29,232 research outputs found
Patients' practices and experiences of using nebuliser therapy in the management of COPD at home.
How patients use their nebulisers at home is vital to ensure effective treatment and optimal health outcomes for patients with chronic obstructive pulmonary disease (COPD). The aim of the study was to identify the practicalities and problems associated with nebuliser use by patients with COPD at home, which may impact on the safety and effectiveness of therapy
On the wake of a Darrieus turbine
The theory and experimental measurements on the aerodynamic decay of a wake from high performance vertical axis wind turbine are discussed. In the initial experimental study, the wake downstream of a model Darrieus rotor, 28 cm diameter and a height of 45.5 cm, was measured in a Boundary Layer Wind Tunnel. The wind turbine was run at the design tip speed ratio of 5.5. It was found that the wake decayed at a slower rate with distance downstream of the turbine, than a wake from a screen with similar troposkein shape and drag force characteristics as the Darrieus rotor. The initial wind tunnel results indicated that the vertical axis wind turbines should be spaced at least forty diameters apart to avoid mutual power depreciation greater than ten per cent
Pupil remapping for high contrast astronomy: results from an optical testbed
The direct imaging and characterization of Earth-like planets is among the
most sought-after prizes in contemporary astrophysics, however current optical
instrumentation delivers insufficient dynamic range to overcome the vast
contrast differential between the planet and its host star. New opportunities
are offered by coherent single mode fibers, whose technological development has
been motivated by the needs of the telecom industry in the near infrared. This
paper presents a new vision for an instrument using coherent waveguides to
remap the pupil geometry of the telescope. It would (i) inject the full pupil
of the telescope into an array of single mode fibers, (ii) rearrange the pupil
so fringes can be accurately measured, and (iii) permit image reconstruction so
that atmospheric blurring can be totally removed. Here we present a laboratory
experiment whose goal was to validate the theoretical concepts underpinning our
proposed method. We successfully confirmed that we can retrieve the image of a
simulated astrophysical object (in this case a binary star) though a pupil
remapping instrument using single mode fibers.Comment: Accepted in Optics Expres
Typography in motion: A framework of moving type use
Typography is increasingly undertaken with and mediated through Information Technologies. One of the most visible manifestations of this change is the expansion from the printed page to screen environments and device displays. Moving type is an example of a new quality of text made possible by the use of new technologies. In this study we propose a framework that can help answer questions such as why type should move at all, what benefits moving type can offer, and how it can be best used to enhance the visual display of text. The framework categorises the uses of moving type, based on whether the movement of text enhances reading, viewing or using of a text, or a combination of the above. The categories are illustrated with examples of existing moving type works, which provided a basis for discussion of various challenges and issues specific to each category
Tweed in Martensites: A Potential New Spin Glass
We've been studying the ``tweed'' precursors above the martensitic transition
in shape--memory alloys. These characteristic cross--hatched modulations occur
for hundreds of degrees above the first--order shape--changing transition. Our
two--dimensional model for this transition, in the limit of infinite elastic
anisotropy, can be mapped onto a spin--glass Hamiltonian in a random field. We
suggest that the tweed precursors are a direct analogy of the spin--glass
phase. The tweed is intermediate between the high--temperature cubic phase and
the low--temperature martensitic phase in the same way as the spin--glass phase
can be intermediate between ferromagnet and antiferromagnet.Comment: 18 pages and four figures (included
Multi-wavelength visibility measurements of the red giant R Doradus
We present visibility measurements of the nearby Mira-like star R Doradus
taken over a wide range of wavelengths (650--990 nm). The observations were
made using MAPPIT (Masked APerture-Plane Interference Telescope), an
interferometer operating at the 3.9-m Anglo-Australian Telescope. We used a
slit to mask the telescope aperture and prism to disperse the interference
pattern in wavelength. We observed in R Dor strong decreases in visibility
within the TiO absorption bands. The results are in general agreement with
theory but differ in detail, suggesting that further work is needed to refine
the theoretical models.Comment: 8 pages; SPIE Conf. 4006 "Interferometry in Optical Astronomy
Optical Interferometry of early-type stars with PAVO@CHARA. I. Fundamental stellar properties
We present interferometric observations of 7 main-sequence and 3 giant stars
with spectral types from B2 to F6 using the PAVO beam combiner at the CHARA
array. We have directly determined the angular diameters for these objects with
an average precision of 2.3%. We have also computed bolometric fluxes using
available photometry in the visible and infrared wavelengths, as well as
space-based ultraviolet spectroscopy. Combined with precise \textit{Hipparcos}
parallaxes, we have derived a set of fundamental stellar properties including
linear radius, luminosity and effective temperature. Fitting the latter to
computed isochrone models, we have inferred masses and ages of the stars. The
effective temperatures obtained are in good agreement (at a 3% level) with
nearly-independent temperature estimations from spectroscopy. They validate
recent sixth-order polynomial (B-V)- empirical relations
\citep{Boyajian2012a}, but suggest that a more conservative third-order
solution \citep{vanBelle2009} could adequately describe the
(V-K)- relation for main-sequence stars of spectral type A0 and
later. Finally, we have compared mass values obtained combining surface gravity
with inferred stellar radius (\textit{gravity mass}) and as a result of the
comparison of computed luminosity and temperature values with stellar
evolutionary models (\textit{isochrone mass}). The strong discrepancy between
isochrone and gravity mass obtained for one of the observed stars,
\,Lyr, suggests that determination of the stellar atmosphere parameters
should be revised.Comment: 13 pages, 9 figures, accepted for publication in MNRA
The Vacuum in Light-Cone Field Theory
This is an overview of the problem of the vacuum in light-cone field theory,
stressing its close connection to other puzzles regarding light-cone
quantization. I explain the sense in which the light-cone vacuum is
``trivial,'' and describe a way of setting up a quantum field theory on null
planes so that it is equivalent to the usual equal-time formulation. This
construction is quite helpful in resolving the puzzling aspects of the
light-cone formalism. It furthermore allows the extraction of effective
Hamiltonians that incorporate vacuum physics, but that act in a Hilbert space
in which the vacuum state is simple. The discussion is fairly informal, and
focuses mainly on the conceptual issues. [Talk presented at {\sc Orbis
Scientiae 1996}, Miami Beach, FL, January 25--28, 1996. To appear in the
proceedings.]Comment: 20 pages, RevTeX, 4 Postscript figures. Minor typos correcte
Light-Cone Quantization of Gauge Fields
Light-cone quantization of gauge field theory is considered. With a careful
treatment of the relevant degrees of freedom and where they must be
initialized, the results obtained in equal-time quantization are recovered, in
particular the Mandelstam-Leibbrandt form of the gauge field propagator. Some
aspects of the ``discretized'' light-cone quantization of gauge fields are
discussed.Comment: SMUHEP/93-20, 17 pages (one figure available separately from the
authors). Plain TeX, all macros include
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