1,795 research outputs found
Developing a computer aided design tool for inclusive design
The purpose of this study was to investigate age-related changes in the performance of a range of movement tasks for integration into a computer aided design (CAD) tool for use in inclusive design
Antiferromagnetism in NiO Observed by Transmission Electron Diffraction
Neutron diffraction has been used to investigate antiferromagnetism since
1949. Here we show that antiferromagnetic reflections can also be seen in
transmission electron diffraction patterns from NiO. The diffraction patterns
taken here came from regions as small as 10.5 nm and such patterns could be
used to form an image of the antiferromagnetic structure with a nanometre
resolution.Comment: 10 pages, 7 figures. Typos corrected. To appear in Physical Review
Letter
Intensity fluctuations in steady state superradiance
Alkaline-earth like atoms with ultra-narrow optical transitions enable
superradiance in steady state. The emitted light promises to have an
unprecedented stability with a linewidth as narrow as a few millihertz. In
order to evaluate the potential usefulness of this light source as an
ultrastable oscillator in clock and precision metrology applications it is
crucial to understand the noise properties of this device. In this paper we
present a detailed analysis of the intensity fluctuations by means of
Monte-Carlo simulations and semi-classical approximations. We find that the
light exhibits bunching below threshold, is to a good approximation coherent in
the superradiant regime, and is chaotic above the second threshold.Comment: 8 pages, 5 figure
Extension of the Huttner-Barnett model to a magnetodielectric medium
The HuttnerBarnett model is extended to a magnetodielectric medium by
adding a new matter field to this model. The eigenoperators for the coupled
system are calculated and electromagnetic field is written in terms of these
operators. The electric and magnetic susceptibility of the medium are
explicitly derived and shown to satisfy the KramersKronig relations. It is
shown that the results obtained in this model are equivalent to the results
obtained from the phenomenological methods.Comment: 25 page
Coherent flash of light emitted by a cold atomic cloud
When a resonant laser sent on an optically thick cold atomic cloud is
abruptly switched off, a coherent flash of light is emitted in the forward
direction. This transient phenomenon is observed due to the highly resonant
character of the atomic scatterers. We analyze quantitatively its
spatio-temporal properties and show very good agreement with theoretical
predictions. Based on complementary experiments, the phase of the coherent
field is reconstructed without interferometric tools.Comment: Submitted to Phys. Rev. Let
Healthcare professional’s guide to cardiopulmonary exercise testing
Cardiopulmonary exercise testing (CPEX) is a valuable clinical tool that has proven indications within the fields of cardiovascular, respiratory and pre-operative medical care. Validated uses include investigation of the underlying mechanism in patients with breathlessness, monitoring functional status in patients with known cardiovascular disease and pre-operative functional state assessment. An understanding of the underlying physiology of exercise, and the perturbations associated with pathological states, is essential for healthcare professionals to provide optimal patient care. Healthcare professionals may find performing CPEX to be daunting, yet this is often due to a lack of local expertise and guidance with testing. We outline the indications for CPEX within the clinical setting, present a typical protocol that is easy to implement, explain the key underlying physiological changes assessed by CPEX, and review the evidence behind its use in routine clinical practice. There is mounting evidence for the use of CPEX clinically, and an ever-growing utilisation of the test within research fields; a sound knowledge of CPEX is essential for healthcare professionals involved in routine patient care
Optical Thomas-Reiche-Kuhn sum rules
The Thomas-Reiche-Kuhn sum rule is a fundamental consequence of the position-momentum commutation relation for an atomic electron and it provides an important constraint on the transition matrix elements for an atom. Analogously, the commutation relations for the electromagnetic field operators in a magnetodielectric medium constrain the properties of the dispersion relations for the medium through four sum rules for the allowed phase and group velocities for polaritons propagating through the medium. These rules apply to all bulk media including the metamaterials designed to provide negative refractive indices. An immediate consequence of this is that it is not possible to construct a medium in which all the polariton modes for a given wavelength lie in the negative-index region
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