779 research outputs found
Supergiant Barocaloric Effects in Acetoxy Silicone Rubber over a Wide Temperature Range: Great Potential for Solid-state Cooling
Solid-state cooling based on caloric effects is considered a viable
alternative to replace the conventional vapor-compression refrigeration
systems. Regarding barocaloric materials, recent results show that elastomers
are promising candidates for cooling applications around room-temperature. In
the present paper, we report supergiant barocaloric effects observed in acetoxy
silicone rubber - a very popular, low-cost and environmentally friendly
elastomer. Huge values of adiabatic temperature change and reversible
isothermal entropy change were obtained upon moderate applied pressures and
relatively low strains. These huge barocaloric changes are associated both to
the polymer chains rearrangements induced by confined compression and to the
first-order structural transition. The results are comparable to the best
barocaloric materials reported so far, opening encouraging prospects for the
application of elastomers in near future solid-state cooling devices.Comment: 19 pages, 7 figures, 2 table
New concepts in echocardiography
If short pulses of high frequency sound are transmitted through the
heart, discontinuities in the tissues will produce reflected sound waves
or "echoes". There wil! be a delay between a pulse transmission and
the arrival of a correspond·mg echo. Together with knowledge of sound
velocity this wi!l enable determination of the distance between the
transmitterfreceiver and the reflecting interface, thus providing information
about cardiac dimensions. Similarly the Doppler effect can be
used to provide further diagnostic information. These applications of
ultrasound (echocardiography) for the detection of cardiac (mal)function
have recently gained acceptance even though interpretation of the
information obtained can be difficult.
Major reasons for this acceptance are probably that, while
Intra-arterial ultrasonic imaging for recanalization by spark erosion
Presently several new methods are being developed to recanalize obstructed arteries during catheterization. Intra-arterial high frequency ultrasonic imaging may be used as a guidance for these new techniques. Spark erosion is a new obstruction removal technology. Experiments have shown that this method can be applied in a selective way. An ultrasonic intra-arterial imaging system allows for the proper indication of the spark erosion catheter relative to the obstruction. The first in vitro results of this study illustrate that integration of catheter tip imaging and spark erosion is possible
Characterization of plaque components with intravascular ultrasound elastography in human femoral and coronary arteries in vitro
BACKGROUND: The composition of plaque is a major determinant of
coronary-related clinical syndromes. Intravascular ultrasound (IVUS)
elastography has proven to be a technique capable of reflecting the
mechanical properties of phantom material and the femoral arterial wall.
The aim of this study was to investigate the capability of intravascular
elastography to characterize different plaque components. METHODS AND
RESULTS: Diseased human femoral (n=9) and coronary (n=4) arteries were
studied in vitro. At each location (n=45), 2 IVUS images were acquired at
different intraluminal pressures (80 and 100 mm Hg). With the use of
cross-correlation analysis on the high-frequency (radiofrequency)
ultrasound signal, the local strain in the tissue was determined. The
strain was color-coded and plotted as an additional image to the IVUS
echogram. The visualized segments were stained on the presence of
collagen, smooth muscle cells, and macrophages. Matching of elastographic
data and histology were performed with the use of the IVUS echogram. The
cross sections were segmented in regions (n=125) that were based on the
strain value on the elastogram. The dominant plaque types in these regions
(fibrous, fibro-fatty, or fatty) were obtained from histology and
correlated with the average strain and echo intensity. The strain for the
3 plaque types as determined by histology differed significantly
(P=0.0002). This difference was mainly evident between fibrous and fatty
tissue (P=0.0004). The plaque types did not reveal echo-intensity
differences in the IVUS echogram (P=0.882). CONCLUSIONS: Different strain
values are found between fibrous, fibro-fatty, and fatty plaque
components, indicating the potential of intravascular elastography to
distinguish different plaque morphologies
A Deformation of Twistor Space and a Chiral Mass Term in N=4 Super Yang-Mills Theory
Super twistor space admits a certain (super) complex structure deformation
that preserves the Poincare subgroup of the symmetry group PSL(4|4) and depends
on 10 parameters. In a previous paper [hep-th/0502076], it was proposed that in
twistor string theory this deformation corresponds to augmenting N=4 super
Yang-Mills theory by a mass term for the left-chirality spinors. In this paper
we analyze this proposal in more detail. We calculate 4-particle scattering
amplitudes of fermions, gluons and scalars and show that they are supported on
holomorphic curves in the deformed twistor space.Comment: 52 pages, 15 figure
On application of Liouville type equations to constructing B\"acklund transformations
It is shown how pseudoconstants of the Liouville-type equations can be
exploited as a tool for construction of the B\"acklund transformations. Several
new examples of such transformations are found. In particular we obtained the
B\"acklund transformations for a pair of three-component analogs of the
dispersive water wave system, and auto-B\"acklund transformations for coupled
three-component KdV-type systems.Comment: 11 pages, no figure
Search for the Radiative Capture d+d->^4He+\gamma Reaction from the dd\mu Muonic Molecule State
A search for the muon catalyzed fusion reaction dd --> ^4He +\gamma in the
dd\mu muonic molecule was performed using the experimental \mu CF installation
TRITON and NaI(Tl) detectors for \gamma-quanta. The high pressure target filled
with deuterium at temperatures from 85 K to 800 K was exposed to the negative
muon beam of the JINR phasotron to detect \gamma-quanta with energy 23.8 MeV.
The first experimental estimation for the yield of the radiative deuteron
capture from the dd\mu state J=1 was obtained at the level n_{\gamma}\leq
2\times 10^{-5} per one fusion.Comment: 9 pages, 3 Postscript figures, submitted to Phys. At. Nuc
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