The relationship of myocardial contraction and electrical excitation—the correlation between scintigraphic phase image analysis and electrophysiologic mapping

Phase imaging derived from equilibrium radionuclide angiography presents the ventricular contraction sequence. It has been widely but only indirectly correlated with the sequence of electrical myocardial activation. We sought to determine the specific relationship between the sequence of phase progression and the sequence of myocardial activation, contraction and conduction, in order to document a noninvasive method that could monitor both. In 7 normal and 9 infarcted dogs, the sequence of phase angle was correlated with the epicardial activation map in 126 episodes of sinus rhythm and pacing from three ventricular sites. In each episode, the site of earliest phase angle was identical to the focus of initial epicardial activation. Similarly, the serial contraction pattern by phase image analysis matched the electrical epicardial activation sequence completely or demonstrated good agreement in approximately 85% of pacing episodes, without differences between normal or infarct groups. A noninvasive method to accurately determine the sequence of contraction may serve as a surrogate for the associated electrical activation sequence or be applied to identify their differences

Measurement of the neutron capture cross section of the s-only isotope 204Pb from 1 eV to 440 keV

The neutron capture cross section of 204Pb has been measured at the CERN n_TOF installation with high resolution in the energy range from 1 eV to 440 keV. An R-matrix analysis of the resolved resonance region, between 1 eV and 100 keV, was carried out using the SAMMY code. In the interval between 100 keV and 440 keV we report the average capture cross section. The background in the entire neutron energy range could be reliably determined from the measurement of a 208Pb sample. Other systematic effects in this measurement could be investigated and precisely corrected by means of detailed Monte Carlo simulations. We obtain a Maxwellian average capture cross section for 204Pb at kT=30 keV of 79(3) mb, in agreement with previous experiments. However our cross section at kT=5 keV is about 35% larger than the values reported so far. The implications of the new cross section for the s-process abundance contributions in the Pb/Bi region are discussed.Comment: 8 pages, 3 figures, article submitted to Phys. Rev.

Measurement of the radiative neutron capture cross section of 206Pb and its astrophysical implications

The (n, gamma) cross section of 206Pb has been measured at the CERN n_TOF facility with high resolution in the energy range from 1 eV to 600 keV by using two optimized C6D6 detectors. In the investigated energy interval about 130 resonances could be observed, from which 61 had enough statistics to be reliably analyzed via the R-matrix analysis code SAMMY. Experimental uncertainties were minimized, in particular with respect to (i) angular distribution effects of the prompt capture gamma-rays, and to (ii) the TOF-dependent background due to sample-scattered neutrons. Other background components were addressed by background measurements with an enriched 208Pb sample. The effect of the lower energy cutoff in the pulse height spectra of the C6D6 detectors was carefully corrected via Monte Carlo simulations. Compared to previous 206Pb values, the Maxwellian averaged capture cross sections derived from these data are about 20% and 9% lower at thermal energies of 5 keV and 30 keV, respectively. These new results have a direct impact on the s-process abundance of 206Pb, which represents an important test for the interpretation of the cosmic clock based on the decay of 238U.Comment: 11 pages, 8 figures, paper to be submitted to Phys. Rev.

New measurement of neutron capture resonances of 209Bi

The neutron capture cross section of Bi209 has been measured at the CERN n TOF facility by employing the pulse-height-weighting technique. Improvements over previous measurements are mainly because of an optimized detection system, which led to a practically negligible neutron sensitivity. Additional experimental sources of systematic error, such as the electronic threshold in the detectors, summing of gamma-rays, internal electron conversion, and the isomeric state in bismuth, have been taken into account. Gamma-ray absorption effects inside the sample have been corrected by employing a nonpolynomial weighting function. Because Bi209 is the last stable isotope in the reaction path of the stellar s-process, the Maxwellian averaged capture cross section is important for the recycling of the reaction flow by alpha-decays. In the relevant stellar range of thermal energies between kT=5 and 8 keV our new capture rate is about 16% higher than the presently accepted value used for nucleosynthesis calculations. At this low temperature an important part of the heavy Pb-Bi isotopes are supposed to be synthesized by the s-process in the He shells of low mass, thermally pulsing asymptotic giant branch stars. With the improved set of cross sections we obtain an s-process fraction of 19(3)% of the solar bismuth abundance, resulting in an r-process residual of 81(3)%. The present (n,gamma) cross-section measurement is also of relevance for the design of accelerator driven systems based on a liquid metal Pb/Bi spallation target.Comment: 10 pages, 5figures, recently published in Phys. Rev.

Resonance capture cross section of 207Pb

The radiative neutron capture cross section of 207Pb has been measured at the CERN neutron time of flight installation n_TOF using the pulse height weighting technique in the resolved energy region. The measurement has been performed with an optimized setup of two C6D6 scintillation detectors, which allowed us to reduce scattered neutron backgrounds down to a negligible level. Resonance parameters and radiative kernels have been determined for 16 resonances by means of an R-matrix analysis in the neutron energy range from 3 keV to 320 keV. Good agreement with previous measurements was found at low neutron energies, whereas substantial discrepancies appear beyond 45 keV. With the present results, we obtain an s-process contribution of 77(8)% to the solar abundance of 207Pb. This corresponds to an r-process component of 23(8)%, which is important for deriving the U/Th ages of metal poor halo stars.Comment: 7 pages, 3 figures, to be published in Phys. Rev.

Development of Diamond Tracking Detectors for High Luminosity Experiments at LHC

During 2006 detectors based on new polycrystalline CVD (pCVD) material were produced as candidates for use in LHC experiments. The first full size diamond pixel module with ATLAS specifications using a $2 \times 6$ cm$^2$ pCVD sample was characterized in the 2006 CERN test beam. Radiation damage studies performed outside of CERN corroborate the radiation hardness of this material. Radiation hardness studies at CERN using the highest quality diamond were deferred until 2007 due to the PS magnet problem. ATLAS, CMS, ALICE and LHCb are planning to use diamond for their beam conditions monitoring systems. Construction of the BCM system for ATLAS was completed in 2006 and the BCM modules were characterized in 2006 CERN test beams. Similar devices are under construction for the CMS, ALICE and LHCb experiments. Single-crystal CVD (scCVD) samples were produced and made available to RD42 institutes. The first scCVD diamond pixel device was constructed and tested in the 2006 CERN test beams. In this report we present the progress and work done by the RD42 collaboration on the development of CVD diamond material for radiation detectors