5,805 research outputs found
Prospects for Detecting Neutrino Signals from Annihilating/Decaying Dark Matter to Account for the PAMELA and ATIC results
Recent PAMELA data show that positron fraction has an excess above several
GeV while anti-proton one is not. Moreover ATIC data indicates that
electron/positron flux have a bump from 300 GeV to 800 GeV. Both annihilating
dark matter (DM) with large boost factor and decaying DM with the life around can account for the PAMELA and ATIC observations if their main final
products are charged leptons (, and ). In this work, we
calculated the neutrino flux arising from and which originate from
annihilating/decaying DM, and estimated the final muon rate in the neutrino
telescopes, namely Antares and IceCube. Given the excellent angular resolution,
Antares and IceCube are promising to discover the neutrino signals from
Galactic center and/or large DM subhalo in annihilating DM scenario, but very
challenging in decaying DM scenario.Comment: 21 pages, 7 figures, 2 tables. V2: references added. V3: the number
density of massive subhalo has been discussed in the appendix; accepted by
PR
2-{2,6-Bis[bis(4-fluorophenyl)methyl]-4-chlorophenylimino} -3-aryliminobutylnickel(II) bromide complexes: Synthesis, characterization, and investigation of their catalytic behavior
The series of 2-{2,6-bis[di(4-fluorophenyl)methyl]-4-chlorophenylimino}-3- aryliminobutane derivatives (L1-L5) and their nickel(II) dibromide complexes (Ni1-Ni5) were synthesized, and all organic compounds were fully characterized by the Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy and by elemental analysis, while the nickel complexes were characterized by FT-IR spectroscopy, elemental analysis, as well as by single-crystal X-ray diffraction for two representative examples, namely Ni1 and Ni4. A distorted tetrahedral geometry was observed for these four-coordinate nickel complexes. Upon the activation with either Methylaluminoxane or modified methylaluminoxane as co-catalyst, all nickel complex precatalysts showed very high activity toward ethylene polymerization with activities of up to 10 7 g(PE)·mol -1 (Ni)·h -1 , and afforded highly branched polyethylene with a bimodal distribution. © 2014 Elsevier B.V
Exploiting Contextual Information for Prosodic Event Detection Using Auto-Context
Prosody and prosodic boundaries carry significant information regarding linguistics and paralinguistics and are important aspects of speech. In the field of prosodic event detection, many local acoustic features have been investigated; however, contextual information has not yet been thoroughly exploited. The most difficult aspect of this lies in learning the long-distance contextual dependencies effectively and efficiently. To address this problem, we introduce the use of an algorithm called auto-context. In this algorithm, a classifier is first trained based on a set of local acoustic features, after which the generated probabilities are used along with the local features as contextual information to train new classifiers. By iteratively using updated probabilities as the contextual information, the algorithm can accurately model contextual dependencies and improve classification ability. The advantages of this method include its flexible structure and the ability of capturing contextual relationships. When using the auto-context algorithm based on support vector machine, we can improve the detection accuracy by about 3% and F-score by more than 7% on both two-way and four-way pitch accent detections in combination with the acoustic context. For boundary detection, the accuracy improvement is about 1% and the F-score improvement reaches 12%. The new algorithm outperforms conditional random fields, especially on boundary detection in terms of F-score. It also outperforms an n-gram language model on the task of pitch accent detection
Discriminating different scenarios to account for the cosmic excess by synchrotron and inverse Compton radiation
The excesses of the cosmic positron fraction recently measured by PAMELA and
the electron spectra by ATIC, PPB-BETS, Fermi and H.E.S.S. indicate the
existence of primary electron and positron sources. The possible explanations
include dark matter annihilation, decay, and astrophysical origin, like
pulsars. In this work we show that these three scenarios can all explain the
experimental results of the cosmic excess. However, it may be difficult
to discriminate these different scenarios by the local measurements of
electrons and positrons. We propose possible discriminations among these
scenarios through the synchrotron and inverse Compton radiation of the primary
electrons/positrons from the region close to the Galactic center. Taking
typical configurations, we find the three scenarios predict quite different
spectra and skymaps of the synchrotron and inverse Compton radiation, though
there are relatively large uncertainties. The most prominent differences come
from the energy band MHz for synchrotron emission and GeV for inverse Compton emission. It might be able to discriminate at least
the annihilating dark matter scenario from the other two given the high
precision synchrotron and diffuse -ray skymaps in the future.Comment: published in Pr
TetraÂkis[μ-2-(3,4-dimethÂoxyÂphenÂyl)acetato]-κ3 O 1,O 1′:O 1;κ3 O 1:O 1,O 1′;κ4 O 1:O 1′-bisÂ{[2-(3,4-dimethÂoxyÂphenÂyl)acetato-κ2 O 1,O 1′](1,10-phenanthroline-κ2 N,N′)erbium(III)}
In the dimeric centrosymmetric title complex, [Er2(C10H11O4)6(C12H8N2)2], the ErIII ion is nine-coordinated by five 2-(3,4-dimethÂoxyÂlphenÂyl)acetic acid (DMPA) ligands via seven O atoms and two N atoms from a bis-chelating 1,10-phenanthroline (phen) ligand in a distorted tricapped trigonal-prismatic geometry. The DMPA ligands are coordinated to the ErIII ion in bis-chelate, bridging and bridging tridentate modes. Relatively weak intraÂmolecular C—H⋯O interÂactions reinforce the stability of the molÂecular structure. InterÂmolecular C—H⋯O interÂactions are also observed
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