Injectable biomimetic hydrogels have great potential for use in regenerative medicine as cellular delivery vectors. However, they can suffer from issues relating to hypoxia, including poor cell ...survival, differentiation, and functional integration owing to the lack of an established vascular network. Here we engineer a hybrid myoglobin:peptide hydrogel that can concomitantly deliver stem cells and oxygen to the brain to support engraftment until vascularisation can occur naturally. We show that this hybrid hydrogel can modulate cell fate specification within progenitor cell grafts, resulting in a significant increase in neuronal differentiation. We find that the addition of myoglobin to the hydrogel results in more extensive innervation within the host tissue from the grafted cells, which is essential for neuronal replacement strategies to ensure functional synaptic connectivity. This approach could result in greater functional integration of stem cell-derived grafts for the treatment of neural injuries and diseases affecting the central and peripheral nervous systems.
We present first results from radio observations with the Murchison Widefield Array seeking to constrain the power spectrum of 21 cm brightness temperature fluctuations between the redshifts of 11.6 ...and 17.9 (113 and 75 MHz). 3 h of observations were conducted over two nights with significantly different levels of ionospheric activity. We use these data to assess the impact of systematic errors at low frequency, including the ionosphere and radio-frequency interference, on a power spectrum measurement. We find that after the 1–3 h of integration presented here, our measurements at the Murchison Radio Observatory are not limited by RFI, even within the FM band, and that the ionosphere does not appear to affect the level of power in the modes that we expect to be sensitive to cosmology. Power spectrum detections, inconsistent with noise, due to fine spectral structure imprinted on the foregrounds by reflections in the signal-chain, occupy the spatial Fourier modes where we would otherwise be most sensitive to the cosmological signal. We are able to reduce this contamination using calibration solutions derived from autocorrelations so that we achieve an sensitivity of 104 mK on comoving scales k ≲ 0.5 h Mpc−1. This represents the first upper limits on the 21 cm power spectrum fluctuations at redshifts 12 ≲ z ≲ 18 but is still limited by calibration systematics. While calibration improvements may allow us to further remove this contamination, our results emphasize that future experiments should consider carefully the existence of and their ability to calibrate out any spectral structure within the EoR window.
Astronomical wide-field imaging of interferometric radio data is computationally expensive, especially for the large data volumes created by modern non-coplanar many-element arrays. We present a new ...wide-field interferometric imager that uses the w-stacking algorithm and can make use of the w-snapshot algorithm. The performance dependences of casa's w-projection and our new imager are analysed and analytical functions are derived that describe the required computing cost for both imagers. On data from the Murchison Widefield Array, we find our new method to be an order of magnitude faster than w-projection, as well as being capable of full-sky imaging at full resolution and with correct polarization correction. We predict the computing costs for several other arrays and estimate that our imager is a factor of 2–12 faster, depending on the array configuration. We estimate the computing cost for imaging the low-frequency Square Kilometre Array observations to be 60 PetaFLOPS with current techniques. We find that combining w-stacking with the w-snapshot algorithm does not significantly improve computing requirements over pure w-stacking. The source code of our new imager is publicly released.
ABSTRACT
Scaling laws of dust, H i gas, and metal mass with stellar mass, specific star formation rate, and metallicity are crucial to our understanding of the build-up of galaxies through their ...enrichment with metals and dust. In this work, we analyse how the dust and metal content varies with specific gas mass (MH i/M⋆) across a diverse sample of 423 nearby galaxies. The observed trends are interpreted with a set of Dust and Element evolUtion modelS (DEUS) – including stellar dust production, grain growth, and dust destruction – within a Bayesian framework to enable a rigorous search of the multidimensional parameter space. We find that these scaling laws for galaxies with −1.0 ≲ log MH i/M⋆ ≲ 0 can be reproduced using closed-box models with high fractions (37–89 ${{\ \rm per\ cent}}$) of supernova dust surviving a reverse shock, relatively low grain growth efficiencies (ϵ = 30–40), and long dust lifetimes (1–2 Gyr). The models have present-day dust masses with similar contributions from stellar sources (50–80 ${{\ \rm per\ cent}}$) and grain growth (20–50 ${{\ \rm per\ cent}}$). Over the entire lifetime of these galaxies, the contribution from stardust (>90 ${{\ \rm per\ cent}}$) outweighs the fraction of dust grown in the interstellar medium (<10 ${{\ \rm per\ cent}}$). Our results provide an alternative for the chemical evolution models that require extremely low supernova dust production efficiencies and short grain growth time-scales to reproduce local scaling laws, and could help solving the conundrum on whether or not grains can grow efficiently in the interstellar medium.
Cryovolcanism on Ceres Ruesch, O.; Platz, T.; Schenk, P. ...
Science (American Association for the Advancement of Science),
09/2016, Volume:
353, Issue:
6303
Journal Article
Peer reviewed
Open access
Volcanic edifices are abundant on rocky bodies of the inner solar system. In the cold outer solar system, volcanism can occur on solid bodies with a water-ice shell, but derived cryovolcanic ...constructs have proved elusive. We report the discovery, using Dawn Framing Camera images, of a landform on dwarf planet Ceres that we argue represents a viscous cryovolcanic dome. Parent material of the cryomagma is a mixture of secondary minerals, including salts and water ice. Absolute model ages from impact craters reveal that extrusion of the dome has occurred recently. Ceres' evolution must have been able to sustain recent interior activity and associated surface expressions. We propose salts with low eutectic temperatures and thermal conductivities as key drivers for Ceres' long-term internal evolution.
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BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
ABSTRACT The Murchison Widefield Array (MWA) has collected hundreds of hours of Epoch of Reionization (EoR) data and now faces the challenge of overcoming foreground and systematic contamination to ...reduce the data to a cosmological measurement. We introduce several novel analysis techniques, such as cable reflection calibration, hyper-resolution gridding kernels, diffuse foreground model subtraction, and quality control methods. Each change to the analysis pipeline is tested against a two-dimensional power spectrum figure of merit to demonstrate improvement. We incorporate the new techniques into a deep integration of 32 hours of MWA data. This data set is used to place a systematic-limited upper limit on the cosmological power spectrum of mK2 at k = 0.27 h Mpc−1 and z = 7.1, consistent with other published limits, and a modest improvement (factor of 1.4) over previous MWA results. From this deep analysis, we have identified a list of improvements to be made to our EoR data analysis strategies. These improvements will be implemented in the future and detailed in upcoming publications.
We present a survey for transient and variable sources, on time-scales from 28 s to ∼1 yr, using the Murchison Widefield Array (MWA) at 182 MHz. Down to a detection threshold of 0.285 Jy, no ...transient candidates were identified, making this the most constraining low-frequency survey to date and placing a limit on the surface density of transients of <4.1 × 10−7 deg−2 for the shortest time-scale considered. At these frequencies, emission from Fast Radio Bursts (FRBs) is expected to be detectable in the shortest time-scale images without any corrections for interstellar or intergalactic dispersion. At an FRB limiting flux density of 7980 Jy, we find a rate of <82 FRBs per sky per day for dispersion measures <700 pc cm−3. Assuming a cosmological population of standard candles, our rate limits are consistent with the FRB rates obtained by Thornton et al. if they have a flat spectral slope. Finally, we conduct an initial variability survey of sources in the field with flux densities ≳0.5 Jy and identify no sources with significant variability in their light curves. However, we note that substantial further work is required to fully characterize both the short-term and low-level variability within this field.
ABSTRACT Detection of the cosmological neutral hydrogen signal from the Epoch of Reionization (EoR) and estimation of its basic physical parameters are principal scientific aims of many current ...low-frequency radio telescopes. Here we describe the Cosmological H i Power Spectrum Estimator (CHIPS), an algorithm developed and implemented with data from the Murchison Widefield Array, to compute the two-dimensional and spherically-averaged power spectrum of brightness temperature fluctuations. The principal motivations for CHIPS are the application of realistic instrumental and foreground models to form the optimal estimator, thereby maximizing the likelihood of unbiased signal estimation, and allowing a full covariant understanding of the outputs. CHIPS employs an inverse-covariance weighting of the data through the maximum likelihood estimator, thereby allowing use of the full parameter space for signal estimation ("foreground suppression"). We describe the motivation for the algorithm, implementation, application to real and simulated data, and early outputs. Upon application to a set of 3 hr of data, we set a 2 upper limit on the EoR dimensionless power at Mpc−1 of mK2 in the redshift range z = 6.2-6.6, consistent with previous estimates.
Acid mine drainage (AMD) is a widespread environmental problem associated with both working and abandoned mining operations, resulting from the microbial oxidation of pyrite in presence of water and ...air, affording an acidic solution that contains toxic metal ions. The generation of AMD and release of dissolved heavy metals is an important concern facing the mining industry. The present study aimed at evaluating the use of low-cost sorbents like coal fly ash, natural clinker and synthetic zeolites to clean-up AMD generated at the Parys Mountain copper–lead–zinc deposit, Anglesey (North Wales), and to remove heavy metals and ammonium from AMD. pH played a very important role in the sorption/removal of the contaminants and a higher adsorbent ratio in the treatment of AMD promoted the increase of the pH, particularly using natural clinker-based faujasite (7.70–9.43) and the reduction of metal concentration. Na-phillipsite showed a lower efficiency as compared to that of faujasite. Selectivity of faujasite for metal removal was, in decreasing order, Fe
>
As
>
Pb
>
Zn
>
Cu
>
Ni
>
Cr. Based on these results, the use of these materials has the potential to provide improved methods for the treatment of AMD.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Summary Background Lithium has neuroprotective effects in cell and animal models of amyotrophic lateral sclerosis (ALS), and a small pilot study in patients with ALS showed a significant effect of ...lithium on survival. We aimed to assess whether lithium improves survival in patients with ALS. Methods The lithium carbonate in amyotrophic lateral sclerosis (LiCALS) trial is a randomised, double-blind, placebo-controlled trial of oral lithium taken daily for 18 months in patients with ALS. Patients aged at least 18 years who had ALS according to the revised El Escorial criteria, had disease duration between 6 and 36 months, and were taking riluzole were recruited from ten centres in the UK. Patients were randomly assigned (1:1) to receive either lithium or matched placebo tablets. Randomisation was via an online system done at the level of the individual by block randomisation with randomly varying block sizes, stratified by study centre and site of disease onset (limb or bulbar). All patients and assessing study personnel were masked to treatment assignment. The primary endpoint was the rate of survival at 18 months and was analysed by intention to treat. This study is registered with Eudract, number 2008-006891-31. Findings Between May 26, 2009, and Nov 10, 2011, 243 patients were screened, 214 of whom were randomly assigned to receive lithium (107 patients) or placebo (107 patients). Two patients discontinued treatment and one died before the target therapeutic lithium concentration could be achieved. 63 (59%) of 107 patients in the placebo group and 54 (50%) of 107 patients in the lithium group were alive at 18 months. The survival functions did not differ significantly between groups (Mantel-Cox log-rank χ2 on 1 df=1·64; p=0·20). After adjusting for study centre and site of onset using logistic regression, the relative odds of survival at 18 months (lithium vs placebo) was 0·71 (95% CI 0·40–1·24). 56 patients in the placebo group and 61 in the lithium group had at least one serious adverse event. Interpretation We found no evidence of benefit of lithium on survival in patients with ALS, but nor were there safety concerns, which had been identified in previous studies with less conventional designs. This finding emphasises the importance of pursuing adequately powered trials with clear endpoints when testing new treatments. Funding The Motor Neurone Disease Association of Great Britain and Northern Ireland.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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