A systematic investigation of the average multiplicities of light charged particles and intermediate mass fragments emitted in peripheral and semiperipheral collisions is presented as a function of ...the beam energy, violence of the collision, and mass of the system. The data have been collected with the FIASCO setup in the reactions {sup 93}Nb+{sup 93}Nb at (17,23,30,38)A MeV and {sup 116}Sn+{sup 116}Sn at (30,38)A MeV. The midvelocity emission has been separated from the emission of the projectile-like fragment. This last component appears to be compatible with an evaporation from an equilibrated source at normal density, as described by the statistical code GEMINI at the appropriate excitation energy. On the contrary, the midvelocity emission presents remarkable differences in both the dependence of the multiplicities on the energy deposited in the midvelocity region and the isotopic composition of the emitted light charged particles.
Total dose and displacement damage irradiations were performed on two references of silicon-based bipolar phototransistors. The evolution of photocurrent and dynamic performances (rise and fall time) ...were analyzed. The main results are presented in this paper.
Optimization of high energy collimator design Formiconi, A.R.; Gunter, D.L.; Vanzi, E. ...
IEEE Symposium Conference Record Nuclear Science 2004,
2004, Volume:
6
Conference Proceeding
Multi-hole collimators are the most important piece of instrumentation in determining the trade-off between spatial resolution and noise of nuclear medicine images. Recently, we discovered that the ...collimator-to-detector gap influences very much the hole-pattern artifacts and we also showed that there exist specific values of the gap that minimize the artifacts: here we call this phenomenon "penumbral masking" (PM). In this paper we studied the matter in more detail and we took into account PM in the problem of designing high-energy collimators, basically, by substituting the conventional hole-array pattern constraint with a mathematical expression of the PM effect. With this approach we found that an optimal solution to the problem always exist while, without the PM concept, for lead an optimal solution exists below 300 KeV, a suboptimal solution can be found within the range 300-320 KeV and no solution at all exist beyond 320 KeV, unless one violates one or both the penetration and the hole array pattern constraints. Thus, one is able to design artifacts-free collimators even if a somewhat lower sensitivity has to be accepted: 20% at 511 KeV with lead. Even with our approach, the weight constraint is a major problem when high-energies are implied but this does not affect the capability of reducing the hole-pattern artifacts. However, even when the theoretically optimal solution may not be feasible, this approach enlightens very much the design of high-energy collimators.
One of the most exciting challenges of neurosciences in the last few years is the real-time recording of neuronal activity with single cell resolution across the entire brain. Thanks to the use of ...optical methods, together with animal models in which the whole encephalon is optically accessible, this goal is getting within reach. In this work, we use a transgenic zebrafish line expressing the genetically encoded calcium indicator GCaMP6s in which binding of calcium ions leads to an increase in the emitted fluorescence of the reporter. GCaMP6s is the most sensitive calcium reporter within the genetically encoded calcium indicator family and allows us to record zebrafish larva neuronal activity with a high signal-to-noise ratio and single neuron resolution. To record the fluorescence emitted by the GCaMP6s reporter we use a custom-made confocal light-sheet microscope (LSM), in which the sample is illuminated with a thin sheet of light and the detection optical axis is perpendicular to the illumination axis. Owing to its intrinsic optical sectioning, this technique provides cellular resolution with high frame-rates and low photobleaching, allowing us to record the neuronal activity of zebrafish larvae with high spatio-temporal resolution. Conventional one-sided illumination LSM can suffer from limitations arising from even low levels of pigmentation in the sample or the presence of other obstructions reducing the quality of the incoming excitation light sheet. This can lead to shadowing in the image and possibly dynamic artefacts when the components responsible for the optical perturbations move. We have therefore implemented an illumination system based on a Bessel beam to overcome these limitations. Due to their nondiffractive and “self-healing” properties Bessel beams improve the quality of the images obtained from zebrafish larvae, reducing shadowing effects and increasing image homogeneity.
Here we propose a method for studying the distribution of genetic material inside a prokaryotic cell by implementing Fluorescence In Situ Hybridization (FISH) with single molecule sensitivity and 3D ...nanometric localization to map the position of ribosomes and selected gene loci.
We present ALMA observations of the dwarf starburst galaxy Henize 2-10 in combination with previous SMA CO observations to probe the molecular environments of natal super star clusters. These ...observations include the HCO\(^+\)(1-0), HCN(1-0), HNC(1-0), and CCH(1-0) molecular lines, as well as 88 GHz continuum with a spatial resolution of \(1''.7\times 1''.6\). After correcting for the contribution from free-free emission to the 88 GHz continuum flux density (\(\sim\) 60% of the 88 GHz emission), we derive a total gas mass for He~2-10 of \(M_{gas} = 4-6\times10^8\) M\(_{\odot}\), roughly 5-20% of the dynamical mass. Based on a principle component analysis, HCO\(^+\) is found to be the best "general" tracer of molecular emission. The line widths and luminosities of the CO emission suggests that the molecular clouds could either be as small as \(\sim 8\) pc, or alternately have enhanced line widths. The CO emission and 88 GHz continuum are anti-correlated, suggesting that either the dust and molecular gas are not cospatial, which could reflect the 88 GHz continuum is dominated by free-free emission. The CO and CCH emission are also relatively anti-correlated, which is consistent with the CCH being photo-enhanced, and/or the CO being dissociated in the regions near the natal super star clusters. The molecular line ratios of regions containing the natal star clusters are different from the line ratios observed for regions elsewhere in the galaxy. In particular, the regions with thermal radio emission all have CO(2-1)/HCO\(^+(1-0) < 16\), and the HCO\(^+\)/CO ratio appears to be correlated with the evolutionary stage of the clusters.
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