Low Surface Brightness Galaxies and the Galaxy Stellar Mass Function

The galaxy stellar mass function (GSMF) has been well measured by the Galaxy And Mass Assembly (GAMA) survey down to a mass of \mstar = 10^{8}\,\msun. Below this mass the values produced so far can only be taken as lower limits on the distribution. One source of this incompleteness is failing to account for undetected low-surface-brightness galaxies (LSBGs) within the fields observed. These galaxies have been known about for some time, however, taking a true census of their population is difficult because of the biases associated with their detection in large surveys. The focus of this thesis is to improve the census of these objects and to try and apply those results to the low-mass end of the GSMF. First the SDSS data used to create the original GAMA catalogues is re-examined for low-surface brightness galaxies (LSBGs). To accomplish this SDSS DR7 imaging was used and a specialised detection algorithm created. This was based on masking sources detected with SDSS \textsc{photo}, combining the {\it gri} images with a weighting that maximises the signal-to-noise (SNR), and smoothing the images. These were then run through a detection algorithm which finds all pixels above a set threshold and groups them based on their proximity to one another. The list of detections is cleaned of contaminants such as diffraction spikes and the faint wings of masked objects. This produces a final list of 343 newly discovered LSBGs. Measuring their $g-i$ and $J-K$ colours shows that most are likely to be at redshifts less than 0.15. The photometry is carried out using a flexible auto aperture for each detection giving surface brightness measurements of $\mu_{r} > 23.7$\,mag arcsec$^{-2}$ and $r$-band magnitudes of $r_{AUTO} \gtrsim 20$\, mag. Through this method we show there are at least 343 new LSBGs within the GAMA fields, however none of these galaxies are bright enough to be within the GAMA main survey limit. It was noticed during the previous work that the detected LSBGs were all visible in VIKING $Z$-band data, and so it was decided to run a more traditional detection algorithm over these data to increase the number of LSBGs detected. This could then be used to create a new GSMF based on the deeper $Z$-band imaging. By using this imaging it will be possible to detect many more faint galaxies than previously and also increase the depth to which surface brightness can be effectively probed. The three GAMA equatorial regions have had mosaics created from the $Z$-band imaging which are searched using \textsc{Source Extractor} (\textsc{SExtractor}) and catalogues of detections are made. These are then compared to the original GAMA catalogues to remove duplicate detections and identify any possible new ones. Criteria are then applied to the source lists to remove any stars or objects which are either not galaxies or artefacts. This then leaves only likely galaxies in the catalogue to be used. The next stage is to create the GSMF based on the data collected, through applying corrections for the volume searched, and the spectroscopic completeness of the objects after they have been binned in $g-i$, $J-K$, and apparent magnitude. The GSMF created is compared to previous versions, namely that from \cite{Baldry+2012}, and a rise in the number density at masses of \mstar \le 10^{8}\,\msun is shown. These can still only be thought of as lower limits however as improvement to the imaging can still be made in future surveys. With a full catalogue obtained using the VIKING Z-band it was decided to revisit the detection algorithm developed in Chapter 2. A pilot study was undertaken to both test the validity of the method, and the suitability of the VIKING images for further study. Whilst applying the detection algorithm to the data improved the ability to detect low surface brightness features within the images, no new galaxies were discovered over the pilot study area of $0.75$ deg$^{2}$. This method applied to the Z-band data, even over the full area, is unlikely to lead to large numbers of new LSBGs. This work has shown that there are still LSBGs in the field to be discovered. The result of finding new LSBGs has been to raise the measurement of the GSMF at low masses, further constraining the number of low mass galaxies in the Universe

Extracellular vesicles can be processed by electrospinning without loss of structure or function

Extracellular vesicles (EVs) are cell-derived bodies proven to have a wide range of therapeutic applications. To date, EVs have almost always been administered by direct injection, which is very likely to hinder their efficacy because of rapid clearance from the injection site. Here we show that EVs can be successfully processed into polymer-based fibres by electrospinning, with no loss of structure or function

A recent whole-genome duplication divides populations of a globally-distributed microsporidian

This is the final version of the article. Available from Oxford University Press via the DOI in this record.The Microsporidia are a major group of intracellular fungi and important parasites of animals including insects, fish, and immunocompromised humans. Microsporidian genomes have undergone extreme reductive evolution but there are major differences in genome size and structure within the group: some are prokaryote-like in size and organisation (<3 Mb of gene-dense sequence) whilst others have more typically eukaryotic genome architectures. To gain fine-scale, population-level insight into the evolutionary dynamics of these tiny eukaryotic genomes, we performed the broadest microsporidian population genomic study to date, sequencing geographically isolated strains of Spraguea, a marine microsporidian infecting goosefish worldwide. Our analysis revealed that population structure across the Atlantic Ocean is associated with a conserved difference in ploidy, with American and Canadian isolates sharing an ancestral whole genome duplication that was followed by widespread pseudogenisation and sorting-out of paralogue pairs. Whilst past analyses have suggested de novo gene formation of microsporidian-specific genes, we found evidence for the origin of new genes from noncoding sequence since the divergence of these populations. Some of these genes experience selective constraint, suggesting the evolution of new functions and local host adaptation. Combining our data with published microsporidian genomes, we show that nucleotide composition across the phylum is shaped by a mutational bias favouring A and T nucleotides, which is opposed by an evolutionary force favouring an increase in genomic GC content. This work reveals ongoing dramatic reorganisation of genome structure and the evolution of new gene functions in modern microsporidians despite extensive genomic streamlining in their common ancestor.The authors would like to thank John Brookfield and David Studholme for helpful discussions. This work was supported by a Marie Curie Intra-European postdoctoral fellowship (T.A.W.) and the European Research Council Advanced Investigator Programme and the Wellcome Trust (grant numbers ERC- 2010- AdG-268701 045404 to T.M.E.) It is also supported by a Royal Society University Research Fellowship (B.A.P.W.)

The new classification of seizures: an overview for the general physician

The International League Against Epilepsy Classification of the Epilepsies, first presented in 1981, has been widely adopted across the globe. In 2017 it was revised to allow for more robust, specific, flexible and logical classification of seizures. A number of new seizure types are recognised. Classification should be timely as it plays a vital role in the diagnosis and management of patients with epilepsy. Accurate classification also underpins epilepsy research from pathophysiology to public health. Here we review the basic and extended forms of the classification. Semiology (symptoms and signs) is used as the foundation for grouping seizures under focal, generalised or of unknown onset. Focal seizures can be further classified by the presence or absence of awareness and motor signs. Generalised seizures engage bilateral networks from the onset and these can be either motor or non-motor. Seizures of unknown onset can be classified as motor, non-motor, tonic–clonic, epileptic spasms, or behaviour arrest

The simulation of action disorganisation in complex activities of daily living

Action selection in everyday goal-directed tasks of moderate complexity is known to be subject to breakdown following extensive frontal brain injury. A model of action selection in such tasks is presented and used to explore three hypotheses concerning the origins of action disorganisation: that it is a consequence of reduced top-down excitation within a hierarchical action schema network coupled with increased bottom-up triggering of schemas from environmental sources, that it is a more general disturbance of schema activation modelled by excessive noise in the schema network, and that it results from a general disturbance of the triggering of schemas by object representations. Results suggest that the action disorganisation syndrome is best accounted for by a general disturbance to schema activation, while altering the balance between top-down and bottom-up activation provides an account of a related disorder - utilisation behaviour. It is further suggested that ideational apraxia (which may result from lesions to left temporoparietal areas and which has similar behavioural consequences to action disorganisation syndrome on tasks of moderate complexity) is a consequence of a generalised disturbance of the triggering of schemas by object representations. Several predictions regarding differences between action disorganisation syndrome and ideational apraxia that follow from this interpretation are detailed

Disrupted iron regulation in the brain and periphery in cocaine addiction

Stimulant drugs acutely increase dopamine neurotransmission in the brain, and chronic use leads to neuroadaptive changes in the mesolimbic dopamine system and morphological changes in basal ganglia structures. Little is known about the mechanisms underlying these changes but preclinical evidence suggests that iron, a coenzyme in dopamine synthesis and storage, may be a candidate mediator. Iron is present in high concentrations in the basal ganglia and stimulant drugs may interfere with iron homeostasis. We hypothesised that morphological brain changes in cocaine addiction relate to abnormal iron regulation in the brain and periphery. We determined iron concentration in the brain, using quantitative susceptibility mapping, and in the periphery, using iron markers in circulating blood, in 44 patients with cocaine addiction and 44 healthy controls. Cocaine-addicted individuals showed excess iron accumulation in the globus pallidus, which strongly correlated with duration of cocaine use, and mild iron deficiency in the periphery, which was associated with low iron levels in the red nucleus. Our findings show that iron dysregulation occurs in cocaine addiction and suggest that it arises consequent to chronic cocaine use. Putamen enlargement in these individuals was unrelated to iron concentrations, suggesting that these are co-occurring morphological changes that may respectively reflect predisposition to, and consequences of cocaine addiction. Understanding the mechanisms by which cocaine affects iron metabolism may reveal novel therapeutic targets, and determine the value of iron levels in the brain and periphery as biomarkers of vulnerability to, as well as progression and response to treatment of cocaine addiction

Polysomnographic and Subjective Sleep Predictors of Alcoholic Relapse

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65219/1/j.1530-0277.1998.tb03995.x.pd

Identification of animal movement patterns using tri-axial magnetometry

BackgroundAccelerometers are powerful sensors in many bio-logging devices, and are increasingly allowing researchers to investigate the performance, behaviour, energy expenditure and even state, of free-living animals. Another sensor commonly used in animal-attached loggers is the magnetometer, which has been primarily used in dead-reckoning or inertial measurement tags, but little outside that. We examine the potential of magnetometers for helping elucidate the behaviour of animals in a manner analogous to, but very different from, accelerometers. The particular responses of magnetometers to movement means that there are instances when they can resolve behaviours that are not easily perceived using accelerometers.MethodsWe calibrated the tri-axial magnetometer to rotations in each axis of movement and constructed 3-dimensional plots to inspect these stylised movements. Using the tri-axial data of Daily Diary tags, attached to individuals of number of animal species as they perform different behaviours, we used these 3-d plots to develop a framework with which tri-axial magnetometry data can be examined and introduce metrics that should help quantify movement and behaviour.ResultsTri-axial magnetometry data reveal patterns in movement at various scales of rotation that are not always evident in acceleration data. Some of these patterns may be obscure until visualised in 3D space as tri-axial spherical plots (m-spheres). A tag-fitted animal that rotates in heading while adopting a constant body attitude produces a ring of data around the pole of the m-sphere that we define as its Normal Operational Plane (NOP). Data that do not lie on this ring are created by postural rotations of the animal as it pitches and/or rolls. Consequently, stereotyped behaviours appear as specific trajectories on the sphere (m-prints), reflecting conserved sequences of postural changes (and/or angular velocities), which result from the precise relationship between body attitude and heading. This novel approach shows promise for helping researchers to identify and quantify behaviours in terms of animal body posture, including heading.ConclusionMagnetometer-based techniques and metrics can enhance our capacity to identify and examine animal behaviour, either as a technique used alone, or one that is complementary to tri-axial accelerometry

Bats Use Magnetite to Detect the Earth's Magnetic Field

While the role of magnetic cues for compass orientation has been confirmed in numerous animals, the mechanism of detection is still debated. Two hypotheses have been proposed, one based on a light dependent mechanism, apparently used by birds and another based on a “compass organelle” containing the iron oxide particles magnetite (Fe3O4). Bats have recently been shown to use magnetic cues for compass orientation but the method by which they detect the Earth's magnetic field remains unknown. Here we use the classic “Kalmijn-Blakemore” pulse re-magnetization experiment, whereby the polarity of cellular magnetite is reversed. The results demonstrate that the big brown bat Eptesicus fuscus uses single domain magnetite to detect the Earths magnetic field and the response indicates a polarity based receptor. Polarity detection is a prerequisite for the use of magnetite as a compass and suggests that big brown bats use magnetite to detect the magnetic field as a compass. Our results indicate the possibility that sensory cells in bats contain freely rotating magnetite particles, which appears not to be the case in birds. It is crucial that the ultrastructure of the magnetite containing magnetoreceptors is described for our understanding of magnetoreception in animals

Heritability of cognitive and emotion processing during functional MRI in a twin sample

Despite compelling evidence that brain structure is heritable, the evidence for the heritability of task-evoked brain function is less robust. Findings from previous studies are inconsistent possibly reflecting small samples and methodological variations. In a large national twin sample, we systematically evaluated heritability of task-evoked brain activity derived from functional magnetic resonance imaging. We used established standardised tasks to engage brain regions involved in cognitive and emotional functions. Heritability was evaluated across a conscious and nonconscious Facial Expressions of Emotion Task (FEET), selective attention Oddball Task, N-back task of working memory maintenance, and a Go-NoGo cognitive control task in a sample of Australian adult twins (N ranged from 136 to 226 participants depending on the task and pairs). Two methods for quantifying associations of heritability and brain activity were utilised; a multivariate independent component analysis (ICA) approach and a univariate brain region-of-interest (ROI) approach. Using ICA, we observed that a significant proportion of task-evoked brain activity was heritable, with estimates ranging from 23% to 26% for activity elicited by nonconscious facial emotion stimuli, 27% to 34% for N-back working memory maintenance and sustained attention, and 32% to 33% for selective attention in the Oddball task. Using the ROI approach, we found that activity of regions specifically implicated in emotion processing and selective attention showed significant heritability for three ROIs, including estimates of 33%–34% for the left and right amygdala in the nonconscious processing of sad faces and 29% in the medial superior prefrontal cortex for the Oddball task. Although both approaches show similar levels of heritability for the Nonconscious Faces and Oddball tasks, ICA results displayed a more extensive network of heritable brain function, including additional regions beyond the ROI analysis. Furthermore, multivariate twin modelling of both ICA networks and ROI activation suggested a mix of common genetic and unique environmental factors that contribute to the associations between networks/regions. Together, the results indicate a complex relationship between genetic factors and environmental interactions that ultimately give rise to neural activation underlying cognition and emotion