Dynamics of charge-displacement channeling in intense laser-plasma interactions

The dynamics of transient electric fields generated by the interaction of high intensity laser pulses with underdense plasmas has been studied experimentally with the proton projection imaging technique. The formation of a charged channel, the propagation of its front edge and the late electric field evolution have been characterised with high temporal and spatial resolution. Particle-in-cell simulations and an electrostatic, ponderomotive model reproduce the experimental features and trace them back to the ponderomotive expulsion of electrons and the subsequent ion acceleration.Comment: 5 figures, accepted for publication in New Journal of Physic

In-room test results at CNAO of an innovative PT treatments online monitor (Dose Profiler)

The use of C, He and O ions as projectiles in Particle Therapy (PT) treatments is getting more and more widespread as a consequence of their enhanced relative biological effectiveness and oxygen enhancement ratio, when compared to the protons one. The advantages related to the incoming radiation improved efficacy are requiring an accurate online monitor of the dose release spatial distribution. Such monitor is necessary to prevent unwanted damage to the tissues surrounding the tumour that can arise, for example, due to morphological changes occurred in the patient during the treatment with respect to the initial CT scan. PT treatments with ions can be monitored by detecting the secondary radiation produced by the primary beam interactions with the patient body along the path towards the target volume. Charged fragments produced in the nuclear process of projectile fragmentation can be emitted at large angles with respect to the incoming beam direction and can be detected with high efficiency in a nearly background-free environment. The Dose Profiler (DP) detector, developed within the INSIDE project, is a scintillating fibre tracker that allows an online reconstruction and backtracking of such secondary charged fragments. The construction and preliminary in-room tests performed on the DP, carried out using the 12C ions beam of the CNAO treatment centre using an anthropomorphic phantom as a target, will be reviewed in this contribution. The impact of the secondary fragments interactions with the patient body will be discussed in view of a clinical application. Furthermore, the results implications for a pre-clinical trial on CNAO patients, foreseen in 2019, will be discussed

Indentation modulus at the macro-scale level measured by Brinell and Vickers indenters by using the primary hardness standard machine at INRiM

In this paper, the experimental procedure and calculation model for the measurement of the indentation modulus by using the primary hardness standard machine at INRiM in the macro-scale range at room temperature is described. The indentation modulus is calculated based on the Doerner-Nix linear model and from accurate measurements of indentation load, displacement, contact stiffness, and hardness indentation imaging. Measurements are performed with both pyramidal (Vickers test) and spherical indenters (Brinell test). Test force is provided by a dead-weight machine, and the occurring displacement is measured by a laser-interferometric system. The geometrical dimensions of both the Vickers and Brinell indentations are measured by means of a micro-mechanical system and optical microscopy imaging techniques. Applied force and indentation depth are measured simultaneously, at a 16 Hz sampling rate, and the resultant loading-unloading indentation curve is obtained. Preliminary tests are performed on metal and alloy samples. Considerations and comments on the accuracy of the proposed method and analysis are discussed

CSF parvalbumin levels reflect interneuron loss linked with cortical pathology in multiple sclerosis

INTRODUCTION AND METHODS: In order to verify whether parvalbumin (PVALB), a protein specifically expressed by GABAergic interneurons, could be a MS-specific marker of grey matter neurodegeneration, we performed neuropathology/molecular analysis of PVALB expression in motor cortex of 40 post-mortem progressive MS cases, with/without meningeal inflammation, and 10 control cases, in combination with cerebrospinal fluid (CSF) assessment. Analysis of CSF PVALB and neurofilaments (Nf-L) levels combined with physical/cognitive/3TMRI assessment was performed in 110 naïve MS patients and in 32 controls at time of diagnosis. RESULTS: PVALB gene expression was downregulated in MS (fold change = 3.7 ± 1.2, P < 0.001 compared to controls) reflecting the significant reduction of PVALB+ cell density in cortical lesions, to a greater extent in MS patients with high meningeal inflammation (51.8, P < 0.001). Likewise, post-mortem CSF-PVALB levels were higher in MS compared to controls (fold change = 196 ± 36, P < 0.001) and correlated with decreased PVALB+ cell density (r = -0.64, P < 0.001) and increased MHC-II+ microglia density (r = 0.74, P < 0.01), as well as with early age of onset (r = -0.69, P < 0.05), shorter time to wheelchair (r = -0.49, P < 0.05) and early age of death (r = -0.65, P < 0.01). Increased CSF-PVALB levels were detected in MS patients at diagnosis compared to controls (P = 0.002). Significant correlation was found between CSF-PVALB levels and cortical lesion number on MRI (R = 0.28, P = 0.006) and global cortical thickness (R = -0.46, P < 0.001), better than Nf-L levels. CSF-PVALB levels increased in MS patients with severe cognitive impairment (mean ± SEM:25.2 ± 7.5 ng/mL) compared to both cognitively normal (10.9 ± 2.4, P = 0.049) and mild cognitive impaired (10.1 ± 2.9, P = 0.024) patients. CONCLUSIONS: CSF-PVALB levels reflect loss of cortical interneurons in MS patients with more severe disease course and might represent an early, new MS-specific biomarker of cortical neurodegeneration, atrophy, and cognitive decline

An inter-laboratory comparison to evaluate the suitability of EN 1787 standard to detect irradiation in plant-origin foods with health benefits

This paper reports the results of a study carried out to verify the applicability of the EN 1787 method, which uses the Electron Spin Resonance (ESR) technique for the identification of irradiated plant-origin foods with health benefits. The method was tested on samples of herbal ingredients of Plant Food Supplements (PFSs), nuts and fresh blueberries. Untreated and irradiated samples of Camellia sinensis (leaves) Ginkgo biloba (leaves), Glycine max (seeds), Silybum marianum (fruits), Vaccinium myrtillus (fruits), almonds, hazelnuts, peanuts, pistachios, walnuts and fresh blueberries were analysed. The work includes an inter-laboratory blind test involving five Italian laboratories that perform routine analyses for the official control of irradiated food. A total of 180 untreated and irradiated samples of PFS ingredients, nuts and fresh blueberries were analysed. The analyses on the irradiated samples were replicated even a long time after irradiation (up to two years depending on the matrix) to test the reliability of the method throughout the shelf life of the products. The results were matrix-dependent: all the 5 kGy irradiated nuts and the 1 kGy-irradiated blueberries were correctly classified, whereas herbal ingredients showed complex ESR spectra with spurious signals which often prevented the correct classification of the sample

Dual-encoded magnetization transfer and diffusion imaging and its application to tract-specific microstructure mapping

We present a novel dual-encoded magnetization transfer (MT) and diffusion-weighted sequence and demonstrate its potential to resolve distinct properties of white matter fiber tracts at the sub-voxel level. The sequence was designed and optimized for maximal MT contrast efficiency. The resulting whole brain 2.6 mm isotropic protocol to measure tract-specific MT ratio (MTR) has a scan time under 7 minutes. Ten healthy subjects were scanned twice to assess repeatability. Two different analysis methods were contrasted: a technique to extract tract-specific MTR using Convex Optimization Modeling for Microstructure Informed Tractography (COMMIT), a global optimization technique; and conventional MTR tractometry. The results demonstrate that the tract-specific method can reliably resolve the MT ratios of major white matter fiber pathways and is less affected by partial volume effects than conventional multi-modal tractometry. Dual-encoded MT and diffusion is expected to both increase the sensitivity to microstructure alterations of specific tracts due to disease, ageing or learning, as well as lead to weighted structural connectomes with more anatomical specificity.Comment: 26 pages, 7 figure

Observation of plasma density dependence of electromagnetic soliton excitation by an intense laser pulse

The experimental evidence of the correlation between the initial electron density of the plasma and electromagnetic soliton excitation at the wake of an intense (1019 Wcm2) and short (1 ps) laser pulse is presented. The spatial distribution of the solitons, together with their late time evolution into post-solitons, is found to be dependent upon the background plasma parameters, in agreement with published analytical and numerical findings. The measured temporal evolution and electrostatic field distribution of the structures are consistent with their late time evolution and the occurrence of multiple merging of neighboring post-solitons. © 2011 American Institute of Physics

The UTfit Collaboration Average of D meson mixing data: Spring 2012

We derive constraints on the parameters $M_{12}$, $\Gamma_{12}$ and $\Phi_{12}$ that describe $D$ meson mixing using all available data, allowing for CP violation. We also provide posterior distributions and predictions for observable parameters appearing in $D$ physics.Comment: 5 pages, 3 figure

Study of shock waves generation, hot electron production and role of parametric instabilities in an intensity regime relevant for the shock ignition

We present experimental results at intensities relevant to Shock Ignition obtained at the sub-ns Prague Asterix Laser System in 2012 . We studied shock waves produced by laser-matter interaction in presence of a pre-plasma. We used a first beam at 1ω (1315 nm) at 7 × 10 13 W/cm 2 to create a pre-plasma on the front side of the target and a second at 3ω (438 nm) at ∼ 10 16 W/cm 2 to create the shock wave. Multilayer targets composed of 25 (or 40 μm) of plastic (doped with Cl), 5 μm of Cu (for Kα diagnostics) and 20 μm of Al for shock measurement were used. We used X-ray spectroscopy of Cl to evaluate the plasma temperature, Kα imaging and spectroscopy to evaluate spatial and spectral properties of the fast electrons and a streak camera for shock breakout measurements. Parametric instabilities (Stimulated Raman Scattering, Stimulated Brillouin Scattering and Two Plasmon Decay) were studied by collecting the back scattered light and analysing its spectrum. Back scattered energy was measured with calorimeters. To evaluate the maximum pressure reached in our experiment we performed hydro simulations with CHIC and DUED codes. The maximum shock pressure generated in our experiment at the front side of the target during laser-interaction is 90 Mbar. The conversion efficiency into hot electrons was estimated to be of the order of ∼ 0.1% and their mean energy in the order ∼50 keV. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributio