The maximum efficiency of nano heat engines depends on more than temperature

Sadi Carnot's theorem regarding the maximum efficiency of heat engines is considered to be of fundamental importance in thermodynamics. This theorem famously states that the maximum efficiency depends only on the temperature of the heat baths used by the engine, but not on the specific structure of baths. Here, we show that when the heat baths are finite in size, and when the engine operates in the quantum nanoregime, a revision to this statement is required. We show that one may still achieve the Carnot efficiency, when certain conditions on the bath structure are satisfied; however if that is not the case, then the maximum achievable efficiency can reduce to a value which is strictly less than Carnot. We derive the maximum efficiency for the case when one of the baths is composed of qubits. Furthermore, we show that the maximum efficiency is determined by either the standard second law of thermodynamics, analogously to the macroscopic case, or by the non increase of the max relative entropy, which is a quantity previously associated with the single shot regime in many quantum protocols. This relative entropic quantity emerges as a consequence of additional constraints, called generalized free energies, that govern thermodynamical transitions in the nanoregime. Our findings imply that in order to maximize efficiency, further considerations in choosing bath Hamiltonians should be made, when explicitly constructing quantum heat engines in the future. This understanding of thermodynamics has implications for nanoscale engineering aiming to construct small thermal machines.Comment: Main text 14 pages. Appendix 60 pages. Accepted in Journal Quantu

Long Term Radiative Behavior of SGR 1900+14

The prolific magnetar SGR 1900+14 showed two outbursts in the last decade and has been closely monitored in the X-rays to track the changes in its radiative properties. We use archival Chandra and XMM-Newton observations of SGR 1900+14 to construct a history of its spectrum and persistent X-ray flux spanning a period of about seven years. We show that the decline of its X-ray flux in these two outburst episodes follows the same trend. The flux begins to decline promptly and rapidly subsequent to the flares, then decreases gradually for about 600 days, at which point it resumes a more rapid decline. Utilizing the high quality spectral data in each epoch, we also study the spectral coevolution of the source with its flux. We find that neither the magnetic field strength nor the magnetospheric properties change over the period spanned by the observations, while the surface temperature as well as the inferred emitting area both decline with time following both outbursts. We also show that the source reached the same minimum flux level in its decline from these two subsequent outbursts, suggesting that this flux level may be its steady quiescent flux.Comment: Accepted for publication in the Ap

Faculty and resident perspectives on ambulatory care education: A collective case study of family medicine, psychiatry, and surgery

Background: Ambulatory care (AC) experiences within medical education are garnering increasing attention. We sought to understand how faculty and residents’ describe their experiences of AC and ambulatory care education (ACEduc) within, between, and across disciplinary contexts.Methods: We designed a Stakian collective case study, applying constructivist grounded theory analytic methods. Using purposive and snowball sampling, we interviewed 17 faculty and residents across three instrumental cases: family medicine, psychiatry, surgery. Through constant comparative analysis, we identified patterns within, between, and across cases.Results: Family medicine and psychiatry saw AC as an inherent part of continuous, longitudinal care; surgery equated AC with episodic experiences in clinic, differentiating it from operating. Across cases, faculty and residents cautiously valued ACEduc, and in particular, considered it important to develop non-medical expert competencies (e.g., communication). However, surgery residents described AC and ACEduc as less interesting and a lower priority than operating. Educational structures mediated these views.Conclusion: Differences between cases highlight a need for further study, as universal assumptions about ACEduc’s purposes and approaches may need to be tempered by situated, contextually-rich perspectives. How disciplinary culture, program structure, and systemic structure influence ACEduc warrant further consideration as does the educational potential for explicitly framing learners’ perspectives

The 2009 outburst of magnetar 1E 1547-5408: Persistent radiative and burst properties

The magnetar 1E~1547$-$5408 recently exhibited two periods of outburst, beginning on 2008 October 3 and 2009 January 22. Here we present an analysis of the persistent radiative evolution and a statistical study of the burst properties during the 2009 outburst using the {\em Swift} X-ray Telescope (XRT). We find that the 1--10 keV flux increased by a factor of $\sim500$ and hardened significantly, peaking $\sim6$ hours after the onset of the outburst. The observed pulsed fraction exhibited an anti-correlation with phase-averaged flux. Properties of the several hundred X-ray bursts during the 2009 outburst were determined and compared to those from other magnetar outburst events. We find that the peaks of the bursts occur randomly in phase but that the folded counts that compose the bursts exhibit a pulse which is misaligned with the persistent pulse phase. We also report a correlation between burst hardness and flux. We compare the hardness-flux evolution of the persistent emission of both outbursts to those from other magnetars and find that although there does exist an overall trend, the degree of hardening for a given increase in flux is not uniform from source to source. These results are discussed in the context of previous results and within the magnetar model.Comment: 10 pages, 9 figures. Accepted for publication in Ap

Near-inertial wave scattering by random flows

The impact of a turbulent flow on wind-driven oceanic near-inertial waves is examined using a linearised shallow-water model of the mixed layer. Modelling the flow as a homogeneous and stationary random process with spatial scales comparable to the wavelengths, we derive a transport (or kinetic) equation governing wave-energy transfers in both physical and spectral spaces. This equation describes the scattering of the waves by the flow which results in a redistribution of energy between waves with the same frequency (or, equivalently, with the same wavenumber) and, for isotropic flows, in the isotropisation of the wave field. The time scales for the scattering and isotropisation are obtained explicitly and found to be of the order of tens of days for typical oceanic parameters. The predictions inferred from the transport equation are confirmed by a series of numerical simulations. Two situations in which near-inertial waves are strongly influenced by flow scattering are investigated through dedicated nonlinear shallow-water simulations. In the first, a wavepacket propagating equatorwards as a result from the $\beta$-effect is shown to be slowed down and dispersed both zonally and meridionally by scattering. In the second, waves generated by moving cyclones are shown to be strongly disturbed by scattering, leading again to an increased dispersion.Comment: Accepted for publication in Phys. Rev. Fluid

On the Extended Emission Around the Anomalous X-ray Pulsar 1E 1547.0-5408

We present an analysis of the extended emission around the anomalous X-ray pulsar 1E 1547.0-5408 using four XMM-Newton observations taken with the source in varying states of outburst as well as in quiescence. We find that the extended emission flux is highly variable and strongly correlated with the flux of the magnetar. Based on this result, as well as on spectral and energetic considerations, we conclude that the extended emission is dominated by a dust-scattering halo and not a pulsar wind nebula (PWN), as has been previously argued. We obtain an upper limit on the 2-10 keV flux of a possible PWN of 4.7e-14 erg/s/cm^2, three times less than the previously claimed value, implying an efficiency for conversion of spin-down energy into nebular luminosity of <9e-4 (assuming a distance of 4 kpc). We do, however, find strong evidence for X-ray emission from the supernova remnant shell surrounding the pulsar, as previously reported.Comment: 16 pages, 3 tables, 4 figures, published in the Astrophysical Journa

Chandra and RXTE Observations of 1E 1547.0-5408: Comparing the 2008 and 2009 Outbursts

We present results from observations of the magnetar 1E 1547.0-5408 (SGR J1550-5418) taken with the Chandra X-ray Observatory and the Rossi X-ray Timing Explorer (RXTE) following the source's outbursts in 2008 October and 2009 January. During the time span of the Chandra observations, which covers days 4 through 23 and days 2 through 16 after the 2008 and 2009 events, respectively, the source spectral shape remained stable, while the pulsar's spin-down rate in the same span in 2008 increased by a factor of 2.2 as measured by RXTE. The lack of spectral variation suggests decoupling between magnetar spin-down and radiative changes, hence between the spin-down-inferred magnetic field strength and that inferred spectrally. We also found a strong anti-correlation between the phase-averaged flux and the pulsed fraction in the 2008 and 2009 Chandra data, but not in the pre-2008 measurements. We discuss these results in the context of the magnetar model.Comment: 4 figures, accepted for publication in Ap

O8-6 Participation in physical education, extra-curricular activities, and community sports among Irish adolescents with and without functional difficulties

BACKGROUND: Physical activity for adolescents with disabilities (AWD) are reported to have even greater health benefits than for adolescents without disabilities (AWoD). The settings for organised physical activity opportunities can include physical education, extra-curricular activities and community sport. Few studies have reported whether there are differences in participation in these settings between AWD and AWoD. The purpose of this study was to report differences in participation in organised physical activity between AWD and AWoD in Ireland. METHODS: Data, were disaggregated by disabilities, from the Irish children sport participation and physical activity 2018 study; a national representative self-report survey. Adolescents selected sports and physical activities they took part in the last 12 months in physical education, extra-curricular activities, and community sports. The child functioning module was completed with data coded according to the Washington group on disability statistics criteria. Data were stratified by gender and school level, with average scores of the number of activities analysed by T-Tests with Hedge's g, and no participation by Chi-square test of independence. RESULTS: The weighted sample included 6646 adolescents (53% female, 68% secondary level), of which 16% reported disabilities. Specific difficulties were sensory (4%), physical (1%), cognitive (7%), and behavioural (9%). More AWD reported they did not do any organised physical activities in all three settings (physical education, p = 0.029, extra-curriculum, p = >.001, community sport p = >.001) than AWoD. Adolescents with behavioural disabilities reported fewer types of physical education activities (males primary, p = .014, g =.31; secondary, p = .008, g = .24) and community sports (male primary, p = >.001, g = .49; female secondary, p = .027, g = .14) than adolescents without behavioural disabilities. CONCLUSIONS: Adolescents with behavioural difficulties were the largest disability group and reported fewer number of organised physical activities than AWoD; reinforcing actions are needed to increase perceived choice of activities. An alarming number of AWD reported no organised physical activities in all three settings. More thorough studies are required to investigate these reasons, and to provide support across settings, whereby differences in participation between adolescents with and without disabilities are not so profound