Chord length sampling with memory effects for spatially heterogeneous Markov media: Application to the rod model.

In this work we propose a modified Chord Length Sampling (CLS) algorithm, endowed with two layers of "memory effects," aimed at solving particle transport problems in one-dimensional spatially nonhomogeneous Markov media. CLS algorithms are a family of Monte Carlo methods which account for the stochastic nature of the media by sampling on-the-fly the random interfaces between material phases during the particle propagation. The possibility for the particles to remember the last crossed interfaces increases the accuracy of these models with respect to reference solutions obtained by solving the Boltzmann equation on a large number of realizations of the Markov media. In previous investigations, CLS models with memory have been tested exclusively for spatially uniform stochastic media: in this paper we extend this class of Monte Carlo methods to the case of spatially nonhomogeneous configurations. The effectiveness and the robustness of the modified CLS are probed considering several benchmark problems with varying material cross sections and Markov media densities. The obtained results are a stepping stone towards a generalization to three-dimensional models.

Investigation on the origin of hot electrons in laser plasma interaction at shock ignition intensities.

Shock Ignition is a two-step scheme to reach Inertial Confinement Fusion, where the precompressed fuel capsule is ignited by a strong shock driven by a laser pulse at an intensity in the order of [Formula: see text] W/cm[Formula: see text]. In this report we describe the results of an experiment carried out at PALS laser facility designed to investigate the origin of hot electrons in laser-plasma interaction at intensities and plasma temperatures expected for Shock Ignition. A detailed time- and spectrally-resolved characterization of Stimulated Raman Scattering and Two Plasmon Decay instabilities, as well as of the generated hot electrons, suggest that Stimulated Raman Scattering is the dominant source of hot electrons via the damping of daughter plasma waves. The temperature dependence of laser plasma instabilities was also investigated, enabled by the use of different ablator materials, suggesting that Two Plasmon Decay is damped at earlier times for higher plasma temperatures, accompanied by an earlier ignition of SRS. The identification of the predominant hot electron source and the effect of plasma temperature on laser plasma interaction, here investigated, are extremely useful for developing the mitigation strategies for reducing the impact of hot electrons on the fuel ignition.

Bremsstrahlung cannon design for shock ignition relevant regime.

We report on the optimization of a BremsStrahlung Cannon (BSC) design for the investigation of laser-driven fast electron populations in a shock ignition relevant experimental campaign at the Laser Megajoule-PETawatt Aquitaine Laser facility. In this regime with laser intensities of 1015 W/cm2-1016 W/cm2, fast electrons with energies ≤100 keV are expected to be generated through Stimulated Raman Scattering (SRS) and Two Plasmon Decay (TPD) instabilities. The main purpose of the BSC in our experiment is to identify the contribution to x-ray emission from bremsstrahlung of fast electrons originating from SRS and TPD, with expected temperatures of 40 keV and 95 keV, respectively. Data analysis and reconstruction of the distributions of x-ray photons incident on the BSC are described.

Common carotid artery pseudoaneurysm after neck dissection: colour Doppler ultrasound and multidetector computed tomography findings.

Common carotid artery pseudoaneurysm is a rare disease, which has been previously unreported in association with neck dissection. We describe the Doppler ultrasound and multidetector computed tomography (CT) findings of a case of carotid pseudoaneurysm, one month after pharyngolaryngectomy with bilateral neck dissection. Multidetector CT confirmed the diagnosis made on the basis of Doppler ultrasound; the high image quality of axial and three-dimensional reconstructions avoided the need for pre-operative conventional angiography. In the presence of a pulsatile cervical mass after neck surgery, pseudoaneurysm of the carotid artery should be included in the differential diagnosis, and multidetector CT can be the sole pre-operative diagnostic imaging modality.

[High-resolution computerized tomography in diffuse forms of bronchiolo-alveolar carcinoma]. / Tomografia Computerizzata con alta risoluzione nelle forme diffuse del carcinoma bronchiolo-alveolare.

Bronchioloalveolar carcinoma (BAC) is a relatively uncommon tumor of the lung accounting for 1 to 9% of all pulmonary neoplasms. Its radiologic appearance is characterized by solitary nodular opacity or diffuse air-space consolidation. The aim of this work is to report the different patterns of this neoplasm, particularly in the diffuse form, and to demonstrate the sensitivity and specificity of HRCT in its early identification. We examined 11 patients affected with multifocal bronchioloalveolar carcinoma to identify HRCT signs which could lead to improved diagnostic criteria. These signs are represented by ground-glass opacity (8/11) and alveolar consolidation (6/11), with a plurilobular, segmentary or lobar distribution. The lesions were bilateral in 8/11 cases and abnormal mediastinal lymph nodes were found in 5/11 cases. Air bronchogram was seen in all cases of ground-glass opacity and in 5/11 cases of air-space consolidation. In conclusion, in our experience, HRCT is a useful tool in the study of BAC, which has a long and slow evolution and is underestimated at chest radiograph in its early stage. Moreover, HRCT can help distinguish this condition from other lung diseases characterized by diffuse air-space consolidations, whose clinical history is useless to make an unquestionable diagnosis.