The \(\gamma\)-ray production mechanism and its localization in blazars are still a matter of debate. The main goal of this paper is to constrain the location of the high-energy emission in the ...blazar TXS 2013+370 and to study the physical and geometrical properties of the inner jet region on sub-pc scales. VLBI observations at 86 GHz and space-VLBI at 22 GHz allowed us to image the jet base with an angular resolution of \(\sim\)0.4 pc. By employing CLEAN imaging and Gaussian model-fitting, we performed a thorough kinematic analysis, which provided estimates of the jet speed, orientation, and component ejection times. Additionally, we studied the jet expansion profile and used the information on the jet geometry to estimate the location of the jet apex. VLBI data were combined with single-dish measurements to search for correlated activity between the radio and \(\gamma\)-ray emission. The high-resolution VLBI imaging revealed the existence of a spatially bent jet, described by moving and stationary features. New jet features are observed to emerge from the core, accompanied by flaring activity in radio bands and \(\gamma\) rays. The analysis of the transverse jet width profile constrains the location of the mm core to lie \(\leq\) 2 pc downstream of the jet apex, and also reveals the existence of a transition from parabolic to conical jet expansion at a distance of \(\sim\)54 pc from the core, corresponding to \(\sim\)1.5\(\times\)10\(^{\rm 6}\) Schwarzschild radii. The cross-correlation analysis reveals a strong correlation between the radio and \(\gamma\)-ray data, with the 1 mm emission lagging \(\sim\)49 days behind the \(\gamma\) rays. Based on this, we infer that the high energy emission is produced at a distance of \(\sim\)1 pc from the VLBI core, suggesting that the seed photon fields for the external Compton mechanism originate either in the dusty torus or in the broad-line region.
We report the results of decade-long (2008-2018) \(\gamma\)-ray to 1 GHz radio monitoring of the blazar 3C 279, including GASP/WEBT, \(\it{Fermi}\) and \(\it{Swift}\) data, as well as polarimetric ...and spectroscopic data. The X-ray and \(\gamma\)-ray light curves correlate well, with no delay > 3 hours, implying general co-spatiality of the emission regions. The \(\gamma\)-ray-optical flux-flux relation changes with activity state, ranging from a linear to a more complex dependence. The behaviour of the Stokes parameters at optical and radio wavelengths, including 43 GHz VLBA images, supports either a predominantly helical magnetic field or motion of the radiating plasma along a spiral path. Apparent speeds of emission knots range from 10 to 37c, with the highest values requiring bulk Lorentz factors close to those needed to explain \(\gamma\)-ray variability on very short time scales. The Mg II emission line flux in the `blue' and `red' wings correlates with the optical synchrotron continuum flux density, possibly providing a variable source of seed photons for inverse Compton scattering. In the radio bands we find progressive delays of the most prominent light curve maxima with decreasing frequency, as expected from the frequency dependence of the \(\tau=1\) surface of synchrotron self-absorption. The global maximum in the 86 GHz light curve becomes less prominent at lower frequencies, while a local maximum, appearing in 2014, strengthens toward decreasing frequencies, becoming pronounced at \(\sim5\) GHz. These tendencies suggest different Doppler boosting of stratified radio-emitting zones in the jet.
Context. Investigating the magnetic field structure in the innermost regions of relativistic jets is fundamental to understanding the crucial physical processes giving rise to jet formation, as well ...as to their extraordinary radiation output up to γ-ray energies. Aims. We study the magnetic field structure of the quasar CTA 102 with 3 and 7 mm VLBI polarimetric observations, reaching an unprecedented resolution (∼50 μas). We also investigate the variability and physical processes occurring in the source during the observing period, which coincides with a very active state of the source over the entire electromagnetic spectrum. Methods. We perform the Faraday rotation analysis using 3 and 7 mm data and we compare the obtained rotation measure (RM) map with the polarization evolution in 7 mm VLBA images. We study the kinematics and variability at 7 mm and infer the physical parameters associated with variability. From the analysis of γ-ray and X-ray data, we compute a minimum Doppler factor value required to explain the observed high-energy emission. Results. Faraday rotation analysis shows a gradient in RM with a maximum value of ∼6 × 104 rad m−2 and intrinsic electric vector position angles (EVPAs) oriented around the centroid of the core, suggesting the presence of large-scale helical magnetic fields. Such a magnetic field structure is also visible in 7 mm images when a new superluminal component is crossing the core region. The 7 mm EVPA orientation is different when the component is exiting the core or crossing a stationary feature at ∼0.1 mas. The interaction between the superluminal component and a recollimation shock at ∼0.1 mas could have triggered the multi-wavelength flares. The variability Doppler factor associated with such an interaction is large enough to explain the high-energy emission and the remarkable optical flare occurred very close in time.
Summary
Background There are limited data regarding the association of actinic keratosis (AK) and other types of nonmelanoma skin cancer (NMSC); studies investigating possible correlation of AK with ...melanocytic naevi are even scarcer. To our knowledge, there are no data examining the risk of AK in people using specific medications.
Objective To investigate constitutional and exposure risk factors leading to AK and the coexistence of AK with NMSC and melanoma.
Methods A multicentre hospital‐based case–control study was performed in Finland, Germany, Greece, Italy, Malta, Poland, Scotland and Spain, including 343 patients with actinic keratosis (AK), 409 with squamous cell carcinoma (SCC), 602 with basal cell carcinoma (BCC), 360 with invasive melanoma and 119 with in situ melanoma, and 686 control subjects. Exposures were assessed by questionnaires that were partly self‐administered and partly filled out by dermatologists. Unconditional logistic regression modelling was used to assess associations including the influence of phenotypic characteristics, presence of naevi, sun‐exposure habits and certain drugs on AK risk.
Results Differences in hair and eye coloration variably influenced the risk for AK, with red hair signifying a seven times higher risk odds ratio (OR) 6·9, 95% confidence interval (CI) 4·34–11·00), and brown – compared with blue – eyes, about a 40% reduced risk (OR 0·61, 95% CI 0·13–0·92). The darker the skin phototype, the lower the risk for AK, with phototype IV exhibiting nine times less risk of developing AK. Some and many freckles on the arms were associated with an OR of 1·8 (95% CI 1·08–2·81) and 3·0 (95% CI 1·10–3·54), respectively, while overall number of naevi and high educational level were inversely associated with AK. Sun exposure, thiazide diuretics and cardiac drugs had a higher risk for AK. SCC was the most frequent (58%) skin neoplasm coexisting with AKs, followed by BCC (30%), melanoma in situ (12%) and invasive melanoma (6%).
Conclusion In this large case–control study from across Europe the expected associations were confirmed for known risk factors. Some possible new risk factors, including cardiac and diuretic drugs, were identified, creating a new field for further investigation in future studies.
Background
Exposure to ultraviolet radiation (UVR) is the most important external risk factor for skin cancer. Outdoor workers, who are exposed to high ambient UVR levels are at increased risk.
...Objective
To compare outdoor with indoor workers in terms of: (i) skin cancer risk factors, and (ii) risk of developing skin cancer.
Methods
Using descriptive methods and a large multicenter European case–control study, we compared risk factor patterns between outdoor (N = 1416) and indoor workers (N = 1863). Risk of developing basal cell carcinoma (BCC), squamous cell carcinoma (SCC), melanoma and actinic keratosis (AK) were analysed by type of work using multivariate logistic regression models, for three categories of work: indoor; farming/construction; other outdoor work.
Results
Although skin phototype was equally distributed by type of work, significantly less outdoor than indoor workers used sunscreen in their own country (44.3% vs. 60.2%), but had more outdoor hobbies (66.2% vs. 58.2%). Outdoor workers had lower educational levels, and felt less confident in understanding medical information and filling medical forms (all P < 0.001). Outdoor workers had more signs of photodamage (78.1% vs. 65.5%) and among the skin cancer patients, 37.7% of outdoor workers vs. 28.6% of indoor workers had ≥2 skin cancers diagnosed during their lifetime. Multivariate logistic regression models showed significantly increased risk of outdoor vs. indoor work for AK (ORother outdoor = 1.55, ORfarming/construction = 2.58), SCC (ORother outdoor = 1.32, ORfarming/construction = 2.77) and BCC (ORother outdoor = 1.53, ORfarming/construction = 1.83). No significant associations were found for melanoma. The risk of all types of skin cancer and AK was significantly increased for workers with ≥5 years of outdoor work.
Conclusions
Outdoor workers had more risk behaviour with similar constitutional skin cancer risk factors: more UV exposure (both occupational and leisure) and less sunscreen use and lower health literacy. This results in higher exposure, more photodamage and an increased risk of developing AK, BCC and SCC.
Diagnosis of toxoplasmic encephalitis (TE) is challenging under the best clinical circumstances. The poor clinical sensitivity of quantitative polymerase chain reaction (qPCR) for Toxoplasma in blood ...and CSF and the limited availability of molecular diagnostics and imaging technology leaves clinicians in resource-limited settings with few options other than empiric treatment.
Here we describe proof of concept for a novel urine diagnostics for TE using Poly-N-Isopropylacrylamide nanoparticles dyed with Reactive Blue-221 to concentrate antigens, substantially increasing the limit of detection. After nanoparticle-concentration, a standard western blotting technique with a monoclonal antibody was used for antigen detection. Limit of detection was 7.8pg/ml and 31.3pg/ml of T. gondii antigens GRA1 and SAG1, respectively. To characterize this diagnostic approach, 164 hospitalized HIV-infected patients with neurological symptoms compatible with TE were tested for 1) T. gondii serology (121/147, positive samples/total samples tested), 2) qPCR in cerebrospinal fluid (11/41), 3) qPCR in blood (10/112), and 4) urinary GRA1 (30/164) and SAG1 (12/164). GRA1 appears to be superior to SAG1 for detection of TE antigens in urine. Fifty-one HIV-infected, T. gondii seropositive but asymptomatic persons all tested negative by nanoparticle western blot and blood qPCR, suggesting the test has good specificity for TE for both GRA1 and SAG1. In a subgroup of 44 patients, urine samples were assayed with mass spectrometry parallel-reaction-monitoring (PRM) for the presence of T. gondii antigens. PRM identified antigens in 8 samples, 6 of which were concordant with the urine diagnostic.
Our results demonstrate nanoparticle technology's potential for a noninvasive diagnostic test for TE. Moving forward, GRA1 is a promising target for antigen based diagnostics for TE.
Context. Blazar AO 0235+164, located at redshift z = 0.94, has undergone several sharp multi-spectral-range flaring episodes during the last decades. In particular, the episodes peaking in 2008 and ...2015, that received extensive multi-wavelength coverage, exhibited interesting behavior. Aims. We study the actual origin of these two observed flares by constraining the properties of the observed photo-polarimetric variability, those of the broad-band spectral energy-distribution and the observed time-evolution behavior of the source as seen by ultra-high resolution total-flux and polarimetric Very-long-baseline interferometry (VLBI) imaging. Methods. The analysis of VLBI images allows us to constrain kinematic and geometrical parameters of the 7 mm jet. We use the Discrete Correlation Function to compute the statistical correlation and the delays between emission at different spectral ranges. Multi-epoch modeling of the spectral energy distributions allows us to propose specific models of emission; in particular for the unusual spectral features observed in this source in the X-ray region of the spectrum during strong multi spectral-range flares. Results. We find that these X-ray spectral features can be explained by an emission component originating in a separate particle distribution than the one responsible for the two standard blazar bumps. This is in agreement with the results of our correlation analysis that do not find a strong correlation between the X-rays and the remaining spectral ranges. We find that both external Compton dominated and synchrotron self-Compton dominated models can explain the observed spectral energy distributions. However, synchrotron self-Compton models are strongly favored by the delays and geometrical parameters inferred from the observations.
We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5-7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. At ...z=0.902 this is the most distant object imaged by the EHT so far. We reconstruct the first images of the source at 230 GHz, at an unprecedented angular resolution of \(\sim\) 20 \(\mu\)as, both in total intensity and in linear polarization. We do not detect source variability, allowing us to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which we associate with the core. The feature is linearly polarized, with a fractional polarization of \(\sim\)5-8% and has a sub-structure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 \(\mu\)as along a position angle PA\(\sim -\)28\(^\circ\). It includes two features with orthogonal directions of polarization (electric vector position angle, EVPA), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of linear polarization, suggestive of a nearly uniform magnetic field. Future EHT observations will probe the variability of the jet structure on \({\mu}\)as scales, while simultaneous multi-wavelength monitoring will provide insight into the high energy emission origin.
The blazar J1924-2914 is a primary Event Horizon Telescope (EHT) calibrator for the Galactic Center's black hole Sagittarius A*. Here we present the first total and linearly polarized intensity ...images of this source obtained with the unprecedented 20 \(\mu\)as resolution of the EHT. J1924-2914 is a very compact flat-spectrum radio source with strong optical variability and polarization. In April 2017 the source was observed quasi-simultaneously with the EHT (April 5-11), the Global Millimeter VLBI Array (April 3), and the Very Long Baseline Array (April 28), giving a novel view of the source at four observing frequencies, 230, 86, 8.7, and 2.3 GHz. These observations probe jet properties from the subparsec to 100-parsec scales. We combine the multi-frequency images of J1924-2914 to study the source morphology. We find that the jet exhibits a characteristic bending, with a gradual clockwise rotation of the jet projected position angle of about 90 degrees between 2.3 and 230 GHz. Linearly polarized intensity images of J1924-2914 with the extremely fine resolution of the EHT provide evidence for ordered toroidal magnetic fields in the blazar compact core.
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