6,312 research outputs found
<i>Chirotherium barthii </i>Kaup 1835 from the Triassic of the Isle of Arran, Scotland
The mould of a track from SE Arran, and several in situ trackways and individual tracks, as well as a partial trackway on a loose block of Triassic sandstone, from western Arran, represent the first verifiable fossil tracks of Chirotherium from the Triassic of Scotland and support a Scythian (Lower Triassic) age for the base of the Auchenhew Beds. The grouping of the IâIV toes with toe V behind and lateral to the group is characteristic of Chirotherium-like tracks. A comparison with European and American Triassic trackways suggests that the tracks belong to the species Chirotherium barthii Kaup, 1835, first described from
Hildburghausen, Germany
A case-control study of medical, psychological and socio-economic factors influencing the severity of chronic rhinosinusitis
BACKGROUND: Chronic rhinosinusitis (CRS) is a common and debilitating disorder. Little is known about the epidemiology of this disease. The aims of the study were to identify differences in socio-economic variables and quality of life between patients with chronic rhinosinusitis and healthy controls, to identify any significant associations between CRS and other medical co-morbidities, psychiatric disease or environmental exposure and to explore the experience of CRS from the perspective of CRS sufferers. METHODS: Participants were recruited from ENT clinics from 30 centres across the UK. They completed a study-specific questionnaire considering environmental, medical and socio-economic factors, and SF-36 and SNOT-22 scores. All participants with CRS were diagnosed by a clinician and categorised as having CRS (with polyposis, without polyposis or allergic fungal rhinosinusitis (AFRS)). Controls included family and friends of those attending ENT outpatient clinics and hospital staff who had no diagnosis of nose or sinus problems and had not been admitted to hospital in the previous 12 months. RESULTS: A total of 1470 study participants (1249 patients and 221 controls) were included in the final analysis. Highly significant differences were seen in generic and disease-specific quality of life scores between CRS sufferers and controls; mean SNOT-22 score 45.0 for CRS compared with 12.1 amongst controls. There were no clear differences in socioeconomic variables including social class, index of multiple deprivation and educational attainment between cases and controls. Common comorbidities with a clear association included respiratory and psychiatric disorders, with a higher frequency of reported upper respiratory tract infections. CONCLUSIONS: CRS is associated with significant impairment in quality of life and with certain medical co-morbidities. In contrast to other common ENT disorders, no socioeconomic differences were found between patients and controls in this study
The Origin and Universality of the Stellar Initial Mass Function
We review current theories for the origin of the Stellar Initial Mass
Function (IMF) with particular focus on the extent to which the IMF can be
considered universal across various environments. To place the issue in an
observational context, we summarize the techniques used to determine the IMF
for different stellar populations, the uncertainties affecting the results, and
the evidence for systematic departures from universality under extreme
circumstances. We next consider theories for the formation of prestellar cores
by turbulent fragmentation and the possible impact of various thermal,
hydrodynamic and magneto-hydrodynamic instabilities. We address the conversion
of prestellar cores into stars and evaluate the roles played by different
processes: competitive accretion, dynamical fragmentation, ejection and
starvation, filament fragmentation and filamentary accretion flows, disk
formation and fragmentation, critical scales imposed by thermodynamics, and
magnetic braking. We present explanations for the characteristic shapes of the
Present-Day Prestellar Core Mass Function and the IMF and consider what
significance can be attached to their apparent similarity. Substantial
computational advances have occurred in recent years, and we review the
numerical simulations that have been performed to predict the IMF directly and
discuss the influence of dynamics, time-dependent phenomena, and initial
conditions.Comment: 24 pages, 6 figures. Accepted for publication as a chapter in
Protostars and Planets VI, University of Arizona Press (2014), eds. H.
Beuther, R. S. Klessen, C. P. Dullemond, Th. Hennin
Obesity, unhappiness, and the challenge of affluence : theory and evidence
Is affluence a good thing? The book "The Challenge of Affluence" by Avner Offer (2006) argues that economic prosperity weakens self-control and undermines human well-being. Consistent with a pessimistic view, we show that psychological distress has been rising through time in modern Great Britain. Taking over-eating as an example, our data reveal that half the British population view themselves as overweight, and that happiness and mental health are worse among fatter people in Britain and Germany. Comparisons also matter. We discuss problems of inference and argue that longitudinal data are needed. We suggest a theory of obesity imitation where utility depends on relative weight
Explicit teaching of models to enrich physical science learning
Good teaching inducts students into science as a human endeavour and demonstrates that scientific knowledge arises from a process of model construction, testing and review. The historical evolution of scientific knowledge is the development and refinement of models to explain scientific observations. The explicit use of models in teaching facilitates metacognitive engagement, which can lead to improved conceptual understanding (Kenyon et al., 2008).
The Science curriculum in Victoria, Australia is modelled on the Australian national curriculum and begins with an explicit aim of students developing an understanding of âthe nature of scientific inquiry and the ability to use a range of scientific inquiry methods.â Models are mentioned frequently in the more detailed curriculum statements. For example, the curriculum strand âScience as a human endeavourâ includes the following statement: âScientific understanding, including models and theories, are contestable and are refined over time through a process of review by the scientific community.â
In this work we present examples of the representation of models in the secondary physical science curriculum and highlight opportunities for enriching the teaching of science through the explicit introduction of the history and nature of the model, with an emphasis on linking to metacognition (Avargil et al., 2017).
REFERENCES
Avargil, S., Lavi, R., & Dori, Y. (2017). Studentsâ Metacognition and Metacognitive Strategies in Science Education, in Y.J. Dori, Z.R. Mevarech, & D.R. Baker (ed.). Cognition, metacognition, and culture in STEM education: Learning, teaching and assessment, Springer International Publishing AG, 33-64.
Kenyon, L., Schwarz, C. & Hug, B. (2008), The Benefits of Scientific Modeling. Science and Children, 46(2), 40-44
Construction and Performance of Highway Soil Subgrades Modified with Atmospheric Fluidized Bed Combustion Residue and Multicone Kiln Dust
In an effort to increase the utilization of by-product materials in highway construction projects, the Kentucky Transportation Cabinet authorized the experimental use of reside from an atmospheric fluidized bed combustion (AFBC) process and multicone kiln dust (MKD), a by-product resulting from the production of lime, as subgrade soil modifiers. This report presents information relative to preconstruction and post-construction laboratory evaluations, construction procedures, construction monitoring activities, and performance evaluations of a highway subgrade solid modified using AFBC spent lime, MKD, Type IP cement, and hydrated lime. An untreated section served as a control section for the project located on Kentucky Route 11 in Lee and Wolfe Counties.
The laboratory testing program consisted of determining select engineering properties of the solid in a natural state and in a state altered by the chemical admixtures. Index tests were performed, moisture density relationships were determined, and bearing ratio and swell tests were performed. Based on the laboratory unconfined compression tests and bearing capacity tests, the two waste by-products significantly improved the shear strength and bearing strength of the subgrade soil. Field monitoring activities were comprised of both construction monitoring and post-construction monitoring. Construction procedures were essentially the same for all admixture types and no significant problems were encountered. Satisfactory moisture and density were achieved. Construction activities were documented through moisture content and density compliance tests. In-place bearing capacity tests and Road Rater deflection tests were performed on the untreated subgrade and again after modification. The analyses indicated significant improvement in subgrade strength after admixture modification.
Post-construction monitoring included determining in-site bearing capacities, assessing moisture conditions and determining soil classifications of the treated and untreated subgrade layers. Road Rater deflection tests were conducted to assess the structural condition of the pavement structure. Results of the field monitoring program confirmed that each chemically modified subgrade continued to exhibit greater strengths than the untreated subgrade section. However, because of non-uniform mixing, the soil-AFBC subgrade sections exhibited severe differential swelling shortly after construction. The bituminous pavement required milling the eliminate humps on the pavement surface. The pavement was overlaid and apparently the subgrade swelling has ceased. However, due to the expansive nature of the AFBC spent lime, future use as a soil modifier could not be recommended. Results of field monitoring activities indicated that MKD was a suitable solid modifier and future use was recommended
Placebo in sports nutrition: a proof-of-principle study involving caffeine supplementation
We investigated the effects of supplement identification on exercise performance with caffeine supplementation. Forty-two trained cyclists (age 37 ± 8 years, body mass [BM] 74.3 ± 8.4 kg, height 1.76 ± 0.06 m, maximum oxygen uptake 50.0 ± 6.8 mL/kg/min) performed a ~30 min cycling time-trial 1 h following either 6 mg/kgBM caffeine (CAF) or placebo (PLA) supplementation and one control (CON) session without supplementation. Participants identified which supplement they believed they had ingested (âcaffeineâ, âplaceboâ, âdon't knowâ) pre- and post-exercise. Subsequently, participants were allocated to subgroups for analysis according to their identifications. Overall and subgroup analyses were performed using mixed-model and magnitude-based inference analyses. Caffeine improved performance vs PLA and CON (P †0.001). Correct pre- and post-exercise identification of caffeine in CAF improved exercise performance (+4.8 and +6.5%) vs CON, with slightly greater relative increases than the overall effect of caffeine (+4.1%). Performance was not different between PLA and CON within subgroups (all P > 0.05), although there was a tendency toward improved performance when participants believed they had ingested caffeine post-exercise (P = 0.06; 87% likely beneficial). Participants who correctly identified placebo in PLA showed possible harmful effects on performance compared to CON. Supplement identification appeared to influence exercise outcome and may be a source of bias in sports nutrition
Keep up with the winners: Experimental evidence on risk taking, asset integration, and peer effects
The paper reports the result of an experimental game on asset integration and risk taking. We find some evidence that winnings in earlier rounds affect risk taking in subsequent rounds, but no evidence that real life wealth outside the experiment affects risk taking. Controlling for past winnings, participants receiving a low endowment in a round engage in more risk taking. We test a âkeeping-up-with-the-Jonesesâ hypothesis and find that subjects seek to keep up with winners, though not necessarily with average earnings. Overall, the evidence suggests that risk taking tracks a reference point affected by social comparisons
The Structure of the Interstellar Medium of Star Forming Galaxies
We present numerical methods for including stellar feedback in galaxy-scale
simulations. We include heating by SNe (I & II), gas recycling and
shock-heating from O-star & AGB winds, HII photoionization, and radiation
pressure from stellar photons. The energetics and time-dependence are taken
directly from stellar evolution models. We implement these in simulations with
pc-scale resolution, modeling galaxies from SMC-like dwarfs and MW analogues to
massive z~2 starburst disks. Absent feedback, gas cools and collapses without
limit. With feedback, the ISM reaches a multi-phase steady state in which GMCs
continuously form, disperse, and re-form. Our primary results include: (1) Star
forming galaxies generically self-regulate at Toomre Q~1. Most of the volume is
in diffuse hot gas with most of the mass in dense GMC complexes. The phase
structure and gas mass at high densities are much more sensitive probes of
stellar feedback physics than integrated quantities (Toomre Q or gas velocity
dispersion). (2) Different feedback mechanisms act on different scales:
radiation & HII pressure are critical to prevent runaway collapse of dense gas
in GMCs. SNe and stellar winds dominate the dynamics of volume-filling hot gas;
however this primarily vents out of the disk. (3) The galaxy-averaged SFR is
determined by feedback. For given feedback efficiency, restricting star
formation to molecular gas or modifying the cooling function has little effect;
but changing feedback mechanisms directly translates to shifts off the
Kennicutt-Schmidt relation. (4) Self-gravity leads to marginally-bound GMCs
with an ~M^-2 mass function with a cutoff at the Jeans mass; they live a few
dynamical times before being disrupted by stellar feedback and turn ~1-10% of
their mass into stars (increasing from dwarfs through starburst galaxies).
Low-mass GMCs are preferentially unbound.Comment: 34 pages, 24 figures, accepted to MNRAS (matches accepted version).
Movies of the simulations are available at
https://www.cfa.harvard.edu/~phopkins/Site/Movies_sbw.htm
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