Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy.

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8±0.7(stat)±6.7(syst) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principles calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.

Testing Hadronic Interactions at Ultrahigh Energies with Air Showers Measured by the Pierre Auger Observatory.

Ultrahigh energy cosmic ray air showers probe particle physics at energies beyond the reach of accelerators. Here we introduce a new method to test hadronic interaction models without relying on the absolute energy calibration, and apply it to events with primary energy 6-16 EeV (E_{CM}=110-170 TeV), whose longitudinal development and lateral distribution were simultaneously measured by the Pierre Auger Observatory. The average hadronic shower is 1.33±0.16 (1.61±0.21) times larger than predicted using the leading LHC-tuned models EPOS-LHC (QGSJetII-04), with a corresponding excess of muons.

Measurement of the proton-air cross section at √s=57 TeV with the Pierre Auger Observatory.

We report a measurement of the proton-air cross section for particle production at the center-of-mass energy per nucleon of 57 TeV. This is derived from the distribution of the depths of shower maxima observed with the Pierre Auger Observatory: systematic uncertainties are studied in detail. Analyzing the tail of the distribution of the shower maxima, a proton-air cross section of [505±22(stat)(-36)(+28)(syst)] mb is found.

Measurement of the depth of maximum of extensive air showers above 10{18} eV.

We describe the measurement of the depth of maximum, X{max}, of the longitudinal development of air showers induced by cosmic rays. Almost 4000 events above 10;{18} eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106{-21}{+35}) g/cm{2}/decade below 10{18.24+/-0.05} eV, and (24+/-3) g/cm{2}/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm{2}. The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed.

The cosmic ray shadow of the Moon observed with the ANTARES neutrino telescope.

One of the main objectives of the ANTARES telescope is the search for point-like neutrino sources. Both the pointing accuracy and the angular resolution of the detector are important in this context and a reliable way to evaluate this performance is needed. In order to measure the pointing accuracy of the detector, one possibility is to study the shadow of the Moon, i.e. the deficit of the atmospheric muon flux from the direction of the Moon induced by the absorption of cosmic rays. Analysing the data taken between 2007 and 2016, the Moon shadow is observed with 3.5 σ statistical significance. The detector angular resolution for downward-going muons is 0 . 73 ∘ ± 0 . 14 ∘ . The resulting pointing performance is consistent with the expectations. An independent check of the telescope pointing accuracy is realised with the data collected by a shower array detector onboard of a ship temporarily moving around the ANTARES location.

Search for patterns by combining cosmic-ray energy and arrival directions at the Pierre Auger Observatory.

Energy-dependent patterns in the arrival directions of cosmic rays are searched for using data of the Pierre Auger Observatory. We investigate local regions around the highest-energy cosmic rays with [Formula: see text] eV by analyzing cosmic rays with energies above [Formula: see text] eV arriving within an angular separation of approximately 15[Formula: see text]. We characterize the energy distributions inside these regions by two independent methods, one searching for angular dependence of energy-energy correlations and one searching for collimation of energy along the local system of principal axes of the energy distribution. No significant patterns are found with this analysis. The comparison of these measurements with astrophysical scenarios can therefore be used to obtain constraints on related model parameters such as strength of cosmic-ray deflection and density of point sources.

Comparative effects of cholera and Bordetella pertussis toxins on cyclic AMP and GTP levels and on lipolysis in rat adipocytes incubated in vitro.

The respective effects of cholera and Bordetella pertussis toxins were studied in time and concentration dependent experiments, following glycerol and fatty acid release, GTP and cAMP levels. Cholera toxin, after a lag time of 30 min, stimulated linearly GTP and cAMP accumulation and lipolysis (maximal effect: 2-fold increase at 5 micrograms/ml). Pertussis toxin presented a biphasic effect both in time and concentration dependent studies. Up to a maximum reached after 2 h with 1.4 units LPF/ml the stimulation affected GTP (3 fold) and cAMP (7 fold) levels, glycerol and fatty acid release (15 fold). Beyond this, an inhibition occurred, yielding a decrease towards basal values of GTP and cAMP content whereas the glycerol and fatty acid release was stopped. These results, which are the first reporting the fluctuation of the GTP content of intact cells challenged with bacterial toxins, show a close relationship between GTP and cyclic AMP levels and lipolytic activity.

Tetradecanoyl phorbol-13-acetate counteracts the responsiveness of cultured thyroid cells to thyrotropin.

We have studied the effects of TPA on the metabolism of porcine thyroid cells cultured for 1-4 days in the absence (control cells) and in the presence of 0.1 mU/ml TSH (TSH cells). The phospholipid turnover, evaluated after a 2 hr incorporation of 32P-phosphate into phospholipids, is markedly modified by the presence of TPA (1.5 microM, 2 hr) in the incubation medium of control and TSH treated cells. The total incorporation is 3-4 times higher than untreated cells, the labelling of phosphatidylinositol (PI) is slightly decreased or unchanged whereas that of phosphatidylcholine (PC) is strongly increased. The increased labelling of PI, promoted by an acute TSH treatment is counteracted by TPA. This TPA effect is not observed when prelabelled cells are challenged for 5 min with the drug. A similar effect is observed when 10 nM TPA is added in the culture medium for 20 hr. The addition of TPA does not affect significantly the protein iodine content in 3 or 4 days control cells incubated for 45 min or 2 hr with 125I-iodine, but dramatically decreases the very high iodination rate of TSH cells. We have tested the TPA effect on the cyclic AMP accumulation for the last 5 min of a 2 hr incubation. TPA inhibits by about 50-80% the stimulation evoked by TSH and only by 10% that evoked by forskolin (0.1 mM). These results suggest a possible link between the PC turnover and the adenylate cyclase responsiveness to TSH and the iodination rate.

Relationships between the GTP content and the TSH-stimulated adenylate cyclase activity of cultured thyroid cells.

The adenylate cyclase activity of a crude membrane fraction derived from cells cultured for 4 days in the presence of TSH (0.1 mU/ml), when acutely stimulated with 25 mU/ml, is 5-8 times higher than that derived from control cells. It has been suggested that changes in the intracellular content of GTP resulting from TSH chronic treatment were the cause of the modified responsiveness of the cyclase. To investigate this hypothesis, a method for GTP determination was developed. The steady-state concentration of GTP in 4-day TSH-treated cells is 2-3 times higher than in 4-day control cells. The increase in GTP content is concentration dependent between 5 and 500 microU/ml TSH in the culture medium. It presents a maximum on day 4 of culture, but remains elevated up to day 5. Nevertheless the GTP content is not the only factor controlling the cyclase activity, indeed the addition of 0.1 mM GTP to membranes from control cells does not increase the response up to the level reached by membranes from TSH-treated cells. Treatment of the cells with virazole, a drug inhibiting the biosynthesis of guanyl nucleotides, greatly decreases the GTP level, but is unable to suppress the positive effect of the TSH chronic treatment on adenylate cyclase activity. These results show that the increase in GTP level resulting from culture of the cells in the presence of minute amounts of TSH is not exclusively linked to adenylate cyclase responsiveness to TSH.

Chronic and acute effects of forskolin on isolated thyroid cell metabolism.

The chronic treatment (2 days or more) of cultured thyroid cells with 1-10 microM forskolin (forskolin-treated cells) sensitizes the response of adenylate cyclase to further acute stimulation by 100 microM forskolin or 10 mU/ml thyrotropin (TSH). This positive regulation, similar to that produced by 0.1 mU/ml TSH (TSH-treated cells), is obtained between 2 and 3 days of culture. The acute response to TSH or forskolin of cells treated for 4 days with forskolin increases with the concentration of forskolin present during the chronic treatment. This result is different from that obtained after a chronic treatment with TSH which induces refractoriness beyond 0.1 mU/ml. These cells are then desensitized to TSH but not to forskolin. When both agonists are mixed together, their acute effect is additive on control, TSH- and forskolin-treated cells. The chronic treatment of cultured thyroid cells with 1-10 microM forskolin produces, just like 0.1 mU/ml TSH, a chronic phospholipid effect characterized by enhanced incorporation of 32Pi into phosphatidylinositol (PI) and phosphatidic acid. The acute challenge of these cells with 100 microM forskolin evokes a reverse phospholipid effect, i.e. a decreased incorporation of 32Pi into PI. The acute stimulation of TSH-treated cells with TSH produces a reverse phospholipid effect whereas the acute stimulation of forskolin-treated cells with TSH gives a normal phospholipid effect as it does on control cells. These results show that the observed effects of TSH on cAMP accumulation and phospholipid turnover are not independent and are regulated in an inverse reciprocal pattern.

Interactions between thyreostimulin and PAF-acether on thyroid cell metabolism.

1-O-Alkyl, 2-acetyl sn-glycerylphosphorylcholine (platelet activating factor (PAF)-acether) originally described as a platelet activating factor, is effective on various parameters in different cells. It seemed interesting to us to test it on porcine thyroid cells cultured for 1 to 5 days in the absence (control cells) or in the presence of 0.1 mU/ml thyreostimulin (TSH cells). At concentrations ranging from 0.5 to 2.5 microM, PAF-acether inhibited significantly the accumulation of cyclic AMP resulting from a 5 min incubation of the cells with TSH (40 mU/ml) or forskolin (0.1 mM). PAF-acether alone did not affect basal cyclic AMP accumulation. The maximal inhibition was obtained on a 3 day culture and amounted to 40-50%. The inhibition was transient and vanished after a 30 min incubation. The effects of PAF-acether (0.5 microM) on phospholipid metabolism depended closely upon the physiological state of the cells and upon the age of the culture. When PAF-acether was incubated for 2 h with [32P]phosphate, it mimicked the effects of TSH, i.e. it increased phosphatidylinositol (PI) labelling on 1 day control cells (expected effect) and decreased it with 1 day TSH cells (reverse effects). The PAF-acether effect was rapid in onset. After cell prelabelling for 2 h in the presence of TSH, PAF-acether added for 15 min completely counteracted the hormone effects on PI and phosphatidylcholine (PC) but increased the phosphatidic acid (PA) labelling. The effect of PAF- acether on PI labelling was partially antagonized by forskolin.(ABSTRACT TRUNCATED AT 250 WORDS)

Observation of the suppression of the flux of cosmic rays above 4 x 10 (19) eV.

The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min.

Upper limit on the diffuse flux of ultrahigh energy tau neutrinos from the Pierre Auger Observatory.

The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of nu(tau) at EeV energies. Assuming an E(nu)(-2) differential energy spectrum the limit set at 90% C.L. is E(nu)(2)dN(nu)(tau)/dE(nu)<1.3 x 10(-7) GeV cm(-2) s(-1) sr(-1) in the energy range 2 x 10(17) eV< E(nu)< 2 x 10(19) eV.

Correlation of the highest-energy cosmic rays with nearby extragalactic objects.

Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these cosmic rays with at least a 99% confidence level from a prescribed a priori test. The correlation we observed is compatible with the hypothesis that the highest-energy particles originate from nearby extragalactic sources whose flux has not been substantially reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources.