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

Using practice effects for targeted trials or sub-group analysis in Alzheimer\u27s disease: How practice effects predict change over time

OBJECTIVE: To describe the presence of practice effects in persons with Alzheimer disease (AD) or mild cognitive impairment (MCI) and to evaluate how practice effects affect cognitive progression and the outcome of clinical trials. METHODS: Using data from a meta-database consisting of 18 studies including participants from the Alzheimer disease Cooperative Study (ADCS) and the Alzheimer Disease Neuroimaging Initiative (ADNI) with ADAS-Cog11 as the primary outcome, we defined practice effects based on the improvement in the first two ADAS-Cog11 scores and then estimated the presence of practice effects and compared the cognitive progression between participants with and without practice effects. The robustness of practice effects was investigated using CDR SB, an outcome independent the definition itself. Furthermore, we evaluated how practice effects can affect sample size estimation. RESULTS: The overall percent of practice effects for AD participants was 39.0% and 53.3% for MCI participants. For AD studies, the mean change from baseline to 2 years was 12.8 points for the non-practice effects group vs 7.4 for the practice effects group; whereas for MCI studies, it was 4.1 for non-practice effects group vs 0.2 for the practice effects group. AD participants without practice effects progressed 0.9 points faster than those with practice effects over a period of 2 years in CDR-SB; whereas for MCI participants, the difference is 0.7 points. The sample sizes can be different by over 35% when estimated based on participants with/without practice effects. CONCLUSION: Practice effects were prevalent and robust in persons with AD or MCI and affected the cognitive progression and sample size estimation. Planning of future AD or MCI clinical trials should account for practice effects to avoid underpower or considers target trials or stratification analysis based on practice effects

Social Support in Nursing: A Review of the Literature

Nursing researchers have been investigating social support in the nursing profession with increasing interest, and the present manuscript reviews the state of the literature: methods, theories, and research findings related to social support in nursing. The aims of the existing research have focused primarily on understanding how the types, amount, and quality of social support received by nurses is associated with lower rates of professional stress, burnout, and intent to leave the profession. There is evidence that nurses in clinical settings value and are benefited by various forms of support from their supervisors. They also report lower distress when they have supportive personal relationships outside of work, although support from managers remains key. Support needs have been examined in different cultures and findings indicate that nursing in some parts of the world can be fraught because of cultural beliefs about the profession and about appropriate ways of enacting support. Less research has addressed the social support that nurses provide to patients and families. An agenda for advancing the literature is offered, with an emphasis on studying support from a communication perspective and learning more about what makes messages more or less supportive in nursing contexts

Air Pollution and Climate Forcing of the Charcoal Industry in Africa

The demand for charcoal in Africa is growing rapidly, driven by urbanization and lack of access to electricity. Charcoal production and use, including plastic burning to initiate combustion, release large quantities of trace gases and particles that impact air quality and climate. Here, we develop an inventory of current (2014) and future (2030) emissions from the charcoal supply chain in Africa that we implement in the GEOS-Chem model to quantify the contribution of charcoal to surface concentrations of PM2.5 and ozone and direct radiative forcing due to aerosols and ozone. We estimate that the charcoal industry in 2014 required 140–460 Tg of biomass and 260 tonnes of plastic and that industry emissions could double by 2030, so that methane emissions from the charcoal industry could outcompete those from open fires by 2025. In 2014, the largest enhancements in PM2.5 (0.5–1.4 μg m–3) and ozone (0.4–0.7 ppbv) occur around the densely populated cities in East and West Africa. Cooling due to aerosols (−100 to −300 mW m–2) is concentrated over dense cities, whereas warming due to ozone is widespread, peaking at 4.2 mW m–2 over the Atlantic Ocean. These effects will worsen with ongoing dependence on this energy source, spurred by rapid urbanization and absence of viable cleaner alternatives

Sequential Simulations During Introductory Part-Time Fieldwork: Design, Implementation, and Student Satisfaction

Background: Simulation is used in various ways in occupational therapy education and is recognized as a replacement for some conventional fieldwork hours. However, design and student satisfaction has had limited exploration. Method: Sequential best practice simulations were designed for Level 1 fieldwork objectives in mental and musculoskeletal practice. The Satisfaction with Simulation Education scale (SSES) and qualitative feedback were used to assess student satisfaction. An exploratory factor analysis was used to validate the SSES in occupational therapy, and a three-factor repeated measures ANOVA was used to determine factors contributing to satisfaction across simulations. Results: A three-factor model of clinical reasoning and ability, facilitator feedback, and reflection was derived. The qualitative data identified authenticity and relevance to clinical practice as two domains not captured by the SSES items. Repeated measures ANOVA revealed a significant interaction of case by SSES factor with mental health clinical reasoning and ability mean scores lower than musculoskeletal means. Conclusion: Occupational therapy students reported high levels of satisfaction for design used to prepare for full-time fieldwork experiences. The SSES captured most contributors to satisfaction, but potential items to enhance the SSES validity in occupational therapy include those related to authenticity and relevance to practice

Weathering microenvironments on feldspar surfaces: implications for understanding fluid-mineral reactions in soils

The mechanisms by which coatings develop on weathered grain surfaces, and their potential impact on rates of fluid-mineral interaction, have been investigated by examining feldspars from a 1.1 ky old soil in the Glen Feshie chronosequence, Scottish highlands. Using the focused ion beam technique, electron-transparent foils for characterization by transmission electron microscopy were cut from selected parts of grain surfaces. Some parts were bare whereas others had accumulations, a few micrometres thick, of weathering products, often mixed with mineral and microbial debris. Feldspar exposed at bare grain surfaces is crystalline throughout and so there is no evidence for the presence of the amorphous 'leached layers' that typically form in acid-dissolution experiments and have been described from some natural weathering contexts. The weathering products comprise sub-μm thick crystallites of an Fe-K aluminosilicate, probably smectite, that have grown within an amorphous and probably organic-rich matrix. There is also evidence for crystallization of clays having been mediated by fungal hyphae. Coatings formed within Glen Feshie soils after ∼1.1 ky are insufficiently continuous or impermeable to slow rates of fluid-feldspar reactions, but provide valuable insights into the complex weathering microenvironments on debris and microbe-covered mineral surfaces

Occupational Therapy Students’ Perceptions of Feedback During Pre-Fieldwork Simulation Debrief: Useful and Why

Simulation is increasingly used in occupational therapy education with the objectives of developing practice skill competency and enhancing clinical reasoning. Debriefing, an integral part of the simulation process, is critical to achieving these objectives. This study sought to determine the types of debrief feedback Master of Science in Occupational Therapy (MScOT) students perceived as most useful and why, and how the advocacy inquiry model of debriefing influenced self-reported increases in clinical reasoning, client care, and planned implementation of feedback in practice. Using an embedded mixed method design with secondary data analysis, sixty-three first-year MScOT students provided 357 descriptions of the most useful feedback they received during 10-minute, facilitator-led debrief sessions after six simulations. Qualitative analysis revealed useful feedback was related to specific skills, interviewing and communication, the process of practice, strengths and encouragement, and client-centeredness. The advocacy inquiry approach was a useful delivery method of feedback. Logistic regression indicated that reported use of the advocacy inquiry model increased the likelihood by 4.7 times that students reported the debrief facilitated clinical reasoning. When advocacy inquiry was used in conjunction with providing feedback on specific skills, students were 5.3 times more likely to report planned implementation of the feedback in practice. Students value a variety of types of feedback during simulation debriefs. Debriefs using the advocacy inquiry method may be particularly useful for facilitating the development of clinical reasoning in the context of simulation-based fieldwork education

Multiple first-order metamagnetic transitions and quantum oscillations in ultrapure

We present measurements on ultra clean single crystals of the bilayered ruthenate metal Sr3Ru2O7, which has a magnetic-field-tuned quantum critical point. Quantum oscillations of differing frequencies can be seen in the resistivity both below and above its metamagnetic transition. This frequency shift corresponds to a small change in the Fermi surface volume that is qualitatively consistent with the small moment change in the magnetisation across the metamagnetic transition. Very near the metamagnetic field, unusual behaviour is seen. There is a strong enhancement of the resistivity in a narrow field window, with a minimum in the resistivity as a function of temperature below 1 K that becomes more pronounced as the disorder level decreases. The region of anomalous behaviour is bounded at low temperatures by two first-order phase transitions. The implications of the results are discussed. PACS: 68.35.Rh, 71.27.+a, 72.15.-v, 74.70.PqComment: 12 pages 4 figures, submitte

Quantum Kinks: Solitons at Strong Coupling

We examine solitons in theories with heavy fermions. These ``quantum'' solitons differ dramatically from semi-classical (perturbative) solitons because fermion loop effects are important when the Yukawa coupling is strong. We focus on kinks in a $(1+1)$--dimensional $\phi^4$ theory coupled to fermions; a large-$N$ expansion is employed to treat the Yukawa coupling $g$ nonperturbatively. A local expression for the fermion vacuum energy is derived using the WKB approximation for the Dirac eigenvalues. We find that fermion loop corrections increase the energy of the kink and (for large $g$) decrease its size. For large $g$, the energy of the quantum kink is proportional to $g$, and its size scales as $1/g$, unlike the classical kink; we argue that these features are generic to quantum solitons in theories with strong Yukawa couplings. We also discuss the possible instability of fermions to solitons.Comment: 21 pp. + 2 figs., phyzzx, JHU-TIPAC-92001