4,524 research outputs found
Five patients with oedema: written for the Wightman Prize in Clinical Medicine, 1962
This is an account of five patients seen in
:. iards 21, 23 and 24 of the Royal Infirmary,
Edinburgh; all the patients suffered from some
form of oedema. The severity of the oedema
varied greatly in the different patients, as did
the factors responsible for its appearance. This
account aims merely to recount the clinical
histories, with special emphasis on the oedema,
and to discuss the causes as revealed in each
patient.In the interests of brevity and clarity, it
has been necessary to omit some of the details of
the history and clinical findings in each patient
where they were not strictly relevant to the
problem of oedema, but any details of special
interest have also been included. Although this
is intended primarily as a clinical account, the
discussion of the pathogenesis of oedema in each
patient must, as so often in medicine today,
delve into mechanisms at a microscopic and even at
a molecular level. At this level, the discussion
runs the risk of either being too brief and
dogmatic, or else too detailed and inconclusive;
and at any level the discussion must inevitably be
incomplete. Many of the theories of the
pathogenesis of oedema are speculative and
controversial, and the more complete the reading
of the literature, the more confusing the
picture becomes. The author has attempted, in
this account, to discuss some of the more
important factors in the production of oedema,
but has tried to avoid confusing himself and the
reader with too much detail.Oedema, which may be defined as a localised or
generalised increase in the volume of the interstitial fluid, can arise in many diseases, and
be the result of the interplay of a number of
factors. These factors are not well understood - but the first patient suffered from oedema of a type where the simpler explanations would seem to
suffice
The role of intermolecular coupling in the photophysics of disordered organic semiconductors: Aggregate emission in regioregular polythiophene
We address the role of excitonic coulping on the nature of photoexcitations
in the conjugated polymer regioregular poly(3-hexylthiophene). By means of
temperature-dependent absorption and photoluminescence spectroscopy, we show
that optical emission is overwhelmingly dominated by weakly coupled
H-aggregates. The relative absorbance of the 0-0 and 0-1 vibronic peaks
provides a powerfully simple means to extract the magnitude of the
intermolecular coupling energy, approximately 5 and 30 meV for films spun from
isodurene and chloroform solutions respectively.Comment: 10 pages, 4 figures, published in Phys. Rev. Let
Surface acoustic wave solid-state rotational micromotor
Surface acoustic waves (SAWs) are used to drive a 1mm diameter rotor at speeds exceeding 9000 rpm and torque of nearly 5 nNm. Unlike recent high-speed SAW rotary motors, however, the present design does not require a fluid coupling layer but interestingly exploits adhesive stiction as an internal preload, a force usually undesirable at these scales; with additional preloads, smaller rotors can be propelled to 15 000 rpm. This solid-state motor has no moving parts except for the rotor and is sufficiently simple to allow integration into miniaturized drive systems for potential use in microfluidic diagnostics, optical switching and microrobotics
Transmitting high power RF acoustic radiation via fluid couplants into superstrates for microfluidics
In this study, surface acoustic radiation is refracted from lithium niobate through a fluid coupling into a thin glass plate. We demonstrate and explain its propagation as an asymmetric Lamb wave along the glass plate with sufficient power to transport fluid droplets across the glass surface at 8 mm/s. Such technology enables the use of standard processing techniques to fabricate an inexpensive and disposable microfluidics device together with the power transmission capabilities of surface acoustic wave devices with an easily renewable coupling
Surface Acoustic Wave Driven Microchannel Flow
We demonstrate that the propagation of surface acoustic waves, arising from the excitation of the acoustic field on a piezoelectric crystal (lithium niobate) substrate, along the sidewalls of microchannels (50 μm or 280 μm wide and 200 μm deep) fabricated in the substrate, can give rise to throughflow with velocities of the order 10 mm/s. This streaming flow in the direction along which the surface acoustic wave propagates is a result of the leakage of acoustic radiation from the substrate walls into the fluid. Good agreement is obtained between these preliminary experimental results with those from numerical simulations of the classical acoustic streaming model. In any case, these results show the potential of surface acoustic wave micropumps to be an effective fluid-driving mechanism for microfluidic devices
Spectroscopy of Seven Cataclysmic Variables with Periods Above Five Hours
We present spectroscopy of seven cataclysmic variable stars with orbital
periods P(orb) greater than 5 hours, all but one of which are known to be dwarf
novae. Using radial velocity measurements we improve on previous orbital period
determinations, or derive periods for the first time. The stars and their
periods are
TT Crt, 0.2683522(5) d;
EZ Del, 0.2234(5) d;
LL Lyr, 0.249069(4) d;
UY Pup, 0.479269(7) d;
RY Ser, 0.3009(4) d;
CH UMa, 0.3431843(6) d; and
SDSS J081321+452809, 0.2890(4) d.
For each of the systems we detect the spectrum of the secondary star,
estimate its spectral type, and derive a distance based on the surface
brightness and Roche lobe constraints. In five systems we also measure the
radial velocity curve of the secondary star, estimate orbital inclinations, and
where possible estimate distances based on the MV(max) vs.P(orb) relation found
by Warner. In concordance with previous studies, we find that all the secondary
stars have, to varying degrees, cooler spectral types than would be expected if
they were on the main sequence at the measured orbital period.Comment: 25 pages, 2 figures, accepted for Publications of the Astronomical
Society of the Pacifi
Droplet manipulation using ZnO/sapphire based saw devices
The hybrid ZnO/Sapphire material is selected to exploit the collective benefits of Zinc Oxide (ZnO) and sapphire for the development of a high performance Surface Acoustic Wave (SAW) device. The microfluidic applications of ZnO/Sapphire layered surface acoustic wave devices are discussed. In addition, acoustic streaming in droplets is investigated using a custom-made ZnO/Sapphire layered device. Experimental results show that a maximum acoustic streaming of ~600 µm/s is achieved when the device is operated at 158 MHz
U Geminorum: a test case for orbital parameters determination
High-resolution spectroscopy of U Gem was obtained during quiescence. We did
not find a hot spot or gas stream around the outer boundaries of the accretion
disk. Instead, we detected a strong narrow emission near the location of the
secondary star. We measured the radial velocity curve from the wings of the
double-peaked H emission line, and obtained a semi-amplitude value that
is in excellent agreement with the obtained from observations in the
ultraviolet spectral region by Sion et al. (1998). We present also a new method
to obtain K_2, which enhances the detection of absorption or emission features
arising in the late-type companion. Our results are compared with published
values derived from the near-infrared NaI line doublet. From a comparison of
the TiO band with those of late type M stars, we find that a best fit is
obtained for a M6V star, contributing 5 percent of the total light at that
spectral region. Assuming that the radial velocity semi-amplitudes reflect
accurately the motion of the binary components, then from our results: K_em =
107+/-2 km/s; K_abs = 310+/-5 km/s, and using the inclination angle given by
Zhang & Robinson(1987); i = 69.7+/-0.7, the system parameters become: M_WD =
1.20+/-0.05 M_sun,; M_RD = 0.42+/-0.04 M_sun; and a = 1.55+/- 0.02 R_sun. Based
on the separation of the double emission peaks, we calculate an outer disk
radius of R_out/a ~0.61, close to the distance of the inner Lagrangian point
L_1/a~0.63. Therefore we suggest that, at the time of observations, the
accretion disk was filling the Roche-Lobe of the primary, and that the matter
leaving the L_1 point was colliding with the disc directly, producing the hot
spot at this location.Comment: 36 pages, 14 figures, ccepted for publication in A
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Hydrogen migration at restructuring palladium-silver oxide boundaries dramatically enhances reduction rate of silver oxide.
Heterogeneous catalysts are complex materials with multiple interfaces. A critical proposition in exploiting bifunctionality in alloy catalysts is to achieve surface migration across interfaces separating functionally dissimilar regions. Herein, we demonstrate the enhancement of more than 104 in the rate of molecular hydrogen reduction of a silver surface oxide in the presence of palladium oxide compared to pure silver oxide resulting from the transfer of atomic hydrogen from palladium oxide islands onto the surrounding surface formed from oxidation of a palladium-silver alloy. The palladium-silver interface also dynamically restructures during reduction, resulting in silver-palladium intermixing. This study clearly demonstrates the migration of reaction intermediates and catalyst material across surface interfacial boundaries in alloys with a significant effect on surface reactivity, having broad implications for the catalytic function of bimetallic materials
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