ϵ Eridani is a nearby, young Sun-like star that hosts a ring of cool debris analogous to the Solar system's Edgeworth–Kuiper belt. Early observations at (sub-)mm wavelengths gave tentative evidence ...of the presence of inhomogeneities in the ring, which have been ascribed to the effect of a putative low eccentricity planet, orbiting close to the ring. The existence of these structures has been recently challenged by high-resolution interferometric millimetre observations. Here, we present the deepest single-dish image of ϵ Eridani at millimetre wavelengths, obtained with the Large Millimetre Telescope Alfonso Serrano (LMT). The main goal of these LMT observations is to confirm (or refute) the presence of non-axisymmetric structure in the disc. The dusty ring is detected for the first time along its full projected elliptical shape. The radial extent of the ring is not spatially resolved and shows no evidence, to within the uncertainties, of dust density enhancements. Additional features of the 1.1 mm map are: (i) the presence of significant flux in the gap between the ring and the star, probably providing the first exo-solar evidence of Poynting–Robertson drag, (ii) an unambiguous detection of emission at the stellar position with a flux significantly above that expected from ϵ Eridani's photosphere, and (iii) the identification of numerous unresolved sources which could correspond to background dusty star-forming galaxies.
Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from ...stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.
The average age of the global human population is increasing, leading to increased interest in the effects of chronic disease and multimorbidity on health resources and patient welfare. It has been ...posited that the average age of the general veterinarian-attended horse population of the UK is also increasing, and therefore it could be assumed that chronic diseases and multimorbidity would pose an increasing risk here also. However, evidence for this trend in ageing is very limited, and the current prevalence of many chronic diseases, and of multimorbidity, is unknown. Using text mining of first-opinion electronic medical records from seven veterinary practices around the UK, Kaplan-Meier and Cox proportional hazard modelling, we were able to estimate the apparent prevalence among veterinarian-attended horses of nine chronic diseases, and to assess their relative effects on median life expectancy following diagnosis. With these methods we found evidence of increasing population age. Multimorbidity affected 1.2% of the study population, and had a significant effect upon survival times, with co-occurrence of two diseases, and three or more diseases, leading to 6.6 and 21.3 times the hazard ratio compared to no chronic disease, respectively. Laminitis was involved in 74% of cases of multimorbidity. The population of horses attended by UK veterinarians appears to be aging, and chronic diseases and their co-occurrence are common features, and as such warrant further investigation.
Caprolactam, a precursor to nylon-6 has been investigated as part of our studies into the polymerization of materials at high pressure. Single-crystal X-ray and neutron powder diffraction data have ...been used to explore the high-pressure phase behavior of caprolactam; two new high pressure solid forms were observed. The transition between each of the forms requires a substantial rearrangement of the molecules and we observe that the kinetic barrier to the conversion can aid retention of phases beyond their region of stability. Form II of caprolactam shows a small pressure region of stability between 0.5 GPa and 0.9 GPa with Form III being stable from 0.9 GPa to 5.4 GPa. The two high-pressure forms have a catemeric hydrogen-bonding pattern compared with the dimer interaction observed in ambient pressure Form I. The interaction between the chains has a marked effect on the directions of maximal compressibility in the structure. Neither of the high-pressure forms can be recovered to ambient pressure and there is no evidence of any polymerization occurring.
Age-related macular degeneration (AMD) is a major health problem in the developed world accounting for approximately half of all blind registrations. Current treatment options are unsuitable for the ...majority of patients and therefore the identification of modifiable risk factors that may inform disease prevention programmes is a priority. This review evaluates the long-held belief that blue light exposure has a role in the pathogenesis of AMD. Laboratory evidence has demonstrated that photochemical reactions in the oxygen-rich environment of the outer retina lead to the liberation of cytotoxic reactive oxygen species (ROS). These ROS cause oxidative stress which is known to contribute to the development of AMD. The precise chromopore that may be involved in the pathogenesis of AMD is unclear but the age pigment lipofuscin is a likely candidate. Its aerobic photoreactivity and adverse effects on antioxidant activity combined with its gradual accumulation over time suggests that its in vivo phototoxicity increases with age despite changes in the absorption characteristics of the crystalline lens. Evidence from animal studies confirms blue light's damaging potential but the results are not directly applicable to macular degeneration in humans. Studies of human macular pigment density and the risk of AMD progression following cataract surgery lend further weight to the hypothesis that blue light exposure has a role in the pathogenesis of AMD but the epidemiological evidence is equivocal. On balance the evidences suggests but does not yet confirm that blue light is a risk factor for AMD. Given the socio-economic impact of this disease and urgent need to identify modifiable risk factors, future work should include a large-scale clinical trial to evaluate the effect of blue blocking filters on AMD progression rates.
Using data from the Fermi Large Area Telescope (LAT), we report the first clear gamma -ray measurement of a delay between flares from the gravitationally lensed images of a blazar. The delay was ...detected in B0218+357, a known double-image lensed system, during a period of enhanced gamma -ray activity with peak fluxes consistently observed to reach > 20-50 x its previous average flux. An auto-correlation function analysis identified a delay in the gamma -ray data of 11.46 + or - 0.16 days (1sigma) that is ~1 day greater than previous radio measurements. Considering that it is beyond the capabilities of the LAT to spatially resolve the two images, we nevertheless decomposed individual sequences of superposing gamma -ray flares/delayed emissions. In three such ~8-10 day-long sequences within a ~4 month span, considering confusion due to overlapping flaring emission and flux measurement uncertainties, we found flux ratios consistent with ~1, thus systematically smaller than those from radio observations. During the first, best-defined flare, the delayed emission was detailed with a Fermi pointing, and we observed flux doubling timescales of ~3-6 hr implying as well extremely compact gamma -ray emitting regions.
In 1953 Medawar pointed out that survival of the genetically disparate (allogeneic) mammalian conceptus contradicts the laws of tissue transplantation. Rapid T cell-induced rejection of all ...allogeneic concepti occurred when pregnant mice were treated with a pharmacologic inhibitor of indoleamine 2,3-dioxygenase (IDO), a tryptophan-catabolizing enzyme expressed by trophoblasts and macrophages. Thus, by catabolizing tryptophan, the mammalian conceptus suppresses T cell activity and defends itself against rejection.
Electronic medical records from first opinion equine veterinary practice may represent a unique resource for epidemiologic research. The appropriateness of this resource for risk factor analyses was ...explored as part of an investigation into clinical and pharmacologic risk factors for laminitis. Amalgamated medical records from seven UK practices were subjected to text mining to identify laminitis episodes, systemic or intra-synovial corticosteroid prescription, diseases known to affect laminitis risk and clinical signs or syndromes likely to lead to corticosteroid use. Cox proportional hazard models and Prentice, Williams, Peterson models for repeated events were used to estimate associations with time to first, or subsequent laminitis episodes, respectively. Over seventy percent of horses that were diagnosed with laminitis suffered at least one recurrence. Risk factors for first and subsequent laminitis episodes were found to vary. Corticosteroid use (prednisolone only) was only significantly associated with subsequent, and not initial laminitis episodes. Electronic medical record use for such analyses is plausible and offers important advantages over more traditional data sources. It does, however, pose challenges and limitations that must be taken into account, and requires a conceptual change to disease diagnosis which should be considered carefully.
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