658 research outputs found
The role of receptivity in the courtship behavior of Podocnemis erythrocephala in captivity
The courtship behavior of Podocnemis erythrocephala (Red-headed Amazon River Turtle) in captivity was studied to examine female receptivity and male response to female rejection. We observed 20 females and 39 males in 150 sessions (3â6Â h/day for a total of 450Â h). In 36% of the trials, there was no interaction between males and females, and 20% of the trials resulted in copulations. All males introduced into tanks approached females, and eventually there was aggression among the males. In 48% of the experiments, females also searched for or approached males. When males initially approached females, they either accepted the maleâs advances (14%), rejected the male passively (38%), or rejected the male aggressively (48%). In 86% of the cases where males were rejected, 4% attempted to approach females again, and in 51% they were ultimately successful
Frequency spectra of cosmic ray air shower radio emission measured with LOPES
Aims. We wish to study the spectral dependence of the radio emission from cosmic-ray air showers around .Methods. We observe short radio pulses in a broad frequency band with the dipole-interferometer LOPES (LOFAR Prototype Station), which is triggered by a particle detector array named Karlsruhe Shower Core and Array Detector (KASCADE). LOFAR is the Low Frequency Array. For this analysis, 23 strong air shower events are selected using parameters from KASCADE. The radio data are digitally beam-formed before the spectra are determined by sub-band filtering and fast Fourier transformation.Results. The resulting electric field spectra fall off to higher frequencies. An average electric field spectrum is fitted with an exponential and , or alternatively, with a power law and a spectral index of . The spectral slope obtained is not consistent within uncertainties and it is slightly steeper than the slope obtained from Monte Carlo simulations based on air showers simulated with CORSIKA (Cosmic Ray Simulations for KASCADE). For the analyzed sample of LOPES events, we do not find any significant dependence of the spectral slope on the electric field amplitude, the azimuth angle, the zenith angle, the curvature radius, nor on the average distance of the antennae from the shower core position. But one of the strongest events was measured during thunderstorm activity in the vicinity of LOPES and shows the longest pulse length measured of and a spectral slope of .Conclusions. We show with two different methods that frequency spectra from air shower radio emission can be reconstructed on event-by-event basis, with only two dozen dipole antennae simultaneously over a broad range of frequencies. According to the obtained spectral slopes, the maximum power is emitted below 40 MHz. Furthermore, the decrease in power to higher frequencies indicates a loss in coherence determined by the shower disc thickness. We conclude that a broader bandwidth, larger collecting area, and longer baselines, as will be provided by LOFAR, are necessary to further investigate the relation of the coherence, pulse length, and spectral slope of cosmic ray air showers
Constraints on the Ultra-High Energy Neutrino Flux from Gamma-Ray Bursts from a Prototype Station of the Askaryan Radio Array
We report on a search for ultra-high-energy (UHE) neutrinos from gamma-ray
bursts (GRBs) in the data set collected by the Testbed station of the Askaryan
Radio Array (ARA) in 2011 and 2012. From 57 selected GRBs, we observed no
events that survive our cuts, which is consistent with 0.12 expected background
events. Using NeuCosmA as a numerical GRB reference emission model, we estimate
upper limits on the prompt UHE GRB neutrino fluence and quasi-diffuse flux from
to GeV. This is the first limit on the prompt UHE GRB
neutrino quasi-diffuse flux above GeV.Comment: 14 pages, 8 figures, Published in Astroparticle Physics Journa
First Constraints on the Ultra-High Energy Neutrino Flux from a Prototype Station of the Askaryan Radio Array
The Askaryan Radio Array (ARA) is an ultra-high energy ( eV) cosmic
neutrino detector in phased construction near the South Pole. ARA searches for
radio Cherenkov emission from particle cascades induced by neutrino
interactions in the ice using radio frequency antennas ( MHz)
deployed at a design depth of 200 m in the Antarctic ice. A prototype ARA
Testbed station was deployed at m depth in the 2010-2011 season and
the first three full ARA stations were deployed in the 2011-2012 and 2012-2013
seasons. We present the first neutrino search with ARA using data taken in 2011
and 2012 with the ARA Testbed and the resulting constraints on the neutrino
flux from eV.Comment: 26 pages, 15 figures. Since first revision, added section on
systematic uncertainties, updated limits and uncertainty band with
improvements to simulation, added appendix describing ray tracing algorithm.
Final revision includes a section on cosmic ray backgrounds. Published in
Astropart. Phys.
Velocity independent constraints on spin-dependent DM-nucleon interactions from IceCube and PICO
[EN] Adopting the Standard Halo Model (SHM) of an isotropic Maxwellian velocity distribution for dark matter (DM) particles in the Galaxy, the most stringent current constraints on their spin-dependent scattering cross-section with nucleons come from the IceCube neutrino observatory and the PICO-60 C3F8 superheated bubble chamber experiments. The former is sensitive to high energy neutrinos from the self-annihilation of DM particles captured in the Sun, while the latter looks for nuclear recoil events from DM scattering off nucleons. Although slower DM particles are more likely to be captured by the Sun, the faster ones are more likely to be detected by PICO. Recent N-body simulations suggest significant deviations from the SHM for the smooth halo component of the DM, while observations hint at a dominant fraction of the local DM being in substructures. We use the method of Ferrer et al. (JCAP 1509: 052, 2015) to exploit the complementarity between the two approaches and derive conservative constraints on DM-nucleon scattering. Our results constrain sigma SD less than or similar to 3x10-39cm2 (6x10-38cm2) at greater than or similar to 90% C.L. for a DM particle of mass 1 TeV annihilating into tau+tau- (bb) with a local density of rho DM=0.3GeV/cm3. The constraints scale inversely with rho DM and are independent of the DM velocity distribution.Aartsen, MG.; Ackermann, M.; Adams, J.; Aguilar, JA.; Ahlers, M.; Ahrens, M.; Alispach, C.... (2020). Velocity independent constraints on spin-dependent DM-nucleon interactions from IceCube and PICO. The European Physical Journal C. 80(9):1-8. https://doi.org/10.1140/epjc/s10052-020-8069-5S18809F. Ferrer, A. Ibarra, S. Wild, JCAP 1509(09), 052 (2015). arXiv:1506.03386 [hep-ph]S. van den Bergh, Publ. Astron. Soc. Pac. 111, 657 (1999). arXiv:astro-ph/9904251G. Bertone, D. Hooper, J. Silk, Phys. Rept. 405, 279 (2005). arXiv:hep-ph/0404175A.K. Drukier, K. Freese, D.N. Spergel, Phys. Rev. D 33, 3495 (1986)M. Kuhlen, N. Weiner, J. Diemand, P. Madau, B. Moore, D. Potter, J. Stadel, M. Zemp, JCAP 1002, 030 (2010). arXiv:0912.2358 [astro-ph.GA]M. Lisanti, L.E. Strigari, J.G. Wacker, R.H. Wechsler, Phys. Rev. D 83, 023519 (2011). arXiv:1010.4300 [astro-ph.CO]Y.Y. Mao, L.E. Strigari, R.H. Wechsler, H.Y. Wu, O. Hahn, Astrophys. J. 764, 35 (2013). arXiv:1210.2721 [astro-ph.CO]L. Necib, M. Lisanti, V. Belokurov, arXiv:1807.02519 [astro-ph.GA]N.W. Evans, C.A.J. OâHare, C. McCabe, Phys. Rev. D 99(2), 023012 (2019). arXiv:1810.11468 [astro-ph.GA]M.G. Aartsen et al. [IceCube Collaboration], Eur. Phys. J. C 77, no. 3, 146 (2017) arXiv:1612.05949 [astro-ph.HE]C. Amole et al., [PICO Collaboration]. Phys. Rev. Lett. 118(25), 251301 (2017). arXiv:1702.07666 [astro-ph.CO]M.T. Frandsen, F. Kahlhoefer, C. McCabe, S. Sarkar, K. Schmidt-Hoberg, JCAP 1201, 024 (2012). arXiv:1111.0292 [hep-ph]K. Choi, C. Rott, Y. Itow, JCAP 1405, 049 (2014). arXiv:1312.0273 [astro-ph.HE]A. Achterberg et al., [IceCube Collaboration]. Astropart. Phys. 26, 155 (2006). arXiv:astro-ph/0604450R. Abbasi et al. [IceCube Collaboration], Nucl. Instrum. Meth. A 601, 294 (2009) arXiv:0810.4930 [physics.ins-det]M.G. Aartsen et al. [IceCube Collaboration], JINST 12, no. 03, P03012 (2017) arXiv:1612.05093 [astro-ph.IM]R. Abbasi et al., [IceCube Collaboration]. Astropart. Phys. 35, 615 (2012). arXiv:1109.6096 [astro-ph.IM]G.J. Feldman, R.D. Cousins, Phys. Rev. D 57, 3873 (1998). https://doi.org/10.1103/PhysRevD.57.3873. arXiv:physics/9711021 [physics.data-an]M. Tanabashi et al. [Particle Data Group], Phys. Rev. D 98, no. 3, 030001 (2018)C. Amole et al. [PICO Collaboration], arXiv:1905.12522 [physics.ins-det]C. Amole et al. [PICO Collaboration], Phys. Rev. D 93, no. 5, 052014 (2016) arXiv:1510.07754 [hep-ex]E. Tollerud et al. [ERFA] Computational Science and Discovery, no 8, 1 (2015) https://doi.org/10.5281/zenodo.1021149J.N. Bahcall, R.K. Ulrich, Rev. Mod. Phys. 60, 297 (1988)T. Mumford et al. [SunPy Community] Computational Science and Discovery, no 8, 1 (2015) arXiv:1505.02563 [astro-ph]V. Gluscevic, M.I. Gresham, S.D. McDermott, A.H.G. Peter, K.M. Zurek, JCAP 1512(12), 057 (2015). arXiv:1506.04454 [hep-ph]A.L. Fitzpatrick, W. Haxton, E. Katz, N. Lubbers, Y. Xu, â, JCAP 1302, 004 (2013). https://doi.org/10.1088/1475-7516/2013/02/004. arXiv:1203.3542 [hep-ph]A. Ibarra, A. Rappelt, JCAP 1708(08), 039 (2017). arXiv:1703.09168 [hep-ph
Frequency spectra of cosmic ray air shower radio emission measured with LOPES
AIMS: We wish to study the spectral dependence of the radio emission from
cosmic-ray air showers around 100 PeV (1017 eV). METHODS: We observe short
radio pulses in a broad frequency band with the dipole-interferometer LOPES
(LOFAR Prototype Station), which is triggered by a particle detector array
named Karlsruhe Shower Core and Array Detector (KASCADE). LOFAR is the Low
Frequency Array. For this analysis, 23 strong air shower events are selected
using parameters from KASCADE. RESULTS: The resulting electric field spectra
fall off to higher frequencies. An average electric field spectrum is fitted
with an exponential, or alternatively, with a power law. The spectral slope
obtained is not consistent within uncertainties and it is slightly steeper than
the slope obtained from Monte Carlo simulations based on air showers simulated
with CORSIKA (Cosmic Ray Simulations for KASCADE). One of the strongest events
was measured during thunderstorm activity in the vicinity of LOPES and shows
the longest pulse length measured of 110 ns and a spectral slope of -3.6.
CONCLUSIONS: We show with two different methods that frequency spectra from air
shower radio emission can be reconstructed on event-by-event basis, with only
two dozen dipole antennae simultaneously over a broad range of frequencies.
According to the obtained spectral slopes, the maximum power is emitted below
40 MHz. Furthermore, the decrease in power to higher frequencies indicates a
loss in coherence determined by the shower disc thickness. We conclude that a
broader bandwidth, larger collecting area, and longer baselines, as will be
provided by LOFAR, are necessary to further investigate the relation of the
coherence, pulse length, and spectral slope of cosmic ray air showers.Comment: 13 pages, 21 figures. Nigl, A. et al. (LOPES Collaboration),
Frequency spectra of cosmic ray air shower radio emission measured with
LOPES, accepted by A&A on 17/06/200
Deathly Drool: Evolutionary and Ecological Basis of Septic Bacteria in Komodo Dragon Mouths
Komodo dragons, the world's largest lizard, dispatch their large ungulate prey by biting and tearing flesh. If a prey escapes, oral bacteria inoculated into the wound reputedly induce a sepsis that augments later prey capture by the same or other lizards. However, the ecological and evolutionary basis of sepsis in Komodo prey acquisition is controversial. Two models have been proposed. The âbacteria as venomâ model postulates that the oral flora directly benefits the lizard in prey capture irrespective of any benefit to the bacteria. The âpassive acquisitionâ model is that the oral flora of lizards reflects the bacteria found in carrion and sick prey, with no relevance to the ability to induce sepsis in subsequent prey. A third model is proposed and analyzed here, the âlizard-lizard epidemicâ model. In this model, bacteria are spread indirectly from one lizard mouth to another. Prey escaping an initial attack act as vectors in infecting new lizards. This model requires specific life history characteristics and ways to refute the model based on these characteristics are proposed and tested. Dragon life histories (some details of which are reported here) prove remarkably consistent with the model, especially that multiple, unrelated lizards feed communally on large carcasses and that escaping, wounded prey are ultimately fed on by other lizards. The identities and evolutionary histories of bacteria in the oral flora may yield the most useful additional insights for further testing the epidemic model and can now be obtained with new technologies
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