Statistical study of multi-frequency emission in blazars

Blazars are active galactic nuclei characterized by ultra-luminous broad-band, non-thermal radio to gamma-ray continuum radiation, and by irregular, rapid flux variability across wavebands. They are divided into two subclasses: BL Lac objects and flat spectrum radio quasars (FSRQs). A primary method employed to probe our understanding of these objects is to study their spectral energy distributions (SEDs). Until recently, however, studies of blazar SEDs have been hindered by an insufficient number of simultaneous observations across the spectrum, a critical deficiency with such variable objects. In this thesis, I discuss the data accumulated by an international, long-term, 35-blazar monitoring program led by the Boston University blazar group. By systematically processing these data, I produce SEDs using measurements obtained on average within nine hours per epoch. Sufficient measurements exist within the data set to study the sources in differing states of activity. I propose a definition of quiescent and active states, and extract measurements for epochs during which the sources were either quiescent or active in the gamma-ray regime. For these epochs, I measure the spectral slopes and statistically analyze the relationships between slopes at the different frequency regimes. While the subclasses exhibit some distinct characteristics in the optical and gamma-ray indices when quiescent, these distinctions are significantly less pronounced when the objects are active. The spectral indices for the FSRQs steepen when active in the optical, flatten in the gamma-ray, and remain flat and stable in the X-ray. Generally, BL Lacs exhibit less pronounced changes between states than do the FSRQs

Modeling the time-dependent polarization of blazars

Linear polarization is an extremely valuable observational tool for probing the dynamic physical conditions of blazar jets. Some patterns are seen in the data, suggestive of order that can be explained by shock waves and helical magnetic field components. However, much disorder is apparent, which implies that turbulence plays a major role as well, especially in the fluctuations of flux and polarization, and perhaps particle acceleration. Here, we present some actual flux and polarization versus time data, plus simulations of model jets. We analyze the output of the simulations in a manner that can be compared with observational data. The results suggest that the ratio of turbulent to ordered magnetic fields varies with time.AST-1615796 - National Science Foundation; NASA; NNX14AQ58G; NNX15AR45

Going batty: the challenges and opportunities of using drones to monitor the behaviour and habitat use of rays

The way an animal behaves in its habitat provides insight into its ecological role. As such, collecting robust, accurate datasets in a time-efficient manner is an ever-present pressure for the field of behavioural ecology. Faced with the shortcomings and physical limitations of traditional ground-based data collection techniques, particularly in marine studies, drones offer a low-cost and efficient approach for collecting data in a range of coastal environments. Despite drones being widely used to monitor a range of marine animals, they currently remain underutilised in ray research. The innovative application of drones in environmental and ecological studies has presented novel opportunities in animal observation and habitat assessment, although this emerging field faces substantial challenges. As we consider the possibility to monitor rays using drones, we face challenges related to local aviation regulations, the weather and environment, as well as sensor and platform limitations. Promising solutions continue to be developed, however, growing the potential for drone-based monitoring of behaviour and habitat use of rays. While the barriers to enter this field may appear daunting for researchers with little experience with drones, the technology is becoming increasingly accessible, helping ray researchers obtain a wide range of highly useful data

A single centre experience with sequential and concomitant chemoradiotherapy in locally advanced stage IV tonsillar cancer

<p>Abstract</p> <p>Background</p> <p>Chemo-radiotherapy offers an alternative to primary surgery and adjuvant therapy for the management of locally advanced stage IV squamous cell carcinomas of the tonsil.</p> <p>Methods</p> <p>A retrospective analysis was performed of the outcomes of 41 patients with locoregionally advanced squamous cell carcinoma of the tonsil treated non-surgically at the Yorkshire Cancer Centre between January 2004 and December 2005. Due to long radiotherapy waiting times, patients received induction chemotherapy with cisplatin and 5-fluorouracil followed by either cisplatin concurrent chemoradiotherapy or radiotherapy alone.</p> <p>Results</p> <p>Median age was 55 years (range 34-76 years) and 28 (68%) patients were male. 35/41 patients (85%) received 2 or more cycles of induction chemotherapy. Following induction chemotherapy, 32/41 patients (78%) had a clinical response. Concomitant chemotherapy was given to 30/41 (73%). All patients received the planned radiotherapy dose with no delays. There were no treatment related deaths. Six (15%) patients had gastrostomy tubes placed before treatment, and 22 (54%) required nasogastric tube placement during or after treatment for nutritional support. 17 patients required unplanned admissions during treatment for supportive care. At 4 months post treatment assessment 35 out of 41 (85%) patients achieved complete clinical and radiographic response. Median follow-up is 38 months (8-61 months). Local and regional control rate in complete responders at 3 years was 91%. Distant metastases have been found in 4 (9.8%) patients. Three year progression-free survival rate in all patients is 75%. The 3-year cause specific survival and overall survival are 75% and 66% respectively.</p> <p>Conclusion</p> <p>Cisplatin-based induction and concurrent chemoradiotherapy provides excellent tumour control with acceptable toxicity for patients with locally advanced tonsillar cancer.</p

Multiwavelength Variations of 3C 454.3 during the November 2010 to January 2011 Outburst

We present multiwavelength data of the blazar 3C 454.3 obtained during an extremely bright outburst from November 2010 through January 2011. These include flux density measurements with the Herschel Space Observatory at five submillimeter-wave and far-infrared bands, the Fermi Large Area Telescope at gamma-ray energies, Swift at X-ray, ultraviolet (UV), and optical frequencies, and the Submillimeter Array at 1.3 mm. From this dataset, we form a series of 52 spectral energy distributions (SEDs) spanning nearly two months that are unprecedented in time coverage and breadth of frequency. Discrete correlation anlaysis of the millimeter, far-infrared, and gamma-ray light curves show that the variations were essentially simultaneous, indicative of co-spatiality of the emission, at these wavebands. In contrast, differences in short-term fluctuations at various wavelengths imply the presence of inhomegeneities in physical conditions across the source. We locate the site of the outburst in the parsec-scale core, whose flux density as measured on 7 mm Very Long Baseline Array images increased by 70 percent during the first five weeks of the outburst. Based on these considerations and guided by the SEDs, we propose a model in which turbulent plasma crosses a conical standing shock in the parsec-scale region of the jet. Here, the high-energy emission in the model is produced by inverse Compton scattering of seed photons supplied by either nonthermal radiation from a Mach disk, thermal emission from hot dust, or (for X-rays) synchrotron radiation from plasma that crosses the standing shock. For the two dates on which we fitted the model SED to the data, the model corresponds very well to the observations at all bands except at X-ray energies, where the spectrum is flatter than observed.Comment: Accepted for publication in Astrophysical Journal. 82 pages, 13 figure

Maximising the impact of global and national physical activity guidelines—the critical role of communication strategies

Objectives Physical activity guidelines are evidence-based statements on recommended physical activity levels for good health. Guidelines, in isolation, are unlikely to increase population levels of physical activity; appropriate and effective communication is fundamental to maximising their impact. The aim of this paper is to provide a planning framework for physical activity guideline communication, including an overview of key audiences, aims and approaches. Methods All authors considered and agreed on the three broad issues to address by consensus. We identified key sources of evidence through scoping of the literature and our knowledge of the research area. Results Whether guidelines are global or national, communication of the physical activity guidelines should be informed by: (1) a situational analysis that considers the context in which the communication will take place and (2) a stakeholder analysis to determine the key target audiences for the communication and their values, needs and preferences. Audiences include policy-makers within and outside the health sector, other key stakeholders, the general public, specific population subgroups, health professionals and non-health professionals with a role in physical activity promotion. The aims and approach to communication will differ depending on the target audience. Conclusion Communication to raise awareness and knowledge of the physical activity guidelines must be supported by policies, environments and opportunities for physical activity. Besides the intrinsic value of the physical activity guidelines, it is essential that substantial effort is put in to diligently planning, funding and implementing their communication from the outset

Storage and export of microbial biomass across the western Greenland Ice Sheet

The Greenland Ice Sheet harbours a wealth of microbial life, yet the total biomass stored or exported from its surface to downstream environments is unconstrained. Here, we quantify microbial abundance and cellular biomass flux within the near-surface weathering crust photic zone of the western sector of the ice sheet. Using groundwater techniques, we demonstrate that interstitial water flow is slow (~10−2 m d−1), while flow cytometry enumeration reveals this pathway delivers 5 × 108 cells m−2 d−1 to supraglacial streams, equivalent to a carbon flux up to 250 g km−2 d−1. We infer that cellular carbon accumulation in the weathering crust exceeds fluvial export, promoting biomass sequestration, enhanced carbon cycling, and biological albedo reduction. We estimate that up to 37 kg km−2 of cellular carbon is flushed from the weathering crust environment of the western Greenland Ice Sheet each summer, providing an appreciable flux to support heterotrophs and methanogenesis at the bed

High Titers of Transmissible Spongiform Encephalopathy Infectivity Associated with Extremely Low Levels of PrPSc in Vivo

Rona Barron - ORCID: 0000-0003-4512-9177 https://orcid.org/0000-0003-4512-9177Diagnosis of transmissible spongiform encephalopathy (TSE) disease in humans and ruminants relies on the detection in post-mortem brain tissue of the protease-resistant form of the host glycoprotein PrP. The presence of this abnormal isoform (PrPSc) in tissues is taken as indicative of the presence of TSE infectivity. Here we demonstrate conclusively that high titers of TSE infectivity can be present in brain tissue of animals that show clinical and vacuolar signs of TSE disease but contain low or undetectable levels of PrPSc. This work questions the correlation between PrPSc level and the titer of infectivity and shows that tissues containing little or no proteinase K-resistant PrP can be infectious and harbor high titers of TSE infectivity. Reliance on protease-resistant PrPSc as a sole measure of infectivity may therefore in some instances significantly underestimate biological properties of diagnostic samples, thereby undermining efforts to contain and eradicate TSEs.https://doi.org/10.1074/jbc.M704329200282pubpub4