Research and Development of the eXtendable Solar Array System

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97139/1/AIAA2012-143.pd

Thin Fisher Zeroes

Biskup et al. [Phys. Rev. Lett. 84 (2000) 4794] have recently suggested that the loci of partition function zeroes can profitably be regarded as phase boundaries in the complex temperature or field planes. We obtain the Fisher zeroes for Ising and Potts models on non-planar (``thin'') regular random graphs using this approach, and note that the locus of Fisher zeroes on a Bethe lattice is identical to the corresponding random graph. Since the number of states appears as a parameter in the Potts solution the limiting locus of chromatic zeroes is also accessible.Comment: 10 pages, 4 figure

Polypharmacy and Antidepressant Acceptability in Comorbid Depression and Type 2 Diabetes

BACKGROUND: Polypharmacy may increase the risk of drug interactions, side-effects and poor adherence. However, the impact of polypharmacy on antidepressant acceptability in individuals with type 2 diabetes (T2DM) is unknown. AIM: In adults with T2DM, to investigate the association between the number of prescribed medications and: i) early antidepressant discontinuation (<32 weeks); ii) switching antidepressant agents. DESIGN: Cohort study using UK primary care data from the years 2000-2018. METHODS: We used cox regression with penalised B-splines to describe the association between the number of concurrently prescribed medications at the time of starting antidepressant treatment, and each of our outcomes. RESULTS: We identified 73,808 individuals with comorbid depression and T2DM starting antidepressant treatment for the first time. The median number of concurrent medications prescribed was 7. Within 32 weeks, 44.26% of participants discontinued antidepressant treatment altogether, and 11.75% of participants switched antidepressant agents. We found an inverse relationship between the number of concurrent medications and discontinuing antidepressant treatment altogether. The median number of 7 concurrent medications was associated with a 65.06% decrease early antidepressant discontinuation HR 0.45, 95% CIs 0.37-0.55). We found no evidence of an association, in our main analysis, between the number of concurrent medications and switching antidepressant agents. CONCLUSIONS: Early discontinuation of antidepressants is common in adults with T2DM. However, individuals with higher levels of concurrent polypharmacy may be more adherent to treatment. These are likely to represent individuals with worse physical/mental health. Individuals with lower levels of concurrent polypharmacy may benefit from adherence support

Association between polypharmacy and depression relapse in individuals with comorbid depression and type 2 diabetes: a UK electronic health record study

BACKGROUND: Individuals with physical comorbidities and polypharmacy may be at higher risk of depression relapse, however, they are not included in the 'high risk of relapse' group for whom longer antidepressant treatment durations are recommended. AIMS: In individuals with comorbid depression and type 2 diabetes (T2DM), we aimed to investigate the association and interaction between depression relapse and (a) polypharmacy, (b) previous duration of antidepressant treatment. METHOD: This was a cohort study using primary care data from the UK Clinical Practice Research Datalink (CPRD) from years 2000 to 2018. We used Cox regression models with penalised B-splines to describe the association between restarting antidepressants and our two exposures. RESULTS: We identified 48 001 individuals with comorbid depression and T2DM, who started and discontinued antidepressant treatment during follow-up. Within 1 year of antidepressant discontinuation, 35% of participants restarted treatment indicating depression relapse. As polypharmacy increased, the rate of restarting antidepressants increased until a maximum of 18 concurrent medications, where individuals were more than twice as likely to restart antidepressants (hazard ratio (HR) = 2.15, 95% CI 1.32-3.51). As the duration of previous antidepressant treatment increased, the rate of restarting antidepressants increased - individuals with a previous duration of ≥25 months were more than twice as likely to restart antidepressants than those who previously discontinued in <7 months (HR = 2.36, 95% CI 2.25-2.48). We found no interaction between polypharmacy and previous antidepressant duration. CONCLUSIONS: Polypharmacy and longer durations of previous antidepressant treatment may be associated with depression relapse following the discontinuation of antidepressant treatment

Prevalence and characteristics of antidepressant prescribing in adults with comorbid depression and type 2 diabetes mellitus: A systematic review and meta-analysis

Background: Treatment guidelines do not provide specific recommendations for antidepressant prescribing in people with type 2 diabetes mellitus (T2DM). It is important to understand the prevalence of antidepressant prescribing and associated patient characteristics, to recognise safety issues or inequalities related to treatment access. Methods and Results: Seven databases were searched using terms related to depression, T2DM and antidepressant medication. From 14,389 reports retrieved, 9 met inclusion criteria. The prevalence of antidepressant prescribing varied considerably between studies from 18% to 87%. Where meta-analyses were possible, the pooled odds ratio for receiving an antidepressant were 1.52 (95% confidence intervals (CIs) 1.28 - 1.82) in women compared to men, 0.53 (95% CIs 0.23-1.20%) in Black and Ethnic Minorities compared to White ethnicity and 1.29 (95% CIs 0.92-1.80) in insulin users compared to individuals with non-insulin controlled T2DM. Conclusions: Antidepressant prescribing is more common in women with T2DM compared to men, however, the difference is less than in the general population. Insulin users, representing individuals with more advanced T2DM, were as likely to be prescribed antidepressants as those who did not use insulin. There is a gap in the literature concerning which antidepressant agents are being prescribed, and alongside which concurrent medications and comorbidities

Fire management in a changing landscape: a case study from Lopé National Park, Gabon

A key management goal in Lopé National Park, Gabon, is to protect regionally-rare savannah ecosystems within the continuous rainforest block. In order to evaluate the impact of existing protection efforts, data on burning season environmental conditions, burning effort and current woody values for savannahs were examined between 1995 and 2008. Results showed (a) spatial heterogeneity in woody values to be correlated with grassy vegetation type (b) a negative relationship between woody vegetation and fire return frequency over the study, suggesting that decreased fire return frequency may favour savannah thickening and (c) that inconsistent burn effort by Park staff, and burns designed for reduced heat, may limit the efficiency of fire to prevent savannah thickening or forest expansion. Optimal humidity and fuel moisture conditions for burning are identified and recommendations made for improving the existing fire plan to achieve the management goal. Modifications will require significant investment of resources and training and require urgent experimental work to disentangle the direct impacts of fire from other processes of vegetation change. Lopé's fire policy should ultimately be a dynamic response to change in the local landscape driven by direct fire impacts or by global climate change

Weighted cue integration in the rodent head direction system

How the brain combines information from different sensory modalities and of differing reliability is an important and still-unanswered question. Using the head direction (HD) system as a model, we explored the resolution of conflicts between landmarks and background cues. Sensory cue integration models predict averaging of the two cues, whereas attractor models predict capture of the signal by the dominant cue. We found that a visual landmark mostly captured the HD signal at low conflicts: however, there was an increasing propensity for the cells to integrate the cues thereafter. A large conflict presented to naive rats resulted in greater visual cue capture (less integration) than in experienced rats, revealing an effect of experience. We propose that weighted cue integration in HD cells arises from dynamic plasticity of the feed-forward inputs to the network, causing within-trial spatial redistribution of the visual inputs onto the ring. This suggests that an attractor network can implement decision processes about cue reliability using simple architecture and learning rules, thus providing a potential neural substrate for weighted cue integration

Weighted cue integration in the rodent head direction system.

How the brain combines information from different sensory modalities and of differing reliability is an important and still-unanswered question. Using the head direction (HD) system as a model, we explored the resolution of conflicts between landmarks and background cues. Sensory cue integration models predict averaging of the two cues, whereas attractor models predict capture of the signal by the dominant cue. We found that a visual landmark mostly captured the HD signal at low conflicts: however, there was an increasing propensity for the cells to integrate the cues thereafter. A large conflict presented to naive rats resulted in greater visual cue capture (less integration) than in experienced rats, revealing an effect of experience. We propose that weighted cue integration in HD cells arises from dynamic plasticity of the feed-forward inputs to the network, causing within-trial spatial redistribution of the visual inputs onto the ring. This suggests that an attractor network can implement decision processes about cue reliability using simple architecture and learning rules, thus providing a potential neural substrate for weighted cue integration

A theoretical account of cue averaging in the rodent head direction system

Head direction (HD) cell responses are thought to be derived from a combination of internal (or idiothetic) and external (or allothetic) sources of information. Recent work from the Jeffery laboratory shows that the relative influence of visual versus vestibular inputs upon the HD cell response depends on the disparity between these sources. In this paper, we present simulation results from a model designed to explain these observations. The model accurately replicates the Knight et al. data. We suggest that cue conflict resolution is critically dependent on plastic remapping of visual information onto the HD cell layer. This remap results in a shift in preferred directions of a subset of HD cells, which is then inherited by the rest of the cells during path integration. Thus, we demonstrate how, over a period of several minutes, a visual landmark may gain cue control. Furthermore, simulation results show that weaker visual landmarks fail to gain cue control as readily. We therefore suggest a second longer term plasticity in visual projections onto HD cell areas, through which landmarks with an inconsistent relationship to idiothetic information are made less salient, significantly hindering their ability to gain cue control. Our results provide a mechanism for reliability-weighted cue averaging that may pertain to other neural systems in addition to the HD system

Hydrogen-poor superluminous stellar explosions

Supernovae (SNe) are stellar explosions driven by gravitational or thermonuclear energy, observed as electromagnetic radiation emitted over weeks or more. In all known SNe, this radiation comes from internal energy deposited in the outflowing ejecta by either radioactive decay of freshly-synthesized elements (typically 56Ni), stored heat deposited by the explosion shock in the envelope of a supergiant star, or interaction between the SN debris and slowly-moving, hydrogen-rich circumstellar material. Here we report on a new class of luminous SNe whose observed properties cannot be explained by any of these known processes. These include four new SNe we have discovered, and two previously unexplained events (SN 2005ap; SCP 06F6) that we can now identify as members. These SNe are all ~10 times brighter than SNe Ia, do not show any trace of hydrogen, emit significant ultra-violet (UV) flux for extended periods of time, and have late-time decay rates which are inconsistent with radioactivity. Our data require that the observed radiation is emitted by hydrogen-free material distributed over a large radius (~10^15 cm) and expanding at high velocities (>10^4 km s^-1). These long-lived, UV-luminous events can be observed out to redshifts z>4 and offer an excellent opportunity to study star formation in, and the interstellar medium of, primitive distant galaxies.Comment: Accepted to Nature. Press embargoed until 2011 June 8, 18:00 U