We report on searches for neutrino sources at energies above 200 GeV in the Northern sky of the Galactic plane, using the data collected by the South Pole neutrino telescope, Ice Cube, and AMANDA. ...The Galactic region considered in this work includes the local arm toward the Cygnus region and our closest approach to the Perseus Arm. The searches are based on the data collected between 2007 and 2009. The analysis presented here are a scan for point sources within the Galactic plane, a search optimized for multiple and extended sources in the Cygnus region, which might be below the sensitivity of the point source scan, and studies of seven pre-selected neutrino source candidates. We investigate neutrino spectra proportional to Esup -2 and Esup -3 in order to cover the entire range of possible neutrino spectra. These represent the most stringent upper limits for soft-spectra neutrino sources within the Galaxy reported to date.
We present results on searches for point-like sources of neutrinos using four years of IceCube data, including the first year of data from the completed 86 string detector. The total livetime of the ...combined data set is 1373 days. For an E super(-2) spectrum, the observed 90% C.L. flux upper limits are ~10 super(-12) TeV super(-1) cm super(-2) s super(-1) for energies between 1 TeV and 1 PeV in the northern sky and ~10 super(-11) TeV super(-1) cm super(-2) s super(-1) for energies between 100 TeV and 100 PeV in the southern sky. This represents a 40% improvement compared to previous publications, resulting from both the additional year of data and the introduction of improved reconstructions. In addition, we present the first results from an all-sky search for extended sources of neutrinos. We update the results of searches for neutrino emission from stacked catalogs of sources and test five new catalogs; two of Galactic supernova remnants and three of active galactic nuclei. In all cases, the data are compatible with the background-only hypothesis, and upper limits on the flux of muon neutrinos are reported for the sources considered.
ABSTRACT We present constraints derived from a search of four years of IceCube data for a prompt neutrino flux from gamma-ray bursts (GRBs). A single low-significance neutrino, compatible with the ...atmospheric neutrino background, was found in coincidence with one of the 506 observed bursts. Although GRBs have been proposed as candidate sources for ultra-high-energy cosmic rays, our limits on the neutrino flux disfavor much of the parameter space for the latest models. We also find that no more than ∼1% of the recently observed astrophysical neutrino flux consists of prompt emission from GRBs that are potentially observable by existing satellites.
IceTop: The surface component of IceCube Abbasi, R.; Aguilar, J.A.; Ahlers, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2013, Letnik:
700
Journal Article
Recenzirano
Odprti dostop
IceTop, the surface component of the IceCube Neutrino Observatory at the South Pole, is an air shower array with an area of 1km2. The detector allows a detailed exploration of the mass composition of ...primary cosmic rays in the energy range from about 100TeV to 1EeV by exploiting the correlation between the shower energy measured in IceTop and the energy deposited by muons in the deep ice. In this paper we report on the technical design, construction and installation, the trigger and data acquisition systems as well as the software framework for calibration, reconstruction and simulation. Finally the first experience from commissioning and operating the detector and the performance as an air shower detector will be discussed.
Heterochromatin is enriched for specific epigenetic factors including Heterochromatin Protein 1a (HP1a), and is essential for many organismal functions. To elucidate heterochromatin organization and ...regulation, we purified Drosophila melanogaster HP1a interactors, and performed a genome-wide RNAi screen to identify genes that impact HP1a levels or localization. The majority of the over four hundred putative HP1a interactors and regulators identified were previously unknown. We found that 13 of 16 tested candidates (83%) are required for gene silencing, providing a substantial increase in the number of identified components that impact heterochromatin properties. Surprisingly, image analysis revealed that although some HP1a interactors and regulators are broadly distributed within the heterochromatin domain, most localize to discrete subdomains that display dynamic localization patterns during the cell cycle. We conclude that heterochromatin composition and architecture is more spatially complex and dynamic than previously suggested, and propose that a network of subdomains regulates diverse heterochromatin functions.
The IceCube Neutrino Observatory, approximately 1km3 in size, is now complete with 86 strings deployed in the Antarctic ice. IceCube detects the Cherenkov radiation emitted by charged particles ...passing through or created in the ice. To realize the full potential of the detector, the properties of light propagation in the ice in and around the detector must be well understood. This report presents a new method of fitting the model of light propagation in the ice to a data set of in situ light source events collected with IceCube. The resulting set of derived parameters, namely the measured values of scattering and absorption coefficients vs. depth, is presented and a comparison of IceCube data with simulations based on the new model is shown.
Aurantiochytrium sp. strain T66 was grown in batch bioreactor cultures in a defined glutamate- and glycerol-containing growth medium. Exponentially growing cells had a lipid content of 13% (w/w) of ...dry weight. A fattening of cells fed excess glycerol occurred in the post-exponential growth phase, after the medium was depleted of N or P. Lipid accumulation was also initiated by O₂ limitation (below 1% of saturation). N starvation per se, or in combination with O₂ limitation, gave the highest lipid content, i.e., 54% to 63% (w/w) of dry weight. The corresponding maximum culture density was 90 to 100 g/l dry biomass. The content of docosahexaenoic acid (22:6n-3) in N starved, well-oxygenated cells reached 29% (w/w) of total fatty acids but increased to 36% to 52% in O₂-limited cells, depending on the time span of the limitation. O₂-limited cells did not accumulate the monounsaturated fatty acids that were normally present. We inferred that the biological explanation is that O₂ limitation hindered the O₂-dependent desaturase(s) and favored the O₂-independent polyunsaturated fatty acid synthase. The highest overall volumetric productivity of docosahexaenoic acid observed was 93 mg/l/h. Additionally, we present a protocol for quantitative lipid extraction, involving heat and protease treatment of freeze-dried thraustochytrids.
Driven by an almost fanatical desire for whatever is new, "modern," and likely to make money, Houston is constantly in the process of remaking itself. Few structures remain from the nineteenth ...century, and even much of the twentieth-century built environment has fallen before the wrecking ball of "progress." Indeed, the demolition of older buildings in Houston can be compared to the destruction of cityscapes such as Berlin, Warsaw, and Tokyo in World War II. But because this wholesale restructuring of Houston's built environment has happened in peacetime, historically minded people have only recently sounded an alarm over what is being lost and the toll this destruction is taking on Houstonians' sense of place. Houston Lost and Unbuilt presents an extensive catalogue of twentieth-century public and commercial buildings that have been lost forever, as well as an intriguing selection of buildings that never made it off the drawing board. The lost buildings (or lost interiors of buildings) span a wide range, from civic gathering places such as the Houston Municipal Auditorium and the Astrodome to commercial enterprises such as the Foley Brothers, Sears Roebuck, and Sakowitz department stores to "Theatre Row" downtown to neighborhoods such as Fourth Ward/Freedmen's Town. Steven Strom's introductions and photo captions describe each significant building's contribution to the civic life of Houston. The "unbuilt" section of the book includes numerous previously unpublished architectural renderings of proposed projects such as a multi-building city center, monorail, and people mover system, all which reflect Houston's fascination with the future and optimism that technology will solve all of the city's problems.
ABSTRACT In this paper searches for flaring astrophysical neutrino sources and sources with periodic emission with the IceCube neutrino telescope are presented. In contrast to time-integrated ...searches, where steady emission is assumed, the analyses presented here look for a time-dependent signal of neutrinos using the information from the neutrino arrival times to enhance the discovery potential. A search was performed for correlations between neutrino arrival times and directions, as well as neutrino emission following time-dependent light curves, sporadic emission, or periodicities of candidate sources. These include active galactic nuclei, soft γ-ray repeaters, supernova remnants hosting pulsars, microquasars, and X-ray binaries. The work presented here updates and extends previously published results to a longer period that covers 4 years of data from 2008 April 5 to 2012 May 16, including the first year of operation of the completed 86 string detector. The analyses did not find any significant time-dependent point sources of neutrinos, and the results were used to set upper limits on the neutrino flux from source candidates.
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