Simple theory for spin-lattice relaxation in metallic rare earth ferromagnets

The spin-lattice relaxation time $\tau_{SL}$ is a key quantity both for the dynamical response of ferromagnets excited by laser pulses and as the speed limit of magneto-optical recording. Extending the theory for the electron paramagnetic resonance of magnetic impurities to spin-lattice relaxation in ferromagnetic rare earths we calculate $\tau_{SL}$ for Gd and find a value of 48 ps in very good agreement with time-resolved spin-polarized photoemission experiments. We argue that the time scale for $\tau_{SL}$ in metals is essentially given by the spin-orbit induced magnetocrystalline anisotropy energy.Comment: 18 pages revtex, 5 uuencoded figure

Phonon-phonon interactions and phonon damping in carbon nanotubes

We formulate and study the effective low-energy quantum theory of interacting long-wavelength acoustic phonons in carbon nanotubes within the framework of continuum elasticity theory. A general and analytical derivation of all three- and four-phonon processes is provided, and the relevant coupling constants are determined in terms of few elastic coefficients. Due to the low dimensionality and the parabolic dispersion, the finite-temperature density of noninteracting flexural phonons diverges, and a nonperturbative approach to their interactions is necessary. Within a mean-field description, we find that a dynamical gap opens. In practice, this gap is thermally smeared, but still has important consequences. Using our theory, we compute the decay rates of acoustic phonons due to phonon-phonon and electron-phonon interactions, implying upper bounds for their quality factor.Comment: 15 pages, 2 figures, published versio

The role of sociocultural perspectives in eating disorder treatment: A study of health professionals

Eating disorders are now often approached as biopsychosocial problems, because they are widely recognised as multifactorial in origin. However, it has been suggested that there is a substantial and unwarranted imbalance within this biopsychosocial framework, with the ‘social’ aspects of the equation relegated to secondary or facilitating factors within treatment contexts. Drawing on data from 12 qualitative interviews with health professionals in a UK region, this article examines the extent to which sociocultural perspectives on eating disorders are valued and explored in eating disorder treatment, with a particular focus on the relationship between eating disorders and gender. As girls/women are widely acknowledged to be disproportionately affected by eating problems, the article draws on feminist perspectives on eating disorders to explore whether the relationships between cultural constructions of femininity and experiences of body/eating distress are actively addressed within treatment. The study reveals high levels of inconsistency in this regard, as while some participants see such issues as central to treatment, others have ‘never really considered’ them before. In addition, the study examines the potential limitations of how such sociocultural issues are conceptualised and addressed, as well as why they might be marginalised in the current climate of evidence-based eating disorder treatment. The article then considers the implications of the findings for thinking about feminist perspectives on eating disorders – and the significance of gender in treatment – at the level of both research and practice

‘Blindness to the obvious’?: Treatment experiences and feminist approaches to eating disorders

Eating disorders (EDs) are now often approached as biopsychosocial problems, but the social or cultural aspects of the equation are often marginalised in treatment - relegated to mere contributory or facilitating factors. In contrast, feminist and socio-cultural approaches are primarily concerned with the relationship between EDs and the social/ cultural construction of gender. Yet although such approaches emerged directly from the work of feminist therapists, the feminist scholarship has increasingly observed, critiqued and challenged the biomedical model from a scholarly distance. As such, this article draws upon data from 15 semi-structured interviews with women in the UK context who have experience of anorexia and/or bulimia in order to explore a series of interlocking themes concerning the relationship between gender identity and treatment. In engaging the women in debate about the feminist approaches (something which has been absent from previous feminist work), the article explores how gender featured in their own understandings of their problem, and the ways in which it was - or rather wasn’t - addressed in treatment. The article also explores the women’s evaluations of the feminist discourse, and their discussions of how it might be implemented within therapeutic and clinical contexts

Drinking and Flying: Does Alcohol Consumption Affect the Flight and Echolocation Performance of Phyllostomid Bats?

In the wild, frugivorous and nectarivorous bats often eat fermenting fruits and nectar, and thus may consume levels of ethanol that could induce inebriation. To understand if consumption of ethanol by bats alters their access to food and general survival requires examination of behavioural responses to its ingestion, as well as assessment of interspecific variation in those responses. We predicted that bats fed ethanol would show impaired flight and echolocation behaviour compared to bats fed control sugar water, and that there would be behavioural differences among species. (Chiroptera, Phyllostomidae) sugar water (44 g of table sugar in 500 ml of water) or sugar water with ethanol before challenging them to fly through an obstacle course while we simultaneously recorded their echolocation calls. We used bat saliva, a non-invasive proxy, to measure blood ethanol concentrations ranging from 0 to >0.3% immediately before flight trials. Flight performance and echolocation behaviour were not significantly affected by consumption of ethanol, but species differed in their blood alcohol concentrations after consuming it.The bats we studied display a tolerance for ethanol that could have ramifications for the adaptive radiation of frugivorous and nectarivorous bats by allowing them to use ephemeral food resources over a wide span of time. By sampling across phyllostomid genera, we show that patterns of apparent ethanol tolerance in New World bats are broad, and thus may have been an important early step in the evolution of frugivory and nectarivory in these animals

Extended longevity of DNA preservation in Levantine Paleolithic sediments, Sefunim Cave, Israel

Paleogenomic research can elucidate the evolutionary history of human and faunal populations. Although the Levant is a key land-bridge between Africa and Eurasia, thus far, relatively little ancient DNA data has been generated from this region, since DNA degrades faster in warm climates. As sediments can be a source of ancient DNA, we analyzed 33 sediment samples from different sedimentological contexts in the Paleolithic layers of Sefunim Cave (Israel). Four contained traces of ancient Cervidae and Hyaenidae mitochondrial DNA. Dating by optical luminescence and radiocarbon indicates that the DNA comes from layers between 30,000 and 70,000 years old, surpassing theoretical expectations regarding the longevity of DNA deposited in such a warm environment. Both identified taxa are present in the zooarchaeological record of the site but have since gone extinct from the region, and a geoarchaeological study suggests little movement of the sediments after their deposition, lending further support to our findings. We provide details on the local conditions in the cave, which we hypothesize were particularly conducive to the long-term preservation of DNA—information that will be pertinent for future endeavors aimed at recovering ancient DNA from the Levant and other similarly challenging contexts

Spin-spin correlation functions of the XXZ-1/2 Heisenberg chain in a magnetic field

Using algebraic Bethe ansatz and the solution of the quantum inverse scattering problem, we compute compact representations of the spin-spin correlation functions of the XXZ-1/2 Heisenberg chain in a magnetic field. At lattice distance m, they are typically given as the sum of m terms. Each term n of this sum, n = 1,...,m is represented in the thermodynamic limit as a multiple integral of order 2n+1; the integrand depends on the distance as the power m of some simple function. The root of these results is the derivation of a compact formula for the multiple action on a general quantum state of the chain of transfer matrix operators for arbitrary values of their spectral parameters.Comment: 34 page

Correlation functions of the XXZ Heisenberg spin-1/2 chain in a magnetic field

Using the algebraic Bethe ansatz method, and the solution of the quantum inverse scattering problem for local spins, we obtain multiple integral representations of the $n$-point correlation functions of the XXZ Heisenberg spin-$1 \over 2$ chain in a constant magnetic field. For zero magnetic field, this result agrees, in both the massless and massive (anti-ferromagnetic) regimes, with the one obtained from the q-deformed KZ equations (massless regime) and the representation theory of the quantum affine algebra ${\cal U}_q (\hat{sl}_2)$ together with the corner transfer matrix approach (massive regime).Comment: Latex2e, 26 page

High frequency sound waves in vitreous silica

We report a molecular dynamics simulation study of the sound waves in vitreous silica in the mesoscopic exchanged momentum range. The calculated dynamical structure factors are in quantitative agreement with recent experimental inelastic neutron and x-ray scattering data. The analysis of the longitudinal and transverse current spectra allows to discriminate between opposite interpretations of the existing experimental data in favour of the propagating nature of the high frequency sound waves.Comment: 4 pages, Revtex, 4 ps figures; to be published in Phys. Rev. Lett., February 198

Gut thinking: the gut microbiome and mental health beyond the head

Background: In recent decades, dominant models of mental illness have become increasingly focused on the head, with mental disorders being figured as brain disorders. However, research into the active role that the microbiome-gut-brain axis plays in affecting mood and behaviour may lead to the conclusion that mental health is more than an internalised problem of individual brains. Objective: This article explores the implications of shifting understandings about mental health that have come about through research into links between the gut microbiome and mental health problems such as depression and anxiety. It aims to analyse the different ways that the lines between mind and body and mental and physical health are re-shaped by this research, which is starting to inform clinical and public understanding. Design: As mental health has become a pressing issue of political and public concern it has become increasingly constructed in socio-cultural and personal terms beyond clinical spaces, requiring a conceptual response that exceeds biomedical inquiry. This article argues that an interdisciplinary critical medical humanities approach is well positioned to analyse the impact of microbiome-gut-brain research on conceptions of mind. Results: The entanglement of mind and matter evinced by microbiome-gut-brain axis research potentially provides a different way to conceptualise the physical and social concomitants of mental distress. Conclusion: Mental health is not narrowly located in the head but is assimilated by the physical body and intermingled with the natural world, requiring different methods of research to unfold the meanings and implications of gut thinking for conceptions of human selfhood