An Apparatus for the Combined Measurement of Seebeck Coefficient and Electrical Resistivity

An apparatus has been designed which allows simultaneous measurements of Seebeck coefficient and electrical resistivity of semiconducting thermoelectric materials from room temperature to 1300K

Model-agnostic variable importance for predictive uncertainty: an entropy-based approach

In order to trust the predictions of a machine learning algorithm, it is necessary to understand the factors that contribute to those predictions. In the case of probabilistic and uncertainty-aware models, it is necessary to understand not only the reasons for the predictions themselves, but also the model's level of confidence in those predictions. In this paper, we show how existing methods in explainability can be extended to uncertainty-aware models and how such extensions can be used to understand the sources of uncertainty in a model's predictive distribution. In particular, by adapting permutation feature importance, partial dependence plots, and individual conditional expectation plots, we demonstrate that novel insights into model behaviour may be obtained and that these methods can be used to measure the impact of features on both the entropy of the predictive distribution and the log-likelihood of the ground truth labels under that distribution. With experiments using both synthetic and real-world data, we demonstrate the utility of these approaches in understanding both the sources of uncertainty and their impact on model performance

Universal circles for quasigeodesic flows

We show that if M is a hyperbolic 3-manifold which admits a quasigeodesic flow, then pi_1(M) acts faithfully on a universal circle by homeomorphisms, and preserves a pair of invariant laminations of this circle. As a corollary, we show that the Thurston norm can be characterized by quasigeodesic flows, thereby generalizing a theorem of Mosher, and we give the first example of a closed hyperbolic 3-manifold without a quasigeodesic flow, answering a long-standing question of Thurston.Comment: This is the version published by Geometry & Topology on 29 November 2006. V4: typsetting correction

Suppression of X-rays during an optical outburst of the helium dwarf nova KL Dra

KL Dra is a helium accreting AM CVn binary system with an orbital period close to 25 mins. Approximately every 60 days there is a 4 mag optical outburst lasting ~10 days. We present the most sensitive X-ray observations made of an AM CVn system during an outburst cycle. A series of eight observations were made using XMM-Newton which started shortly after the onset of an optical outburst. We find that X-rays are suppressed during the optical outburst. There is some evidence for a spectral evolution of the X-ray spectrum during the course of the outburst. A periodic modulation is seen in the UV data at three epochs -- this is a signature of the binary orbital or the super-hump period. The temperature of the X-ray emitting plasma is cooler compared to dwarf novae, which may suggest a wind is the origin of a significant fraction of the X-ray flux.Comment: Accepted by MNRA

Recovery priorities of people with psychosis in acute mental health in-patient settings: a Q-methodology study.

Background: Personal recovery from psychosis has been explored extensively in community samples but there has been little exploration with people currently receiving care from an acute mental health in-patient setting. Aims: The aim of this study was to explore the personal recovery priorities of people experiencing psychosis who are currently receiving care from an acute mental health in-patient ward. Method: A Q-methodology mixed-methods approach was adopted. Thirty-eight participants were recruited from an outer London acute mental health hospital. They were required to sort 54 statements regarding personal recovery from most important to least important to reflect their recovery priorities. Thirty-six were included in the final analysis. Results: Analysis revealed four distinct viewpoints relating to factors that promote recovery in the acute mental health in-patient setting. These were: stability, independence and ‘keeping a roof over your head’; hope, optimism and enhancing well-being; personal change, self-management and social support; and symptom reduction through mental health support. Conclusions: Acute mental health in-patient wards need to ensure that they are considering the personal recovery needs of in-patients. Symptom reduction was valued by some, but broad psychosocial factors were also of priority

The subjective experience of recovery from psychosis in an acute mental health inpatient setting

Background: Experiences of recovery from psychosis have been well explored but not with service users in the acute stages of psychosis. This study aimed to explore the subjective experiences of recovery from psychosis from the perspective of service users receiving acute mental health inpatient care. Methods: Ten participants undertook a semi-structured interview examining their experiences of recovery from psychosis during acute mental health inpatient care. Data were analysed using Interpretative Phenomenological Analysis (IPA). Results: Five superordinate themes emerged: “My future is just being ripped out in front of me”: Living with psychosis is a struggle; “Would you want to be in here?”: Traumatic experience of being in hospital; “I know roughly why I got ill anyway and what caused this”: A journey towards reaching an understanding; Recovery/Rehabilitation/Recuperation: A process of evolution; and “You need all the help you can get”: Facilitators of Recovery. Conclusions: This study highlighted that mental health inpatient settings are not settings where everyone can be in recovery or approaching recovery. For some participants, recovery appeared to be an empty signifier, and is a word used by services but does not necessarily correspond with their experiences of mental health inpatient settings

The long term optical behaviour of helium accreting AM CVn binaries

We present the results of a two and a half year optical photometric monitoring programme covering 16 AM CVn binaries using the Liverpool Telescope on La Palma. We detected outbursts in seven systems, one of which (SDSS J0129) was seen in outburst for the first time. Our study coupled with existing data shows that ~1/3 of these helium-rich accreting compact binaries show outbursts. The orbital period of the outbursting systems lie in the range 24-44 mins and is remarkably consistent with disk-instability predictions. The characteristics of the outbursts seem to be broadly correlated with their orbital period (and hence mass transfer rate). Systems which have short periods (<30 min) tend to exhibit outbursts lasting 1--2 weeks and often show a distinct `dip' in flux shortly after the on-set of the burst. We explore the nature of these dips which are also seen in the near-UV. The longer period bursters show higher amplitude events (5 mag) that can last several months. We have made simulations to estimate how many outbursts we are likely to have missed.Comment: Accepted for publication in MNRA

Detection of accretion X-rays from QS Vir: cataclysmic or a lot of hot air?

An XMM-Newton observation of the nearby "pre-cataclysmic" short-period (P_orb = 3.62 hr) binary QS Vir (EC 13471-1258) revealed regular narrow X-ray eclipses when the white dwarf passed behind its M2-4 dwarf companion. The X-ray emission provides a clear signature of mass transfer and accretion onto the white dwarf. The low-resolution XMM-Newton EPIC spectra are consistent with a cooling flow model and indicate an accretion rate of Mdot= 1.7\times10^-13M\odot/yr. At 48 pc distant, QS Vir is then the second nearest accreting cataclysmic variable known, with one of the lowest accretion rates found to date for a non-magnetic system. To feed this accretion through a wind would require a wind mass loss rate of Mdot ~ 2 \times 10^-12M\odot/yr if the accretion efficiency is of the order of 10%. Consideration of likely mass loss rates for M dwarfs suggests this is improbably high and pure wind accretion unlikely. A lack of accretion disk signatures also presents some difficulties for direct Roche lobe overflow. We speculate that QS Vir is on the verge of Roche lobe overflow, and that the observed mass transfer could be supplemented by upward chromospheric flows on the M dwarf, analogous to spicules and mottles on the Sun, that escape the Roche surface to be subsequently swept up into the white dwarf Roche lobe. If so, QS Vir would be in a rare evolutionary phase lasting only a million years. The X-ray luminosity of the M dwarf estimated during primary eclipse is L_X = 3 \times 10^28 erg/s, which is consistent with that of rapidly rotating "saturated" K and M dwarfs.Comment: ApJ in pres