A fast, non-iterative algorithm for quantitative integration of X-ray differential phase-contrast images

X-ray phase contrast imaging is gaining importance as an imaging tool. However, it is common for X-ray phase detection techniques to be sensitive to the derivatives of the phase. Therefore, the integration of differential phase images is a fundamental step both to access quantitative pixel content and for further analysis such as segmentation. The integration of noisy data leads to artefacts with a severe impact on image quality and on its quantitative content. In this work, an integration method based on the Wiener filter is presented and tested using simulated and real data obtained with the edge illumination differential X-ray phase imaging method. The method is shown to provide high image quality while preserving the quantitative pixel content of the integrated image. In addition, it requires a short computational time making it suitable for large datasets

The transition from refraction to Ultra-Small-Angle X-ray Scattering (USAXS) in a laboratory phase-based X-ray microscope for soft tissue imaging

We report on a laboratory-based x-ray microscope allowing for phase-contrast imaging of soft tissue samples. The used beam tracking approach allows retrieval of Ultra-Small-Angle X-ray Scattering (USAXS) or dark field alongside attenuation and differential phase. We show the dependence of the refraction and dark field signal on the size of the imaged features. The application of the technique to a biological sample is also demonstrated

A laboratory-based, low-energy, multi-modal x-ray microscope with user-defined resolution

We report on the development of a low-energy x-ray phase-based microscope using intensity-modulation masks for single-shot retrieval of three contrast channels: transmission, refraction, and ultra-small-angle scattering or dark field. The retrieval method is based on beam tracking, an incoherent and phase-based imaging approach. We demonstrate that the spatial resolution of this imaging system does not depend on focal spot size nor detector pixel pitch, as opposed to conventional and propagation-based x-ray imaging, and it is only dependent on the mask aperture size. This result enables the development of a multi-resolution microscope where multi-scale samples can be explored on different length scales by adjusting only the mask aperture size, without other modifications. Additionally, we show an extended capability of the system to resolve periodic structures below the resolution limit imposed by the mask apertures, which potentially extends dark-field imaging beyond its conventional use

Laboratory-based x-ray dark-field microscopy

We demonstrate the capability of laboratory-based x-ray microscopes, using intensity-modulation masks, to access the submicron length scale in the dark-field contrast channel while maintaining micron resolution in the resolved (refraction and attenuation) channels. The dark-field contrast channel reveals the presence of ensembles of samples' features below the system resolution. Resolved refraction and attenuation channels provide multimodal high-resolution imaging down to the micron scale. We investigate the regimes of modulated and unmodulated dark field as well as refraction, quantifying their dependence on the relationship between feature size in the imaged object and aperture size in the intensity-modulation mask. We propose an analytical model to link the measured signal with the sample's microscopic properties. Finally, we demonstrate the relevance of the microscopic dark-field contrast channel in applications from both the life and physical sciences, providing proof-of-concept results for imaging collagen bundles in cartilage and dendritic growth in lithium batteries

Peroxisomal PEX7 Receptor Affects Cadmium-Induced ROS and Auxin Homeostasis in Arabidopsis Root System

Peroxisomes are important in plant physiological functions and stress responses. Through the production of reactive oxygen and nitrogen species (ROS and RNS), and antioxidant defense enzymes, peroxisomes control cellular redox homeostasis. Peroxin (PEX) proteins, such as PEX7 and PEX5, recognize peroxisome targeting signals (PTS1/PTS2) important for transporting proteins from cytosol to peroxisomal matrix. pex7-1 mutant displays reduced PTS2 protein import and altered peroxisomal metabolism. In this research we analyzed the role of PEX7 in the Arabidopsis thaliana root system exposed to 30 or 60 μM CdSO4. Cd uptake and translocation, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) levels, and reactive oxygen species (ROS) and reactive nitrogen species (RNS) levels and catalase activity were analyzed in pex7-1 mutant primary and lateral roots in comparison with the wild type (wt). The peroxisomal defect due to PEX7 mutation did not reduce Cd-uptake but reduced its translocation to the shoot and the root cell peroxisomal signal detected by 8-(4-Nitrophenyl) Bodipy (N-BODIPY) probe. The trend of nitric oxide (NO) and peroxynitrite in pex7-1 roots, exposed/not exposed to Cd, was as in wt, with the higher Cd-concentration inducing higher levels of these RNS. By contrast, PEX7 mutation caused changes in Cd-induced hydrogen peroxide (H2O2) and superoxide anion (O2●−) levels in the roots, delaying ROS-scavenging. Results show that PEX7 is involved in counteracting Cd toxicity in Arabidopsis root system by controlling ROS metabolism and affecting auxin levels. These results add further information to the important role of peroxisomes in plant responses to Cd

MRP4 over-expression has a role on both reducing nitric oxide-dependent antiplatelet effect and enhancing ADP induced platelet activation

The impact of inhibition of multidrug resistance protein 4 (MRP4) on nitric oxide (NO) resistance and on ADP-induced platelet aggregation is unknown. The aim of this investigation was to verify whether platelet NO resistance correlates with MRP4 expression and evaluate whether this can be reduced by in vitro MRP4 inhibition mediated by cilostazol. Moreover, we assessed if inhibition of MRP4-mediated transport reduces ADP-induced platelet reactivity. The inhibitory effect of sodium nitroprusside (SNP), a NO-donor that enhances cyclic guanosine monophosphate (cGMP) cytosolic concentration, was assessed in platelets obtained from aspirin treated patients and in a control population. The inhibitory effect of SNP was evaluated by ADP-induced aggregation in SNP-treated platelets. The impact of MRP4 on ADP-induced platelet aggregation was performed in high on aspirin residual platelet reactivity (HARPR) patients and compared to healthy volunteers (HV), and a control cohort (CTR). In aspirin-treated patients with high levels of MRP4, reduced SNP inhibition was found compared to those with low levels of MRP4. MRP4 inhibition by cilostazol significantly reduced ADP-induced platelet aggregation in HARPR population, and to a lesser extent in HV and CTR populations. In conclusion, cilostazol can mitigate the hyper-reactive platelet phenotype of HARPR patients by reducing residual ADP-induced platelet aggregation and increasing NO-dependent endothelial antiplatelet effects

From Data to Phenomena: A Kantian Stance

This paper investigates some metaphysical and epistemological assumptions behind Bogen and Woodward's data-to-phenomena inferences. I raise a series of points and suggest an alternative possible Kantian stance about data-to-phenomena inferences. I clarify the nature of the suggested Kantian stance by contrasting it with McAllister's view about phenomena as patterns in data sets

Evaluation of neutron induced reaction cross sections in the resolved and unresolved resonance region at EC-JRC-IRMM

Recent efforts made at the EC-JRC-IRMM to produce evaluated cross section data files for neutron induced reactions are described as well as the methodology applied in both the resolved and unresolved resonance. For the resolved resonance region the paper focuses on a recent evaluation of isotopes present in natural cadmium. For the unresolved resonance region results for gold are presented.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Quantitative characterization of amyloid deposits in murine models of alzheimer disease by phase-contrast x-ray imaging

Alzheimer's is a neurodegenerative disease that is the most common form of dementia, but there is still no definitive cure for this disease. The noninvasive X-ray Phase Contrast Tomography (XPCT) imaging technique was used to study brain tissues in mouse models of Alzheimer's disease, AP-PS1 and APP23. The XPCT technique enabled high-resolution imaging of brain tissues, distinguishing between different brain structures, such as amyloid deposits and neuronal cells. In addition, the XPCT technique provided detailed information on the distribution and morphology of amyloid deposits in AP-PS1 and APP23 mice putting in evidence the differences between these two models. This work demonstrates the effectiveness of this technique in supporting Alzheimer's studies and evaluating new therapeutic strategies.Comment: 14 pages, 8 figure