4,487 research outputs found
Scalar arguments of the mathematical functions defining molecular and turbulent transport of heat and mass in compressible fluids
The advectionâdiffusion equations defining control volume conservation laws in micrometeorological research are analysed to resolve discrepancies in their appropriate scalar variables for heat and mass transport. A scalar variable that is conserved during vertical motions enables the interpretation of turbulent mixing as âdiffusionâ. Gas-phase heat advection is shown to depend on gradients in the potential temperature (Ξ), not the temperature (T). Since conduction and radiation depend on T, advectionâdiffusion of heat depends on gradients of both Ξ and T. Conservation of Ξ (the first Law of Thermodynamics) requires including a pressure covariance term in the definition of the turbulent heat flux. Mass advection and diffusion are universally agreed to depend directly on gradients in the gas âconcentrationâ (c), a nonetheless ambiguous term. Depending upon author, c may be defined either as a dimensionless proportion or as a dimensional density, with non-trivial differences for the gas phase. Analyses of atmospheric law, scalar conservation and similarity theory demonstrate that mass advectionâdiffusion in gases depends on gradients, not in density but rather in a conserved proportion. Flux-tower researchers are encouraged to respect the meteorological tradition of writing conservation equations in terms of scalar variables that are conserved through simple air motions.The authors received funding support from Andalusian regional
government project GEOCARBO (P08-RNM-3721),
the National Institute for Agrarian Research and Technology
(INIA; SUM2006â00010-00â00), the Spanish flux-tower network
CARBORED-ES (Science Ministry project CGL2010-
22193-C04â02), and the European Commission collaborative
project GHG Europe (FP7/2007-2013; grant agreement
244122)
Generation of optimal trajectories for Earth hybrid pole sitters
A pole-sitter orbit is a closed path that is constantly above one of the Earth's poles, by means of continuous low thrust. This work proposes to hybridize solar sail propulsion and solar electric propulsion (SEP) on the same spacecraft, to enable such a pole-sitter orbit. Locally-optimal control laws are found with a semi-analytical inverse method, starting from a trajectory that satisfies the pole-sitter condition in the Sun-Earth circular restricted three-body problem. These solutions are subsequently used as first guess to find optimal orbits, using a direct method based on pseudospectral transcription. The orbital dynamics of both the pure SEP case and the hybrid case are investigated and compared. It is found that the hybrid spacecraft allows savings on propellant mass fraction. Finally, it is shown that for sufficiently long missions, a hybrid pole-sitter, based on mid-term technology, enables a consistent reduction in the launch mass for a given payload, with respect to a pure SEP spacecraft
Ingesting a high-dose carbohydrate solution during the cycle section of a simulated olympicdistance triathlon improves subsequent run performance
The well-established ergogenic benefit of ingesting carbohydrates during single-discipline endurance sports has only been tested once within an Olympic-distance (OD) triathlon. The aim of the present study was to compare the effect of ingesting a 2:1 maltodextrin/fructose solution with a placebo on simulated OD triathlon performance. Six male and 4 female amateur triathletes (age, 25 ± 7 years; body mass, 66.8 ± 9.2 kg; peak oxygen uptake, 4.2 ± 0.6 L·minâ1) completed a 1500-m swim time-trial and an incremental cycle test to determine peak oxygen uptake before performing 2 simulated OD triathlons. The swim and cycle sections of the main trials were of fixed intensities, while the run section was completed as a time-trial. Two minutes prior to completing every quarter of the cycle participants consumed 202 ± 20 mL of either a solution containing 1.2 g·minâ1 of maltodextrin plus 0.6 g·minâ1 of fructose at 14.4% concentration (CHO) or a sugar-free, fruit-flavored drink (PLA). The time-trial was 4.0% ± 1.3% faster during the CHO versus PLA trial, with run times of 38:43 ± 1:10 min:s and 40:22 ± 1:18 min:s, respectively (p = 0.010). Blood glucose concentrations were higher in the CHO versus PLA trial (p < 0.001), while perceived stomach upset did not differ between trials (p = 0.555). The current findings show that a 2:1 maltodextrin/fructose solution (1.8 g·minâ1 at 14.4%) ingested throughout the cycle section of a simulated OD triathlon enhances subsequent 10-km run performance in triathletes. </jats:p
Deformation effects in the Si+C and Si+Si reaction Search
The possible occurence of highly deformed configurations is investigated in
the Ca and Ni di-nuclear systems as formed in the
Si+C,Si reactions by using the properties of emitted light
charged particles. Inclusive as well as exclusive data of the heavy fragments
and their associated light charged particles have been collected by using the
{\sc ICARE} charged particle multidetector array. The data are analysed by
Monte Carlo CASCADE statistical-model calculations using a consistent set of
parameters with spin-dependent level densities. Significant deformation effects
at high spin are observed as well as an unexpected large Be cluster
emission of a binary nature.Comment: 3 pages latex, 2 eps figures, paper presented in "wokshop on physics
with multidetector array (pmda2000)Calcutta, India (to be published at
PRAMANA, journal of Physics, India
Telerehabilitation Versus Standard Care for Improving Cognitive Function and Quality of Life for Adults with Traumatic Brain Injury: a Systematic Review
ABSTRACT
Traumatic brain injury (TBI) is the most significant cause of death and severe disability following major trauma within Australia. Populations at risk include young adults aged 15 to 34, older adults, and military personnel. The main form of intervention following traumatic brain injury is rehabilitation, which places a large demand on the healthcare system. Telerehabilitation involves interventions delivered via telecommunication, which can improve accessibility and reduce this burden. There have been no systematic reviews conducted on the effectiveness of telerehabilitation in treating traumatic brain injury.
Purpose: To examine the effectiveness of telerehabilitation for adults with traumatic brain injury.
Methods: A systematic search of Medline, Embase, the Cumulative Index of Nursing and Allied Health Literature (CINAHL), Scopus, The Cochrane Library, OTSeeker and Google Scholar was conducted. Studies were included with participants aged 18 to 64 with traumatic brain injury and receiving telerehabilitation interventions. Methodological quality was assessed using the critical appraisal tools: Critical Appraisal Skills Programme (CASP) checklist for randomised controlled trials, and McMaster Critical Review for Quantitative Studies for non-randomised studies.
Results: Three randomised controlled trials, one pseudo-randomised controlled trial, one case-control trial and one pre-post case series were included in this systematic review. Critical appraisal of the included studies revealed overall methodological quality to be moderate. A range of interventions with differing parameters were used as part of telerehabilitation. Collectively, there is some consistent evidence to indicate that telerehabilitation may be equally effective as other forms of care in the delivery of cognitive and psychological interventions, in addressing memory and depressive symptoms for adults with mild to severe traumatic brain injury. However, it is unclear if it is superior to other forms of care.
Conclusions: A small number of studies have investigated the effect of telerehabilitation for adults with traumatic brain injury. The current evidence base is limited due to lack of standardised intervention parameters, outcomes measures and robust sample size. Despite these limitations, telerehabilitation may offer a complementary model of care for adults with traumatic brain injury, especially in instances where traditional models of care may not be readily accessible (such as those in rural and remote areas)
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"I feel like everyone does it" - adolescents' perceptions and awareness of the association between humour, banter, and cyberbullying
Literature has acknowledged the alliance between face-to-face bullying behaviours and humour. However, comparably, little is known regarding humour and cyberbullying. Humour may be a motivating factor and, as such, explain why some individuals engage in cyberbullying. This study aimed to gain insight into adolescentsâ views and perceptions of how humour and âbanterâ play a role within cyberbullying. Seven focus groups were carried out with 28 United Kingdom based secondary school students (female =20, male=8) aged between 11 and 15 years old. Reflexive thematic analysis identified three prominent overarching themes which became salient across each focus group: Banter as a social interaction, Online misinterpretation, and âBadâ banter and cyberbullying. Results indicate young people have a shared understanding of online humoristic aggressive behaviours, such as online banter, describing them as ambiguous and difficult to interpret. Participants demonstrated an understanding of how ambiguity, caused by the online environment combined with banter interactions, can be interpreted as perceived or fully acknowledged cyberbullying behaviour. Motivations for these behaviours are considered within the findings of the data analysis and previous literature. Findings are discussed with potential preventative implications and considerations for future research
Polyethylene and metal debris generated by non-articulating surfaces of modular acetabular components
We report a prospective study of the liner-metal interfaces of modular uncemented acetabular components as sources of debris. We collected the pseudomembrane from the screw-cup junction and the empty screw holes of the metal backing of 19 acetabula after an average implantation of 22 months. Associated osteolytic lesions were separately collected in two cases. The back surfaces of the liners and the screws were examined for damage, and some liners were scanned by electron microscopy. The tissues were studied histologically and by atomic absorption spectrophotometry to measure titanium content. The pseudomembrane from the screw-cup junction contained polyethylene debris in seven specimens and metal debris in ten. The material from empty screw holes was necrotic tissue or dense fibroconnective tissue with a proliferative histiocytic infiltrate and foreign-body giant-cell reaction. It contained polyethylene debris in 14 cases and metal in five. The two acetabular osteolytic lesions also showed a foreign-body giant-cell reaction to particulate debris. The average titanium levels in pseudomembranes from the screw-cup junction and the empty screw holes were 959 micrograms/g (48 to 11,900) and 74 micrograms/g (0.72 to 331) respectively. The tissue from the two lytic lesions showed average titanium levels of 139 and 147 micrograms/g respectively. The back surfaces of the PE liners showed surface deformation, burnishing, and embedded metal debris. All 30 retrieved screws demonstrated fretting at the base of the head and on the proximal shaft. Non-articular modular junctions create new interfaces for the generation of particulate debris, which may cause granulomatous reaction
Slow cross-symmetry phase relaxation in complex collisions
We discuss the effect of slow phase relaxation and the spin off-diagonal
-matrix correlations on the cross section energy oscillations and the time
evolution of the highly excited intermediate systems formed in complex
collisions. Such deformed intermediate complexes with strongly overlapping
resonances can be formed in heavy ion collisions, bimolecular chemical
reactions and atomic cluster collisions. The effects of quasiperiodic energy
dependence of the cross sections, coherent rotation of the hyperdeformed
intermediate complex, Schr\"odinger cat states and
quantum-classical transition are studied for Mg+Si heavy ion
scattering.Comment: 10 pages including 2 color ps figures. To be published in Physics of
Atomic Nuclei (Yadernaya fizika
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