IceTop is the surface component of the IceCube Observatory, composed of frozen water tanks at the top of IceCube's strings. Data from this detector can be analyzed in different ways with the goal of ...measuring cosmic ray spectrum and composition. The shower size S125 from IceTop alone can be used as a proxy for primary energy, and unfolded into an all-particle spectrum. In addition, S125 from the surface can be combined with high-energy muon energy loss information from the deep IceCube detector for those air showers which pass through both. Using these coincident events in a complementary analysis, both the spectrum and mass composition of primary cosmic rays can be extracted in parallel using a neural network. Both of these analyses have been performed on three years of IceTop and IceCube data. Both all-particle spectra as well as individual spectra for elemental groups are presented.
The IceTop detector is the surface component of the IceCube Observatory: an array of 81 ‘‘stations’’ of two frozen water tanks. Each tank contains two photosensors, and is sensitive to both the ...electromagnetic component of cosmic ray air showers as well as surface muons. While the electromagnetic component dominates in tanks close to the shower core, the signals from muons become more pronounced at large distances and at high zenith angles. Additionally, the deeply-buried in-ice component of IceCube can measure the high-energy penetrating muons from air showers. Together, these detectors can study the distributions of these air shower muons, and by comparing to the predictions of various hadronic interaction models, use them to constrain these models.
The IceCube Observatory includes both a deep in-ice array of 86 strings of sensors, and a surface array of 81 stations of frozen water tank detectors (IceTop). These multiple detectors make it ...possible to measure different cosmic ray air shower components, and to combine these measurements to determine both the spectrum and composition of cosmic rays. This work focuses on two analyses of 3 years of IceCube/IceTop data, from 2010–2013. In one, IceTop alone is used to measure an all-particle spectrum using an assumed composition model. In the other, coincidence events which trigger both IceTop and IceCube are used to create individual spectra for four different nuclear groups (protons, helium, oxygen, and iron).
Sediment metal concentrations were assessed in five different beach regions (n = 183) of KwaZulu-Natal (KZN) province in South Africa. Metal distribution revealed that Cr, Cu, Mo, Cd, Zn, Hg and As ...exceed the background upper continental crust values suggesting their anthropogenic origin (mining, agricultural and industrial) apart from natural geological inputs (gold placer deposits and heavy minerals). Various geochemical indices (Geoaccumulation index, Enrichment factor and Degree of contamination) confirmed that the sediment samples are extremely contaminated with Cr, Cd and Hg. Further, Hg and Cd were main contributors (60–90%) to the ecological threat in sediments. Hazard index estimated a high hazard potential of Hg in near future. Finally, present study together with our previous results portray the status of KZN coast with special significance to Hg contamination/enrichment. Thus, future researches are recommended to investigate the environmental and human health implications of mercury exposure in this coastal province.
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•Acid leachable metals in beaches of KwaZulu-Natal province in South Africa•Transport and deposition of metals due to human activities•Presence of metals above permissible limit•Identification of enrichment of metals through geochemical indices
A baseline study on metal concentrations in sediments was initiated from the Sodwana Bay and St. Lucia, adjacent to marine protected areas (MPAs) of South Africa. They were analysed to identify the ...acid leachable metal (ALM) (Fe, Mg, Mn, Cr, Cu, Mo, Ni, Co, Pb, Cd, Zn and Hg) concentration pattern. Metal distribution in 65 sediment samples exhibits higher abundances of Cr, Mo, Cd and Hg compared to the Upper Continental Crust. We relate the enrichment of these metals to beach placer deposits and activities related to former gold mining. Geochemical indices affirmed that Cr and Hg caused contamination, and Hg posed ~90% harmful effect on the biological community. These beach sediments, however, host lower metal concentrations compared to many worldwide beaches and other beaches in South Africa. This study suggests that it is largely unaffected by human activities, however, the overabundance of Hg demands regular monitoring.
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•Acid leachable metals in beaches of Marine Protected Areas in South Africa•Transport and deposition of metals due to human activities•Presence of metals above permissible limit•Identification of enrichment of metals through geochemical indices
Peritonsillar abscess (PTA) in pediatric patients is a challenging condition to diagnose and treat, and recurrence can occur in up to 15% of patients. This condition can be managed in various ...settings and there may be outcome differences depending on the choice of inpatient/outpatient management. The objective of this study was to evaluate immediate and long-term outcomes, specifically recurrence, after PTA management in the inpatient versus outpatient setting as well as specific patient characteristics leading to hospital management decisions.
We conducted a retrospective cohort study of all suspected cases of PTA seen at a tertiary pediatric hospital from 2008 to 2017, and 566 confirmed cases of PTA were included in this study. Demographics, PTA management, recurrence, and subsequent tonsillectomy (immediate or within 1 year of diagnosis) were ascertained from patient medical records. We compared characteristics of patients seen in the inpatient and outpatient setting using Chi-squared and Wilcoxon-Mann-Whitney tests.
Patients treated in the outpatient setting were more likely to be older and have a lower rate of recurrent ear infections (p < 0.0001 and p = 0.01 respectively). Additionally, no differences in gender, Down Syndrome, or autism were found. Patients who were admitted were more likely to undergo immediate tonsillectomy within a month or tonsillectomy within one year (p < 0.0001 and p = 0.02 respectively), whereas patients in the outpatient setting were more likely to receive antibiotics alone (p < 0.0001). Outpatient management was associated with no differences in recurrence rate within 30 days (p = 0.56). However, recurrence was associated with older age, a history of recurrent tonsillitis, but not a history of ear infections (p = 0.005, p < 0.0001, and p = 0.49 respectively). A history of recurrent ear infections, recurrent tonsillitis and recurrent PTAs were associated with the decision to pursue a tonsillectomy (p = 0.003, p = 0.03, and p < 0.0001 respectively).
Patients seen in the outpatient setting are more likely to receive antibiotics alone as their initial treatment, likely a result of certain clinical characteristics and presenting features as well as uncertain diagnosis. Inpatient status was associated with a younger age and a history of ear infections while recurrence was associated with a history of recurrent tonsillitis and older age. The recurrence rates for outpatient management were not statistically different than inpatient, suggesting that triaging and treatment of patients was occurring appropriately. The association of tonsillectomies in the inpatient group within 12 months is likely due to the higher rate of preexisting tonsil issues considering that recurrent tonsillitis, ear infections and a higher rate of PTA recurrence were all statistically correlated.
We have remotely mapped optical scattering and absorption in glacial ice at the South Pole for wavelengths between 313 and 560 nm and depths between 1100 and 2350 m. We used pulsed and continuous ...light sources embedded with the AMANDA neutrino telescope, an array of more than six hundred photomultiplier tubes buried deep in the ice. At depths greater than 1300 m, both the scattering coefficient and absorptivity follow vertical variations in concentration of dust impurities, which are seen in ice cores from other Antarctic sites and which track climatological changes. The scattering coefficient varies by a factor of seven, and absorptivity (for wavelengths less than ∼450 nm) varies by a factor of three in the depth range between 1300 and 2300 m, where four dust peaks due to stadials in the late Pleistocene have been identified. In our absorption data, we also identify a broad peak due to the Last Glacial Maximum around 1300 m. In the scattering data, this peak is partially masked by scattering on residual air bubbles, whose contribution dominates the scattering coefficient in shallower ice but vanishes at ∼1350 m where all bubbles have converted to nonscattering air hydrates. The wavelength dependence of scattering by dust is described by a power law with exponent −0.90 ± 0.03, independent of depth. The wavelength dependence of absorptivity in the studied wavelength range is described by the sum of two components: a power law due to absorption by dust, with exponent −1.08 ± 0.01 and a normalization proportional to dust concentration that varies with depth; and a rising exponential due to intrinsic ice absorption which dominates at wavelengths greater than ∼500 nm.
We present results of a Monte Carlo study of the sensitivity of the planned IceCube detector to predicted fluxes of muon neutrinos at TeV to PeV energies. A complete simulation of the detector and ...data analysis is used to study the detector’s capability to search for muon neutrinos from potential sources such as active galaxies and gamma-ray bursts (GRBs). We study the effective area and the angular resolution of the detector as a function of muon energy and angle of incidence. We present detailed calculations of the sensitivity of the detector to both diffuse and pointlike neutrino fluxes, including an assessment of the sensitivity to neutrinos detected in coincidence with GRB observations. After three years of data taking, IceCube will be able to detect a point-source flux of
E
ν
2×d
N
ν
/d
E
ν
=7×10
−9 cm
−2
s
−1
GeV at a 5
σ significance, or, in the absence of a signal, place a 90% c.l. limit at a level of
E
ν
2×d
N
ν
/d
E
ν
=2×10
−9 cm
−2
s
−1
GeV. A diffuse
E
−2 flux would be detectable at a minimum strength of
E
ν
2×d
N
ν
/d
E
ν
=10
−8 cm
−2
s
−1
sr
−1
GeV. A GRB model following the formulation of Waxman and Bahcall would result in a 5
σ effect after the observation of 200 bursts in coincidence with satellite observations of the gamma rays.
Muon track reconstruction and data selection techniques in AMANDA Ahrens, J.; Bai, X.; Bay, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2004, Letnik:
524, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The Antarctic Muon And Neutrino Detector
Array (AMANDA) is a high-energy neutrino telescope operating at the geographic South Pole. It is a lattice of photo-multiplier tubes buried deep in the polar ...ice between 1500 and
2000
m
. The primary goal of this detector is to discover astrophysical sources of high-energy neutrinos. A high-energy muon neutrino coming through the earth from the Northern Hemisphere can be identified by the secondary muon moving upward through the detector.
The muon tracks are reconstructed with a maximum likelihood method. It models the arrival times and amplitudes of Cherenkov photons registered by the photo-multipliers. This paper describes the different methods of reconstruction, which have been successfully implemented within
AMANDA. Strategies for optimizing the reconstruction performance and rejecting background are presented. For a typical analysis procedure the direction of tracks are reconstructed with about 2° accuracy.
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