| 331. |
- Karamehmetoglu, Emir, et al.
(författare)
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OGLE-2014-SN-131 : A long-rising Type Ibn supernova from a massive progenitor
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 602
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Tidskriftsartikel (refereegranskat)abstract
- Context. Type Ibn supernovae (SNe Ibn) are thought to be the core-collapse explosions of massive stars whose ejecta interact with He-rich circumstellar material (CSM). Aims. We report the discovery of a SN Ibn, with the longest rise-time ever observed, OGLE-2014-SN-131. We discuss the potential powering mechanisms and the progenitor nature of this peculiar stripped-envelope (SE), circumstellar-interacting SN. Methods. Optical photometry and spectroscopy were obtained with multiple telescopes including VLT, NTT, and GROND. We compare light curves and spectra with those of other known SNe Ibn and Ibc. CSM velocities are derived from the spectral analysis. The SN light curve is modeled under di ff erent assumptions about its powering mechanism (56Ni decay, CSM-interaction, magnetar) in order to estimate the SN progenitor parameters. Results. OGLE-2014-SN-131 spectroscopically resembles SNe Ibn such as SN 2010al. Its peak luminosity and post-peak colors are also similar to those of other SNe Ibn. However, it shows an unprecedentedly long rise-time and a much broader light curve compared to other SNe Ibn. Its bolometric light curve can be reproduced by magnetar and CSM-interaction models, but not by a 56Ni-decay powering model. Conclusions. To explain the unusually long rise-time, the broad light curve, the light curve decline, and the spectra characterized by narrow emission lines, we favor a powering mechanism where the SN ejecta are interacting with a dense CSM. The progenitor of OGLE-2014-SN-131 was likely a Wolf-Rayet star with a mass greater than that of a typical SN Ibn progenitor, which expelled the CSM that the SN is interacting with.
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| 332. |
- Karltun, E., et al.
(författare)
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Surface reactivity of poorly-ordered minerals in podzol B horizons
- 2000
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 94:04-feb, s. 265-288
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Tidskriftsartikel (refereegranskat)abstract
- The surface reactivity of mineral soil horizons from three podzolised forest soils in Scandinavia was examined. The amount of accumulated C was low, between 1.8 and 2.3% in the top of the B horizons. Selective extractions in combination with infrared (IR) spectroscopy and transmission electron microscopy (TEM) indicated a predominance of poorly-ordered imogolite-type materials (ITM) in the oxalate extractable fraction in an examined B horizons. The presence of well-ordered imogolite was only indicated in the Nyanget B3 horizon. A large proportion of free Fe was removed by ammonium oxalate. Comparisons of Mossbauer spectra (both at room temperature and at 4.2 K) before and after treatment with ammonium oxalate showed that the oxalate treatment resulted in a removal of a (super)paramagnetic Fe3+ phase? probably ferrihydrite. A comparison of the Mossbauer Fe3+ parameters at room temperature and 4.2 K indicated a close intergrowth of a ferrihydrite-like oxide with a magnetically neutral matrix, e.g., allophane. The specific surface area (SSA) was determined by N-2 adsorption before and after treatment of the samples with acid ammonium oxalate. The loss of SSA after oxalate treatment was considerable in the B horizon where only between 3.8 to 13.38 of the original SSA remained after treatment. The point of zero charge salt effect (PZSE) increased with depth in the B horizon from between 4.4 and 5.1 in the upper horizons to between 5.7 and 7.7 in the lower part of the B horizon. The increased PZSE with depth paralleled a decrease in the ratio of pyrophosphate soluble C to oxalate soluble Fe + Al. The affinity for SO42-. a goad indicator of the presence of active surface hydroxyls, was measured by comparing the H+ buffering capacity of a sample titrated in 2.5 mM Na2SO4 with a sample titrated in 5 mh I NaNO3,. The buffering capacity of the soil in the Na2SO4, electrolyte was well correlated with the amount of oxalate minus pyrophosphate soluble Fe + Al (r(2) = 0.88). The sulphate exchange capacity was considerably higher than CEC, especially in lower parts of the B horizon. The calculated surface area of the oxalate soluble material (OSM) ranged between 74 and 289 m(2) g(-1) and the calculated surface site density of the same material ranged between 0.6 to 3.3 site nm(-2). It was concluded that the surface reactivity in the B horizons is dominated by the poorly-ordered variable-charge oxides resulting in a low capacity to retain cations but a high capacity for adsorption of weak acid anions like SO42- and organic acids.
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| 333. |
- Kemp, John P, et al.
(författare)
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Does bone resorption stimulate periosteal expansion? A cross sectional analysis of β-C-telopeptides of type I collagen (CTX), genetic markers of the RANKL pathway, and periosteal circumference as measured by pQCT.
- 2014
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Ingår i: Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research. - : Wiley. - 1523-4681. ; 29:4, s. 1015-1024
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Tidskriftsartikel (refereegranskat)abstract
- We hypothesised that bone resorption acts to increase bone strength through stimulation of periosteal expansion. Hence, we examined whether bone resorption, as reflected by serum β-C-telopeptides of type I collagen (CTX), is positively associated with periosteal circumference (PC), in contrast to inverse associations with parameters related to bone remodelling such as cortical bone mineral density (BMDC ). CTX and mid-tibial pQCT scans were available in 1130 adolescents (mean age 15.5 years) from the Avon Longitudinal Study of Parents and Children (ALSPAC). Analyses were adjusted for age, gender, time of sampling, tanner stage, lean mass, fat mass and height. CTX was positively related to PC [β= 0.19 (0.13, 0.24)] (coefficient=SD change per SD increase in CTX, 95% CI)], but inversely associated with BMDC [β= -0.46 (-0.52,-0.40)] and cortical thickness [β= -0.11 (-0.18, -0.03)]. CTX was positively related to bone strength as reflected by the strength-strain index (SSI) [β= 0.09 (0.03, 0.14)]. To examine the causal nature of this relationship, we then analysed whether SNPs within key osteoclast regulatory genes, known to reduce areal/cortical BMD, conversely increase PC. Fifteen such genetic variants within or proximal to genes encoding RANK, RANKL and OPG were identified by literature search. Six of the 15 alleles that were inversely related to BMD were positively related to CTX (P<0.05 cut-off) (n=2379). Subsequently, we performed a meta-analysis of associations between these SNPs and PC in ALSPAC (n=3382), Gothenburg Osteoporosis and Obesity Determinants (GOOD) (n=938) and the Young Finns Study (YFS) (n=1558). Five of the 15 alleles that were inversely related to BMD were positively related to PC (P<0.05 cut-off). We conclude that despite having lower BMD, individuals with a genetic predisposition to higher bone resorption have greater bone size, suggesting that higher bone resorption is permissive for greater periosteal expansion.
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| 334. |
- Kiss, Nicole, et al.
(författare)
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Exercise and Nutritional Approaches to Combat Cancer-Related Bone and Muscle Loss.
- 2020
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Ingår i: Current osteoporosis reports. - : Springer Science and Business Media LLC. - 1544-2241 .- 1544-1873. ; 18:3, s. 291-300
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE OF REVIEW: The aim of this narrative review is to summarise recent literature on the effects of exercise and nutrition interventions alone or in combination on muscle and bone loss in people with cancer.RECENT FINDINGS: There is emerging evidence to support the inclusion of targeted exercise and nutrition strategies to counter loss of muscle and bone associated with cancer treatments. Although research in this field is advancing, the optimal exercise and nutrition prescription to combat cancer-related bone and muscle loss remain unknown. This review identifies specific components of nutrition and exercise interventions that are promising although require further exploration through studies designed to determine the effect on muscle and bone. A focused research effort is required to elucidate the full potential of exercise and nutrition intervention for people with cancer at risk of bone and muscle loss.
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| 335. |
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| 336. |
- Kool, Erik C., et al.
(författare)
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AT 2017gbl : a dust obscured TDE candidate in a luminous infrared galaxy
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 498:2, s. 2167-2195
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Tidskriftsartikel (refereegranskat)abstract
- We present the discovery with Keck of the extremely infrared (IR) luminous transient AT 2017gbl, coincident with the Northern nucleus of the luminous infrared galaxy (LIRG) IRAS 23436+5257. Our extensive multiwavelength follow-up spans ∼900 d, including photometry and spectroscopy in the optical and IR, and (very long baseline interferometry) radio and X-ray observations. Radiative transfer modelling of the host galaxy spectral energy distribution and long-term pre-outburst variability in the mid-IR indicate the presence of a hitherto undetected dust obscured active galactic nucleus (AGN). The optical and near-IR spectra show broad ∼2000 km s−1 hydrogen, He i, and O i emission features that decrease in flux over time. Radio imaging shows a fast evolving compact source of synchrotron emission spatially coincident with AT 2017gbl. We infer a lower limit for the radiated energy of 7.3 × 1050 erg from the IR photometry. An extremely energetic supernova would satisfy this budget, but is ruled out by the radio counterpart evolution. Instead, we propose AT 2017gbl is related to an accretion event by the central supermassive black hole, where the spectral signatures originate in the AGN broad line region and the IR photometry is consistent with re-radiation by polar dust. Given the fast evolution of AT 2017gbl, we deem a tidal disruption event (TDE) of a star a more plausible scenario than a dramatic change in the AGN accretion rate. This makes AT 2017gbl the third TDE candidate to be hosted by a LIRG, in contrast to the so far considered TDE population discovered at optical wavelengths and hosted preferably by post-starburst galaxies.
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| 337. |
- Koslicki, David, et al.
(författare)
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ARK : Aggregation of Reads by K-Means for Estimation of Bacterial Community Composition
- 2015
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Motivation Estimation of bacterial community composition from high-throughput sequenced 16S rRNA gene amplicons is a key task in microbial ecology. Since the sequence data from each sample typically consist of a large number of reads and are adversely impacted by different levels of biological and technical noise, accurate analysis of such large datasets is challenging. Results There has been a recent surge of interest in using compressed sensing inspired and convex-optimization based methods to solve the estimation problem for bacterial community composition. These methods typically rely on summarizing the sequence data by frequencies of low-order k-mers and matching this information statistically with a taxonomically structured database. Here we show that the accuracy of the resulting community composition estimates can be substantially improved by aggregating the reads from a sample with an unsupervised machine learning approach prior to the estimation phase. The aggregation of reads is a pre-processing approach where we use a standard K-means clustering algorithm that partitions a large set of reads into subsets with reasonable computational cost to provide several vectors of first order statistics instead of only single statistical summarization in terms of k-mer frequencies. The output of the clustering is then processed further to obtain the final estimate for each sample. The resulting method is called Aggregation of Reads by K-means (ARK), and it is based on a statistical argument via mixture density formulation. ARK is found to improve the fidelity and robustness of several recently introduced methods, with only a modest increase in computational complexity. Availability An open source, platform-independent implementation of the method in the Julia programming language is freely available at https://github.com/dkoslicki/ARK. A Matlab implementation is available at http://www.ee.kth.se/ctsoftware.
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| 338. |
- Laurent, T.C., et al.
(författare)
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Functions of hyaluronan
- 1995
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Ingår i: Annals of the Rheumatic Diseases. ; 54, s. 429-
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Tidskriftsartikel (refereegranskat)
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| 339. |
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| 340. |
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