We present the results of the first IceCube search for dark matter annihilation in the center of the Earth. Weakly interacting massive particles (WIMPs), candidates for dark matter, can scatter off ...nuclei inside the Earth and fall below its escape velocity. Over time the captured WIMPs will be accumulated and may eventually self-annihilate. Among the annihilation products only neutrinos can escape from the center of the Earth. Large-scale neutrino telescopes, such as the cubic kilometer IceCube Neutrino Observatory located at the South Pole, can be used to search for such neutrino fluxes. Data from 327 days of detector livetime during 2011/2012 were analyzed. No excess beyond the expected background from atmospheric neutrinos was detected. The derived upper limits on the annihilation rate of WIMPs in the Earth and the resulting muon flux are an order of magnitude stronger than the limits of the last analysis performed with data from IceCube's predecessor AMANDA. The limits can be translated in terms of a spin-independent WIMP-nucleon cross section. For a WIMP mass of 50 GeV this analysis results in the most restrictive limits achieved with IceCube data.
The Milky Way is expected to be embedded in a halo of dark matter particles, with the highest density in the central region, and decreasing density with the halo-centric radius. Dark matter might be ...indirectly detectable at Earth through a flux of stable particles generated in dark matter annihilations and peaked in the direction of the Galactic Center. We present a search for an excess flux of muon (anti-) neutrinos from dark matter annihilation in the Galactic Center using the cubic-kilometer-sized IceCube neutrino detector at the South Pole. There, the Galactic Center is always seen above the horizon. Thus, new and dedicated veto techniques against atmospheric muons are required to make the southern hemisphere accessible for IceCube. We used 319.7 live-days of data from IceCube operating in its 79-string configuration during 2010 and 2011. No neutrino excess was found and the final result is compatible with the background. We present upper limits on the self-annihilation cross-section, , for WIMP masses ranging from 30 GeV up to 10 TeV, assuming cuspy (NFW) and flat-cored (Burkert) dark matter halo profiles, reaching down to cm s , and cm s for the channel, respectively.
The giant radio galaxy 4C 73.08 has been observed with the Westerbork Telescope at a wavelength of 21 cm. The radio map obtained is a significant improvement upon previous maps in terms of the ...combination of high dynamic range, sensitivity and angular resolution. The new map shows that the jet, previously thought to be one-sided, is probably symmetrical with one arm almost lost in the background of extended lobe emission. The brighter, more compact lobe also displays more intense emission from its hotspot and jet. The jets line up well with the nucleus and hotspots, although the hotspot on one side deviates from the lobe major axis. The unusual feature of the radio source's morphology is the existence of curved ridges running transverse to the source major axis. Three of the other galaxies in the 4C 73.08 group are also weak radio sources. We further detect radio emission from the foreground galaxies NGC 2957 and 2963, which form a small group. A background galaxy has double radio components of moderate size which we have mapped; there is an optical companion at the same redshift. Another extended source may be associated with a Two Micron All Sky Survey galaxy.
IceCube is a neutrino observatory deployed in the glacial ice at the geographic South Pole. The
ν
μ
energy unfolding described in this paper is based on data taken with IceCube in its 79-string ...configuration. A sample of muon neutrino charged-current interactions with a purity of 99.5% was selected by means of a multivariate classification process based on machine learning. The subsequent unfolding was performed using the software
Truee
. The resulting spectrum covers an E
ν
-range of more than four orders of magnitude from 125 GeV to 3.2 PeV. Compared to the Honda atmospheric neutrino flux model, the energy spectrum shows an excess of more than
1.9
σ
in four adjacent bins for neutrino energies
E
ν
≥
177.8
TeV
. The obtained spectrum is fully compatible with previous measurements of the atmospheric neutrino flux and recent IceCube measurements of a flux of high-energy astrophysical neutrinos.
We report on the measurement of the all-particle cosmic ray energy spectrum with the IceTop air shower array in the energy range from 1.58 PeV to 1.26 EeV. The IceTop air shower array is the surface ...component of the IceCube Neutrino Observatory at the geographical South Pole. The analysis was performed using only information from IceTop. The data used in this work were taken from June 1, 2010 to May 13, 2011. During that period the IceTop array consisted of 73 stations, compared to 81 in its final configuration. The measured spectrum exhibits a clear deviation from a single power law above the knee around 4 PeV and below 1 EeV. We observe spectral hardening around 18 PeV and steepening around 130 PeV.
Van Paradijs et al report the detection of a transient and fading optical source in the error box associated with the gamma-ray burst GRB970228, less than 21 hours after the burst. The optical ...transient appears to be associated with a faint galaxy, suggesting that the burst occurred in that galaxy and thus that gamma-ray bursts in general lie at cosmological distance.
In all known genetic polymers, molecular recognition via hydrogen bonding between complementary subunits underpins their ability to encode and transmit information, to form sequence-defined duplexes, ...and to fold into catalytically active forms. Reversible covalent interactions between complementary subunits provide a different way to encode information, and potentially function, in sequence-defined oligomers. Here, we examine six oligoarylacetylene trimers composed of aniline and benzaldehyde subunits. Four of these trimers self-pair to form two-rung duplex structures, and two form macrocyclic 1,3-folded structures. The equilibrium proportions of these structures can be driven to favor each of the observed structures almost entirely depending upon the concentration of trimers and an acid catalyst. Quenching the acidic trimer solutions with an organic base kinetically traps all species such that they can be isolated and characterized. Mixtures of complementary trimers form exclusively sequence-specific 3-rung duplexes. Our results suggest that reversible covalent bonds could in principle guide the formation of more complex folded conformations of longer oligomers.
Genetic biopolymers utilize defined sequences and monomer-specific molecular recognition to store and transfer information. Synthetic polymers that mimic these attributes using reversible covalent ...chemistry for base-pairing pose unique synthetic challenges. Here, we describe a solid-phase synthesis methodology for the efficient construction of ethynyl benzene oligomers with specific sequences of aniline and benzaldehyde subunits. Handling these oligomers is complicated by the fact that they often exhibit multiple conformations because of intra- or intermolecular pairing. We describe conditions that allow the dynamic behavior of these oligomers to be controlled so that they may be manipulated and characterized without needing to mask the recognition units with protecting groups.
Optimally assigning streaming tasks to network machines is a key factor that influences a large data-stream-processing system's performance. Although researchers have prototyped and investigated ...various algorithms for task placement in data stream management systems, taxonomies and surveys of such algorithms are currently unavailable. To tackle this knowledge gap, the authors identify a set of core placement design characteristics and use them to compare eight placement algorithms. They also present a heuristic decision tree that can help designers judge how suitable a given placement solution might be to specific problems.
Gamma-ray burst (GRB) 111215A was bright at X-ray and radio frequencies, but not detected in the optical or near-infrared (nIR) down to deep limits. We have observed the GRB afterglow with the ...Westerbork Synthesis Radio Telescope and Arcminute Microkelvin Imager at radio frequencies, with the William Herschel Telescope and Nordic Optical Telescope in the nIR/optical, and with the Chandra X-ray Observatory. We have combined our data with the Swift X-Ray Telescope monitoring, and radio and millimetre observations from the literature to perform broad-band modelling, and determined the macro- and microphysical parameters of the GRB blast wave. By combining the broad-band modelling results with our nIR upper limits we have put constraints on the extinction in the host galaxy. This is consistent with the optical extinction we have derived from the excess X-ray absorption, and higher than in other dark bursts for which similar modelling work has been performed. We also present deep imaging of the host galaxy with the Keck I telescope, Spitzer Space Telescope, and Hubble Space Telescope (HST), which resulted in a well-constrained photometric redshift, giving credence to the tentative spectroscopic redshift we obtained with the Keck II telescope, and estimates for the stellar mass and star formation rate of the host. Finally, our high-resolution HST images of the host galaxy show that the GRB afterglow position is offset from the brightest regions of the host galaxy, in contrast to studies of optically bright GRBs.
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