A new perturbative approach to the adiabatic approximation

A new and intuitive perturbative approach to time-dependent quantum mechanics problems is presented, which is useful in situations where the evolution of the Hamiltonian is slow. The state of a system which starts in an instantaneous eigenstate of the initial Hamiltonian is written as a power series which has a straightforward diagrammatic representation. Each term of the series corresponds to a sequence of "adiabatic" evolutions, during which the system remains in an instantaneous eigenstate of the Hamiltonian, punctuated by transitions from one state to another. The first term of this series is the standard adiabatic evolution, the next is the well-known first correction to it, and subsequent terms can be written down essentially by inspection. Although the final result is perhaps not terribly surprising, it seems to be not widely known, and the interpretation is new, as far as we know. Application of the method to the adiabatic approximation is given, and some discussion of the validity of this approximation is presented.Comment: 9 pages. Added references, discussion of previous results, expanded upon discussion of main result and application of i

Rigid-Band Shift of the Fermi Level in a Strongly Correlated Metal: Sr(2-y)La(y)RuO(4)

We report a systematic study of electron doping of Sr2RuO4 by non-isovalent substitution of La^(3+) for Sr^(2+). Using a combination of de Haas-van Alphen oscillations, specific heat, and resistivity measurements, we show that electron doping leads to a rigid-band shift of the Fermi level corresponding to one doped electron per La ion, with constant many-body quasiparticle mass enhancement over the band mass. The susceptibility spectrum is substantially altered and enhanced by the doping but this has surprisingly little effect on the strength of the unconventional superconducting pairing.Comment: 4 pages, 3 figure

Formation of a Nematic Fluid at High Fields in Sr3Ru2O7

In principle, a complex assembly of strongly interacting electrons can self-organise into a wide variety of collective states, but relatively few such states have been identified in practice. We report that, in the close vicinity of a metamagnetic quantum critical point, high purity Sr3Ru2O7 possesses a large magnetoresistive anisotropy, consistent with the existence of an electronic nematic fluid. We discuss a striking phenomenological similarity between our observations and those made in high purity two-dimensional electron fluids in GaAs devices.Comment: 14 pages, 3 figures, 11 extra pages of supplementary informatio

A condensed-mass advection based model for the simulation of liquid polar stratospheric clouds

International audienceWe present a condensed-mass advection based model (MADVEC) designed to simulate the condensation/evaporation of liquid polar stratospheric cloud (PSC) particles. A (Eulerian-in-radius) discretization scheme is used, making the model suitable for use in global or mesoscale chemistry and transport models (CTMs). The mass advection equations are solved using an adaption of the weighted average flux (WAF) scheme. We validate the numerical scheme using an analytical solution for multicomponent aerosols. The physics of the model are tested using a test case designed by Meilinger et al. (1995). The results from this test corroborate the composition gradients across the size distribution under rapid cooling conditions that were reported in earlier studies.</p

Sensory environment on health-related outcomes of hospital patients

Background: Hospital environments have recently received renewed interest, with considerable investments into building and renovating healthcare estates. Understanding the effectiveness of environmental interventions is important for resource utilisation and providing quality care. Objectives: To assess the effect of hospital environments on adult patient health-related outcomes. Search methods: We searched: the Cochrane Central Register of Controlled Trials (last searched January 2006); MEDLINE (1902 to December 2006); EMBASE (January 1980 to February 2006); 14 other databases covering health, psychology, and the built environment; reference lists; and organisation websites. This review is currently being updated (MEDLINE last search October 2010), see Studies awaiting classification. Selection criteria: Randomised and non-randomised controlled trials, controlled before-and-after studies, and interrupted times series of environmental interventions in adult hospital patients reporting health-related outcomes. Data collection and analysis: Two review authors independently undertook data extraction and 'Risk of bias' assessment. We contacted authors to obtain missing information. For continuous variables, we calculated a mean difference (MD) or standardized mean difference (SMD), and 95% confidence intervals (CI) for each study. For dichotomous variables, we calculated a risk ratio (RR) with 95% confidence intervals (95% CI). When appropriate, we used a random-effects model of meta-analysis. Heterogeneity was explored qualitatively and quantitatively based on risk of bias, case mix, hospital visit characteristics, and country of study. Main results: Overall, 102 studies have been included in this review. Interventions explored were: 'positive distracters', to include aromas (two studies), audiovisual distractions (five studies), decoration (one study), and music (85 studies); interventions to reduce environmental stressors through physical changes, to include air quality (three studies), bedroom type (one study), flooring (two studies), furniture and furnishings (one study), lighting (one study), and temperature (one study); and multifaceted interventions (two studies). We did not find any studies meeting the inclusion criteria to evaluate: art, access to nature for example, through hospital gardens, atriums, flowers, and plants, ceilings, interventions to reduce hospital noise, patient controls, technologies, way-finding aids, or the provision of windows. Overall, it appears that music may improve patient-reported outcomes such as anxiety; however, the benefit for physiological outcomes, and medication consumption has less support. There are few studies to support or refute the implementation of physical changes, and except for air quality, the included studies demonstrated that physical changes to the hospital environment at least did no harm. Authors' conclusions: Music may improve patient-reported outcomes in certain circumstances, so support for this relatively inexpensive intervention may be justified. For some environmental interventions, well designed research studies have yet to take place

Berom cultural beliefs and attitudes towards mental health problems in Nigeria: a mixed-methods study

Beliefs and attitudes are essential in mental health discourse. However, cultural beliefs and attitudes towards mental health problems (ATMHPs) among the Berom people of Nigeria are under-researched. The present studies made original contributions using the Cultural Identity Model (CIM) as predictors to investigate ATMHPs, and semi-structured interviews to further explain the potential impact of cultural beliefs on MHPs. In study-1, N = 140 participants responded to questionnaires on ATMHPs and were analysed using multivariate multiple regression in RStudio. Study-2 interviewed N = 13 participants (n = 7 laypeople; n = 6 practitioners). Interviews were recorded, transcribed and analysed thematically. Study-1 findings showed CIM as a non-significant predictor of ATMHPs. However, in study-2, four themes emerged: Cultural beliefs that MHPs are caused by spiritual forces; Berom indigenous preference for traditional healing; Christian religious healing in Berom communities; and Western-trained mental health practitioners' perception of lay service-users. The authors concluded that the Berom traditional and Christian religious healings are beneficial

Probing the AGN Unification Model at redshift z ∼\sim 3 with MUSE observations of giant Lyα\alpha nebulae

A prediction of the classic active galactic nuclei (AGN) unification model is the presence of ionisation cones with different orientations depending on the AGN type. Confirmations of this model exist for present times, but it is less clear in the early Universe. Here, we use the morphology of giant Ly$\alpha$ nebulae around AGNs at redshift z$\sim$3 to probe AGN emission and therefore the validity of the AGN unification model at this redshift. We compare the spatial morphology of 19 nebulae previously found around type I AGNs with a new sample of 4 Ly$\alpha$ nebulae detected around type II AGNs. Using two independent techniques, we find that nebulae around type II AGNs are more asymmetric than around type I, at least at radial distances $r>30$~physical kpc (pkpc) from the ionizing source. We conclude that the type I and type II AGNs in our sample show evidence of different surrounding ionising geometries. This suggests that the classical AGN unification model is also valid for high-redshift sources. Finally, we discuss how the lack of asymmetry in the inner parts (r$\lesssim$30 pkpc) and the associated high values of the HeII to Ly$\alpha$ ratios in these regions could indicate additional sources of (hard) ionizing radiation originating within or in proximity of the AGN host galaxies. This work demonstrates that the morphologies of giant Ly$\alpha$ nebulae can be used to understand and study the geometry of high redshift AGNs on circum-nuclear scales and it lays the foundation for future studies using much larger statistical samples.Comment: 15 pages, 13 figures, accepted for publication in MNRA

Interaction between vortices in models with two order parameters

The interaction energy and force between widely separated strings is analyzed in a field theory having applications to superconducting cosmic strings, the SO(5) model of high-temperature superconductivity, and solitons in nonlinear optics. The field theory has two order parameters, one of which is broken in the vacuum (giving rise to strings), the other of which is unbroken in the vacuum but which could nonetheless be broken in the core of the string. If this does occur, there is an effect on the energetics of widely separated strings. This effect is important if the length scale of this second order parameter is longer than that of the other fields in the problem.Comment: 11 pages, 3 figures. Minor changes in the text. Accepted for publication in Phys. Rev.