Charged pions from Ni on Ni collisions between 1 and 2 AGeV

Charged pions from Ni + Ni reactions at 1.05, 1.45 and 1.93 AGeV are measured with the FOPI detector. The mean $\pi^{\pm}$ multiplicities per mean number of participants increase with beam energy, in accordance with earlier studies of the Ar + KCl and La + La systems. The pion kinetic energy spectra have concave shape and are fitted by the superposition of two Boltzmann distributions with different temperatures. These apparent temperatures depend only weakly on bombarding energy. The pion angular distributions show a forward/backward enhancement at all energies, but not the $\Theta = 90^0$ enhancement which was observed in case of the Au + Au system. These features also determine the rapidity distributions which are therefore in disagreement with the hypothesis of one thermal source. The importance of the Coulomb interaction and of the pion rescattering by spectator matter in producing these phenomena is discussed.Comment: 22 pages, Latex using documentstyle[12pt,a4,epsfig], to appear in Z. Phys.

Small-animal SPECT and SPECT/CT: application in cardiovascular research

Preclinical cardiovascular research using noninvasive radionuclide and hybrid imaging systems has been extensively developed in recent years. Single photon emission computed tomography (SPECT) is based on the molecular tracer principle and is an established tool in noninvasive imaging. SPECT uses gamma cameras and collimators to form projection data that are used to estimate (dynamic) 3-D tracer distributions in vivo. Recent developments in multipinhole collimation and advanced image reconstruction have led to sub-millimetre and sub-half-millimetre resolution SPECT in rats and mice, respectively. In this article we review applications of microSPECT in cardiovascular research in which information about the function and pathology of the myocardium, vessels and neurons is obtained. We give examples on how diagnostic tracers, new therapeutic interventions, pre- and postcardiovascular event prognosis, and functional and pathophysiological heart conditions can be explored by microSPECT, using small-animal models of cardiovascular disease

Micro-computed tomography characterization of tissue engineering scaffolds: Effects of pixel size and rotation step

Quantitative assessment of micro-structure of materials is of key importance in many fields including tissue engineering, biology, and dentistry. Micro-computed tomography (µ-CT) is an intensively used non-destructive technique. However, the acquisition parameters such as pixel size and rotation step may have significant effects on the obtained results. In this study, a set of tissue engineering scaffolds including examples of natural and synthetic polymers, and ceramics were analyzed. We comprehensively compared the quantitative results of µ-CT characterization using 15 acquisition scenarios that differ in the combination of the pixel size and rotation step. The results showed that the acquisition parameters could statistically significantly affect the quantified mean porosity, mean pore size, and mean wall thickness of the scaffolds. The effects are also practically important since the differences can be as high as 24% regarding the mean porosity in average, and 19.5 h and 166 GB regarding the characterization time and data storage per sample with a relatively small volume. This study showed in a quantitative manner the effects of such a wide range of acquisition scenarios on the final data, as well as the characterization time and data storage per sample. Herein, a clear picture of the effects of the pixel size and rotation step on the results is provided which can notably be useful to refine the practice of µ-CT characterization of scaffolds and economize the related resources.This article is a result of the project FROn-THERA (NORTE-01-0145-FEDER-000023), supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). IFC thanks the Portuguese Foundation for Science and Technology (FCT) for the Ph.D. scholarship (SFRH/BD/99555/2014). JMO also thanks the FCT for the funds provided under the program Investigador FCT 2012 and 2015 (IF/00423/2012 and IF/01285/2015).info:eu-repo/semantics/publishedVersio

Shape of collective flow in highly central Au(150 A MeV)+Au collisions

Using the FOPI facility at GSI, charged particles (1 ≤Z≤6) produced in the Au(150 A MeV)+Au reaction have been measured at laboratory angles 1.20 < Θlab < 300. Highly central collisions have been selected with two criteria, both dealing with the longitudinal and transverse degrees of freedom of the reaction. The relevance of this selection method is supported by QMD calculations which indicate that such criteria are able to select mean impact parameters less than 2 fm. Bias effects introduced by the criteria have been evaluated. The centre-of-mass polar angle distributions of low energy clusters emitted in these central collisions, have been extracted: the intensity ratio deduced for a transverse to longitudinal emission is found to be R= 1.4 −0.4 +0.2 . Model comparisons using QMD are presented. The value of R appears to depend sensitively on the nucleon-nucleon cross section, σnn. Within this model, a value of σ=25+ - 5 mb is derived