Thermodynamics of itinerant metamagnetic transitions

Theoretical studies of the metamagnetism and anomalous phase of Sr3Ru2O7 have focused on the role of van Hove singularities, although much experimental evidence points towards quantum criticality having a large effect. We investigate the magnetic and thermodynamic properties of systems where magnetic field tunes through such a peak in the electronic density of states. We study the generic case of a van Hove singularity in 2D. We see that in combination with the requirement of number conservation and interaction effects the peak in the density of states produces several interesting phenomena including raising the critical field of the transition above naive estimates, altering the relationship between temperature and field scales and creating a distinctive double-peak structure in the electronic specific heat. We show that this apparent non-Fermi liquid behaviour can be caused at mean-field level by a peak in the density of states.Comment: 6 pages, 4 figure

Non-equilibrium conductivity at quantum critical points

Quantum criticality provides an important route to revealing universal non-equilibrium behaviour. A canonical example of a quantum critical point is the Bose-Hubbard model, which we study under the application of an electric field. A Boltzmann transport formalism and $\epsilon$-expansion are used to obtain the non-equilibrium conductivity and current noise. This approach allows us to explicitly identify how a universal non-equilibrium steady state is maintained, by identifying the rate-limiting step in balancing Joule heating and dissipation to a heat bath. It also reveals that the non-equilibrium distribution function is very far from a thermal distribution.Comment: 5 pages, 2 figure

Addressing the needs of international postgraduate students: the role of social capital

Self-evidently, international students are likely to have considerable informational and social needs when coming to study in the UK. This paper reports the findings of a small study of such needs among international postgraduate students in the School of Health Sciences. It was an interview study, with twelve students participating. Though the study was designed to support the creation of an online resource, the findings suggest that meeting those needs satisfactorily requires a multi-faceted approach. Both face-to-face and online processes are needed to help students to develop the social capital necessary to success in undertaking the course, getting to know the university, and adjusting to life in England

Psychostimulants as Cognitive Enhancers: The Prefrontal Cortex, Catecholamines and Attention Deficit Hyperactivity Disorder

Psychostimulants exert behavioral-calming and cognition-enhancing actions in the treatment of attention deficit hyperactivity disorder (ADHD). Contrary to early views, extensive research demonstrates that these actions are not unique to ADHD. Specifically, when administered at low and clinically-relevant doses, psychostimulants improve a variety of behavioral and cognitive processes dependent on the prefrontal cortex (PFC) in subjects with and without ADHD. Despite the longstanding clinical use of these drugs, the neural mechanisms underlying their cognition-enhancing/therapeutic actions have only recently begun to be examined. At behaviorally-activating doses, psychostimulants produce large and widespread increases in extracellular levels of brain catecholamines. In contrast, cognition-enhancing doses of psychostimulants exert regionally-restricted actions, elevating extracellular catecholamine levels and enhancing neuronal signal processing preferentially within the PFC. Additional evidence suggests a prominent role of PFC α2- and D1 receptors in the behavioral and electrophysiological actions of low-dose psychostimulants. These and other observations indicate a pivotal role of PFC catecholamines in the cognition-enhancing and therapeutic actions of psychostimulants as well as other drugs used in the treatment of ADHD. This information may be particularly relevant for the development of novel pharmacological treatments for ADHD and other conditions associated with PFC dysregulation

Mixing with Medics

Historians are increasingly required to produce research that makes an impact. This is particularly the case for medical historians, partly because of our funders' expectations, but also because there is a sense that medical history can inform today's thorny debates about health. Unfortunately, many historians struggle to make an impact. I suggest that participating in medical conferences (broadly defined), not only provides opportunities to make an impact on the medical community, but also offers chances to observe and participate in medical history as it happens

Partnerships: survey respondents' perceptions of inter-professional collaboration to address alcohol-related harms in England

Tackling alcohol-related harms crosses agency and professional boundaries, requiring collaboration between health, criminal justice, education and social welfare institutions. It is a key component of most multicomponent programmes in the United States, Australia and Europe. Partnership working, already embedded in service delivery structures, is a core mechanism for delivery of the new UK Government Alcohol Strategy. This article reports findings from a study of alcohol partnerships across England. The findings are based on a mix of open discussion interviews with key informants and on semi-structured telephone interviews with 90 professionals with roles in local alcohol partnerships. Interviewees reported the challenges of working within a complex network of interlinked partnerships, often within hierarchies under an umbrella partnership, some of them having a formal duty of partnership. The new alcohol strategy has emerged at a time of extensive reorganisation within health, social care and criminal justice structures. Further development of a partnership model for policy implementation would benefit from consideration of the incompatibility arising from required collaboration and from tensions between institutional and professional cultures. A clearer analysis of which aspects of partnership working provide ‘added value’ is needed

Coexistence of amplitude and frequency modulations in intracellular calcium dynamics

The complex dynamics of intracellular calcium regulates cellular responses to information encoded in extracellular signals. Here, we study the encoding of these external signals in the context of the Li-Rinzel model. We show that by control of biophysical parameters the information can be encoded in amplitude modulation, frequency modulation or mixed (AM and FM) modulation. We briefly discuss the possible implications of this new role of information encoding for astrocytes.Comment: 4 pages, 4 figure

Brain Circuits of Methamphetamine Place Reinforcement Learning: The Role of the Hippocampus-VTA Loop

The reinforcing effects of addictive drugs including methamphetamine (METH) involve the midbrain ventral tegmental area (VTA). VTA is primary source of dopamine (DA) to the nucleus accumbens (NAc) and the ventral hippocampus (VHC). These three brain regions are functionally connected through the hippocampal-VTA loop that includes two main neural pathways: the bottom-up pathway and the top-down pathway. In this paper, we take the view that addiction is a learning process. Therefore, we tested the involvement of the hippocampus in reinforcement learning by studying conditioned place preference (CPP) learning by sequentially conditioning each of the three nuclei in either the bottom-up order of conditioning; VTA, then VHC, finally NAc, or the top-down order; VHC, then VTA, finally NAc. Following habituation, the rats underwent experimental modules consisting of two conditioning trials each followed by immediate testing (test 1 and test 2) and two additional tests 24 h (test 3) and/or 1 week following conditioning (test 4). The module was repeated three times for each nucleus. The results showed that METH, but not Ringer's, produced positive CPP following conditioning each brain area in the bottom-up order. In the top-down order, METH, but not Ringer's, produced either an aversive CPP or no learning effect following conditioning each nucleus of interest. In addition, METH place aversion was antagonized by coadministration of the N-methyl-d-aspartate (NMDA) receptor antagonist MK801, suggesting that the aversion learning was an NMDA receptor activation-dependent process. We conclude that the hippocampus is a critical structure in the reward circuit and hence suggest that the development of target-specific therapeutics for the control of addiction emphasizes on the hippocampus-VTA top-down connection