Breaking degeneracy in jet dynamics: multi-epoch joint modelling of the BL Lac PKS 2155-304

Supermassive black holes can launch powerful jets which can be some of the most luminous multi-wavelength sources; decades after their discovery their physics and energetics are still poorly understood. The past decade has seen a dramatic improvement in the quality of available data, but despite this improvement the semi-analytical modelling of jets has advanced slowly: simple one-zone models are still the most commonly employed method of interpreting data, in particular for AGN jets. These models can roughly constrain the properties of jets but they cannot unambiguously couple their emission to the launching regions and internal dynamics, which can be probed with simulations. However, simulations are not easily comparable to observations because they cannot yet self-consistently predict spectra. We present an advanced semi-analytical model which accounts for the dynamics of the whole jet, starting from a simplified parametrization of Relativistic Magnetohydrodynamics in which the magnetic flux is converted into bulk kinetic energy. To benchmark the model we fit six quasisimultaneous, multi-wavelength spectral energy distributions of the BL Lac PKS 2155-304 obtained by the TANAMI program, and we address the degeneracies inherent to such a complex model by employing a state-of-the-art exploration of parameter space, which so far has been mostly neglected in the study of AGN jets. We find that this new approach is much more effective than a single-epoch fit in providing meaningful constraints on model parameters.Comment: Accepted for publication on MNRA

The Walt Disney Company: A Corporate Strategy Analysis

Walt Disney is a completely integrated media powerhouse. Films provide material for theme parks and resorts, consumer products, and even a cruise ship. Network and cable broadcasting is also a part of the integrated Disney package. None of Disney’s competitors are as successfully integrated. Still, in spite of a long record of success, Disney is facing more competition on many fronts and, like other media and entertainment companies, must continue to adapt to a changing technological and social environment

Combining timing characteristics with physical broad-band spectral modelling of black hole X-ray binary GX 339–4

GX 339–4 is a black hole X-ray binary that is a key focus of accretion studies, since it goes into outburst roughly every 2–3 yr. Tracking of its radio, infrared (IR), and X-ray flux during multiple outbursts reveals tight broad-band correlations. The radio emission originates in a compact, self-absorbed jet; however, the origin of the X-ray emission is still debated: jet base or corona? We fit 20 quasi-simultaneous radio, IR, optical, and X-ray observations of GX 339–4 covering three separate outbursts in 2005, 2007, 2010–2011, with a composite corona+jet model, where inverse Compton emission from both regions contributes to the X-ray emission. Using a recently proposed identifier of the X-ray variability properties known as power-spectral hue, we attempt to explain both the spectral and evolving timing characteristics, with the model. We find the X-ray spectra are best fit by inverse Compton scattering in a dominant hot corona (kT_e ∼ hundreds of keV). However, radio and IR-optical constraints imply a non-negligible contribution from inverse Compton scattering off hotter electrons (kT_e ≥ 511 keV) in the base of the jets, ranging from a few up to ∼50 per cent of the integrated 3–100 keV flux. We also find that the physical properties of the jet show interesting correlations with the shape of the broad-band X-ray variability of the source, posing intriguing suggestions for the connection between the jet and corona

Combining timing characteristics with physical broad-band spectral modelling of black hole X-ray binary GX 339-4

GX 339-4 is a black hole X-ray binary that is a key focus of accretion studies, since it goes into outburst roughly every 2-3 yr. Tracking of its radio, infrared (IR), and X-ray flux during multiple outbursts reveals tight broad-band correlations. The radio emission originates in a compact, self-absorbed jet; however, the origin of the X-ray emission is still debated: jet base or corona? We fit 20 quasi-simultaneous radio, IR, optical, and X-ray observations of GX 339-4 covering three separate outbursts in 2005, 2007, 2010-2011, with a composite corona+jet model, where inverse Compton emission from both regions contributes to the X-ray emission. Using a recently proposed identifier of the X-ray variability properties known as power-spectral hue, we attempt to explain both the spectral and evolving timing characteristics, with the model. We find the X-ray spectra are best fit by inverse Compton scattering in a dominant hot corona (kT(e) similar to hundreds of keV). However, radio and IR-optical constraints imply a non-negligible contribution from inverse Compton scattering off hotter electrons (kT(e) >= 511 keV) in the base of the jets, ranging from a few up to similar to 50 per cent of the integrated 3-100 keV flux. We also find that the physical properties of the jet show interesting correlations with the shape of the broad-band X-ray variability of the source, posing intriguing suggestions for the connection between the jet and corona

Large amplitude solitary waves in and near the Earth's magnetosphere, magnetopause and bow shock: Polar and Cluster observations

International audienceSolitary waves with large electric fields (up to 100's of mV/m) have been observed throughout the magnetosphere and in the bow shock. We discuss observations by Polar at high altitudes ( ~ 4-8 RE ), during crossings of the plasma sheet boundary and cusp, and new measurements by Polar at the equatorial magnetopause and by Cluster near the bow shock, in the cusp and at the plasma sheet boundary. We describe the results of a statistical study of electron solitary waves observed by Polar at high altitudes. The mean solitary wave duration was ~ 2 ms. The waves have velocities from ~ 1000 km/s to > 2500 km/s. Observed scale sizes (parallel to the magnetic field) are on the order of 1-10lD, with eF/kTe from ~ 0.01 to O(1). The average speed of solitary waves at the plasma sheet boundary is faster than the average speed observed in the cusp and at cusp injections. The amplitude increases with both velocity and scale size. These observations are all consistent with the identification of the solitary waves as electron hole modes. We also report the discovery of solitary waves at the magnetopause, observed in Polar data obtained at the subsolar equatorial magnetopause. Both positive and negative potential structures have been observed with amplitudes up to ~ 25 mV/m. The velocities range from 150 km/s to >2500 km/s, with scale sizes the order of a kilometer (comparable to the Debye length). Initial observations of solitary waves by the four Cluster satellites are utilized to discuss the scale sizes and time variability of the regions where the solitary waves occur. Preliminary results from the four Cluster satellites have given a glimpse of the spatial and temporal variability of the occurrence of solitary waves and their association with other wave modes. In all the events studied, significant differences were observed in the waveforms observed simultaneously at the four locations separated by ~ 1000 km. When solitary waves were seen at one satellite, they were usually also seen at the other satellites within an interval of a few seconds. In association with an energetic electron injection and a highly compressed magnetosphere, Cluster has observed the largest amplitude solitary waves (>750 mV/m) ever reported in the outer magnetosphere

Neutrophil/lymphocyte ratio predicts chemotherapy outcomes in patients with advanced colorectal cancer

BACKGROUND: Advances in the treatment of metastatic colorectal cancer (mCRC) in the last decade have significantly improved survival; however, simple biomarkers to predict response or toxicity have not been identified, which are applicable to all community oncology settings worldwide. The use of inflammatory markers based on differential white-cell counts, such as the neutrophil/ lymphocyte ratio (NLR), may be simple and readily available biomarkers. METHODS: Clinical information and baseline laboratory parameters were available for 349 patients, from two independent cohorts, with unresectable mCRC receiving first-line palliative chemotherapy. Associations between baseline prognostic variables, including inflammatory markers such as the NLR and tumour response, progression and survival were investigated. RESULTS: In the training cohort, combination-agent chemotherapy (P ¼ 0.001) and NLRp5 (P ¼ 0.003) were associated with improved clinical benefit. The ECOG performance status X1 (P ¼ 0.002), NLR45 (P ¼ 0.01), hypoalbuminaemia (P ¼ 0.03) and single-agent chemotherapy (Po0.0001) were associated with increased risk of progression. The ECOG performance status X1 (P ¼ 0.004) and NLR45 (P ¼ 0.002) predicted worse overall survival (OS). The NLR was confirmed to independently predict OS in the validation cohort (Po0.0001). Normalisation of the NLR after one cycle of chemotherapy in a subset of patients resulted in improved progression-free survival (P ¼ 0.012). CONCLUSION: These results have highlighted NLR as a potentially useful clinical biomarker of systemic inflammatory response in predicting clinically meaningful outcomes in two independent cohorts. Results of this study have also confirmed the importance of a chronic systemic inflammatory response influencing clinical outcomes in patients with mCRC