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The fates of massive galaxies are tied to the evolution of their central supermassive black holes (BHs), due to the influence of AGN feedback. Correlations within simulated galaxy populations suggest that the masses of BHs are governed by properties of their host dark matter haloes, such as the binding energy and assembly time, at a given halo mass. However, the full picture must be more complex, as galaxy mergers have also been shown to influence the growth of BHs and the impact of AGN. In this study, we investigate this problem through a controlled experiment, using the genetic modification technique to adjust the assembly history of a Milky Way-like galaxy simulated with the EAGLE model. We change the halo assembly time (and hence the binding energy) in the absence of any disruptive merger events, and find little change in the integrated growth of the BH. We attribute this to the angular momentum support provided by a galaxy disc, which reduces the inflow of gas towards the BH and effectively decouples the BH's growth from the halo's properties. Introducing major mergers into the assembly history disrupts the disc, causing the BH to grow ≈4 × more massive and inject feedback that reduces the halo baryon fraction by a factor of ≈2 and quenches star formation. Merger events appear essential to the diversity in BH masses in EAGLE, and we also show that they increase the halo binding energy; correlations between these quantities may therefore be the result of merger events. [ABSTRACT FROM AUTHOR]

We investigate how the X-ray circumgalactic medium (CGM) of present-day galaxies depends on galaxy morphology and azimuthal angle using mock observations generated from the EAGLE cosmological hydrodynamic simulation. By creating mock stacks of eROSITA -observed galaxies oriented to be edge-on, we make several observationally testable predictions for galaxies in the stellar mass range M ⋆ = 1010.7–11.2 M⊙. The soft X-ray CGM of disc galaxies is between 60 and 100 per cent brighter along the semimajor axis compared to the semiminor axis, between 10 and 30 kpc. This azimuthal dependence is a consequence of the hot (T > 106 K) CGM being non-spherical: specifically, it is flattened along the minor axis such that denser and more luminous gas resides in the disc plane and corotates with the galaxy. Outflows enrich and heat the CGM preferentially perpendicular to the disc, but we do not find an observationally detectable signature along the semiminor axis. Spheroidal galaxies have hotter CGMs than disc galaxies related to spheroids residing at higher halo masses, which may be measurable through hardness ratios spanning the 0.2–1.5 keV band. While spheroids appear to have brighter CGMs than discs for the selected fixed M ⋆ bin, this owes to spheroids having higher stellar and halo masses within that M ⋆ bin, and obscures the fact that both simulated populations have similar total CGM luminosities at the exact same M ⋆. Discs have brighter emission inside 20 kpc and more steeply declining profiles with radius than spheroids. We predict that the eROSITA 4-yr all-sky survey should detect many of the signatures we predict here, although targeted follow-up observations of highly inclined nearby discs after the survey may be necessary to observe some of our azimuthally dependant predictions. [ABSTRACT FROM AUTHOR]

We use zoom simulations to show how merger-driven disruption of the gas disc in a galaxy provides its central active galactic nucleus (AGN) with fuel to drive outflows that entrain and expel a significant fraction of the circumgalactic medium (CGM). This in turn suppresses replenishment of the interstellar medium, causing the galaxy to quench up to several Gyr after the merger. We start by performing a zoom simulation of a present-day star-forming disc galaxy with the EAGLE galaxy formation model. Then, we re-simulate the galaxy with controlled changes to its initial conditions, using the genetic modification technique. These modifications either increase or decrease the stellar mass ratio of the galaxy's last significant merger, which occurs at |$z$| ≈ 0.74. The halo reaches the same present-day mass in all cases, but changing the mass ratio of the merger yields markedly different galaxy and CGM properties. We find that a merger can unlock rapid growth of the central supermassive black hole if it disrupts the co-rotational motion of gas in the black hole's vicinity. Conversely, if a less disruptive merger occurs and gas close to the black hole is not disturbed, the AGN does not strongly affect the CGM, and consequently the galaxy continues to form stars. Our result illustrates how a unified view of AGN feedback, the baryon cycle and the interstellar medium is required to understand how mergers and quenching are connected over long time-scales. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine a "low-dose protocol" which provides acceptable diagnostic accuracy for detection of root fractures in unrestored anterior maxillary teeth, using an ex vivo model. 48 maxillary anterior teeth, half with horizontal or oblique root fractures, were imaged using CBCT in an anthropomorphic model. Nine X-ray exposure combinations were used, including the manufacturer's standard ("reference") exposure and high-resolution settings ("HiRes"), by varying kV, exposure time, and rotation angle. Measurements of Dose Area Product (DAP) were recorded. Five dental radiologists assessed the scans for root fractures and judged image quality. Parameters of diagnostic accuracy were calculated, including area under the Receiver Operating Characteristic curve (Az). Objective measures of image quality were made at the same exposure combinations using an image quality phantom. Although there was a significant linear relationship between DAP and mean Az, only the lowest DAP exposure combination had a mean Az significantly different to the reference exposure. There was no significant effect on other diagnostic accuracy parameters when using HiRes compared with the reference exposure. There was a significant positive relationship between DAP and contrast resolution. HiRes did not significantly improve contrast resolution and made a small improvement to spatial resolution. Scope existed for radiation dose reduction compared with the manufacturer's guidance. There was no improvement in diagnostic accuracy using HiRes settings. A cautious recommendation for this CBCT machine is that it is possible to achieve a dose reduction of about 20% compared with the reference exposure parameters. [ABSTRACT FROM AUTHOR]

We examine the influence of dark matter halo assembly on the evolution of a simulated ∼ L ⋆ galaxy. Starting from a zoom-in simulation of a star-forming galaxy evolved with the EAGLE galaxy formation model, we use the genetic modification technique to create a pair of complementary assembly histories: one in which the halo assembles later than in the unmodified case, and one in which it assembles earlier. Delayed assembly leads to the galaxy exhibiting a greater present-day star formation rate than its unmodified counterpart, while in the accelerated case the galaxy quenches at z ≃ 1, and becomes spheroidal. We simulate each assembly history nine times, adopting different seeds for the random number generator used by EAGLE's stochastic subgrid implementations of star formation and feedback. The systematic changes driven by differences in assembly history are significantly stronger than the random scatter induced by this stochasticity. The sensitivity of ∼ L ⋆ galaxy evolution to dark matter halo assembly follows from the close coupling of the growth histories of the central black hole (BH) and the halo, such that earlier assembly fosters the formation of a more massive BH, and more efficient expulsion of circumgalactic gas. In response to this expulsion, the circumgalactic medium reconfigures at a lower density, extending its cooling time and thus inhibiting the replenishment of the interstellar medium. Our results indicate that halo assembly history significantly influences the evolution of ∼ L ⋆ central galaxies, and that the expulsion of circumgalactic gas is a crucial step in quenching them. [ABSTRACT FROM AUTHOR]

Human DNA methylation data have been used to develop biomarkers of ageing, referred to as 'epigenetic clocks', which have been widely used to identify differences between chronological age and biological age in health and disease including neurodegeneration, dementia and other brain phenotypes. Existing DNA methylation clocks have been shown to be highly accurate in blood but are less precise when used in older samples or in tissue types not included in training the model, including brain. We aimed to develop a novel epigenetic clock that performs optimally in human cortex tissue and has the potential to identify phenotypes associated with biological ageing in the brain. We generated an extensive dataset of human cortex DNA methylation data spanning the life course (n = 1397, ages = 1 to 108 years). This dataset was split into 'training' and 'testing' samples (training: n = 1047; testing: n = 350). DNA methylation age estimators were derived using a transformed version of chronological age on DNA methylation at specific sites using elastic net regression, a supervised machine learning method. The cortical clock was subsequently validated in a novel independent human cortex dataset (n = 1221, ages = 41 to 104 years) and tested for specificity in a large whole blood dataset (n = 1175, ages = 28 to 98 years). We identified a set of 347 DNA methylation sites that, in combination, optimally predict age in the human cortex. The sum of DNA methylation levels at these sites weighted by their regression coefficients provide the cortical DNA methylation clock age estimate. The novel clock dramatically outperformed previously reported clocks in additional cortical datasets. Our findings suggest that previous associations between predicted DNA methylation age and neurodegenerative phenotypes might represent false positives resulting from clocks not robustly calibrated to the tissue being tested and for phenotypes that become manifest in older ages. The age distribution and tissue type of samples included in training datasets need to be considered when building and applying epigenetic clock algorithms to human epidemiological or disease cohorts. [ABSTRACT FROM AUTHOR]

Modern observational and analytical techniques now enable the direct measurement of star formation histories and the inference of galaxy assembly histories. However, current theoretical predictions of assembly are not ideally suited for direct comparison with such observational data. We therefore extend the work of prior examinations of the contribution of ex situ stars to the stellar mass budget of simulated galaxies. Our predictions are specifically tailored for direct testing with a new generation of observational techniques by calculating ex situ fractions as functions of galaxy mass and morphological type, for a range of surface brightnesses. These enable comparison with results from large field of view (FoV) Integral Field Unit (IFU) spectrographs, and increasingly accurate spectral fitting, providing a look-up method for the estimated accreted fraction. We furthermore provide predictions of ex situ mass fractions as functions of galaxy mass, galactocentric radius, and environment. Using z  = 0 snapshots from the 100 and 25 cMpc3 EAGLE (Evolution and Assembly of GaLaxies and their Environments) simulations, we corroborate the findings of prior studies, finding that ex situ fraction increases with stellar mass for central and satellite galaxies in a stellar mass range of 2 × 107 to 1.9 × 1012 M⊙. For those galaxies of mass M * > 5 × 108 M⊙, we find that the total ex situ mass fraction is greater for more extended galaxies at fixed mass. When categorizing satellite galaxies by their parent group/cluster halo mass, we find that the ex situ fraction decreases with increasing parent halo mass at fixed galaxy mass. This apparently counterintuitive result may be due to high passing velocities within large cluster haloes inhibiting efficient accretion on to individual galaxies. [ABSTRACT FROM AUTHOR]

We examine the connection between the properties of the circumgalactic medium (CGM) and the quenching and morphological evolution of central galaxies in the EAGLE and IllustrisTNG simulations. The simulations yield very different median CGM mass fractions, f CGM, as a function of halo mass, M 200, with low-mass haloes being significantly more gas-rich in IllustrisTNG than in EAGLE. Nonetheless, in both cases scatter in f CGM at fixed M 200 is strongly correlated with the specific star formation rate and the kinematic morphology of central galaxies. The correlations are strongest for ∼ L ⋆ galaxies, corresponding to the mass scale at which AGN feedback becomes efficient. This feedback elevates the CGM cooling time, preventing gas from accreting on to the galaxy to fuel star formation, and thus establishing a preference for quenched, spheroidal galaxies to be hosted by haloes with low f CGM for their mass. In both simulations, f CGM correlates negatively with the host halo's intrinsic concentration, and hence with its binding energy and formation redshift, primarily because early halo formation fosters the rapid early growth of the central black hole (BH). This leads to a lower f CGM at fixed M 200 in EAGLE because the BH reaches high accretion rates sooner, whilst in IllustrisTNG it occurs because the central BH reaches the mass threshold at which AGN feedback is assumed to switch from thermal to kinetic injection earlier. Despite these differences, there is consensus from these state-of-the-art simulations that the expulsion of efficiently cooling gas from the CGM is a crucial step in the quenching and morphological evolution of central galaxies. [ABSTRACT FROM AUTHOR]

Davies et al. established that for L * galaxies the fraction of baryons in the circumgalactic medium (CGM) is inversely correlated with the mass of their central supermassive black holes (BHs) in the EAGLE hydrodynamic simulation. The interpretation is that, over time, a more massive BH has provided more energy to transport baryons beyond the virial radius, which additionally reduces gas accretion and star formation. We continue this research by focusing on the relationship between the (1) BH masses (M BH), (2) physical and observational properties of the CGM, and (3) galaxy colours for Milky Way-mass systems. The ratio of the cumulative BH feedback energy over the gaseous halo binding energy is a strong predictor of the CGM gas content, with BHs injecting significantly higher than the binding energy resulting in gas-poor haloes. Observable tracers of the CGM, including |$\rm {C\, \small{IV}}$|⁠ , |$\rm {O\, \small{VI}}$|⁠ , and |${\rm {H\, \small{I}}}$| absorption line measurements, are found to be effective tracers of the total z ∼ 0 CGM halo mass. We use high-cadence simulation outputs to demonstrate that BH feedback pushes baryons beyond the virial radius within 100 Myr time-scales, but that CGM metal tracers take longer (0.5–2.5 Gyr) to respond. Secular evolution of galaxies results in blue, star-forming or red, passive populations depending on the cumulative feedback from BHs. The reddest quartile of galaxies with M * = 1010.2−10.7 M⊙ (median u − r  = 2.28) has a CGM mass that is 2.5 times lower than the bluest quartile (u − r  = 1.59). We propose observing strategies to indirectly ascertain f CGM via metal lines around galaxies with measured M BH. We predict statistically detectable declines in |$\rm {C\, \small{IV}}$| and |$\rm {O\, \small{VI}}$| covering fractions with increasing M BH for central galaxies with M * = 1010.2−10.7M⊙. [ABSTRACT FROM AUTHOR]

We examine the origin of scatter in the relationship between the gas fraction and mass of dark matter haloes hosting present-day ∼ L ⋆ central galaxies in the EAGLE simulations. The scatter is uncorrelated with the accretion rate of the central galaxy's black hole (BH), but correlates strongly and negatively with the BH's mass, implicating differences in the expulsion of gas by active galactic nucleus feedback, throughout the assembly of the halo, as the main cause of scatter. Haloes whose central galaxies host undermassive BHs also tend to retain a higher gas fraction, and exhibit elevated star formation rates (SFRs). Diversity in the mass of central BHs stems primarily from diversity in the dark matter halo binding energy, as these quantities are strongly and positively correlated at fixed halo mass, such that ∼ L ⋆ galaxies hosted by haloes that are more (less) tightly bound develop central BHs that are more (less) massive than is typical for their halo mass. Variations in the halo gas fraction at fixed halo mass are reflected in both the soft X-ray luminosity and thermal Sunyaev–Zel'dovich flux, suggesting that the prediction of a strong coupling between the properties of galaxies and their halo gas fractions can be tested with measurements of these diagnostics for galaxies with diverse SFRs but similar halo masses. [ABSTRACT FROM AUTHOR]

We present the first results of the ALMA Fornax Cluster Survey: a complete ALMA survey of all members of the Fornax galaxy cluster that were detected in H  i or in the far-infrared with Herschel. The sample consists of a wide variety of galaxy types, ranging from giant ellipticals to spiral galaxies and dwarfs, located in all (projected) areas of the cluster. It spans a mass range of 10∼8.5–11 M⊙. The CO(1–0) line was targeted as a tracer for the cold molecular gas, along with the associated 3 mm continuum. CO was detected in 15 of the 30 galaxies observed. All 8 detected galaxies with stellar masses below 3 × 109 M⊙ have disturbed molecular gas reservoirs; only 7 galaxies are regular/undisturbed. This implies that Fornax is still a very active environment, having a significant impact on its members. Both detections and non-detections occur at all projected locations in the cluster. Based on visual inspection, and the detection of molecular gas tails in alignment with the direction of the cluster centre, in some cases ram pressure stripping is a possible candidate for disturbing the molecular gas morphologies and kinematics. Derived gas fractions in almost all galaxies are lower than expected for field objects with the same mass, especially for the galaxies with disturbed molecular gas, with differences of sometimes more than an order of magnitude. The detection of these disturbed molecular gas reservoirs reveals the importance of the cluster environment for even the tightly bound molecular gas phase. [ABSTRACT FROM AUTHOR]

In most studies of dust in galaxies, dust is only detected from its emission to approximately the optical radius of the galaxy. By combining the signal of 110 spiral galaxies observed as part of the Herschel Reference Survey, we are able to improve our sensitivity by an order of magnitude over that for a single object. Here we report the direct detection of dust from its emission that extends out to at least twice the optical radius. We find that the distribution of dust is consistent with an exponential at all radii with a gradient of ~-1.7 dex R-125. Our dust temperature declines linearly from ~25 K in the centre to 15 K at R25 from where it remains constant out to ~2.0 R25. The surface density of dust declines with radius at a similar rate to the surface density of stars but more slowly than the surface density of the star-formation rate. Studies based on dust extinction and reddening of high-redshift quasars have concluded that there are substantial amounts of dust in intergalactic space. By combining our results with the number counts and angular correlation function from the SDSS, we show that with Milky Way-type dust we can explain the reddening of the quasars by the dust within galactic discs alone. Given the uncertainties in the properties of any intergalactic dust, we cannot rule out its existence, but our results show that statistical investigations of the dust in galactic haloes that use the reddening of high-redshift objects must take account of the dust in galactic discs. [ABSTRACT FROM AUTHOR]

We use the published photometry and spectroscopy of 22 galaxies in the Herschel Reference Survey to determine that the value of the dust mass absorption coefficient Kd at a wavelength of 500 µm is K500 = 0.051-0.026+0.070 m² kg-1. We do so by taking advantage of the fact that the dust-to-metals ratio in the interstellar medium of galaxies appears to be constant. We argue that our value for Kd supersedes that of James et al. - who pioneered this approach for determining Kd - because we take advantage of superior data, and account for a number of significant systematic effects that they did not consider. We comprehensively incorporate all methodological and observational contributions to establish the uncertainty on our value, which represents a marked improvement on the oft-quoted 'order-of-magnitude' uncertainty on Kd. We find no evidence that the value of Kd differs significantly between galaxies, or that it correlates with any other measured or derived galaxy properties. We note, however, that the availability of data limits our sample to relatively massive (109.7 < M* < 1011.0 Mʘ), high metallicity (8.61 < [12 + log10O/H] < 8.86) galaxies; future work will allow us to investigate a wider range of systems. [ABSTRACT FROM AUTHOR]

Objectives: Current guidelines highlight the need to optimize exposure parameters on CBCT equipment to levels that are as low as diagnostically acceptable. This systematic review aimed to answer the question "Can altering operating potential (kV) and tube current exposure time product (mAs) on CBCT machines reduce radiation dose to patients undergoing dental and/ or maxillofacial scans without a detrimental impact on image quality/diagnostic accuracy?" Methods: Studies were selected and results reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. For each individual study, two authors (RG and JD or KH) independently extracted data using a specifically designed collection form, and an overall quality value was assigned using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. Any disagreements in the overall quality value of a study were resolved by discussion between the current authors. Results: Nearly 75% of studies were considered to be of low or very low methodological quality using the GRADE system, and more studies stated that their results applied only in the specific situations they had investigated. However, most studies demonstrated that patient dose reduction is possible without a clinically relevant reduction in image quality. Conclusions: For many CBCT machines, it should be possible to optimize one, or more, of the investigated exposure parameters and therefore reduce patient radiation dose, while maintaining diagnostic image quality for some diagnostic tasks. However, more rigorous research is still required. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to develop a low-dose protocol suitable for cone beam CT (CBCT) examination of an impacted maxillary canine in children by using a combination of dosimetry with subjective and objective image quality assessment. Methods: Radiation dose and image quality measurements were made using a dental CBCT machine. An image quality phantom was used to investigate the relationship between objective image quality and dose-area product (DAP) for a broad range of exposure settings. Subjective image quality assessment was achieved using a paediatric skull phantom submerged in a water bath for the same range of exposure settings. Eight clinicians assessed each CBCT data set for nine aspects of image quality using a five-point rating scale of agreement. Results: Acceptable image quality, defined using subjective judgements by the clinicians of the skull phantom images, was achievable with DAP values of 127 mGy cm² or greater and a polytetrafluoroethylene (PTFE) contrast-to-noise ratio (CNR) of 4.8 or greater. A cautious choice was made to recommend a low-dose protocol of 80 kV and 3 mA for implementation into clinical practice, corresponding to a DAP value of 146 mGy ² and a PTFE CNR of 5.0. Conclusion: A low-dose protocol for this particular CBCT machine was established which represents as much as a 50% reduction compared with manufacturer's recommendations. Advances in knowledge: To the authors' best knowledge, this is the first study that addresses dose optimization in paediatric clinical protocols in dental CBCT. Furthermore, this study explores the relationship between radiation dose, objective and subjective image quality. [ABSTRACT FROM AUTHOR]

We have previously described the results of a search for low surface brightness (LSB) objects in data drawn from an east–west strip of the Virgo cluster and have compared this to a large-area strip outside the cluster. In this paper, we compare the cluster east–west data with new data along a cluster north–south strip and with data obtained for the Ursa Major (UMa) cluster and fields around the spiral galaxy M101. Our intention is to look for differences in the nature of the dwarf galaxy population with location in the cluster and within other environments. These uniform data sets reach central surface brightness values of ∼26 Bμ, and an apparent B magnitude of 21 for a Virgo cluster distance of 16 Mpc). Over a north–south strip area of ∼15 deg2, we find ∼22 LSB objects per square degree. This compares with ∼4 deg−2 in both the UMa and the M101 fields. These results are very similar to what we have previously found for the east–west cluster strip and for other fields outside the cluster. There are far more small LSB features detected in Virgo cluster fields and we associate them with an extensive cluster dwarf galaxy population. In the cluster north–south strip there is an average dwarf-to-giant number ratio of 31 ± 9, which is much higher than would be expected from observations of galaxies in the Local Group, but significantly less than that required by Λ cold dark matter galaxy formation models. The dwarf-to-giant ratios in UMa and M101 are consistent with those in the Local Group. Comparing the cluster east–west and north–south data, we find clear differences in the way the number density of dwarfs decreases with cluster radius and the distributions of galaxy magnitudes and sizes. The north–south strip covers a region of the cluster that contains not only the main cluster region associated with M87, but also two more distant infalling clouds. Additionally, the north–south strip lies approximately along the extended filamentary structure associated with Virgo while the east–west strip is perpendicular to it. We interpret the differences between the two strips as being due to these different environments. We suggest that the Virgo cluster is assembling itself out of subclusters and clouds that are already rich in dwarf galaxies compared to the environment of the general field. There is no evidence for any systematic difference in dwarf galaxy ( colour between dwarf galaxies of different magnitudes or in different parts of the Virgo cluster. A typical value of = 1.8 is consistent with the colours of a wide range of stellar systems including the globular clusters of the central elliptical galaxy M87, but is bluer than is typical for giant ellipticals. We discuss and interpret our results in the context of various physical processes that are thought to act on galaxies as they form and evolve. Additionally, we give images and positions of possible new dwarf galaxy companions of M101. [ABSTRACT FROM AUTHOR]

The HIDEEP survey was carried out in an attempt to find objects having low inferred neutral hydrogen column densities, yet it found a distribution that was strongly peaked at . In an attempt to understand this distribution and similar survey results, we model H i profiles of gas discs and use simple simulations of objects having a wide range of H i properties in the presence of an ionizing background. We find that inferred column density values, which are found by averaging total H i masses over some disc area, do not vary strongly with central column density for detectable objects, so that even a population having a wide range of Nmax values will give rise to a strongly peaked distribution of values. We find that populations of objects having a wide range of model parameters give rise to inferred column density distributions around . However, populations of fairly massive objects having a wide range of central column densities work best in reproducing the HIDEEP data, and these populations are also consistent with observed Lyman limit absorber counts. It may be necessary to look two orders of magnitude fainter than HIDEEP limits to detect ionized objects having central column densities , but the inferred column densities of already detected objects might be lower if their radii could be estimated more accurately. [ABSTRACT FROM AUTHOR]

According to the cold dark matter (CDM) hierarchical clustering theory of galaxy and large-scale structure formation, there should be numerous low-mass dark matter haloes present in the Universe today. If these haloes contain sufficient stars, they should be detectable as low-luminosity stellar systems or dwarf galaxies. We have previously described a new detection method for faint low surface brightness objects and we have shown that there are relatively large numbers of very faint dwarf galaxies in the nearby Virgo cluster. In this paper, we present results from a similar survey carried out on the Millennium Galaxy strip, which runs along the celestial equator and samples a very different galaxy environment. We show that the dwarf-to-giant galaxy number ratio along this strip ranges from 0.7 : 1 to, at most, 6 : 1, corresponding to a flat luminosity function ( to −1.0). This is very different to our value of 20 : 1 for the Virgo cluster. There is no population of low surface brightness dwarf galaxies in the field that have gone undetected by the redshift surveys. This result is exactly opposite to what CDM models predict for the environmental dependence of the dark matter mass function, which is that there are proportionally more small dark matter haloes in lower-density environments. [ABSTRACT FROM AUTHOR]

ABSTRACT We present skirt (Stellar Kinematics Including Radiative Transfer), a new Monte Carlo radiative transfer code that allows the calculation of the observed stellar kinematics of a dusty galaxy. The code incorporates the effects of both absorption and scattering by interstellar dust grains, and calculates the Doppler shift of the emerging radiation exactly by taking into account the velocities of the emitting stars and the individual scattering dust grains. The code supports arbitrary distributions of dust through a cellular approach, whereby the integration through the dust is optimized by means of a novel efficient trilinear interpolation technique. We apply our modelling technique to calculate the observed kinematics of realistic models for dusty disc galaxies. We find that the effects of dust on the mean projected velocity and projected velocity dispersion are severe for edge-on galaxies. For galaxies which deviate more than a few degrees from exactly edge-on, the effects are already strongly reduced. As a consequence, dust attenuation cannot serve as a possible way to reconcile the discrepancy between the observed shallow slopes of the inner rotation curves of low surface brightness galaxies and the predictions of cold dark matter cosmological models. For face-on galaxies, the velocity dispersion increases with increasing dust mass owing to scattering, but the effects are limited, even for extended dust distributions. Finally, we show that serious errors can be made when the individual velocities of the dust grains are neglected in the calculations. [ABSTRACT FROM AUTHOR]

ABSTRACT Some Lyman continuum photons are likely to escape from most galaxies, and these can play an important role in ionizing gas around and between galaxies, including gas that gives rise to Lyman-alpha absorption. Thus the gas surrounding galaxies and in the intergalactic medium will be exposed to varying amounts of ionizing radiation depending upon the distances, orientations and luminosities of any nearby galaxies. The ionizing background can be recalculated at any point within a simulation by adding the flux from the galaxies to a uniform quasar contribution. Normal galaxies are found to almost always make some contribution to the ionizing background radiation at a redshift of zero, as seen by absorbers and at random points in space. Assuming that ∼2 per cent of ionizing photons escape from a galaxy such as the Milky Way, we find that normal galaxies make a contribution of at least 30–40 per cent of the assumed quasar background. Lyman-alpha absorbers with a wide range of neutral column densities are found to be exposed to a wide range of ionization rates, although the distribution of photoionization rates for absorbers is found to be strongly peaked. On average, fewer highly ionized absorbers are found to arise further from luminous galaxies, while local fluctuations in the ionization rate are seen around galaxies having a wide range of properties. [ABSTRACT FROM AUTHOR]

PAX6 is essential for ocular morphogenesis. Mutations in the PAX6gene produce various phenotypes, including aniridia, Peters’ anomaly, foveal hypoplasia, autosomal dominant keratitis and congenital cataracts. PAX6 functions as a transcription factor and has two DNA binding domains (a paired domain and a homeodomain) which are joined by a linker, and a transactivation domain enriched in proline, serine and threonine (PST) at the C-terminus. The mechanism of PAX6 function is not clearly understood, and few target genes in vertebrates have been identified. We examined disease-causing missense mutations in the PST domain to understand how they affect the function of PAX6. Upon examining the DNA samples of aniridia patients, we identified three missense mutations in the PST domain: P375Q (a novel mutation) and the previously reported Q422R and X423L mutations. On the basis of functional analysis, the P375Q mutant appears to have a normal transactivation activity but lower DNA binding through the paired domain than the wild-type. The Q422R mutation resulted in the loss of DNA binding ability of the PAX6 homeodomain. Substitution analyses of the C-terminal amino acid (codon 422) indicated that an amino acid at codon 422 is required for DNA binding of the homeodomain of intact PAX6 and that the polarity and charge of the side-chain of the terminal amino acid influence this binding. [ABSTRACT FROM PUBLISHER]

To identify a dose as low as diagnostically acceptable and a threshold level of image quality for cone beam CT (CBCT) imaging root canals, using maxillary first molar (M1M) second mesiobuccal (MB2) canals of varying complexity for two CBCT scanners. Dose–area product (DAP) and contrast-to-noise ratio (CNR) were measured for two scanners at a range of exposure parameters. Subjective-image-quality assessment at the same exposures was performed for three M1Ms of varying MB2 complexity, positioned in an anthropomorphic phantom. Nine raters (three endodontists, three dental radiologists and three junior staff) assessed canal visibility, using a 5-point confidence scale rating. Identification of simple-moderate MB2 canal complexity was achieved at a range of protocols, with DAP values of ≥209.3 and ≥203.2 mGy cm² and CNRs of 3 and 7.6 for Promax®3D and Accuitomo-F170® respectively. For complex canal anatomy, target subjective image quality was not achieved, even at the highest DAP values for both scanners. Junior staff classified significantly more images as undiagnostic compared with senior staff (p = 0.043). In this first study to address optimisation of CBCT imaging of root canal anatomy, a similar threshold dose for both scanners was identified for M1Ms with simple-moderate MB2 canal complexity. Increasing dose to enhance visualisation of more complex canal anatomy was ineffective. Selection of standard protocols (while avoiding lower kV/mA protocols) instead of high-resolution scans was a practical means of reducing patient dose. CNR is not a transferable measure of image quality. [ABSTRACT FROM AUTHOR]

The evidence for diagnostic accuracy using cone beam computed tomography (CBCT) for dental applications depends heavily on ex vivo research, but there is little knowledge of whether the model used affects the diagnostic accuracy results. The objective of this study was to determine the impact of different designs of anthropomorphic models on diagnostic accuracy for the specific task of dental root fracture detection. Horizontal or oblique root fracture was induced in 24 of 48 permanent maxillary incisors. The 48 teeth were scanned by CBCT using standard clinical exposure factors on five occasions, each with a different model design. Scans were viewed by five dental and maxillofacial radiologists, who each made a forced diagnosis of fracture or no fracture in each root and a judgment on root fracture using a five-point confidence scale. Sensitivity (Se), specificity (Sp) and areas under receiver operating characteristic (ROC) curve (Az) were calculated for each observer for each model. There were no significant differences between the diagnostic accuracy measurements recorded using different models. There were, however, numerous significant differences between observers using the same anthropomorphic model. Despite the differences in X-ray attenuation between the five model designs, the results suggest that the anthropomorphic model does not affect the results of diagnostic accuracy studies on root fracture using this CBCT machine at standard clinical exposures. This provides some confidence in the previously published evidence. The interobserver diagnosis differences indicate that research using only two observers could provide misleading results. [ABSTRACT FROM AUTHOR]

Unlike Pho85 of Saccharomyces cerevisiae, the highly related PHOA cyclin-dependent kinase (CDK) of Aspergillus nidulans plays no role in regulation of enzymes involved in phosphorous acquisition but instead modulates differentiation in response to environmental conditions, including limited phosphorous. Like PHO85, Aspergillus phoA is a nonessential gene. However, we find that expression of dominant-negative PHOA inhibits growth, suggesting it may have an essential but redundant function. Supporting this we have identified another cyclin-dependent kinase, PHOB, which is 77% identical to PHOA. Deletion of phoB causes no phenotype, even under phosphorous-limited growth conditions. To investigate the function of phoA/phoB, double mutants were selected from a cross of strains containing null alleles and by generating a temperature-sensitive allele of phoA in a ΔphoB background. Double-deleted ascospores were able to germinate but had a limited capacity for nuclear division, suggesting a cell cycle defect. Longer germination revealed morphological defects. The temperature-sensitive phoA allele caused both nuclear division and polarity defects at restrictive temperature, which could be complemented by expression of mammalian CDK5. Therefore, an essential function exists in A. nidulans for the Pho85-1ike kinase pair PHOA and PHOB, which may involve cell cycle control and morphogenesis. [ABSTRACT FROM AUTHOR]