492 research outputs found

    Cross-sections for heavy atmospheres: H₂O continuum

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    Most of the exoplanets detected up to now transit in front of their host stars, allowing for the generation of transmission spectra; the study of exoplanet atmospheres relies heavily upon accurate analysis of these spectra. Recent discoveries mean that the study of atmospheric signals from low-mass, temperate worlds are becoming increasingly common. The observed transit depth in these planets is small and more difficult to analyze. Analysis of simulated transmission spectra for two small, temperate planets (GJ 1214 b and K2-18 b) is presented, giving evidence for significant differences in simulated transit depth when the water vapor continuum is accounted for when compared to models omitting it. These models use cross-sections from the CAVIAR lab experiment for the water self-continuum up to 10,000 cm−1; these cross-sections exhibit an inverse relationship with temperature, hence lower-temperature atmospheres are the most significantly impacted. Including the water continuum strongly affects transit depths, increasing values by up to 60 ppm, with the differences for both planets being detectable with the future space missions Ariel and JWST. It is imperative that models of exoplanet spectra move toward adaptive cross-sections, increasingly optimized for H2O-rich atmospheres. This necessitates including absorption contribution from the water vapor continuum into atmospheric simulations

    War on video: Combat footage, vernacular video analysis and military culture from within

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    open access articleIn this article we present an ethnomethodological study of a controversial case of ‘friendly fire’ from the Iraq War in which leaked video footage, war on video, acquired particular significance. We examine testimony given during a United States Air Force (USAF) investigation of the incident alongside transcribed excerpts from the video to make visible the methods employed by the investigators to assess the propriety of the actions of the pilots involved. With a focus on the way in which the USAF investigators pursued their own analysis of language-in-use in their discussions with the pilots about what had been captured on the video, we turn attention to the background expectancies that analytical work was grounded in. These ‘vernacular’ forms of video analysis and the expectancies which inform them constitute, we suggest, an inquiry into military culture from within that culture. As such, attending to them provides insights into that culture

    Protocol for a pragmatic cluster randomised controlled trial for reducing irrational antibiotic prescribing among children with upper respiratory infections in rural China.

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    Introduction: Irrational use of antibiotics is a serious issue within China and internationally. In 2012, the Chinese Ministry of Health issued a regulation for antibiotic prescriptions limiting them to <20% of all prescriptions for outpatients, but no operational details have been issued regarding policy implementation. This study aims to test the effectiveness of a multidimensional intervention designed to reduce the use of antibiotics among children (aged 2–14 years old) with acute upper respiratory infections in rural primary care settings in China, through changing doctors’ prescribing behaviours and educating parents/caregivers. Methods and analysis: This is a pragmatic, parallelgroup, controlled, cluster-randomised superiority trial, with blinded evaluation of outcomes and data analysis, and un-blinded treatment. From two counties in Guangxi Province, 12 township hospitals will be randomised to the intervention arm and 13 to the control arm. In the control arm, the management of antibiotics prescriptions will continue through usual care via clinical consultations. In the intervention arm, a provider and patient/caregiver focused intervention will be embedded within routine primary care practice. The provider intervention includes operational guidelines, systematic training, peer review of antibiotic prescribing and provision of health education to patient caregivers. We will also provide printed educational materials and educational videos to patients’ caregivers. The primary outcome is the proportion of all prescriptions issued by providers for upper respiratory infections in children aged 2–14 years old, which include at least one antibiotic. Ethics and dissemination: The trial has received ethical approval from the Ethics Committee of Guangxi Provincial Centre for Disease Control and Prevention, China. The results will be disseminated through workshops, policy briefs, peer-reviewed publications, local and international conferences. Trial registration number: ISRCTN14340536; Pre-results

    A Gauge Invariant Unitary Theory for Pion Photoproduction

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    A covariant, unitary and gauge invariant theory for pion photoproduction on a single nucleon is presented. To achieve gauge invariance at the operator level one needs to include both the πN\pi N and ÎłÏ€N\gamma\pi N thresholds. The final amplitude can be written in terms of a distorted wave in the final πN\pi N channel provided one includes additional diagrams to the standard Born term in which the photon is coupled to the final state pion and nucleon. These additional diagrams are required in order to satisfy gauge invariance.Comment: 4 pages, LaTeX, 1 figure as a separate uuencoded compressed tar fil

    Solution of the Bethe-Salpeter equation for pion-nucleon scattering

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    A relativistic description of pion-nucleon scattering based on the four-dimensional Bethe-Salpeter equation is presented. The kernel of the equation consists of s- and u-channel nucleon and delta pole diagrams, as well as rho and sigma exchange in the t-channel. The Bethe-Salpeter equation is solved by means of a Wick rotation, and good fits are obtained to the s- and p-wave phase shifts up to 360 MeV pion laboratory energy. The coupling constants determined by the fits are consistent with the commonly accepted values in the literature.Comment: 34 pages, RevTeX; 7 figures. Several references added, a few typos corrected. Accepted for publication in Physical Review

    Size does matter: crocodile mothers react more to the voice of smaller offspring

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    Parental care is widespread in Archosaurs (birds, crocodilians, dinosaurs and pterosaurs), and this group provides a useful model for the evolution of parent-offspring interactions. While offspring signalling has been well-studied in birds, the modulation of parental care in crocodilians remains an open question. Here we show that acoustic communication has a key role in the dynamics of crocodilian’ mother-offspring relationships. We found embedded information about the emitter’s size in juvenile calls of several species, and experimentally demonstrated that Nile crocodile mothers breeding in the wild are less receptive to the calls of larger juveniles. Using synthetized sounds, we further showed that female’ reaction depends on call pitch, an important cue bearing size information. Changes in acoustic interactions may thus go with the break of maternal care as well as dispersal of juvenile crocodilians. This process could have characterized other archosaurs displaying rapid early growth such as dinosaurs and pterosaurs

    What is the structure of the Roper resonance?

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    We investigate the structure of the nucleon resonance N^*(1440) (Roper) within a coupled-channel meson exchange model for pion-nucleon scattering. The coupling to pipiN states is realized effectively by the coupling to the sigmaN, piDelta and rhoN channels. The interaction within and between these channels is derived from an effective Lagrangian based on a chirally symmetric Lagrangian, which is supplemented by well known terms for the coupling of the Delta isobar, the omega meson and the 'sigma', which is the name given here to the strong correlation of two pions in the scalar-isoscalar channel. In this model the Roper resonance can be described by meson-baryon dynamics alone; no genuine N^*(1440) (3 quark) resonance is needed in order to fit piN phase shifts and inelasticities.Comment: 55 pages, 14 figure

    Scaling of axial muscle architecture in juvenile Alligator mississippiensis reveals an enhanced performance capacity of accessory breathing mechanisms

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    From Wiley via Jisc Publications RouterHistory: received 2020-11-16, rev-recd 2021-07-08, accepted 2021-07-12, pub-electronic 2021-07-23Article version: VoRPublication status: PublishedFunder: Biotechnology and Biological Sciences Research Council; Id: http://dx.doi.org/10.13039/501100000268; Grant(s): BB/I021116/1Funder: National Science Foundation; Id: http://dx.doi.org/10.13039/100000001; Grant(s): 17565187Abstract: Quantitative functional anatomy of amniote thoracic and abdominal regions is crucial to understanding constraints on and adaptations for facilitating simultaneous breathing and locomotion. Crocodilians have diverse locomotor modes and variable breathing mechanics facilitated by basal and derived (accessory) muscles. However, the inherent flexibility of these systems is not well studied, and the functional specialisation of the crocodilian trunk is yet to be investigated. Increases in body size and trunk stiffness would be expected to cause a disproportionate increase in muscle force demands and therefore constrain the basal costal aspiration mechanism, necessitating changes in respiratory mechanics. Here, we describe the anatomy of the trunk muscles, their properties that determine muscle performance (mass, length and physiological cross‐sectional area [PCSA]) and investigate their scaling in juvenile Alligator mississippiensis spanning an order of magnitude in body mass (359 g–5.5 kg). Comparatively, the expiratory muscles (transversus abdominis, rectus abdominis, iliocostalis), which compress the trunk, have greater relative PCSA being specialised for greater force‐generating capacity, while the inspiratory muscles (diaphragmaticus, truncocaudalis ischiotruncus, ischiopubis), which create negative internal pressure, have greater relative fascicle lengths, being adapted for greater working range and contraction velocity. Fascicle lengths of the accessory diaphragmaticus scaled with positive allometry in the alligators examined, enhancing contractile capacity, in line with this muscle's ability to modulate both tidal volume and breathing frequency in response to energetic demand during terrestrial locomotion. The iliocostalis, an accessory expiratory muscle, also demonstrated positive allometry in fascicle lengths and mass. All accessory muscles of the infrapubic abdominal wall demonstrated positive allometry in PCSA, which would enhance their force‐generating capacity. Conversely, the basal tetrapod expiratory pump (transversus abdominis) scaled isometrically, which may indicate a decreased reliance on this muscle with ontogeny. Collectively, these findings would support existing anecdotal evidence that crocodilians shift their breathing mechanics as they increase in size. Furthermore, the functional specialisation of the diaphragmaticus and compliance of the body wall in the lumbar region against which it works may contribute to low‐cost breathing in crocodilians
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