331 research outputs found
QT dispersion as an attribute of T-loop morphology
BACKGROUND: The suggestion that increased QT dispersion (QTD) is due to
increased differences in local action potential durations within the
myocardium is wanting. An alternative explanation was sought by relating
QTD to vectorcardiographic T-loop morphology. METHODS AND RESULTS: The T
loop is characterized by its amplitude and width (defined as the spatial
angle between the mean vectors of the first and second halves of the
loop). We reasoned that small, wide ("pathological") T loops produce
larger QTD than large, narrow ("normal") loops. To quantify the
relationship between QTD and T-loop morphology, we used a program for
automated analysis of ECGs and a database of 1220 standard simultaneous
12-lead ECGs. For each ECG, QT durations, QTD, and T-loop parameters were
computed. T-loop amplitude and width were dichotomized, with 250 microV
(small versus large amplitudes) and 30 degrees (narrow versus wide loops)
taken as thresholds. Over all 1220 ECGs, QTDs were smallest for large,
narrow T loops (54.2+/-27.1 ms) and largest for small, wide loops (69.
5+/-33.5 ms; P<0.001). CONCLUSIONS: QTD is an attribute of T-loop
morphology, as expressed by T-loop amplitude and width
Mid-frequency aperture arrays: the future of radio astronomy
Aperture array (AA) technology is at the forefront of new developments and
discoveries in radio astronomy. Currently LOFAR is successfully demonstrating
the capabilities of dense and sparse AA's at low frequencies. For the
mid-frequencies, from 450 to 1450MHz, AA's still have to prove their scientific
value with respect to the existing dish technology. Their large field-of-view
and high flexibility puts them in an excellent position to do so. The Aperture
Array Verification Program is dedicated to demonstrate the feasibility of AA's
for science in general and SKA in particular. For the mid-frequency range this
has lead to the development of EMBRACE, which has already demonstrated the
enormous flexibility of AA systems by observing HI and a pulsar simultaneously.
It also serves as a testbed to demonstrate the technological reliability and
stability of AA's. The next step will put AA technology at a level where it can
be used for cutting-edge science. In this paper we discuss the developments to
move AA technology from an engineering activity to a fully science capable
instrument. We present current results from EMBRACE, ongoing tests of the
system, and plans for EMMA, the next step in mid-frequency AA technology.Comment: 8 pages, 7 figures, proceedings of Resolving The Sky - Radio
Astronomy: Past, Present and Future (RTS2012), April 17-20, 2012, Manchester,
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