Potassium Efflux from Myocardial Cells Induced by Defibrillator Shock

A transient, dose-dependent cardiac depression was produced by defibrillator shocks in an isolated, working canine heart preparation perfused with oxygenated arterial blood from a support dog. Accompanying this depression was an efflux of potassium (K+ ), forced out of the myocardial cells by the passage of defibrillating current. The transient increase in extracellular K + concentration was recorded graphically in the venous outflow. It was found that 5-msec rectangular wave shocks, from three to ten times defibrillatory current threshold, released doserelated pulses of K+ . We conclude that because extracellular K + is a myocardial depressant, at least part of the myocardial depression after defibrillation is caused by the release of K+ from the myocardial cells

Self-attraction effect and correction on three absolute gravimeters

The perturbations of the gravitational field due to the mass distribution of an absolute gravimeter have been studied. The so called Self Attraction Effect (SAE) is crucial for the measurement accuracy, especially for the International Comparisons, and for the uncertainty budget evaluation. Three instruments have been analysed: MPG-2, FG5-238 and IMPG-02. The SAE has been calculated using a numerical method based on FEM simulation. The observed effect has been treated as an additional vertical gravity gradient. The correction (SAC) to be applied to the computed g value has been associated with the specific height level, where the measurement result is typically reported. The magnitude of the obtained corrections is of order 1E-8 m/s2.Comment: 14 pages, 8 figures, submitted to Metrologi

Correction due to finite speed of light in absolute gravimeters

Correction due to finite speed of light is among the most inconsistent ones in absolute gravimetry. Formulas reported by different authors yield corrections scattered up to 8 $\mu$Gal with no obvious reasons. The problem, though noted before, has never been studied, and nowadays the correction is rather postulated than rigorously proven. In this paper we make an attempt to revise the subject. Like other authors, we use physical models based on signal delays and the Doppler effect, however, in implementing the models we additionally introduce two scales of time associated with moving and resting reflectors, derive a set of rules to switch between the scales, and establish the equivalence of trajectory distortions as obtained from either time delay or distance progression. The obtained results enabled us to produce accurate correction formulas for different types of instruments, and to explain the differences in the results obtained by other authors. We found that the correction derived from the Doppler effect is accountable only for $\frac23$ of the total correction due to finite speed of light, if no signal delays are considered. Another major source of inconsistency was found in the tacit use of simplified trajectory models

Efficacy and safety of the reciprocal pulse defibrillator current waveform

The efficacy and safety of a new defibrillating current waveform, consisting of a low-tilt 5 ms trapezoidal pulse followed closely by a second identical pulse of opposite polarity, was tested m seven isolated, perfused, working canine hearts suspended in an isoresistive, isosmotic shock bath at 37 oC. The efficacy and safety of the reciprocal pulse was compared with a single 5 ms pulse, a single 10 ms pulse, and a dual (unidirectional) 5 ms pulse waveform. The mean threshold average current densities for the 5 ms single pulse, 10 ms single pulse, dual 5 ms pulse, and reciprocal pulse (absolute values) were 50, 38, 36, and 37 mA/cm2, respectively. The corresponding mean threshold energy densities in the shock bath were 2.8, 2.9, 2.9, and 3.1 mJ/cm3. Despite the differences in threshold current density among the waveforms, no differences in safety factor (shock strength for 50 per cent post-shock depression, divided by threshold shock strength) were found among the waveforms. The current safety factors were 5.4, 5.4, 5.6, and 5.5 for the 5 ms single pulse, 10 ms single pulse, dual unidirectional pulse and reciprocal pulse, respectively. The corresponding energy density safety factors were 25, 27, 29, and 27. Thus the use of this reciprocal pulse waveform provides no advantage in efficacy or safety over waveforms of the same total duration

New Photodetection Method Using Unbalanced Sidebands for Squeezed Quantum Noise in Gravitational Wave Interferometer

Homodyne detection is one of the ways to circumvent the standard quantum limit for a gravitational wave detector. In this paper it will be shown that the same quantum-non-demolition effect using homodyne detection can be realized by heterodyne detection with unbalanced RF sidebands. Furthermore, a broadband quantum-non-demolition readout scheme can also be realized by the unbalanced sideband detection.Comment: 9 pages, 5 figure

Results of the First Coincident Observations by Two Laser-Interferometric Gravitational Wave Detectors

We report an upper bound on the strain amplitude of gravitational wave bursts in a waveband from around 800Hz to 1.25kHz. In an effective coincident observing period of 62 hours, the prototype laser interferometric gravitational wave detectors of the University of Glasgow and Max Planck Institute for Quantum Optics, have set a limit of 4.9E-16, averaging over wave polarizations and incident directions. This is roughly a factor of 2 worse than the theoretical best limit that the detectors could have set, the excess being due to unmodelled non-Gaussian noise. The experiment has demonstrated the viability of the kind of observations planned for the large-scale interferometers that should be on-line in a few years time.Comment: 11 pages, 2 postscript figure

A nonlinear detection algorithm for periodic signals in gravitational wave detectors

We present an algorithm for the detection of periodic sources of gravitational waves with interferometric detectors that is based on a special symmetry of the problem: the contributions to the phase modulation of the signal from the earth rotation are exactly equal and opposite at any two instants of time separated by half a sidereal day; the corresponding is true for the contributions from the earth orbital motion for half a sidereal year, assuming a circular orbit. The addition of phases through multiplications of the shifted time series gives a demodulated signal; specific attention is given to the reduction of noise mixing resulting from these multiplications. We discuss the statistics of this algorithm for all-sky searches (which include a parameterization of the source spin-down), in particular its optimal sensitivity as a function of required computational power. Two specific examples of all-sky searches (broad-band and narrow-band) are explored numerically, and their performances are compared with the stack-slide technique (P. R. Brady, T. Creighton, Phys. Rev. D, 61, 082001).Comment: 9 pages, 3 figures, to appear in Phys. Rev.

Comparison between two mobile absolute gravimeters: optical versus atomic interferometers

We report a comparison between two absolute gravimeters: the LNE-SYRTE cold atoms gravimeter and FG5#220 of Leibniz Universit\"at of Hannover. They rely on different principles of operation: atomic and optical interferometry. Both are movable which enabled them to participated to the last International Comparison of Absolute Gravimeters (ICAG'09) at BIPM. Immediately after, their bilateral comparison took place in the LNE watt balance laboratory and showed an agreement of 4.3 +/- 6.4 {\mu}Gal

Perturbations of the local gravity field due to mass distribution on precise measuring instruments: a numerical method applied to a cold atom gravimeter

We present a numerical method, based on a FEM simulation, for the determination of the gravitational field generated by massive objects, whatever geometry and space mass density they have. The method was applied for the determination of the self gravity effect of an absolute cold atom gravimeter which aims at a relative uncertainty of 10-9. The deduced bias, calculated with a perturbative treatment, is finally presented. The perturbation reaches (1.3 \pm 0.1) \times 10-9 of the Earth's gravitational field.Comment: 12 pages, 7 figure