The millisecond-duration radio flashes known as fast radio bursts (FRBs) represent an enigmatic astrophysical phenomenon. Recently, the sub-arcsecond localization (∼100 mas precision) of FRB 121102 ...using the Very Large Array has led to its unambiguous association with persistent radio and optical counterparts, and to the identification of its host galaxy. However, an even more precise localization is needed in order to probe the direct physical relationship between the millisecond bursts themselves and the associated persistent emission. Here, we report very-long-baseline radio interferometric observations using the European VLBI Network and the 305 m Arecibo telescope, which simultaneously detect both the bursts and the persistent radio emission at milliarcsecond angular scales and show that they are co-located to within a projected linear separation of 40 pc ( 12 mas angular separation, at 95% confidence). We detect consistent angular broadening of the bursts and persistent radio source (∼2-4 mas at 1.7 GHz), which are both similar to the expected Milky Way scattering contribution. The persistent radio source has a projected size constrained to be 0.7 pc ( 0.2 mas angular extent at 5.0 GHz) and a lower limit for the brightness temperature of T b 5 × 10 7 K . Together, these observations provide strong evidence for a direct physical link between FRB 121102 and the compact persistent radio source. We argue that a burst source associated with a low-luminosity active galactic nucleus or a young neutron star energizing a supernova remnant are the two scenarios for FRB 121102 that best match the observed data.
Climatic conditions and cultural practices in the sub-tropical and tropical high-rainfall regions in which sugarcane is grown in Australia are conducive to rapid carbon and nitrogen cycling. Previous ...research has identified substantial exchanges of methane (CH
4) and nitrous oxide (N
2O) between sugarcane soils and the atmosphere. However, that research has been mostly short-term. This paper describes recent work aimed at quantifying exchanges of CH
4 and N
2O from fertilised sugarcane soils over whole growing seasons. Micrometeorological and chamber techniques provided continuous measurements of gas emissions in whole-of-season studies in a burnt-cane crop on an acid sulfate soil (ASS) that was fertilised with 160
kg nitrogen (N)
ha
−1 as urea in the south of the sugarcane belt (Site 1), and in a crop on a more representative trash-blanketed soil fertilised with 150
kg urea-N
ha
−1 in the north (Site 2). Site 1 was a strong source of CH
4 with a seasonal emission (over 342 days) of 19.9
kg CH
4
ha
−1. That rate corresponds to 0.5–5% of those expected from rice and wetlands. The many drains in the region appear to be the main source. The net annual emission of CH
4 at Site 2 over 292 days was essentially zero, which contradicts predictions that trash-blankets on the soil are net CH
4 sinks. Emissions of N
2O from the ASS at Site 1 were extraordinarily large and prolonged, totalling 72.1
kg
N
2O
ha
−1 (45.9
kg
N
ha
−1) and persisting at substantial rates for 5 months. The high porosity and frequent wetting with consequent high water filled pore space and the high carbon content of the soil appear to be important drivers of N
2O production. At Site 2, emissions were much smaller, totalling 7.4
kg
N
2O
ha
−1 (4.7
kg
N
ha
−1), most of which was emitted in less than 3 months. The emission factors for N
2O (the proportion of fertiliser nitrogen emitted as N
2O–N) were 21% at Site 1 and 2.8% at Site 2. Both factors exceed the default national inventory value of 1.25%. Calculations suggest that annual N
2O production from Australian sugarcane soils is around 3.8
kt
N
2O, which is about one-half a previous estimate based on short-term measurements, and although ASS constitute only about 4% of Australia's sugarcane soils, they could contribute about 25% of soil emissions of N
2O from sugarcane. The uptake of 50–94
t
CO
2
ha
−1 from the atmosphere by the crops at both sites was offset by emissions of CH
4 and N
2O to the atmosphere amounting to 22
t
CO
2-e
ha
−1 at Site 1 and 2
t
CO
2-e
ha
−1 at Site 2.
Abstract Background Endovascular graft designs incorporating sidebranches, fenestrations and scallops offer a minimally-invasive alternative to open surgery and hybrid approaches for thoracoabdominal ...aortic aneurysms (TAAA). Our unit has offered total endovascular TAAA repair to selected higher-risk patients since 2008. We report the largest UK series to date of total endovascular TAAA repair. Methods Retrospective analysis of a prospectively-maintained operative database. Results 31 patients (21 male, 10 female) median age 71 years (range 58–84), with TAAA (12 Crawford type I, 13 type III, 6 type IV), median diameter 6.4 (4.3 (mycotic)- 9.9) underwent endovascular TAAA repair (total 48 sidebranches, 26 fenestrations, 13 scallops) between July 2008 and January 2011. Median operating time 225 min (65–540 min), X-ray screening time 58 min (4–212 min), contrast dose 175 ml (70–500 ml), blood loss 325 ml (100–400 ml). Median post-operative length of hospital stay 6 days (2–22 days). Three patients (3/31, 9.7%) died within 30 days of operation: multisystem organ failure (1) acute renal failure and paraplegia (1) and paraplegia (1). There were no other cases of in-hospital organ failure, paraplegia or major complications. The median change in pre-discharge from pre-operative renal function was 3.4% deterioration in eGFR (range: 32.7% deterioration to 73.0% improvement) One patient presented with late-onset paraparesis, a second developed acute renal failure 8 months after repair. One early high-pressure endoleak (type 3) required correction. Three patients had died by median follow-up 12 months (1–36), 2 from heart disease and one from haemopericardium secondary to acute dissection of the ascending aorta (the dissection did not involve, nor extend close to, the endovascular graft). Conclusions Total endovascular repair of TAAA offers patients a minimally-invasive alternative to open surgery with early results at least comparable to those seen with open or hybrid surgical approaches.
Fenestrated endovascular repair of abdominal aortic aneurysms has been proposed as an alternative to open surgery for juxtarenal and pararenal abdominal aortic aneurysms. At present, the evidence ...base for this procedure is predominantly limited to single-center or single-operator series. The aim of this study was to present nationwide early results of fenestrated endovascular repair in the United Kingdom.
All patients who underwent fenestrated endovascular repair between January 2007 and December 2010 at experienced institutions in the United Kingdom(>10 procedures) were retrospectively studied by use of the GLOBALSTAR database. Site-reported data relating to patient demographics, aneurysm morphology, procedural details, and outcome were recorded. Data from 318 patients were obtained from 14 centers. Primary procedural success was achieved in 99% (316/318); perioperative mortality was 4.1%, and intraoperative target vessel loss was observed in 5 of 889 target vessels (0.6%). The early reintervention (<30 days) rate was 7% (22/318). There were 11 deaths during follow-up; none were aneurysm-related. Survival by Kaplan-Meier analysis was 94% (SE 0.01), 91% (0.02), and 89% (0.02) at 1, 2, and 3 years, respectively. Freedom from target vessel loss was 93% (0.02), 91% (0.02), and 85% (0.06), and freedom from late secondary intervention (>30 days) was 90% (0.02), 86% (0.03), and 70% (0.08) at 1, 2, and 3 years.
In this national sample, fenestrated endovascular repair has been performed with a high degree of technical and clinical success. Late survival and target vessel patency are satisfactory. These results support continued use and evaluation of this technique for juxtarenal aneurysms, but illustrate the need for a more robust evidence base.
The Arecibo Observatory (AO) is a multidisciplinary research and education facility that is recognized worldwide as a leading facility in astronomy, planetary, and atmospheric and space sciences. ...AO's cornerstone research instrument was the 305-m William E. Gordon telescope. On December 1, 2020, the 305-m telescope collapsed and was irreparably damaged. In the three weeks following the collapse, AO's scientific and engineering staff and the AO users community initiated extensive discussions on the future of the observatory. The community is in overwhelming agreement that there is a need to build an enhanced, next-generation radar-radio telescope at the AO site. From these discussions, we established the set of science requirements the new facility should enable. These requirements can be summarized briefly as: 5 MW of continuous wave transmitter power at 2 - 6 GHz, 10 MW of peak transmitter power at 430 MHz (also at 220MHz under consideration), zenith angle coverage 0 to 48 deg, frequency coverage 0.2 to 30 GHz and increased Field-of-View. These requirements determine the unique specifications of the proposed new instrument. The telescope design concept we suggest consists of a compact array of fixed dishes on a tiltable, plate-like structure with a collecting area equivalent to a 300m dish. This concept, referred to as the Next Generation Arecibo Telescope (NGAT), meets all of the desired specifications and provides significant new science capabilities to all three research groups at AO. This whitepaper presents a sample of the wide variety of the science that can be achieved with the NGAT, the details of the telescope design concept and the need for the new telescope to be located at the AO site. We also discuss other AO science activities that interlock with the NGAT in the white paper.
The millisecond-duration radio flashes known as Fast Radio Bursts (FRBs) represent an enigmatic astrophysical phenomenon. Recently, the sub-arcsecond localization (~ 100mas precision) of FRB121102 ...using the VLA has led to its unambiguous association with persistent radio and optical counterparts, and to the identification of its host galaxy. However, an even more precise localization is needed in order to probe the direct physical relationship between the millisecond bursts themselves and the associated persistent emission. Here we report very-long-baseline radio interferometric observations using the European VLBI Network and the 305-m Arecibo telescope, which simultaneously detect both the bursts and the persistent radio emission at milliarcsecond angular scales and show that they are co-located to within a projected linear separation of < 40pc (< 12mas angular separation, at 95% confidence). We detect consistent angular broadening of the bursts and persistent radio source (~ 2-4mas at 1.7GHz), which are both similar to the expected Milky Way scattering contribution. The persistent radio source has a projected size constrained to be < 0.7pc (< 0.2mas angular extent at 5.0GHz) and a lower limit for the brightness temperature of T_b > 5 x 10^7K. Together, these observations provide strong evidence for a direct physical link between FRB121102 and the compact persistent radio source. We argue that a burst source associated with a low-luminosity active galactic nucleus or a young neutron star energizing a supernova remnant are the two scenarios for FRB121102 that best match the observed data.
There has been an explosion of new findings recently giving us insights into the involvement of microglia in central nervous system (CNS) disorders. A host of new molecular tools and mouse models of ...disease are increasingly implicating this enigmatic type of nervous system cell as a key player in conditions ranging from neurodevelopmental disorders such as autism to neurodegenerative disorders such as Alzheimer's disease and chronic pain. Contemporaneously, diverse roles are emerging for microglia in the healthy brain, from sculpting developing neuronal circuits to guiding learning-associated plasticity. Understanding the physiological functions of these cells is crucial to determining their roles in disease. Here we focus on recent developments in our rapidly expanding understanding of the function, as well as the dysfunction, of microglia in disorders of the CNS.
Recent findings challenge the concept that microglia solely function in disease states in the central nervous system (CNS). Rather than simply reacting to CNS injury, infection, or pathology, ...emerging lines of evidence indicate that microglia sculpt the structure of the CNS, refine neuronal circuitry and network connectivity, and contribute to plasticity. These physiological functions of microglia in the normal CNS begin during development and persist into maturity. Here, we develop a conceptual framework for functions of microglia beyond neuroinflammation and discuss the rich repertoire of signaling and communication motifs in microglia that are critical both in pathology and for the normal physiology of the CNS.
Evidence is accumulating that microglia, once thought of largely as injury-response cells for the brain, play important roles in shaping neuronal circuitry and influencing synaptic plasticity.
Neuropathic pain is a common and severely disabling state that affects millions of people worldwide. Such pain can be experienced after nerve injury or as part of diseases that affect peripheral ...nerve function, such as diabetes and AIDS; it can also be a component of pain in other conditions, such as cancer. Following peripheral nerve injury, microglia in the spinal cord become activated. Recent evidence indicates that activated microglia are key cellular intermediaries in the pathogenesis of nerve injury-induced pain hypersensitivity because P2X
4 purinoceptors and p38 mitogen-activated protein kinase, which are present in activated microglia, are required molecular mediators. It is important to establish how these molecules are activated in spinal microglia following nerve injury and how they cause signaling to neurons in the dorsal horn pain transmission network. Answers to these questions could lead to new strategies that assist in the diagnosis and management of neuropathic pain – strategies not previously anticipated by a neuron-centric view of pain plasticity in the dorsal horn.
The detection and processing of painful stimuli in afferent sensory neurons is critically dependent on a wide range of different types of voltage- and ligand-gated ion channels, including sodium, ...calcium, and TRP channels, to name a few. The functions of these channels include the detection of mechanical and chemical insults, the generation of action potentials and regulation of neuronal firing patterns, the initiation of neurotransmitter release at dorsal horn synapses, and the ensuing activation of spinal cord neurons that project to pain centers in the brain. Long-term changes in ion channel expression and function are thought to contribute to chronic pain states. Many of the channels involved in the afferent pain pathway are permeable to calcium ions, suggesting a role in cell signaling beyond the mere generation of electrical activity. In this article, we provide a broad overview of different calcium-permeable ion channels in the afferent pain pathway and their role in pain pathophysiology.
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