13,269 research outputs found
Holder exponent spectra for human gait
The stride interval time series in normal human gait is not strictly
constant, but fluctuates from step to step in a complex manner. More precisely,
it has been shown that the control process for human gait is a fractal random
phenomenon, that is, one with a long-term memory. Herein we study the Holder
exponent spectra for the slow, normal and fast gaits of 10 young healthy men in
both free and metronomically triggered conditions and establish that the stride
interval time series is more complex than a monofractal phenomenon. A slightly
multifractal and non-stationary time series under the three different gait
conditions emerges.Comment: 23 pages, 12 figures, 9 Table
Behavior of materials in vacuum Final report, Jun. 1967 - Sep. 1968
Outgassed materials condensed on magnesium overcoated aluminum mirrors irradiated with ultraviolet radiation in vacuu
The effects of label design characteristics on perceptions of genetically modified food
Objective. To explore the effects on perceptions of labelling food for genetically modified content. Background: there is increasing public pressure for the compulsory labelling of genetically modified food content on all food products, and yet little is known about how the design and content of such food labels will influence product perceptions. The current research draws upon warning label research - a field in which the effect of label design manipulations on perceptions of, and responses to, potential or perceived risks is well documented. Method. Two experiments are reported that investigate how label design features influence the perception of genetically modified foods. The effects of label colour (red, blue and green), wording style (definitive vs. probabilistic and explicit vs. non-explicit) and information source (government agency, consumer group and manufacturer) on hazard perceptions and purchase intentions were measured. Results. Hazard perceptions and purchase intentions were both influenced by label design characteristics in predictable ways. Any reference to genetic modification, even if the label is stating that the product is free of genetically modified ingredients, increased hazard perception, and decreased purchase intentions, relative to a no-label condition. Conclusion. Label design effects generalise from warning label research to influence the perception of genetically modified foods in predictable ways. Application. The design of genetically modified food labels. Ā© 2012 Copyright Taylor and Francis Group, LLC
Structure determination from powder data : Mogul and CASTEP
When solving the crystal structure of complex molecules from powder data, accurately locating the global minimum can be challenging, particularly where the number of internal degrees of freedom is large. The program Mogul provides a convenient means to access typical torsion angle ranges for fragments related to the molecule of interest. The impact that the application of modal torsion angle constraints has on the structure determination process of two structure solution attempts using DASH is presented. Once solved, accurate refinement of a molecular structure against powder data can also present challenges. Geometry optimisation using density functional theory in CASTEP is shown to be an effective means to locate hydrogen atom positions reliably and return a more accurate description of molecular conformation and intermolecular interactions than global optimisation and Rietveld refinement alone
Microscopic calculation of the phonon-roton branch in superfluid He
Diffusion Monte Carlo results for the phonon-roton excitation branch in bulk
liquid He at zero temperature are presented. The sign problem associated to
the excited wave function has been dealt both with the fixed-node approximation
and the released-node technique. The upper bounds provided by the fixed-node
approximation are shown to become exact when using the released-node method. An
excellent agreement with experimental data is achieved both at the equilibrium
and near the freezing densities.Comment: 12 pages, RevTex, 3 ps figures include
Superfluidity of bosons on a deformable lattice
We study the superfluid properties of a system of interacting bosons on a
lattice which, moreover, are coupled to the vibrational modes of this lattice,
treated here in terms of Einstein phonon model. The ground state corresponds to
two correlated condensates: that of the bosons and that of the phonons. Two
competing effects determine the common collective soundwave-like mode with
sound velocity , arising from gauge symmetry breaking: i) The sound velocity
(corresponding to a weakly interacting Bose system on a rigid lattice) in
the lowest order approximation is reduced due to reduction of the repulsive
boson-boson interaction, arising from the attractive part of phonon mediated
interaction in the static limit. ii) the second order correction to the sound
velocity is enhanced as compared to the one of bosons on a rigid lattice when
the the boson-phonon interaction is switched on due to the retarded nature of
phonon mediated interaction. The overall effect is that the sound velocity is
practically unaffected by the coupling with phonons, indicating the robustness
of the superfluid state. The induction of a coherent state in the phonon
system, driven by the condensation of the bosons could be of experimental
significance, permitting spectroscopic detections of superfluid properties of
the bosons. Our results are based on an extension of the Beliaev - Popov
formalism for a weakly interacting Bose gas on a rigid lattice to that on a
deformable lattice with which it interacts.Comment: 12 pages, 14 figures, to appear in Phys. Rev.
Demonstration of an inductively coupled ring trap for cold atoms
We report the first demonstration of an inductively coupled magnetic ring trap for cold atoms. A uniform, ac magnetic field is used to induce current in a copper ring, which creates an opposing magnetic field that is time-averaged to produce a smooth cylindrically symmetric ring trap of radius 5 mm. We use a laser-cooled atomic sample to characterize the loading efficiency and adiabaticity of the magnetic potential, achieving a vacuum-limited lifetime in the trap. This technique is suitable for creating scalable toroidal waveguides for applications in matter-wave interferometry, offering long interaction times and large enclosed areas
Superfluid density and condensate fraction in the BCS-BEC crossover regime at finite temperatures
The superfluid density is a fundamental quantity describing the response to a
rotation as well as in two-fluid collisional hydrodynamics. We present
extensive calculations of the superfluid density \rho_s in the BCS-BEC
crossover regime of a uniform superfluid Fermi gas at finite temperatures. We
include strong-coupling or fluctuation effects on these quantities within a
Gaussian approximation. We also incorporate the same fluctuation effects into
the BCS single-particle excitations described by the superfluid order parameter
\Delta and Fermi chemical potential \mu, using the Nozi\`eres and Schmitt-Rink
(NSR) approximation. This treatment is shown to be necessary for consistent
treatment of \rho_s over the entire BCS-BEC crossover. We also calculate the
condensate fraction N_c as a function of the temperature, a quantity which is
quite different from the superfluid density \rho_s. We show that the mean-field
expression for the condensate fraction N_c is a good approximation even in the
strong-coupling BEC regime. Our numerical results show how \rho_s and N_c
depend on temperature, from the weak-coupling BCS region to the BEC region of
tightly-bound Cooper pair molecules. In a companion paper by the authors
(cond-mat/0609187), we derive an equivalent expression for \rho_s from the
thermodynamic potential, which exhibits the role of the pairing fluctuations in
a more explicit manner.Comment: 32 pages, 12 figure
Researching DIY Cultures: Towards a Situated Ethical Practice for Activist-Academia
The empirical study of DIY culture and feminist cultural activism is a flourishing interdisciplinary research area particularly in the USA, Canada, Australia and UK. This has enabled a growth in participant-researchers doing research on their own DIY cultures and activist communities of belonging. Tensions occur here for the participant-researcher in relation to conventional data collection methods, ethical and moral decisions and modes of research dissemination. This article develops discussions of dilemmas experienced by the authors during doctoral research projects on DIY punk, roller derby and queer feminist music cultures. We detail the possibilities and tensions met when the participant-researcher encounters existing subcultural theories, ethical codes of practice, data collection methods and the dissemination of academic research. In addition we offer insights into the under-documented emotional impacts and moments of crisis the participant-researcher needs to attend to when carrying out research with/in personal and political communities of belonging. In conclusion, we offer a series of recommendations for a situated ethical practice for research with/in DIY cultures in relation to engaged data generation
Deceptive appearance of a normal variant of scaphoid bone in a teenage patient: a diagnostic challenge
Scaphoid fractures are a common injury in late teens and mid twenties with a peak period in skeletally immature children at about 15 years of age, although considered to be rare in first decade of life, its exact incidence in early teen age remains to be a subject of debate. We report an unusual case of anatomical variation of scaphoid bone at the level of waist which could potentially cause diagnostic confusion. A 14-years-old boy presented in the fracture clinic 2 weeks after injury to his Right wrist which was managed in a scaphoid cast. X-ray examinations, both at the time of injury and later on in the fracture clinic revealed features suspicious of a fracture at the level of waist of the scaphoid bone, however the clinical examination did not correlate with imaging, in view of that radiological imaging of the unaffected side was performed for comparison, which revealed it to be an anatomical variant of scaphoid at this age. To our knowledge there are very few cases of such variation reported in literature in this age group of patients. This case highlights the importance of anatomical variants in scaphoid bone in this age group, which might pose a diagnostic challenge and the need for appropriate management plan and reassurance to avoid unnecessary anxiety
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