Improved visualization of X-ray phase contrast volumetric data through artifact-free integrated differential images

Artifacts arising when differential phase images are integrated is a common problem to several X-ray phase-based experimental techniques. The combination of noise and insufficient sampling of the high-frequency differential phase signal leads to the formation of streak artifacts in the projections, translating into poor image quality in the tomography slices. In this work, we apply a non-iterative integration algorithm proven to reduce streak artifacts in planar (2D) images to a differential phase tomography scan. We report on how the reduction of streak artifacts in the projections improves the quality of the tomography slices, especially in the directions different from the reconstruction plane. Importantly, the method is compatible with large tomography datasets in terms of computation time

Invasive Crayfish moving Northwards: management challenges and policy implications at the local scale

Freshwater ecosystems in Italy, as most European countries, have been severely impacted by the invasion of alien crayfish. The two most widespread species in Trentino (NE Italy) are Procambarus clarkii and Faxionus limosus; for both species, the high elevation and cold climate of most of the Trentino territory represent a climatic barrier to their northwards spread. Procambarus clarkii is present in one small lake at 950 m asl, and Faxionus limosus in a group of 5 lakes at 450 m asl, over an area of about 80km2. the introduction of both species is associated with fish restocking, and lead to the extinction of existing populations of the native stone crayfish Austropotamobius pallipes. The Management Plan of Austropotamobius pallipes in Trentino listed the eradication/containment of these IAS populations among the conservation priorities for the native populations. The eradication campaigns of P. clarkii started in 2018 with a release/recapture campaign aimed at assessing the abundance of the populations, and continued in 2020, 2021, 2022. As a result, the capture efficiency decreased, suggesting a population reduction trend. The containment of Faxionus limosus is more difficult, given its presence in a higher number of lakes, three of which are hydrologically connected. A first containment campaign to prevent its spread in the river network is planned for summer 2023. The financial support to these activities has been granted by the local Nature 2000 networks and by the local administrations, which have also promoted the communication with citizens and stakeholders to raise consensus and collaboratio

Edge-Illumination X-Ray Dark-Field Tomography

Dark-field imaging is an x-ray technique used to highlight subpixel, typically micrometer-scale, density fluctuations. It is often used alongside standard attenuation-based and also phase-contrast x-ray imaging, which both see regular use in tomography. We present x-ray dark-field computed tomography (CT) with a laboratory edge-illumination setup. The dark-field contrast is shown to increase linearly with the x-ray path length through the imaged object, a prerequisite for the use of standard tomographic reconstruction approaches. A multimaterial, custom-built phantom is used to show how dark-field contrast CT can complement attenuation contrast CT for the separation of materials based on their microstructure. As an example of a more complex, biological sample, we present a model rat heart. We show, by comparison with attenuation contrast tomography, that dark-field enables the identification of additional structures undetected through the attenuation contrast channel, as well as offering a consistently sharper reconstructed image

A laboratory-based beam tracking x-ray imaging method achieving two-dimensional phase sensitivity and isotropic resolution with unidirectional undersampling

Beam tracking X-ray Phase Contrast Imaging is a “Shack-Hartmann” type approach which uses a pre-sample mask to split the x-rays into “beamlets” which are interrogated by a detector with sufficient resolution. The ultimate spatial resolution is determined by the size of the mask apertures, however achieving this resolution level requires “stepping” the sample or the mask in increments equal to the aperture size (“dithering”). If an array of circular apertures is used (which also provides two-dimensional phase sensitivity) instead of long parallel slits, this stepping needs to be carried out in two directions, which lengthens scan times significantly. We present a mask design obtained by offsetting rows of circular apertures, allowing for two-dimensional sensitivity and isotropic resolution while requiring sample or mask stepping in one direction only. We present images of custom-built phantoms and biological specimens, demonstrating that quantitative phase retrieval and near aperture-limited spatial resolutions are obtained in two orthogonal directions

Dynamic Multicontrast X-Ray Imaging Method Applied to Additive Manufacturing

We present a dynamic implementation of the beam-tracking x-ray imaging method providing absorption, phase, and ultrasmall angle scattering signals with microscopic resolution and high frame rate. We demonstrate the method’s ability to capture dynamic processes with 22-ms time resolution by investigating the melting of metals in laser additive manufacturing, which has so far been limited to single-modality synchrotron radiography. The simultaneous availability of three contrast channels enables earlier segmentation of droplets, tracking of powder dynamic, and estimation of unfused powder amounts, demonstrating that the method can provide additional information on melting processes

Characterization of fast magnetosonic waves driven by interaction between magnetic fields and compact toroids

Magnetosonic waves are low-frequency, linearly polarized magnetohydrodynamic (MHD) waves that can be excited in any electrically conducting fluid permeated by a magnetic field. They are commonly found in space, responsible for many well-known features, such as heating of the solar corona and acceleration of energetic electrons in Earth's inner magnetosphere. In this work, we present observations of magnetosonic waves driven by injecting compact toroid (CT) plasmas into a static Helmholtz magnetic field at the Big Red Ball (BRB) Facility at Wisconsin Plasma Physics Laboratory (WiPPL). We first identify the wave modes by comparing the experimental results with the MHD theory, and then study how factors such as the background magnetic field affect the wave properties. Since this experiment is part of an ongoing effort of forming a target plasma with tangled magnetic fields as a novel fusion fuel for magneto-inertial fusion (MIF, aka magnetized target fusion), we also discuss a future possible path of forming the target plasma based on our current results

Applicazione del Piano di gestione del gambero di Fiume autoctono (Austropotamobius pallipes complex) in Trentino: primi risultati

Il monitoraggio del gambero di Fiume Austropotamobius pallipes complex e dei suoi habitat è stato effettuato nell’estate-autunno 2019-2021 nel territorio della Provincia Autonoma di Trento, quale primo triennio di implementazione del Piano di gestione del gambero di Fiume in Trentino realizzato nell’ambito del Progetto Europeo Life+T.E.N. Sono stati selezionati 224 corpi idrici, 26 dei quali situati all’interno della Rete Natura 2000. Indagini svolte sul campo hanno portato ad escludere 79 siti per via della mancanza delle caratteristiche essenziali alla vita del gambero. Nei rimanenti siti sono state rilevate le caratteristiche ambientali degli habitat e la presenza/assenza della specie. Sono 42 le popolazioni rilevate mentre 2 ulteriori popolazioni sono segnalate ma non sono state indagate. Per definire lo stato di conservazione delle popolazioni presenti, è stata valutata l’abbondanza di 35 popolazioni e, tra queste, sono stati rilevati i dati biometrici e la presenza/assenza di infestazioni evidenti da parassiti e patogeni di 28 popolazioni. Le principali minacce rilevate, rappresentate dall’alterazione degli habitat e dalla presenza di due specie aliene invasive, Procambarus clarkii e Faxonius limosus, in uno e sei siti rispettivamente, suggeriscono una strategia gestionale che favorisca il miglioramento delle condizioni ecologiche degli ambienti acquatici e una maggiore connessione tra di essi e garantisca il controllo della diffusione delle specie aliene e dei loro patogeniThe monitoring of the crayfish Austropotamobius pallipes complex and its habitats was carried out in the summer-autumn 2019-2021 in the territory of the Autonomous Province of Trento, as the first three years of implementation of the Crayfish Management Plan in Trentino which represented one of the outcomes of the European Project Life+T.E.N. Two hundred- twenty-four water bodies were selected, 26 of which are located within the Natura 2000 network. Seventy-nine of these sites were found to be unsuitable after the field survey of the environmental characteristics. In the remaining sites, which were conformed to be suitable, we surveyed the environmental characteristics of the habitats and the presence/absence of the species, which was detected/confirmed in 42 populations, while 2 further populations are signalled but were not investigated. Population abundance was measured in 35 populations and biometric data, the presence/absence of visible infestations by parasites and pathogens were measured in 28 of those populations, to assess the conservation status of the populations. The main detected threats for the populations of A. pallipes are represented by habitat alteration and the presence of the two invasive alien species Procambarus clarkii and Faxonius limosus in one and six sites respectively. The threats suggest a management strategy that would increase the ecological conditions and connectivity of the aquatic habitats and ensure the control of the spread of alien species and their pathogens