The decay Z -> neutrino antineutrino photon in the Standard Model

A complete study of the one-loop induced decay Z -> neutrino antineutrino photon is presented within the framework of the Standard Model. The advantages of using a nonlinear gauge are stressed. We have found that the main contributions come from the electric dipole and the magnetic dipole transitions of the Z gauge boson and the neutrino, respectively. We obtain a branching ratio B=7.16E-10, which is about four orders of magnitude smaller than the bound recentely obtained by the L3 collaboration and thus it leaves open a window to search for new physics effects in single-photon decays of the Z boson.Comment: REVTEX,15 pp, 5 eps figures, Approved for publication in Physical Review

Scalar meson dynamics in Chiral Perturbation Theory

A comparison of the linear sigma model (L$\sigma$M) and Chiral Perturbation Theory (ChPT) predictions for pion and kaon dynamics is presented. Lowest and next-to-leading order terms in the ChPT amplitudes are reproduced if one restricts to scalar resonance exchange. Some low energy constants of the order $p^4$ ChPT Lagrangian are fixed in terms of scalar meson masses. Present values of these low energy constants are compatible with the L$\sigma$M dynamics. We conclude that more accurate values would be most useful either to falsify the L$\sigma$M or to show its capability to shed some light on the controversial scalar physics.Comment: 9 pages, REVTeX 4.0. Final version accepted for publicatio

Insights into the high-energy γ-ray emission of Markarian 501 from extensive multifrequency observations in the Fermi era

We report on the γ-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) γ-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 ± 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 ± 0.14, and the softest one is 2.51 ± 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size ≲0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (≃1044 erg s-1) constitutes only a small fraction (∼10-3) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude. © 2011. The American Astronomical Society

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Novel dielectric nanoparticles (DNP) doped nano-engineered glass based optical fiber for fiber laser

We have developed the technology for making of dielectric nano-particles (DNP) doped nano-engineered glass based optical fibers. Two kinds of DNP containing silica glass based Yb2O3 doped fibers are made successfully through solution doping (SD) technique. One: Yb2O3 doped yttria-rich alumino-silica nano-particles based optical fiber developed during drawing of D-shaped low RI resin coated large mode area (LMA) optical fiber from the modified preform which annealed at 1450-1550°C for 3 hours under heating and cooling rates of 20ºC/min and other: Yb2O3 doped zirconia-germanium-alumino (ZGA) rich yttria-silica nano-particles based optical fibers developed during drawing of normal RI coated single mode optical fiber from the modified preform which annealed at 1000-1100°C for 3 hr under heating and cooling rates of 20°C/min. Fabrication of Yb2O3 doped yttria-rich alumino-silica nano-particles based D-shaped low RI coated large core optical fibers having core diameter around 20.0-30.0 micron was made. The size of DNP nano-particles was maintained within 5-10 nm under doping of 0.20 mole% of fluorine. The start fiber preforms are studied by means of EPMA, EDX, and electron diffraction analyses, revealing phase-separated nano-sized ytterbium-rich areas in their cores. There is a great need to engineer the composition as well as doping levels of different elements within the core glass during the preform making stages to generate phase-separated Yb2O3 doped DNP nano particles in the fiber. The matter concentrates on making of Yb2O3 doped DNP containing optical fibers along with material characterizations, study of spectroscopic properties, photo-darkening phenomena, and lasing characteristics. Such kind of nano-engineered glass based optical fibers shows good lasing efficiency with improved photodarkening (PD) phenomena compared to the standard silica glass based optical fibers

Yb₂O₃ doped yttrium-alumino-silicate nano-particles based LMA optical fibers for high-power fiber lasers

Yb2O3 doped yttrium-rich alumino-silicate nanoparticles based D- and P- (pentagonal) shaped optical fibers with core diameter ~30-35 µm are fabricated using the conventional MCVD process and solution doping technique. Parameters of different stages of the fiber preforms fabrication are optimized to get uniform distributions of Al, Y, F, and Yb ions in the core region, ensured by the data of an EPMA analysis. In the presence of small amounts of fluorine, the size of nano-particles is maintained within 5-10 nm; the EDX data reveal that the nano-particles are rich in yttrium-alumino-silicate phase and are dispersed uniformly across the preforms core. The critical parameters of the processes involved at the fibers fabrication along with the nano-structuring and spectroscopic features are highlighted. It is shown experimentally that the drawn D- and P- shaped fibers support high laser efficiency (80% at 976-nm pumping) and demonstrate negligible photodarkening

Chemoinformatics and artificial intelligence colloquium: progress and challenges in developing bioactive compounds

We report the main conclusions of the first Chemoinformatics and Artificial Intelligence Colloquium, Mexico City, June 15–17, 2022. Fifteen lectures were presented during a virtual public event with speakers from industry, academia, and non-for-profit organizations. Twelve hundred and ninety students and academics from more than 60 countries. During the meeting, applications, challenges, and opportunities in drug discovery, de novo drug design, ADME-Tox (absorption, distribution, metabolism, excretion and toxicity) property predictions, organic chemistry, peptides, and antibiotic resistance were discussed. The program along with the recordings of all sessions are freely available at https://www.difacquim.com/english/events/2022-colloquium/. © 2022, The Author(s).Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]