485 research outputs found
An X-Ray View of the Jet-Cycle in the Radio Loud AGN 3C120
We present a study of the central engine in the broad-line radio galaxy 3C120
using a multi-epoch analysis of a deep XMM-Newton observation and two deep
Suzaku pointings (in 2012). In order to place our spectral data into the
context of the disk-disruption/jet-ejection cycles displayed by this object, we
monitor the source in the UV/X-ray bands, and in the radio band. We find three
statistically acceptable spectral models, a disk-reflection model, a jet-model
and a jet+disk model. Despite being good descriptions of the data, the
disk-reflection model violates the radio constraints on the inclination, and
the jet-model has a fine-tuning problem, requiring a jet contribution exceeding
that expected. Thus, we argue for a composite jet+disk model. Within the
context of this model, we verify the basic predictions of the jet-cycle
paradigm, finding a truncated/refilling disk during the Suzaku observations and
a complete disk extending down to the innermost stable circular orbit (ISCO)
during the XMM-Newton observation. The idea of a refilling disk is further
supported by the detection of the ejection of a new jet knot approximately one
month after the Suzaku pointings. We also discover a step-like event in one of
the Suzaku pointings in which the soft band lags the hard band. We suggest that
we are witnessing the propagation of a disturbance from the disk into the jet
on a timescale set by the magnetic field.Comment: 14 pages, 10 figures, accepted for publication in Ap
Airfoil Selection and Wingsail Design for an Autonomous Sailboat
Part of the Advances in Intelligent Systems and Computing book series (AISC, volume 1092)Ocean exploration and monitoring with autonomous platforms can provide researchers and decision makers with valuable data, trends and insights into the largest ecosystem on Earth. Regardless of the recognition of the importance of such platforms in this scenario, their design and development remains an open challenge. In particular, energy efficiency, control and robustness are major concerns with implications in terms of autonomy and sustainability. Wingsails allow autonomous boats to navigate with increased autonomy, due to lower power consumption, and greater robustness, due to simpler control. Within the scope of a project that addresses the design, development and deployment of a rigid wing autonomous sailboat to perform long term missions in the ocean, this paper summarises the general principles for airfoil selection and wingsail design in robotic sailing, and are given some insights on how these aspects influence the autonomous sailboat being developed by the authors.info:eu-repo/semantics/publishedVersio
RESULTS OF THE FIRST SIMULTANEOUS X-RAY, OPTICAL, AND RADIO CAMPAIGN ON THE BLAZAR PKS 1622-297
Coordinated X-ray, optical, and radio observations of the blazar PKS 1622-297 were obtained during a three-week campaign in 2006 using the Rossi X-Ray Timing Explorer (RXTE), the University of Michigan Radio Astronomy Observatory, and optical telescopes at Cerro Tololo Inter-American Observatory. The RXTE observations indicate that this object is a comparatively weak X-ray emitter for a Flat-Spectrum Radio Quasar. The observed broadband spectral shape indicates that X-rays were most likely produced by the Inverse Compton processes. Optical observations of this object produced unexpected results in that this object appeared redder when in a bright state and bluer when in a faint state, contrary to the observed behavior of BL Lac objects
New Multiwavelength Observations of PKS 2155-304 and Implications for the Coordinated Variability Patterns of Blazars
The TeV blazar PKS 2155--304 was the subject of an intensive 2 week optical
and near-infrared observing campaign in 2004 August with the CTIO 0.9m
telescope. During this time, simultaneous X-ray data from RXTE were also
obtained. We compare the results of our observations to the results from two
previous simultaneous multiwavelength campaigns on PKS 2155-304. We conclude
that the correlation between the X-ray and UV/optical variability is strongest
and the time lag is shortest (only a few hours) when the object is brightest.
As the object becomes fainter, the correlations are weaker and the lags longer,
increasing to a few days. Based on the results of four campaigns, we find
evidence for a linear relationship between the mean optical brightness and lag
time of X-ray and UV/optical events. Furthermore, we assert that this behavior,
along with the different multiwavelength flare lag times across different flux
states is consistent with a highly relativistic shock propagating down the jet
producing the flares observed during a high state. In a quiescent state, the
variability is likely to be due to a number of factors including both the jet
and contributions outside of the jet, such as the accretion disk.Comment: 23 pages, 8 figures, to be published in the Astrophysical Journal,
volume 67
Editorial: Translational insights into mechanisms and therapy of organ dysfunction in sepsis and trauma
Multiple organ dysfunction or even failure after sepsis or trauma is due to a dysregulated host response. Currently, besides (surgical) source control (e.g., control of bleeding or drainage of abscesses) and administration of antimicrobial drugs, therapeutic approaches are limited to supportive care. Advances in our understanding of the key pathophysiological pathways involved in the excessive inflammation triggered by trauma, sepsis and/or ischemia-reperfusion have had limited impact. The 28 article in this Research Topic focus on the molecular mechanisms behind (hyper) inflammation after sepsis or trauma, with special emphasis on preclinical and translational studies that target potential organ-protective and/or -resuscitative therapeutic strategies. Most studies report rodent models of trauma and elective surgery (three articles), non-microbial hyper-inflammation induced with endotoxin exposure (LPS; seven articles) and chemical pancreatitis (one article), and cecal ligation and puncture-induced sepsis (six articles). Additional papers summarize investigations of human material (six articles) or fully-resuscitated large animal models (two articles). These article are complimented by four reviews and a commentary
The TREAT-NMD advisory committee for therapeutics (TACT): an innovative de-risking model to foster orphan drug development
Despite multiple publications on potential therapies for neuromuscular diseases (NMD) in cell and animal models only a handful reach clinical trials. The ability to prioritise drug development according to objective criteria is particularly critical in rare diseases with large unmet needs and a limited numbers of patients who can be enrolled into clinical trials. TREAT-NMD Advisory Committee for Therapeutics (TACT) was established to provide independent and objective guidance on the preclinical and development pathway of potential therapies (whether novel or repurposed) for NMD. We present our experience in the establishment and operation of the TACT. TACT provides a unique resource of recognized experts from multiple disciplines. The goal of each TACT review is to help the sponsor to position the candidate compound along a realistic and well-informed plan to clinical trials, and eventual registration. The reviews and subsequent recommendations are focused on generating meaningful and rigorous data that can enable clear go/no-go decisions and facilitate longer term funding or partnering opportunities. The review process thereby acts to comment on viability, de-risking the process of proceeding on a development programme. To date TACT has held 10 review meeting and reviewed 29 program applications in several rare neuromuscular diseases: Of the 29 programs reviewed, 19 were from industry and 10 were from academia; 15 were for novel compounds and 14 were for repurposed drugs; 16 were small molecules and 13 were biologics; 14 were preclinical stage applications and 15 were clinical stage applications. 3 had received Orphan drug designation from European Medicines Agency and 3 from Food and Drug Administration. A number of recurrent themes emerged over the course of the reviews and we found that applicants frequently require advice and education on issues concerned with preclinical standard operating procedures, interactions with regulatory agencies, formulation, repurposing, clinical trial design, manufacturing and ethics. Over the 5 years since its establishment TACT has amassed a body of experience that can be extrapolated to other groups of rare diseases to improve the community's chances of successfully bringing new rare disease drugs to registration and ultimately to marke
Novel gene expression responses in the ovine abomasal mucosa to infection with the gastric nematode Teladorsagia circumcincta
Infection of sheep with the gastric nematode Teladorsagia circumcincta results in distinct Th2-type changes in the mucosa, including mucous neck cell and mast cell hyperplasia, eosinophilia, recruitment of IgA/IgE producing cells and neutrophils, altered T-cell subsets and mucosal hypertrophy. To address the protective mechanisms generated in animals on previous exposure to this parasite, gene expression profiling was carried out using samples of abomasal mucosa collected pre- and post- challenge from animals of differing immune status, using an experimental model of T. circumcincta infection. Recently developed ovine cDNA arrays were used to compare the abomasal responses of sheep immunised by trickle infection with worm-naïve sheep, following a single oral challenge of 50 000 T. circumcincta L3. Key changes were validated using qRT-PCR techniques. Immune animals demonstrated highly significant increases in levels of transcripts normally associated with cytotoxicity such as granulysin and granzymes A, B and H, as well as mucous-cell derived transcripts, predominantly calcium-activated chloride channel 1 (CLCA1). Challenge infection also induced up-regulation of transcripts potentially involved in initiating or modulating the immune response, such as heat shock proteins, complement factors and the chemokine CCL2. In contrast, there was marked infection-associated down-regulation of gene expression of members of the gastric lysozyme family. The changes in gene expression levels described here may reflect roles in direct anti-parasitic effects, immuno-modulation or tissue repair. (Funding; DEFRA/SHEFC (VT0102) and the BBSRC (BB/E01867X/1))
Novel gene expression responses in the ovine abomasal mucosa to infection with the gastric nematode Teladorsagia circumcincta
Infection of sheep with the gastric nematode Teladorsagia circumcincta results in distinct Th2-type changes in the mucosa, including mucous neck cell and mast cell hyperplasia, eosinophilia, recruitment of IgA/IgE producing cells and neutrophils, altered T-cell subsets and mucosal hypertrophy. To address the protective mechanisms generated in animals on previous exposure to this parasite, gene expression profiling was carried out using samples of abomasal mucosa collected pre- and post- challenge from animals of differing immune status, using an experimental model of T. circumcincta infection. Recently developed ovine cDNA arrays were used to compare the abomasal responses of sheep immunised by trickle infection with worm-naïve sheep, following a single oral challenge of 50 000 T. circumcincta L3. Key changes were validated using qRT-PCR techniques. Immune animals demonstrated highly significant increases in levels of transcripts normally associated with cytotoxicity such as granulysin and granzymes A, B and H, as well as mucous-cell derived transcripts, predominantly calcium-activated chloride channel 1 (CLCA1). Challenge infection also induced up-regulation of transcripts potentially involved in initiating or modulating the immune response, such as heat shock proteins, complement factors and the chemokine CCL2. In contrast, there was marked infection-associated down-regulation of gene expression of members of the gastric lysozyme family. The changes in gene expression levels described here may reflect roles in direct anti-parasitic effects, immuno-modulation or tissue repair. (Funding; DEFRA/SHEFC (VT0102) and the BBSRC (BB/E01867X/1))
Disk-Jet Connection in the Radio Galaxy 3C 120
We present the results of extensive multi-frequency monitoring of the radio
galaxy 3C 120 between 2002 and 2007 at X-ray, optical, and radio wave bands, as
well as imaging with the Very Long Baseline Array (VLBA). Over the 5 yr of
observation, significant dips in the X-ray light curve are followed by
ejections of bright superluminal knots in the VLBA images. Consistent with
this, the X-ray flux and 37 GHz flux are anti-correlated with X-ray leading the
radio variations. This implies that, in this radio galaxy, the radiative state
of accretion disk plus corona system, where the X-rays are produced, has a
direct effect on the events in the jet, where the radio emission originates.
The X-ray power spectral density of 3C 120 shows a break, with steeper slope at
shorter timescale and the break timescale is commensurate with the mass of the
central black hole based on observations of Seyfert galaxies and black hole
X-ray binaries. These findings provide support for the paradigm that black hole
X-ray binaries and active galactic nuclei are fundamentally similar systems,
with characteristic time and size scales linearly proportional to the mass of
the central black hole. The X-ray and optical variations are strongly
correlated in 3C 120, which implies that the optical emission in this object
arises from the same general region as the X-rays, i.e., in the accretion
disk-corona system. We numerically model multi-wavelength light curves of 3C
120 from such a system with the optical-UV emission produced in the disk and
the X-rays generated by scattering of thermal photons by hot electrons in the
corona. From the comparison of the temporal properties of the model light
curves to that of the observed variability, we constrain the physical size of
the corona and the distances of the emitting regions from the central BH.Comment: Accepted for publication in the Astrophysical Journal. 28 pages, 21
figures, 2 table
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
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