Phase Contrast Imaging with Coded Apertures Using Laboratory-Based X-ray Sources

X‐ray phase contrast imaging is a powerful technique that allows detection of changes in the phase of x‐ray wavefronts as they pass through a sample. As a result, details not visible in conventional x‐ray absorption imaging can be detected. Until recently the majority of applications of phase contrast imaging were at synchrotron facilities due to the availability of their high flux and coherence; however, a number of techniques have appeared recently that allow phase contrast imaging to be performed using laboratory sources. Here we describe a phase contrast imaging technique, developed at University College London, that uses two coded apertures. The x‐ray beam is shaped by the pre‐sample aperture, and small deviations in the x‐ray propagation direction are detected with the help of the detector aperture. In contrast with other methods, it has a much more relaxed requirement for the source size (it works with source sizes up to 100 μm). A working prototype coded‐aperture system has been built. An x‐ray detector with directly deposited columnar CsI has been used to minimize signal spill‐over into neighboring pixels. Phase contrast images obtained with the system have demonstrated its effectiveness for imaging low‐absorption materials

Effects of signal diffusion on x-ray phase contrast images

We discuss the problem of signal diffusion among neighbouring pixels in x-ray phase contrast imaging (XPCi) specifically for coded-aperture (CA) XPCi, but many of the discussed observations are directly transferable to other XPCi modalities. CA XPCi exploits the principle of pixel edge illumination by means of two CA masks. The first mask, placed in contact with the detector, creates insensitive regions between adjacent pixels; the second one, placed immediately before the sample, creates individual beams impinging on the boundaries between sensitive and insensitive regions on the detector, as created by the detector mask. In this way, edge illumination is achieved for all pixels of an area detector illuminated by a divergent and polychromatic beam generated by a conventional source. As the detector mask redefines the resolution properties of the detector, sample dithering can be used to effectively increase the system spatial resolution, without having to apply any post-processing procedure (e. g., deconvolution). This however creates artifacts in the form of secondary fringes (which have nothing to do with phase-related secondary fringes) if there is signal diffusion between adjacent pixels. In non-dithered images, signal diffusion between adjacent pixels causes a reduction in image contrast. This effect is investigated both theoretically and experimentally, and its direct implications on image quality are discussed. The interplay with the sample positioning with respect to the detector pixel matrix, which also has an effect on the obtained image contrast, is also discussed. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3606442

Unlocking the Fertilizer Potential of Waste-Derived Biochar

Mankind is facing a phosphorus (P) crisis. P recycling from anthropogenic waste is critical to close the P loop. Pyrolysis could be the ideal treatment for materials, such as sewage sludge (SS), producing a safe, nutrient-rich biochar product while sequestering the inherent carbon (C). However, pyrolyzed sewage sludge typically contains low levels of potassium (K) and plant available P, making the material rather unsuitable for use as fertilizer. Here, a novel treatment was investigated to produce an optimized P and K biochar fertilizer. We doped sewage sludge with a low-cost mineral (2 and 5% potassium acetate) and pyrolyzed it at 700 °C. The percentage water extractable of the total P content in biochar increased by 237 times with 5% K addition compared to the undoped biochar. After six water extractions, all of the K and 16% of P were obtained. Further optimization is feasible through adjustments of the biochar pH or doping the feedstock with other forms of K. Using X-ray absorption near-edge spectroscopy (XANES) and synchrotron X-ray fluorescence (XRF) mapping, we identified highly soluble potassium hydrogen phosphate up to 200−300 μm below the biochar surface. This simple and cost-effective modification enables the use of sewage sludge as safe biochar fertilizer with tailored P availability that also supplies K, improves soil properties, and sequesters C

Chemical imaging of single catalyst particles with scanning μ-XANES-CT and μ-XRF-CT

The physicochemical state of a catalyst is a key factor in determining both activity and selectivity; however these materials are often not structurally or compositionally homogeneous. Here we report on the 3-dimensional imaging of an industrial catalyst, Mo-promoted colloidal Pt supported on carbon. The distribution of both the active Pt species and Mo promoter have been mapped over a single particle of catalyst using microfocus X-ray fluorescence computed tomography. X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure revealed a mixed local coordination environment, including the presence of both metallic Pt clusters and Pt chloride species, but also no direct interaction between the catalyst and Mo promoter. We also report on the benefits of scanning μ-XANES computed tomography for chemical imaging, allowing for 2- and 3-dimensional mapping of the local electronic and geometric environment, in this instance for both the Pt catalyst and Mo promoter throughout the catalyst particle

An in-situ synchrotron XAS methodology for surface analysis under high temperature, pressure and shear

The complex tribochemical nature of lubricated tribological contacts is inaccessible in real time without altering their initial state. To overcome this issue, a new design of a pin-on-disc tribological apparatus was developed and combined with synchrotron X-ray absorption spectroscopy (XAS). Using the designed apparatus, it is possible to study in situ the transient decomposition reactions of various oil additives on different surfaces under a wide range of realistic operating conditions of contact pressure (1.0–3.0 GPa), temperature (25–120 °C), and sliding speed (30–3000 rpm or 0.15–15 m/s). To test the apparatus, several tribological tests were performed at different shearing times ranging from 2.5 to 60 min. These tests were carried out under helium atmosphere at a temperature of 80  °C, contact pressure of 2.2 GPa, and sliding speed of 50 rpm. The XAS experiments indicate that the zinc dialkyldithiophosphate antiwear additive decomposes in the oil to form a tribofilm on the iron surface at different reaction kinetics from the ones of the thermal film. The tribofilm composition evolves much faster than the one of the thermal film, which confirms that the formation of the tribofilm is a thermally activated process similar to the one of the thermal film but accelerated by shear. Furthermore, the results indicate that the sulfur of the formed film, whether a tribofilm or a thermal film, appears initially in the form of sulfate, with some sulfide, which under heat or shear is reduced into mainly sulfide

Advancing fault diagnosis in aircraft landing gear: an innovative two-tier machine learning approach with intelligent sensor data management

Revolutionizing aircraft safety, this study unveils a pioneering two-tier machine learning model specifically designed for advanced fault diagnosis in aircraft landing gear systems. Addressing the critical gap in traditional diagnostic methods, our approach deftly navigates the challenges of sensor data anomalies, ensuring robust and accurate real-time health assessments. This innovation not only promises to enhance the reliability and safety of aviation but also sets a new benchmark in the application of intelligent machine-learning solutions in high-stakes environments. Our method is adept at identifying and compensating for data anomalies caused by faulty or uncalibrated sensors, ensuring uninterrupted health assessment. The model employs a simulation-based dataset reflecting complex hydraulic failures to train robust machine learning classifiers for fault detection. The primary tier focuses on fault classification, whereas the secondary tier corrects sensor data irregularities, leveraging redundant sensor inputs to bolster diagnostic precision. Such integration markedly improves classification accuracy, with empirical evidence showing an increase from 95.88% to 98.76% post-imputation. Our findings also underscore the importance of specific sensors—particularly temperature and pump speed—in evaluating the health of landing gear, advocating for their prioritized usage in monitoring systems. This approach promises to revolutionize maintenance protocols, reduce operational costs, and significantly enhance the safety measures within the aviation industry, promoting a more resilient and data-informed safety infrastructure

Proof-of-concept demonstration of edge-illumination x-ray phase contrast imaging combined with tomosynthesis.

In this note we present the first proof-of-concept results on the potential effectiveness of the edge-illumination x-ray phase contrast method (in its 'coded-aperture' based lab implementation) combined with tomosynthesis. We believe that, albeit admittedly preliminary (e.g. we only present phantom work), these results deserve early publication in a note primarily for four reasons. First, we fully modelled the imaging acquisition method, and validated the simulation directly with experimental results. This shows that the implementation of the method in the new geometry is understood, and thus that it will be possible to use the model to simulate more complex scenarios in the future. Secondly, we show that a strong phase contrast signal is preserved in the reconstructed tomosynthesis slices: this was a concern, as the high spatial frequency nature of the signal makes it sensitive to any filtration-related procedure. Third, we show that, despite the non-optimized nature of the imaging prototype used, we can perform a full angular scan at acceptable dose levels and with exposure times not excessively distant from what is required by clinical practice. Finally, we discuss how the proposed phase contrast method, unlike other approaches apart from free-space propagation (which however requires a smaller focal spot, thus reducing the flux and increasing exposure times), can be easily implemented in a tomosynthesis geometry suitable for clinical use. In summary, we find that these technical results indicate a high potential for the combination of the two methods. Combining slice separation with detail enhancement provided by phase effects would substantially increase the detectability of small lesions and/or calcifications, which we aim to demonstrate in the next steps of this study

Laparoscopic herniorrhaphy in children with acute inflammatory diseases of the abdominal cavity

Institutul de Cercetări științifice în Chirurgia Pediatrică, Universitatea Națională de Cercetări Medicale „N.Pirogov”, Moscova, Rusia, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Prezența unui proces inflamator-distructiv acut în cavitatea abdominală este pe larg considerată ca o contraindicație pentru herniorafia laparoscopică simultană. Material și metode: În perioada 2010-2012, 240 de copii cu vîrsta 5-14 ani, au fost spitalizați cu manifestările clinice ale abdomenului acut și au fost supuși intervențiilor chirurgicale urgente. În timpul laparoscopiei la 29 pacienți (18 băieți și 11 fete) a fost depistat processus vaginalis persistent (PVP): în 25 de cazuri unilateral și în 4 cazuri - bilateral. Nouăsprezece copii din acest lot au fost diagnosticați cu formele distructive ale apendicitei acute (în 6 cazuri complicate cu peritonită locală), 5 – cu pelvioperitonită, 4 – cu limfadenită mezenterică acută și 1 copil – cu apoplexie ovariană. La toți pacienții au fost efectuate intervenții simultane – asanarea focarului inflamator și ligaturarea subcutanată endo-asistată (SEAL) a PVP. Rezultate: Nu a fost înregistrat nici un caz de conversie. După intervenția de asanare a focarului inflamator (apendicectomie, rezecție de ovar, etc.) a fost efectuată SEAL conform metodei modificate de autori. Durata SEAL nu a depășit 6 minute pentru hernia unilaterală și 9 minute în cazuri bilaterale. Postoperator toți copii au primit un tratament standard. În toate cazurile evoluția postoperatorie a fost favorabilă. Complicații abdominale sau la nivelul canalului inghinal nu au fost înregistrate. Examenul ultrasonor și testele de laborator au confirmat rezolvarea completă a procesului inflamator. Toți pacienții au fost externați complet recuperați. Concluzii: Herniorafia laparoscopică simultană la copiii cu procese acute inflamatorii în cavitatea abdominală nu este urmată de elevarea riscului complicațiilor postoperatorii.Introduction: The presence of an acute inflammatory and destructive process in the abdominal cavity is commonly a contraindication to the one-stage laparoscopic herniorrhaphy. Material and methods: From 2010 to 2012, 240 children, 5-14 years of age, were admitted to hospital with a clinical picture of acute abdomen and all of them were urgently operated on. During laparoscopy in 29 patients (18 boys and 11 girls) a persisted processus vaginalis (PPV) was found: unilateral in 25 cases and bilateral in 4 cases. In 19 children from this group destructive forms of acute appendicitis (in 6 cases complicated by local peritonitis) were diagnosed as well as 5 – pelvioperitonitis, 4 – acute mesenteric lymphadenitis, and 1 – ovarian apoplexy. All patients underwent simultaneous procedures – both inflammatory focus treatment and subcutaneous endo-assisted ligation (SEAL) of PPV. Results: There was no conversion in any case. After the intervention for treatment of inflammatory focus (appendectomy, ovarian resection, etc.) the SEAL was performed according to our modification. SEAL duration was not more than 6 minutes for unilateral hernia and 9 minutes for bilateral. Postoperatively, all children received a standard therapy. In all cases the postoperative period was favorable. Complications in abdominal cavity or inguinal canals were not registered. Ultrasound examination and blood tests confirmed a complete relief of the inflammatory process. All patients were discharged with full recovery. Conclusions: Simultaneous laparoscopic herniorrhaphy in children with acute inflammation in the abdominal cavity does not increase the risk of postoperative complications

Experimental infection of H5N1 HPAI in BALB/c mice

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