Self-organizing neural organoids represent a promising in vitro platform with which to model human development and disease
. However, organoids lack the connectivity that exists in vivo, which limits ...maturation and makes integration with other circuits that control behaviour impossible. Here we show that human stem cell-derived cortical organoids transplanted into the somatosensory cortex of newborn athymic rats develop mature cell types that integrate into sensory and motivation-related circuits. MRI reveals post-transplantation organoid growth across multiple stem cell lines and animals, whereas single-nucleus profiling shows progression of corticogenesis and the emergence of activity-dependent transcriptional programs. Indeed, transplanted cortical neurons display more complex morphological, synaptic and intrinsic membrane properties than their in vitro counterparts, which enables the discovery of defects in neurons derived from individuals with Timothy syndrome. Anatomical and functional tracings show that transplanted organoids receive thalamocortical and corticocortical inputs, and in vivo recordings of neural activity demonstrate that these inputs can produce sensory responses in human cells. Finally, cortical organoids extend axons throughout the rat brain and their optogenetic activation can drive reward-seeking behaviour. Thus, transplanted human cortical neurons mature and engage host circuits that control behaviour. We anticipate that this approach will be useful for detecting circuit-level phenotypes in patient-derived cells that cannot otherwise be uncovered.
Radio relics are Mpc-scale diffuse radio sources at the peripheries of galaxy clusters which are thought to trace outgoing merger shocks. We present XMM–Newton and Suzaku observations of the galaxy ...cluster Abell 2744 (z = 0.306), which reveal the presence of a shock front 1.5 Mpc east of the cluster core. The surface-brightness jump coincides with the position of a known radio relic. Although the surface-brightness jump indicates a weak shock with a Mach number
$\mathcal {M}=1.7_{-0.3}^{+0.5}$
, the plasma in the post-shock region has been heated to a very high temperature (∼13 keV) by the passage of the shock wave. The low-acceleration efficiency expected from such a weak shock suggests that mildly relativistic electrons have been re-accelerated by the passage of the shock front.
Abstract
The Last Journey is a large-volume, gravity-only, cosmological
N
-body simulation evolving more than 1.24 trillion particles in a periodic box with a side length of 5.025 Gpc. It was ...implemented using the HACC simulation and analysis framework on the BG/Q system Mira. The cosmological parameters are chosen to be consistent with the results from the Planck satellite. A range of analysis tools have been run in situ to enable a diverse set of science projects and, at the same time, keep the resulting data amount manageable. Analysis outputs have been generated starting at redshift
z
∼ 10 to allow for construction of synthetic galaxy catalogs using a semianalytic modeling approach in postprocessing. As part of our in situ analysis pipeline, we employ a new method for tracking halo substructures, introducing the concept of subhalo cores. The production of multiwavelength synthetic sky maps is facilitated by generating particle light cones in situ, also beginning at
z
∼ 10. We provide an overview of the simulation setup and generated data products; a first set of analysis results is presented. A subset of the data is publicly available.
ABSTRACT
The Bullet cluster (1E 0657-55.8) is a massive merging system at redshift z = 0.296, known to host a powerful radio halo and a relic. Here we present high fidelity MeerKAT L-band (0.9–1.7 ...GHz) observations of the Bullet cluster, where we trace a larger extent of both the halo and relic in comparison to previous studies. The size of the recovered halo is 1.6 Mpc × 1.3 Mpc and the largest linear size of the relic is ∼988 kpc. We detect a new decrement feature on the southern outskirts of the halo emission, where a region appears to have a lower surface brightness in comparison to its surroundings. The larger extension on the outskirts of the halo is faint, which suggests lower relativistic electron density or a weaker magnetic field. An in-band spectral index map of the halo reveals radial steepening towards the edges, likely due to synchrotron electron ageing. The integrated spectral index of the radio halo is 1.1 ± 0.2. We perform a radio−X-ray surface brightness point-to-point analysis, which reveals a linear correlation for the radio halo. This indicates that the halo emission is produced by primary re-acceleration mechanisms. Finally, we derive a radio Mach number of $\mathcal {M}_R$ = 4.6 ± 0.9 for the relic shock region, which is higher than the Mach number inferred by earlier analyses based on X-ray data. Discrepancies between radio and X-ray Mach numbers have been observed for multiple systems, studies suggest that this is due to various factors, including relic orientation.
ABSTRACT
We aim to carry out a radio study of the SoUthern Cluster sCale Extended Source Survey (SUCCESS) sample consisting of 20 massive (M500 > 5 × 1014 M⊙), nearby (redshift <0.3) and southern ...(−50° < δ < −30°) galaxy clusters detected by the Planck satellite and the South Pole Telescope. Here, we report targeted GMRT observations (325/610 MHz) for a subsample of nine clusters. We also use the first data release of MeerKAT Galaxy Cluster Legacy Survey (1283 MHz) for five of these nine clusters. The properties of the mini-halo in RXC J0528.9-3927, a candidate mini-halo in A3322, the radio halo and candidate double relics in A3399, and the radio halo in RXC J0232.2-4420 are presented. We also report a detection of candidate radio relics at distances 1 and 1.9 Mpc from the centre of RXC J0232.2-4420. The southeast relic of A3399 is consistent with the radio power–mass scaling relation for radio relics, while the candidate relics around RXC J0232.2-4420 are outliers. This indicates an origin of the candidate relics near RXC J0232.2-4420 to be independent of this cluster and a cluster merger-shock origin for the relic in A3399. In this subsample of clusters, 1/9 hosts a radio halo and double relics, 1/9 hosts a radio halo and 2/9 host mini-haloes. The dynamical states based on X-ray morphology show that A3399 is a disturbed cluster; however, the radio halo cluster RXC J0232.2-4420 is relaxed, and the mini-halo clusters have intermediate morphologies, adding to the cases of the less commonly found associations.
ABSTRACT
We report the discovery of a unique object in the MeerKAT Galaxy Cluster Legacy Survey (MGCLS) using the machine learning anomaly detection framework astronomaly. This strange, ring-like ...source is 30′ from the MGCLS field centred on Abell 209, and is not readily explained by simple physical models. With an assumed host galaxy at redshift 0.55, the luminosity (1025 W Hz−1) is comparable to powerful radio galaxies. The source consists of a ring of emission 175 kpc across, quadrilateral enhanced brightness regions bearing resemblance to radio jets, two ‘ears’ separated by 368 kpc, and a diffuse envelope. All of the structures appear spectrally steep, ranging from −1.0 to −1.5. The ring has high polarization (25 per cent) except on the bright patches (<10 per cent). We compare this source to the Odd Radio Circles recently discovered in ASKAP data and discuss several possible physical models, including a termination shock from starburst activity, an end-on radio galaxy, and a supermassive black hole merger event. No simple model can easily explain the observed structure of the source. This work, as well as other recent discoveries, demonstrates the power of unsupervised machine learning in mining large data sets for scientifically interesting sources.
Context.
During their lifetimes, galaxy clusters grow through the accretion of matter from the filaments of the large-scale structure and from mergers with other clusters. These mergers release a ...large amount of energy into the intracluster medium (ICM) through merger shocks and turbulence. These phenomena are associated with the formation of radio sources known as radio relics and radio halos, respectively. Radio relics and halos are unique proxies for studying the complex properties of these dynamically active regions of clusters and the microphysics of the ICM more generally.
Aims.
Abell 3667 is a spectacular example of a merging system that hosts a large pair of radio relics. Due to its proximity (
z
= 0.0553) and large mass, the system enables the study of these sources to a uniquely high level of detail. However, being located at Dec = −56.8°, the cluster could only be observed with a limited number of radio facilities.
Methods.
We observed Abell 3667 with MeerKAT as part of the MeerKAT Galaxy Cluster Legacy Survey. We used these data to study the large-scale emission of the cluster, including its polarisation and spectral properties. The results were then compared with simulations.
Results.
We present the most detailed view of the radio relic system in Abell 3667 to date, with a resolution reaching 3 kpc. The relics are filled with a network of filaments with different spectral and polarisation properties that are likely associated with multiple regions of particle acceleration and local enhancements of the magnetic field. Conversely, the magnetic field in the space between filaments has strengths close to what would be expected in unperturbed regions at the same cluster-centric distance. Comparisons with magnetohydrodynamic cosmological and Lagrangian simulations support the idea of filaments as multiple acceleration sites. Our observations also confirm the presence of an elongated radio halo, developed in the wake of the bullet-like sub-cluster that merged from the south-east. Finally, we associate the process of magnetic draping with a thin polarised radio source surrounding the remnant of the bullet’s cool core.
Conclusions.
Our observations have unveiled the complexity of the interplay between the thermal and non-thermal components in the most active regions of a merging cluster. Both the intricate internal structure of radio relics and the direct detection of magnetic draping around the merging bullet are powerful examples of the non-trivial magnetic properties of the ICM. Thanks to its sensitivity to polarised radiation, MeerKAT will be transformational in the study of these complex phenomena.
Joining of engineering ceramics Fernie, J A; Drew, R A L; Knowles, K M
International materials reviews,
09/2009, Volume:
54, Issue:
5
Journal Article
Peer reviewed
Engineering ceramics such as alumina, zirconia, silicon nitride and silicon carbide can now be manufactured reliably with reproducible properties. As such, they are of increasing interest to ...industry, particularly for use in demanding environments, where their thermomechanical performance is of critical importance, with applications ranging from fuel cells to cutting tools. One aspect common to virtually all applications of engineering ceramics is that eventually they must be joined with another material, most usually a metal. The joining of engineering ceramics to metals is not always easy. There are two main considerations. The first consideration is the basic difference in atomic bonding: the ionic or covalent bonding of the ceramic, compared to the metallic bond. The second consideration is the mismatch in the coefficient of thermal expansion. In general, ceramics have a lower coefficient of thermal expansion than metals and, if high tensile forces are produced in the ceramic, either as a consequence of operating conditions or from the joining procedure itself, failure can occur. The plethora of joining processes available will be reviewed in this article, placing them in context from both an academic and commercial perspective. Comment will be made on research reporting advances on known technology, as well as introducing 'newer' technologies developed over the last 10 years. Finally, reviews and commentary will be made on the potential applications of the various joining processes in the commercial environment.
Background/Aims
The Chicago Classification for diagnosis of esophageal motility disorders by high‐resolution manometry (HRM) is based on single water swallows (SWS). Emerging data suggest that a ...“Rapid Drink Challenge” (RDC) increases sensitivity for motility disorders. This study establishes normal values and diagnostic thresholds for RDC in clinical practice.
Methods
Two cohort studies were performed in patients with dysphagia or reflux symptoms (development and validation sets). Healthy subjects and patient controls provided reference values. Ten SWS and two 200‐mL RDC were performed. Primary diagnosis for SWS was established by the Chicago Classification. Abnormal RDC was defined by impaired esophagogastric junction (EGJ) function (elevated integrated relaxation pressure during RDC IRP‐RDC); incomplete inhibition of contractility during and ineffective contraction after RDC. Diagnostic thresholds identified in the development set were prospectively tested in the validation set.
Results
Normal values were determined in healthy (n=95; age 37.8 ± 12) and patient controls (n=44; age 46.4 ± 15). Development and validation sets included 178 (54 ± 17 years) and 226 (53 ± 16 years) patients, respectively. Integrated relaxation pressure during RDC was higher for SWS than RDC in all groups (overall P<.001), except achalasia. Rapid Drink Challenge suppressed contractility, except in achalasia type III, spasm, and hypercontractile motility disorders (P<.001). An effective after‐contraction was present more often in health than disease (P<.001). Optimal diagnostic thresholds identified in the development set (IRP‐RDC ≥12 mmHg achalasia, IRP‐RDC ≥ 8mmHg “all cause” EGJ dysfunction), were confirmed in the validation set (both, sensitivity ~85%, specificity >95%).
Conclusions
Rapid Drink Challenge contributes clinically relevant information to routine HRM studies, especially in patients with EGJ dysfunction.
Emerging data suggest that a 200‐mL Rapid Drink Challenge (RDC) test provides additional information during esophageal high‐resolution manometry (HRM). We present normal values for RDC from healthy volunteers and patient controls and establish diagnostic thresholds for esophagogastric junction (EGJ) and peristaltic dysfunction. Rapid Drink Challenge is simple to perform during routine HRM studies and appears to increase diagnostic yield for symptomatic EGJ outflow obstruction and other, clinically relevant, motility disorders.
We present a high-precision mass model of the galaxy cluster MACSJ0416.1-2403, based on a strong-gravitational-lensing analysis of the recently acquired Hubble Space Telescope Frontier Fields (HFF) ...imaging data. Taking advantage of the unprecedented depth provided by HST/Advanced Camera for Survey observations in three passbands, we identify 51 new multiply imaged galaxies, quadrupling the previous census and bringing the grand total to 68, comprising 194 individual lensed images. Having selected a subset of the 57 most securely identified multiply imaged galaxies, we use the lenstool software package to constrain a lens model comprised of two cluster-scale dark-matter haloes and 98 galaxy-scale haloes. Our best-fitting model predicts image positions with an rms error of 0.68 arcsec, which constitutes an improvement of almost a factor of 2 over previous, pre-HFF models of this cluster. We find the total projected mass inside a 200 kpc aperture to be (1.60 ± 0.01) x 10^sup 14^ M.., a measurement that offers a three-fold improvement in precision, reaching the per cent level for the first time in any cluster. Finally, we quantify the increase in precision of the derived gravitational magnification of high-redshift galaxies and find an improvement by a factor of ~2.5 in the statistical uncertainty. Our findings impressively confirm that HFF imaging has indeed opened the domain of high-precision mass measurements for massive clusters of galaxies.(ProQuest: ... denotes formulae/symbols omitted.)
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