Why multi-tracer surveys beat cosmic variance

Galaxy surveys that map multiple species of tracers of large-scale structure can improve the constraints on some cosmological parameters far beyond the limits imposed by a simplistic interpretation of cosmic variance. This enhancement derives from comparing the relative clustering between different tracers of large-scale structure. We present a simple but fully generic expression for the Fisher information matrix of surveys with any (discrete) number of tracers, and show that the enhancement of the constraints on bias-sensitive parameters are a straightforward consequence of this multi-tracer Fisher matrix. In fact, the relative clustering amplitudes between tracers are eigenvectors of this multi-tracer Fisher matrix. The diagonalized multi-tracer Fisher matrix clearly shows that while the effective volume is bounded by the physical volume of the survey, the relational information between species is unbounded. As an application, we study the expected enhancements in the constraints of realistic surveys that aim at mapping several different types of tracers of large-scale structure. The gain obtained by combining multiple tracers is highest at low redshifts, and in one particular scenario we analyzed, the enhancement can be as large as a factor of ~3 for the accuracy in the determination of the redshift distortion parameter, and a factor ~5 for the local non-Gaussianity parameter. Radial and angular distance determinations from the baryonic features in the power spectrum may also benefit from the multi-tracer approach.Comment: New references included; 9 pages, 9 figure

‘The new degree?’ Constructing internships in the third sector

The recent economic recession has impacted substantially on the graduate labour market, with many graduates now struggling to find secure employment in professional careers. In this context, temporary, unpaid ‘internships’ have emerged as increasingly important as a ‘way in’ to work for this group. Yet while there has been much media and policy debate on internships, academic consideration has been scant. This paper begins to address this knowledge gap by drawing on a study of interns in a third sector environmental organisation. The research findings reveal that unpaid internships were rationalised through a complex mix of political motivations, career ambitions and lifestyle aims, but these intersected in important ways with social class. These findings are not only of empirical interest, contributing to our knowledge of graduate negotiations of precarity, but also of theoretical value, extending our understanding of young people’s agency and motivations in transitions into work

Turning Outward

How do we live well? Building on the philosophical tradition of Plato, Simone Weil, and Iris Murdoch, I argue that a moral agent may reach eudaimonia by cultivating an inner life of 'attention,' a humble disposition consisting of vulnerability to and appreciation of truth, qua a dialectical desire for the Good. I call this process 'turning outward.

Interindividual methylomic variation across blood, cortex, and cerebellum: implications for epigenetic studies of neurological and neuropsychiatric phenotypes

Given the tissue-specific nature of epigenetic processes, the assessment of disease-relevant tissue is an important consideration for epigenome-wide association studies (EWAS). Little is known about whether easily accessible tissues, such as whole blood, can be used to address questions about interindividual epigenomic variation in inaccessible tissues, such as the brain. We quantified DNA methylation in matched DNA samples isolated from whole blood and 4 brain regions (prefrontal cortex, entorhinal cortex, superior temporal gyrus, and cerebellum) from 122 individuals. We explored co-variation between tissues and the extent to which methylomic variation in blood is predictive of interindividual variation identified in the brain. For the majority of DNA methylation sites, interindividual variation in whole blood is not a strong predictor of interindividual variation in the brain, although the relationship with cortical regions is stronger than with the cerebellum. Variation at a subset of probes is strongly correlated across tissues, even in instances when the actual level of DNA methylation is significantly different between them. A substantial proportion of this co-variation, however, is likely to result from genetic influences. Our data suggest that for the majority of the genome, a blood-based EWAS for disorders where brain is presumed to be the primary tissue of interest will give limited information relating to underlying pathological processes. These results do not, however, discount the utility of using a blood-based EWAS to identify biomarkers of disease phenotypes manifest in the brain. We have generated a searchable database for the interpretation of data from blood-based EWAS analyses (http://epigenetics.essex.ac.uk/ bloodbrain/)

Challenges and Opportunities for Next-Generation Manufacturing in Space

With commercial space travel now a reality, the idea that people might spend time on other planets in the future seems to have greater potential. To make this possible, however, there needs to be flexible means for manufacturing in space to enable tooling or resources to be created when needed to handle unexpected situations. Next-generation manufacturing paradigms offer significant potential for the kind of flexibility that might be needed; however, they can result in increases in computation time compared to traditional control methods that could make many of the computing resources already available on earth attractive for use. Furthermore, resilience is a significant focus of next-generation manufacturing strategies, and one way to enable resilience for space manufacturing would be to have backup controllers available on earth. These types of considerations raise questions about remote control and monitoring, as well as privacy of the data involved in such practices, that must be considered. This work provides a perspective on several topics tied to remote control and monitoring for manufacturing in space

Loneliness and Sense of Belonging in Aphasia

More than 90% of people with aphasia feel isolated, which can lead to physical illness, depression, and suicide. We sought to determine whether loneliness differs between people with and without aphasia, and, if so, to identify treatable factors associated with loneliness in people with aphasia. We found that participants with aphasia were significantly lonelier than controls; that perceived frequency of social support was significantly related with loneliness only in controls; and, that participants with aphasia reported a significantly diminished sense of belonging. No demographic or stroke-related variables were linked with loneliness in our samples. Suggestions for treatment research are offered

Increased DNA methylation near TREM2 is consistently seen in the superior temporal gyrus in Alzheimer's disease brain

Although mutations within the TREM2 gene have been robustly associated with Alzheimer's disease, it is not known whether alterations in the regulation of this gene are also involved in pathogenesis. Here, we present data demonstrating increased DNA methylation in the superior temporal gyrus in Alzheimer's disease brain at a CpG site located 289 bp upstream of the transcription start site of the TREM2 gene in 3 independent study cohorts using 2 different technologies (Illumina Infinium 450K methylation beadchip and pyrosequencing). A meta-analysis across all 3 cohorts reveals consistent AD-associated hypermethylation (p = 3.47E-08). This study highlights that extending genetic studies of TREM2 in AD to investigate epigenetic changes may nominate additional mechanisms by which disruption to this gene increases risk