808 research outputs found
Delayed alignments in the N=Z nuclei 84Mo and 88Ru
No full textThe yrast band of the N=Z nucleus 84Mo has been extended up to the 10+ state. Its moment of inertia varies smoothly up to this state (rotational frequency 0.6 MeV). The new data confirm the systematic delay of the particle alignment frequency in N=Z nuclei with respect to the neighboring N>Z nuclei, which has been suggested as a signature of the neutron-proton pairing interaction. Projected shell model calculations performed for the heaviest N=Z nuclei studied so far, 84Mo and 88Ru, predict that the confirmation of a possible enhancement of the neutron-proton residual interaction requires the observation of still higher spins in these nuclei
Band Termination in the N=Z Odd-Odd Nucleus 46V
No full textHigh spin states in the odd-odd N=Z nucleus 46V have been identified. At low spin, the T=1 isobaric analog states of 46Ti are established up to Iπ=6+. Other high spin states, including the band terminating state, are tentatively assigned to the same T=1 band. The T=0 band built on the low-lying 3+ isomer is observed up to the 1f7/2-shell termination at Iπ=15+. Both signatures of a negative parity T=0 band are observed up to the terminating states at Iπ=16- and Iπ=17-, respectively. The structure of this band is interpreted as a particle-hole excitation from the 1d3/2 shell. Spherical shell model calculations are found to be in excellent agreement with the experimental results
Accuracy of quantification in SPECT myocardial imaging
No full textSingle photon emission computed tomography (SPECT) of the myocardium accounts for the vast majority of nuclear cardiology procedures performed worldwide. This is mainly due to its wide availability, and its established and clinically validated diagnostic and prognostic accuracy. It is due to the availability of quantitative software allowing for reliable and reproducible assessments of myocardial perfusion and function. For many SPECT images were obtained using the Filtered Back Projection (FBP) reconstruction algorithm. Recently, due major advances in hardware and software developments 3-D Iterative Reconstruction algorithms became widely available in nuclear cardiology departments. These SPECT reconstruction algorithms offer improved spatial resolution and image contrast as well as accurate implementation of attenuation and scatter corrections. More recently, the hybrid imaging modality SPECT/CT became more widely available radiotracer distribution as well as for computed tomography. In recent years, research into the effect of attenuation and scatter corrections has concluded that combining CT attenuation correction with scatter correcting provides a precise quantification of radiopharmaceutical distribution obtained in SPECT research. Although the method has been proven to attain “clean” images for a variety of diagnostic means, its effects under respiratory cardiac motions using SPECT and high resolution algorithms in 3-D iterative reconstruction imaging is yet to be tested.
This study aims to determine the efficacy and quantitative accuracy for 3-D iterative reconstruction algorithms when compared to FBP techniques for cardiac SPECT images. The study will attempt to investigate the issue of respiratory induced cardiac motion and to demonstrate its effect on spatial resolution, image contrast and quantification in nuclear cardiology on SPECT images reconstructed using FBP and Flash (OSEM) 3-D algorithms.
We carried out two types of investigations involving experimental measurements carried out on three different phantoms, and Monte Carlo simulations using the GATE package. For the experimental part, we used a Siemens Symbia T16 SPECT/CT scanner to acquire SPECT/CT images using a Tc99m point source, a cardiac insert and a cardiac anthropomorphic phantom; data was acquired, reconstructed and analysed using standard clinical protocols available on Symbia T16 SPECT/CT scanner. We also looked at CT based attenuation and scatter corrections to study their effect on image quality and quantification
High-spin behavior of multiple bands in the N = Z + 1 nucleus 81Zr: A possible probe of enhanced neutron-proton correlations
No full textA new experimental investigation of the level scheme of the N=Z+1 nucleus 81Zr is reported. An additional band assigned to the [431]1∕2+ orbital has been observed and the known [422]5∕2+ and [301]3∕2− bands have been extended to higher spins. The behavior of these bands is compared to that of the bands in the isotonic nucleus 79Sr, for which some new experimental data are presented. Comparison is also made to the even-even N=Z and N=Z+2 neighbors. The band structures are discussed in the framework of the projected shell model
Evolution of collectivity along the N=Z line: The 84Mo nucleus
No full textThe reaction 58Ni(28Si,2nγ) at 90 MeV incident energy has been used to populate the N=Z nucleus 84Mo. The GASP array was used together with the ISIS Silicon ball, which allowed a subtraction of the charged particle channels in the γ-γ coincidences. The only known transition 21+→01+ of 443.8 keV in 84Mo has been found in coincidence with a γ ray of 673.5±0.4 keV which was assigned as the second (41+→21+) yrast transition. The behavior of the resulting yrast line indicates that 84Mo is a transitional nucleus. The correlation between the excitation energies of the 21+ and 41+ levels of the N=Z nuclei reveals a systematic deviation from the average behavior defined by all collective even-even nuclei
First identification of excited states in the N = Z + 1 nucleus 89Ru
No full textHigh-spin excited states have been identified for the first time in the N=Z+1 nucleus 89Ru with the reaction 54Fe(40Ca,αnγ) at 130 MeV, using the GASP array, the ISIS Silicon array, and the n-Ring detector system. The observed structure is discussed within systematics of the N=45 isotones and is compared with shell model calculations
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