Metastable Flux Configurations and de Sitter Spaces

We derive stability conditions for the critical points of the no-scale scalar potential governing the dynamics of the complex structure moduli and the axio-dilaton in compactifications of type IIB string theory on Calabi-Yau three-folds. We discuss a concrete example of a T^6 orientifold. We then consider the four-dimensional theory obtained from compactifications of type IIB string theory on non-geometric backgrounds which are mirror to rigid Calabi-Yau manifolds and show that the complex structure moduli fields can be stabilized in terms of H_{RR} only, i.e. with no need of orientifold projection. The stabilization of all the fields at weak coupling, including the axio-dilaton, may require to break supersymmetry in the presence of H_{NS} flux or corrections to the scalar potential.Comment: 24 page

The future of returning genetic test results for psychiatric conditions

Background: Genome-wide association studies are rapidly advancing our understanding of the genetic architecture of complex psychiatric conditions. In order to use findings from these studies for enhanced clinical prediction, we need to gain a better understanding of the issues surrounding the return of complex genetic results. Methods: We review the current literature on genetic literacy in the population, the public’s interest in receiving genetic test results for psychiatric conditions, how individuals react to and interpret their genetic results for psychiatric conditions, and gaps in our knowledge that will be critical to address before returning genetic results for psychiatric conditions. Results: We find that in hypothetical scenarios genetic test results indicating increased risk for a psychiatric condition lowers an individual’s confidence to control behavior, reduces self-agency, and negatively impacts affect. Individuals may believe that a change in behavior is important, but there is little evidence that genetic test results indicating increased risk for a psychiatric condition are associated with behavior change. The negative impact of results indicating an increased risk may stem from common misconceptions of complex disorders that exist in approximately 25% to 35% of individuals studied. Conclusions: Individuals with these misunderstandings about the role of genetic factors in complex disorders may have a belief in genetic determinism, the idea that behaviors and characteristics are determined solely by one’s genetic information. Regardless of one’s genetic knowledge, a majority of people are interested in receiving genetic feedback for psychiatric conditions, highlighting a need for effective communication of these genetic test results.https://scholarscompass.vcu.edu/gradposters/1069/thumbnail.jp

Structure Through Colour: A Pixel Approach Towards Understanding Galaxies

We present a study of pixel Colour Magnitude Diagrams (pCMDs) for a sample of 69 nearby galaxies chosen to span a wide range of Hubble types. Our goal is to determine how useful a pixel approach is for studying galaxies according to their stellar light distributions and content. The galaxy images were analysed on a pixel-by-pixel basis to reveal the structure of the individual pCMDs. We find that the average surface brightness (or projected mass density) in each pixel varies according to galaxy type. Early-type galaxies exihibit a clear ``prime sequence'' and some pCMDs of face-on spirals reveal ``inverse-L'' structures. We find that the colour dispersion at a given magnitude is found to be approximately constant in early-type galaxies but this quantity varies in the mid and late-types. We investigate individual galaxies and find that the pCMDs can be used to pick out morphological features. We discuss the discovery of ``Red Hooks'' in the pCMDs of six early-type galaxies and two spirals and postulate their origins. We develop quantitative methods to characterise the pCMDs, including measures of the blue-to-red light ratio and colour distributions of each galaxy and we organise these by morphological type. We compare the colours of the pixels in each galaxy with the stellar population models of Bruzual & Charlot (2003) to calculate star formation histories for each galaxy type and compare these to the stellar mass within each pixel. Maps of pixel stellar mass and mass-to-light ratio are compared to galaxy images. We apply the pCMD technique to three galaxies in the Hubble Ultra Deep Field to test the usefulness of the analysis at high redshift. We propose that these results can be used as part of a new system of automated classification of galaxies that can be applied at high redshift.Comment: 16 pages, 20 figures, MNRAS, accepted. For high resolution figures see: http://www.nottingham.ac.uk/~ppxmml/lcm_2007.pd

Multi-centre, multi-vendor reproducibility of 7T QSM and R2* in the human brain: Results from the UK7T study

Introduction We present the reliability of ultra-high field T2* MRI at 7T, as part of the UK7T Network's “Travelling Heads” study. T2*-weighted MRI images can be processed to produce quantitative susceptibility maps (QSM) and R2* maps. These reflect iron and myelin concentrations, which are altered in many pathophysiological processes. The relaxation parameters of human brain tissue are such that R2* mapping and QSM show particularly strong gains in contrast-to-noise ratio at ultra-high field (7T) vs clinical field strengths (1.5–3T). We aimed to determine the inter-subject and inter-site reproducibility of QSM and R2* mapping at 7T, in readiness for future multi-site clinical studies. Methods Ten healthy volunteers were scanned with harmonised single- and multi-echo T2*-weighted gradient echo pulse sequences. Participants were scanned five times at each “home” site and once at each of four other sites. The five sites had 1× Philips, 2× Siemens Magnetom, and 2× Siemens Terra scanners. QSM and R2* maps were computed with the Multi-Scale Dipole Inversion (MSDI) algorithm (https://github.com/fil-physics/Publication-Code). Results were assessed in relevant subcortical and cortical regions of interest (ROIs) defined manually or by the MNI152 standard space. Results and Discussion Mean susceptibility (χ) and R2* values agreed broadly with literature values in all ROIs. The inter-site within-subject standard deviation was 0.001–0.005 ppm (χ) and 0.0005–0.001 ms−1 (R2*). For χ this is 2.1–4.8 fold better than 3T reports, and 1.1–3.4 fold better for R2*. The median ICC from within- and cross-site R2* data was 0.98 and 0.91, respectively. Multi-echo QSM had greater variability vs single-echo QSM especially in areas with large B0 inhomogeneity such as the inferior frontal cortex. Across sites, R2* values were more consistent than QSM in subcortical structures due to differences in B0-shimming. On a between-subject level, our measured χ and R2* cross-site variance is comparable to within-site variance in the literature, suggesting that it is reasonable to pool data across sites using our harmonised protocol. Conclusion The harmonized UK7T protocol and pipeline delivers on average a 3-fold improvement in the coefficient of reproducibility for QSM and R2* at 7T compared to previous reports of multi-site reproducibility at 3T. These protocols are ready for use in multi-site clinical studies at 7T

Solar sail science mission applications and advancement : solar sailing: concepts, technology, missions

Solar sailing has long been envisaged as an enabling or disruptive technology. The promise of open-ended missions allows consideration of radically new trajectories and the delivery of spacecraft to previously unreachable or unsustainable observation outposts. A mission catalogue is presented of an extensive range of potential solar sail applications, allowing identification of the key features of missions which are enabled, or significantly enhance, through solar sail propulsion. Through these considerations a solar sail application-pull technology development roadmap is established, using each mission as a technology stepping-stone to the next. Having identified and developed a solar sail application-pull technology development roadmap, this is incorporated into a new vision for solar sailing. The development of new technologies, especially for space applications, is high-risk. The advancement difficulty of low technology readiness level research is typically underestimated due to a lack of recognition of the advancement degree of difficulty scale. Recognising the currently low technology readiness level of traditional solar sailing concepts, along with their high advancement degree of difficulty and a lack of near-term applications a new vision for solar sailing is presented which increases the technology readiness level and reduces the advancement degree of difficulty of solar sailing. Just as the basic principles of solar sailing are not new, they have also been long proven and utilised in spacecraft as a low-risk, high-return limited-capability propulsion system. It is therefore proposed that this significant heritage be used to enable rapid, near-term solar sail future advancement through coupling currently mature solar sail, and other, technologies with current solar sail technology developments. As such the near-term technology readiness level of traditional solar sailing is increased, while simultaneously reducing the advancement degree of difficulty along the solar sail application-pull technology development roadmap

Attitudes and Opinions About Direct-to-Consumer Genetic Testing in Undergraduate Science Students

Background: There has been exponential growth in the number of direct-to-consumer genetic testing kits sold in the past decade. Consumers utilize direct-to-consumer genetic tests for a number of reasons which include learning about one’s ancestry and potential ways to manage health. Emerging adults tend to be early adopters of new technologies; however, there has been little research regarding the opinions about direct-to-consumer genetic testing in emerging adults. Methods: Data came from a study conducted in an upper-level biology course focusing on understanding undergraduate science students’ overall experiences with receiving personalized genetic testing results from 23andMe. The present study used data collected at the baseline assessment which assessed their opinions and attitudes about direct-to-consumer genetic testing (N=133). Results: Over 80% of participants would recommend direct-to-consumer genetic testing options including carrier status reports, DNA ancestry reports, wellness reports, and trait reports to others. However, participants were not as confident that others would be able to accurately interpret their test results. Additionally, more than two-thirds of the participants stated that they would ask a healthcare provider to help interpret their personalized genetic test results. Conclusions: Participants lack confidence in both their ability to interpret their own results and others to interpret their results. It is important for direct-to-consumer genetic testing companies to educate consumers before providing results in order to minimize potential harms due to misinterpretation of results. Further research is needed to assess motivations to participate in direct-to-consumer genetic testing, impact of testing, and understanding of genetic testing results in emerging adults.https://scholarscompass.vcu.edu/gradposters/1124/thumbnail.jp

2MASS Galaxies in the Fornax Cluster Spectroscopic Survey

The Fornax Cluster Spectroscopic Survey (FCSS) is an all-object survey of a region around the Fornax Cluster of galaxies undertaken using the 2dF multi-object spectrograph on the Anglo-Australian Telescope. Its aim was to obtain spectra for a complete sample of all objects with 16.5 < b_j < 19.7 irrespective of their morphology (i.e. including `stars', `galaxies' and `merged' images). We explore the extent to which (nearby) cluster galaxies are present in 2MASS. We consider the reasons for the omission of 2MASS galaxies from the FCSS and vice versa. We consider the intersection (2.9 square degrees on the sky) of our data set with the infra-red 2 Micron All-Sky Survey (2MASS), using both the 2MASS Extended Source Catalogue (XSC) and the Point Source Catalogue (PSC). We match all the XSC objects to FCSS counterparts by position and also extract a sample of galaxies, selected by their FCSS redshifts, from the PSC. We confirm that all 114 XSC objects in the overlap sample are galaxies, on the basis of their FCSS velocities. A total of 23 Fornax Cluster galaxies appear in the matched data, while, as expected, the remainder of the sample lie at redshifts out to z = 0.2 (the spectra show that 61% are early type galaxies, 18% are intermediate types and 21% are strongly star forming).The PSC sample turns out to contain twice as many galaxies as does the XSC. However, only one of these 225 galaxies is a (dwarf) cluster member. On the other hand, galaxies which are unresolved in the 2MASS data (though almost all are resolved in the optical) amount to 71% of the non-cluster galaxies with 2MASS detections and have redshifts out to z=0.32.Comment: 5 pages, accepted by A&A, resubmitted due to missing reference

The Millennium Galaxy Catalogue: Bulge/Disc Decomposition of 10095 Nearby Galaxies

We have modelled the light distribution in 10095 galaxies from the Millennium Galaxy Catalogue (MGC), providing publically available structural catalogues for a large, representative sample of galaxies in the local Universe. Three different models were used: (1) a single Sersic function for the whole galaxy, (2) a bulge-disc decomposition model using a de Vaucouleurs (R^{1/4}) bulge plus exponential disc, (3) a bulge-disc decomposition model using a Sersic (R^{1/n}) bulge plus exponential disc. Repeat observations for 700 galaxies demonstrate that stable measurements can be obtained for object components with a half-light radius comparable to, or larger than, the seeing half-width at half maximum. We show that with careful quality control, robust measurements can be obtained for large samples such as the MGC. We use the catalogues to show that the galaxy colour bimodality is due to the two-component nature of galaxies (i.e. bulges and discs) and not to two distinct galaxy populations. We conclude that understanding galaxy evolution demands the routine bulge-disc decomposition of the giant galaxy population at all redshifts.Comment: Accepted for publication in MNRAS. 23 pages, 20 figure

Multivariate analysis of 1.5 million people identifies genetic associations with traits related to self-regulation and addiction

Behaviors and disorders related to self-regulation, such as substance use, antisocial behavior and attention-deficit/hyperactivity disorder, are collectively referred to as externalizing and have shared genetic liability. We applied a multivariate approach that leverages genetic correlations among externalizing traits for genome-wide association analyses. By pooling data from ~1.5 million people, our approach is statistically more powerful than single-trait analyses and identifies more than 500 genetic loci. The loci were enriched for genes expressed in the brain and related to nervous system development. A polygenic score constructed from our results predicts a range of behavioral and medical outcomes that were not part of genome-wide analyses, including traits that until now lacked well-performing polygenic scores, such as opioid use disorder, suicide, HIV infections, criminal convictions and unemployment. Our findings are consistent with the idea that persistent difficulties in self-regulation can be conceptualized as a neurodevelopmental trait with complex and far-reaching social and health correlates

Multi-Site Harmonization of 7 Tesla MRI Neuroimaging Protocols

Increasing numbers of 7 tesla (7T) magnetic resonance imaging (MRI) scanners are in research and clinical use. 7T MRI can increase the scanning speed, spatial resolution and contrast-to-noise-ratio of many neuroimaging protocols, but technical challenges in implementation have been addressed in a variety of ways across sites. In order to facilitate multi-centre studies and ensure consistency of findings across sites, it is desirable that 7T MRI sites implement common high-quality neuroimaging protocols that can accommodate different scanner models and software versions. With the installation of several new 7T MRI scanners in the United Kingdom, the UK7T Network was established with an aim to create a set of harmonized structural and functional neuroimaging sequences and protocols. The Network currently includes five sites, which use three different scanner platforms, provided by two different vendors. Here we describe the harmonization of functional and anatomical imaging protocols across the three different scanner models, detailing the necessary changes to pulse sequences and reconstruction methods. The harmonized sequences are fully described, along with implementation details. Example datasets acquired from the same subject on all Network scanners are made available. Based on these data, an evaluation of the harmonization is provided. In addition, the implementation and validation of a common system calibration process is described. Keywords 7 tesla; MRI; Harmonization; anatomical; functional; Scanner calibration;The UK7T Network and this work was funded by the UK's Medical Research Council (MRC). [MR/N008537/1]. Centre funding The Wellcome Centre for Integrative Neuroimaging is supported by core funding from the Wellcome Trust (203139/Z/16/Z). Cardiff University Brain Research Imaging Centre is supported by the UK Medical Research Council (MR/M008932/1) and the Wellcome Trust (WT104943). This research was co-funded by the NIHR Cambridge Biomedical Research Centre. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care. Individual funding CTR is funded by a Sir Henry Dale Fellowship from the Wellcome Trust and the Royal Society [098436/Z/12/B]