PKS 1510-089 is a flat spectrum radio quasar strongly variable in the optical and GeV range. We search for low-state VHE gamma-ray emission from PKS 1510-089. We aim to characterize and model the ...source in a broad-band context, which would provide a baseline over which high states and flares could be better understood. We use daily binned Fermi-LAT flux measurements of PKS 1510-089 to characterize the GeV emission and select the observation periods of MAGIC during low state of activity. For the selected times we compute the average radio, IR, optical, UV, X-ray and gamma-ray emission to construct a low-state spectral energy distribution of the source. The broadband emission is modelled within an External Compton scenario with a stationary emission region through which plasma and magnetic field are flowing. We perform also the emission-model-independent calculations of the maximum absorption in the broad line region (BLR) using two different models. Results. The MAGIC telescopes collected 75 hrs of data during times when the Fermi-LAT flux measured above 1 GeV was below 3x10-8cm-2s-1, which is the threshold adopted for the definition of a low gamma-ray activity state. The data show a strongly significant (9.5{\sigma}) VHE gamma-ray emission at the level of (4.27+-0.61stat)x10-12cm-2s-1 above 150GeV, a factor 80 smaller than the highest flare observed so far from this object. Despite the lower flux, the spectral shape is consistent with earlier detections in the VHE band. The broad-band emission is compatible with the EC scenario assuming a large emission region located beyond the BLR. For the first time the gamma-ray data allow us to place a limit on the location of the emission region during a low gamma-ray state of a FSRQ. For the used model of the BLR, the 95% C.L. on the location of the emission region allows us to place it at the distance >74% of the outer radius of the BLR.
Antimony has properties similar to arsenic with some of its compounds toxic to humans. Therefore it is necessary to control the wastes accumulated by anthropogenic activities, such as mining, where ...it is in tailings to be released to the environment. According to the Environment Protection Agency, the maximum value in sediments is 11.2 mg Sb kg–1 and the Earth’s crust average is 0.2 mg Sb kg–1. In this semiarid area, the drainage basin El Carrizal is impacted with wastes of an abandoned gold mine at the Mining District El Triunfo (MD – ET) which have tailings with 17,600 mg kg–1 of antimony. In the main dry river (arroyo), the Sb content is between 0.6 and 122 mg kg–1. This element is transported from the source throughout the fluvial basin to discharge into the Pacific Ocean. In the arroyo mouth we collected one sedimentary core and the sediment from dunes (28.6 – 45.7 and 6.43 – 7.74 mg Sb kg–1). This research concluded the antimony is enriched in this semiarid system, with Normalized Enrichment Factors severely enriched mainly in arroyo sediments close to the MD-ET
Regulation of LPA receptor function by estrogens González-Arenas, Aliesha; Avendaño-Vázquez, S. Eréndira; Cabrera-Wrooman, Alejandro ...
Biochimica et biophysica acta,
February 2008, 2008-Feb, 2008-02-00, Letnik:
1783, Številka:
2
Journal Article
Recenzirano
Odprti dostop
17β-Estradiol induced LPA1 receptor desensitization in C9 cells stably expressing LPA1 receptors and transiently expressing estrogen receptor α. Such desensitization was evidenced by a reduction in ...lysophosphatidic acid-mediated Ca2+mobilization and it was associated to receptor phosphorylation and internalization. These effects of 17β-estradiol were rapid (taking place over 5 min) and were blocked by the estrogen receptor antagonist ICI 182780. Similarly, inhibitors of phosphoinositide 3-kinase (wortmannin and LY294002) and of protein kinase C (staurosporine and Gö 6976) blocked 17β-estradiol-induced LPA1 receptor desensitization and phosphorylation. Confocal microscopy evidenced LPA1 receptor internalization in response to 17β-estradiol treatment. Association between LPA1 receptors and protein kinase C α was suggested by co-immunoprecipitation assays. Protein kinase C α was associated with LPA1 receptors in the absence of stimulus and such association further increased in a dynamic fashion in response to 17β-estradiol. The results demonstrated that in C9 cells estrogens modulate LPA1 action through estrogen receptor α with the participation of protein kinase C α and phosphoinositide 3-kinase.
Fast radio bursts (FRBs) are bright flashes observed typically at GHz frequencies with millisecond duration, whose origin is likely extragalactic. Their nature remains mysterious, motivating searches ...for counterparts at other wavelengths. FRB 121102 is so far the only source known to repeatedly emit FRBs and is associated with a host galaxy at redshift \(z \simeq 0.193\). We conducted simultaneous observations of FRB 121102 with the Arecibo and MAGIC telescopes during several epochs in 2016--2017. This allowed searches for millisecond-timescale burst emission in very-high-energy (VHE) gamma rays as well as the optical band. While a total of five FRBs were detected during these observations, no VHE emission was detected, neither of a persistent nature nor burst-like associated with the FRBs. The average integral flux upper limits above 100 GeV at 95% confidence level are \(6.6 \times 10^{-12}~\mathrm{photons\ cm^{-2}\ s^{-1}}\) (corresponding to luminosity \(L_{\rm VHE} \lesssim 10^{45}~\mathrm{erg\ s^{-1}}\)) over the entire observation period, and \(1.2 \times 10^{-7}~ \mathrm{photons\ cm^{-2}\ s^{-1}}\) (\(L_{\rm VHE} \lesssim 10^{49}~\mathrm{erg\ s^{-1}}\)) over the total duration of the five FRBs. We constrain the optical U-band flux to be below 8.6 mJy at 5-\(\sigma\) level for 1-ms intervals around the FRB arrival times. A bright burst with U-band flux \(29~\mathrm{mJy}\) and duration \(\sim 12\) ms was detected 4.3 s before the arrival of one FRB. However, the probability of spuriously detecting such a signal within the sampled time space is 1.5% (2.2 \(\sigma\), post-trial), i.e. consistent with the expected background. We discuss the implications of the obtained upper limits for constraining FRB models.
Clusters of galaxies are the largest known gravitationally bound structures in the Universe, with masses around \(10^{15}\ M_\odot\), most of it in the form of dark matter. The ground-based Imaging ...Atmospheric Cherenkov Telescope MAGIC made a deep survey of the Perseus cluster of galaxies using almost 400 h of data recorded between 2009 and 2017. This is the deepest observational campaign so far on a cluster of galaxies in the very high energy range. We search for gamma-ray signals from dark matter particles in the mass range between 200 GeV and 200 TeV decaying into standard model pairs. We apply an analysis optimized for the spectral and morphological features expected from dark matter decays and find no evidence of decaying dark matter. From this, we conclude that dark matter particles have a decay lifetime longer than \(\sim10^{26}\)~s in all considered channels. Our results improve previous lower limits found by MAGIC and represent the strongest limits on decaying dark matter particles from ground-based gamma-ray instruments.
The MAGIC telescopes observed S2 0109+22 in 2015 July during its flaring activity in high energy gamma rays observed by Fermi-LAT. We analyse the MAGIC data to characterise the very high energy (VHE) ...gamma-ray emission of S2 0109+22, which belongs to the subclass of intermediate synchrotron peak (ISP) BL Lac objects. We study the multi-frequency emission in order to investigate the source classification. Finally, we compare the source long-term behaviour to other VHE gamma-ray emitting (TeV) blazars. We performed a temporal and spectral analysis of the data centred around the MAGIC interval of observation (MJD 57225-57231). Long-term radio and optical data have also been investigated using the discrete correlation function. The redshift of the source is estimated through optical host-galaxy imaging and also using the amount of VHE gamma-ray absorption. The quasi-simultaneous multi-frequency spectral energy distribution (SED) is modelled with the conventional one-zone synchrotron self-Compton (SSC) model. MAGIC observations resulted in the detection of the source at a significance level of \(5.3\,\sigma\). The VHE gamma-ray emission of S2 0109+22 is variable on a daily time scale. VHE gamma-ray luminosity of the source is lower than the average of TeV BL Lacs. The optical polarization, and long-term optical/radio behaviour of the source are different from the general population of TeV blazars. All these findings agree with the classification of the source as an ISP BL Lac object. We estimate the source redshift as \(z = 0.36 \pm 0.07\). The SSC parameters describing the SED are rather typical for blazars.
A neutrino with energy of \(\sim\)290 TeV, IceCube-170922A, was detected in coincidence with the BL Lac object TXS~0506+056 during enhanced gamma-ray activity, with chance coincidence being rejected ...at \(\sim 3\sigma\) level. We monitored the object in the very-high-energy (VHE) band with the MAGIC telescopes for \(\sim\)41 hours from 1.3 to 40.4 days after the neutrino detection. Day-timescale variability is clearly resolved. We interpret the quasi-simultaneous neutrino and broadband electromagnetic observations with a novel one-zone lepto-hadronic model, based on interactions of electrons and protons co-accelerated in the jet with external photons originating from a slow-moving plasma sheath surrounding the faster jet spine. We can reproduce the multiwavelength spectra of TXS 0506+056 with neutrino rate and energy compatible with IceCube-170922A, and with plausible values for the jet power of \(\sim 10^{45} - 4 \times 10^{46} {\rm erg \ s^{-1}}\). The steep spectrum observed by MAGIC is concordant with internal \(\gamma\gamma\) absorption above a few tens of GeV entailed by photohadronic production of a \(\sim\)290 TeV neutrino, corroborating a genuine connection between the multi-messenger signals. In contrast to previous predictions of predominantly hadronic emission from neutrino sources, the gamma-rays can be mostly ascribed to inverse Compton up-scattering of external photons by accelerated electrons. The X-ray and VHE bands provide crucial constraints on the emission from both accelerated electrons and protons. We infer that the maximum energy of protons in the jet co-moving frame can be in the range \(\sim 10^{14}\) to \(10^{18}\) eV.
Perchlorate is known to suppress thyroid function by inhibiting uptake of iodide by the human thyroid at doses of 200 mg/day or greater. A study was conducted to investigate the potential effects of ...perchlorate in dunking water on thyroid function in newborns and school-age children. A total of 162 school-age children and 9784 newborns were studied in three proximate cities in northern Chile that have different concentrations of perchlorate in drinking water: Taltal (100 to 120 μg/L), Chañaral (5 to μg/L), and Antofagasta (non-detectable: <4 μg/L). Among schoolchildren, no difference was found in thyroidstimulating hormone levels or goiter prevalence among lifelong residents of Taltal or Chañaral compared with those of Antofagasta, after adjusting for age, sex, and urinary iodine. No presumptive cases of congenital hypothyroidism were detected in Taltal or Chañaral; seven cases were detected in Antofagasta Neonatal thyrobd-stimulaing hormone levels were significantly lower in Taltal compared with Antofagasta; this is opposite to the known pharmacobgical effect of perchlorate, and the magnitude of difference did not seem to be clinically significant. These findings do not support the hypothesis that perchlorate in drinking water at concentrations as high as 100 to 120 μg/L suppresses thyroid function in newborns or school-age children.
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