lead to a better understanding of immune changes in the tumor microenvironment and TDLNs, and how they affect clinical outcome

Composite Higgs Sketch

The coupling of a composite Higgs to the standard model fields can deviate substantially from the standard model values. In this case perturbative unitarity might break down before the scale of compositeness is reached, which would suggest that additional composites should lie well below this scale. In this paper we account for the presence of an additional spin 1 custodial triplet of rhos. We examine the implications of requiring perturbative unitarity up to the compositeness scale and find that one has to be close to saturating certain unitarity sum rules involving the Higgs and the rho couplings. Given these restrictions on the parameter space we investigate the main phenomenological consequences of the spin 1 triplet. We find that they can substantially enhance the Higgs di-photon rate at the LHC even with a reduced Higgs coupling to gauge bosons. The main existing LHC bounds arise from di-boson searches, especially in the experimentally clean channel where the charged rhos decay to a W-boson and a Z, which then decay leptonically. We find that a large range of interesting parameter space with 700 GeV < m(rho) < 2 TeV is currently experimentally viable.Comment: 37 pages, 12 figures; v4: sum rule corrected, conclusions unchange