Hierarchical structure and chemical composition of complementary segments of the fruiting bodies of Fomes fomentarius fungi fine-tune the compressive properties.

Humanity is often fascinated by structures and materials developed by Nature. While structural materials such as wood have been widely studied, the structural and mechanical properties of fungi are still largely unknown. One of the structurally interesting fungi is the polypore Fomes fomentarius. The present study deals with the investigation of the light but robust fruiting body of F. fomentarius. The four segments of the fruiting body (crust, trama, hymenium, and mycelial core) were examined. The comprehensive analysis included structural, chemical, and mechanical characterization with particular attention to cell wall composition, such as chitin/chitosan and glucan content, degree of deacetylation, and distribution of trace elements. The hymenium exhibited the best mechanical properties even though having the highest porosity. Our results suggest that this outstanding strength is due to the high proportion of skeletal hyphae and the highest chitin/chitosan content in the cell wall, next to its honeycomb structure. In addition, an increased calcium content was found in the hymenium and crust, and the presence of calcium oxalate crystals was confirmed by SEM-EDX. Interestingly, layers with different densities as well as layers of varying calcium and potassium depletion were found in the crust. Our results show the importance of considering the different structural and compositional characteristics of the segments when developing fungal-inspired materials and products. Moreover, the porous yet robust structure of hymenium is a promising blueprint for the development of advanced smart materials.

Absorption Correction for 3D Elemental Distributions of Dental Composite Materials Using Laboratory Confocal Micro-X-ray Fluorescence Spectroscopy.

Confocal micro-X-ray fluorescence (micro-XRF) spectroscopy facilitates three-dimensional (3D) elemental imaging of heterogeneous samples in the micrometer range. Laboratory setups using X-ray tube excitation render the method accessible for diverse research fields but interpretation of results and quantification remain challenging. The attenuation of X-rays in composites depends on the photon energy as well as on the composition and density of the material. For confocal micro-XRF, attenuation severely impacts elemental distribution information, as the signal from deeper layers is distorted by superficial layers. Absorption correction and quantification of fluorescence measurements in heterogeneous composite samples have so far not been reported. Here, an absorption correction approach for confocal micro-XRF combining density information from microcomputed tomography (micro-CT) data with laboratory X-ray absorption spectroscopy (XAS) and synchrotron transmission measurements is presented. The energy dependency of the probing volume is considered during the correction. The methodology is demonstrated on a model composite sample consisting of a bovine tooth with a clinically used restoration material.

Quantitative Analysis and 2D/3D Elemental Imaging of Cocoa Beans Using X-ray Fluorescence Techniques.

As an important raw material for the confectionery industry, the cocoa bean (Theobroma cacao L.) has to meet certain legal requirements in terms of food safety and maximum contaminant levels in order to enter the cocoa market. Understanding the enrichment and distribution of essential minerals but also toxic metals is of utmost importance for improving the nutritional quality of this economically important raw food material. We present three X-ray fluorescence (XRF) techniques for elemental bio-imaging of intact cocoa beans and one additional XRF technique for quantitative analysis of cocoa pellets. The interrelation of all the methods presented gives a detailed picture of the content and 3D-resolved distribution of elements in complete cocoa beans for the first time.

Chemical mapping of teeth in 2D and 3D: X-ray fluorescence reveals hidden details in dentine surrounding fillings.

X-rays are frequently used for characterizing both tooth tissues and dental materials. Whereas radiographs and tomography utilize absorption contrast for retrieving details, chemical mapping is usually achieved by energy dispersive X-ray (EDX) analysis that is stimulated under vacuum in electron microscopes. However, the relatively dense mineralized composition of teeth, and the frequent inclusion of a large range of elements in filling materials raise the possibility that other X-ray based techniques such as X-ray fluorescence (XRF) spectroscopy may strongly contribute to investigations of a large variety of dental structures. By exploiting the fluorescence excited by micron sized X-rays (µXRF) it is possible to map minute quantities of a large range of elements (from aluminum to uranium), where spectra containing signals from multiple different elements can be resolved non-destructively and concomitantly. The high penetration depth of X-rays makes XRF highly effective at detecting variable compositions with information emerging from tooth tissues situated well beneath the sample surface. The method supports minimal sample preparation and, different from electron microscopy, it facilitates investigation of hydrated dental materials. Direct comparison of µXRF and confocal µXRF (CµXRF) with SEM-EDX reveals micro zones of chemical heterogeneity in the complex 3D architecture of root canal fillings. These methods reproducibly clarify the mutual arrangement of biomaterials in both fresh fillings as well as in repeatedly treated old teeth of unknown history. The results showcase the complementarity of X-ray and electron based elemental mapping for dental materials research. STATEMENT OF SIGNIFICANCE: Chemical characterization of mineralized tissues such as tooth dentine is often performed using energy dispersive X-ray spectroscopy (EDS/EDX) analysis by scanning electron microscopy (SEM). The widespread use of electron microscopes and simplified detector designs have made this form of chemical and structural analysis extremely popular. However, excitation by electrons is limited to the upper microns of the tissue, and these may not well represent the chemical composition of the bulk. Especially when heavier elements are of interest and when dental filling materials exhibit diffusion into the tooth, little is known about the spatial distribution. Here we show how complementary X-ray fluorescence data originating by electron and X-ray excitation can help visualize the distribution and impregnation of heavy elements through teeth, e.g. for root canal treatment.

Pulmonary hypertension after shunt closure in patients with simple congenital heart defects.

BACKGROUND: Patients with simple shunt lesions, such as atrial septal defect (ASD), ventricular septal defect (VSD) and persistent arterial duct (PDA) remain at risk of developing pulmonary hypertension (PH) even after correction of their cardiac defect. We aimed to assess the contemporary prevalence of PH in a well characterized nationwide group of patients based on the German National Register for Congenital Heart Defects. METHODS AND RESULTS: We included all patients >16 years of age with an isolated diagnosis of ASD, VSD or PDA. Only patients with previous surgical or interventional closure of the defect were included. Patients with genetic syndromes were excluded. Out of 49,597 CHD patients in the register we identified 825 patients with closed, isolated simple defects (52% ASD, 41% VSD, 7% PDA). Of these, 25 (3%) developed PH after a median follow-up of 16 years from defect closure. The risk of PH increased significantly with age at follow-up (p < 0.0001) and age at repair (p < 0.0001) on logistic regression analysis Patients with PH were significantly more likely to be symptomatic (59% vs. 9% in NYHA class ≥2, p < 0.0001) and had significantly higher mortality (hazard ratio 13.4, p < 0.0001) compared to the remaining patients. CONCLUSIONS: Based on data from the German National Register CHD Register we report a PH prevalence of 3.0% in patients with corrected, simple lesions. Patients with PH were more symptomatic and had significantly increased mortality risk. Life-long surveillance and low threshold for workup is recommended to ascertain diagnosis of PH, which has important prognostic and clinical implications.