Firing-Induced Microstructural Properties of Quasi-Diamagnetic Carbonate-Based Porous Ceramics: a <Superscript>1</Superscript>H NMR Relaxation Correlation Study

This study deals with the application of two-dimensional proton nuclear magnetic resonance relaxometry (2D ¹H NMR-R) to the characterization of porous ceramics nearly free of magnetic compounds. Different microstructural properties were obtained by firing a diamagnetic mixture of kaolin, calcium, and magnesium carbonate over a wide range of maximum temperatures (600–1100 °C) and firing times at the maximum temperature (soaking times) (0–10 h). The 2D ¹H NMR-R method relies on the correlated measurement of ¹H longitudinal (T ₁) and transverse (T ₂) relaxation times of pore-filling water by which the properties of the interconnected pore space may be investigated. In the absence of significant magnetic susceptibility effect due to para- and ferro-magnetic compounds, the 2D ¹H NMR-R maps allow studying the conjoint effects on pore size distribution and inter-pore coupling due to the variations in both time and temperature of firing. The NMR experiments were performed with a low-field ¹H NMR sensor, which allows non-destructive and in situ analysis. For ceramic specimens fired at 600 and 700 °C, the fraction of smallest pores increases with firing time at the expenses of those with intermediate size. The pore shrinkage occurring at this stage, and likely associated with the transformation of kaolinite in metakaolinite, is affected in a similar way by soaking time and firing temperature, in line with the concept of equivalent firing temperature. At temperatures from 800 to 1100 °C, the structural modifications involving interconnectivity and average pore size are driven primarily by firing temperature and, secondarily, by soaking time. The 2D ¹H NMR-R results are confirmed by more traditional, but destructive, mineralogical, and structural analyses like X-ray powder diffraction, helium pycnometry, mercury intrusion porosimetry, and nitrogen adsorption/desorption method.     

A feasibility study of X‐ray phase‐contrast mammographic tomography at the Imaging and Medical beamline of the Australian Synchrotron

Results are presented of a recent experiment at the Imaging and Medical beamline of the Australian Synchrotron intended to contribute to the implementation of low‐dose high‐sensitivity three‐dimensional mammographic phase‐contrast imaging, initially at synchrotrons and subsequently in hospitals and medical imaging clinics. The effect of such imaging parameters as X‐ray energy, source size, detector resolution, sample‐to‐detector distance, scanning and data processing strategies in the case of propagation‐based phase‐contrast computed tomography (CT) have been tested, quantified, evaluated and optimized using a plastic phantom simulating relevant breast‐tissue characteristics. Analysis of the data collected using a Hamamatsu CMOS Flat Panel Sensor, with a pixel size of 100 µm, revealed the presence of propagation‐based phase contrast and demonstrated significant improvement of the quality of phase‐contrast CT imaging compared with conventional (absorption‐based) CT, at medically acceptable radiation doses.     

The role of copper(II) and zinc(II) in the degradation of human and murine IAPP by insulin‐degrading enzyme

Amylin or islet amyloid polypeptide (IAPP) is a 37‐residue peptide hormone secreted from the pancreatic islets into the blood circulation and is cleared by peptidases in the kidney. IAPP aggregates are strongly associated with β‐cell degeneration in type 2 diabetes, as demonstrated by the fact that more than 95% of patients exhibit IAPP amyloid upon autopsy. Recently, it has been reported that metal ions such as copper(II) and zinc(II) are implicated in the aggregation of IAPP as well as able to modulate the proteolytic activity of IAPP degrading enzymes. For this reason, in this work, the role of the latter metal ions in the degradation of IAPP by insulin‐degrading enzyme (IDE) has been investigated by a chromatographic and mass spectrometric combined method. The latter experimental approach allowed not only to assess the overall metal ion inhibition of the human and murine IAPP degradation by IDE but also to have information on copper‐ and zinc‐induced changes in IAPP aggregation. In addition, IDE cleavage site preferences in the presence of metal ions are rationalized as metal ion‐induced changes in substrate accessibility. Copyright © 2014 John Wiley & Sons, Ltd.     

Charge transfer complexes of some N-methylated thiohydantoins with molecular iodine

Using a series of N-methylated thiohydantoins as substrates, the donor properties of the sulfur atom are measured by determining the stability constants (K) of their adducts with molecular iodine. The K's have been determined by recording the UV-visible spectra of several CH₂Cl₂ solutions with different amounts of the reagents. The experimental data fit the 1:1 adduct model for all the compounds. The K values, compared with those previously found for the unsubstituted hydantoins and with those obtained for 5-methyl-2-thiohydantoin, show that the hydrogen-bonding interaction between the NH hydrogen and the S-bonded iodine plays an important role in determining the stability of the adduct. The K values obtained for several pentaatomic rings, all containing the thioureido group  HN C() NH , are discussed on the basis of the influence of the substituents at C-4 and C-5 on the donor properties of the sulfur atom.     

Human mobility and COVID-19 initial dynamics

Nonlinear Dynamics - Countries in Europe took different mobility containment measures to curb the spread of COVID-19. The European Commission asked mobile network operators to share on a...     

Noise Reduction in Spur Gear Systems

This article lists some tips for reducing gear case noise. With this aim, a static analysis was carried out in order to describe how stresses resulting from meshing gears affect the acoustic emissions. Different parameters were taken into account, such as the friction, material, and lubrication, in order to validate ideas from the literature and to make several comparisons. Furthermore, a coupled Eulerian–Lagrangian (CEL) analysis was performed, which was an innovative way of evaluating the sound pressure level of the aforementioned gears. Different parameters were considered again, such as the friction, lubrication, material, and rotational speed, in order to make different research comparisons. The analytical results agreed with those in the literature, both for the static analysis and CEL analysis—for example, it was shown that changing the material from steel to ductile iron improved the gear noise, while increasing the rotational speed or the friction increased the acoustic emissions. Regarding the CEL analysis, air was considered a perfect gas, but its viscosity or another state equation could have also been taken into account. Therefore, the above allowed us to state that research into these scientific fields will bring about reliable results.     

Permutation Entropy-Based Interpretability of Convolutional Neural Network Models for Interictal EEG Discrimination of Subjects with Epileptic Seizures vs. Psychogenic Non-Epileptic Seizures

The differential diagnosis of epileptic seizures (ES) and psychogenic non-epileptic seizures (PNES) may be difficult, due to the lack of distinctive clinical features. The interictal electroencephalographic (EEG) signal may also be normal in patients with ES. Innovative diagnostic tools that exploit non-linear EEG analysis and deep learning (DL) could provide important support to physicians for clinical diagnosis. In this work, 18 patients with new-onset ES (12 males, 6 females) and 18 patients with video-recorded PNES (2 males, 16 females) with normal interictal EEG at visual inspection were enrolled. None of them was taking psychotropic drugs. A convolutional neural network (CNN) scheme using DL classification was designed to classify the two categories of subjects (ES vs. PNES). The proposed architecture performs an EEG time-frequency transformation and a classification step with a CNN. The CNN was able to classify the EEG recordings of subjects with ES vs. subjects with PNES with 94.4% accuracy. CNN provided high performance in the assigned binary classification when compared to standard learning algorithms (multi-layer perceptron, support vector machine, linear discriminant analysis and quadratic discriminant analysis). In order to interpret how the CNN achieved this performance, information theoretical analysis was carried out. Specifically, the permutation entropy (PE) of the feature maps was evaluated and compared in the two classes. The achieved results, although preliminary, encourage the use of these innovative techniques to support neurologists in early diagnoses.     

Effect of Natural Deep Eutectic Solvents on trans-Resveratrol Photo-Chemical Induced Isomerization and 2,4,6-Trihydroxyphenanthrene Electro-Cyclic Formation

trans-Resveratrol is a natural bioactive compound with well-recognized health promoting effects. When exposed to UV light, this compound can undergo a photochemically induced trans/cis isomerization and a 6π electrochemical cyclization with the subsequent formation of 2,4,6-trihydroxyphenanthrene (THP). THP is a potentially harmful compound which can exert genotoxic effects. In this work we improved the chromatographic separation and determination of the two resveratrol isomers and of THP by using a non-commercial pentafluorophenyl stationary phase. We assessed the effect of natural deep eutectic solvents (NaDES) as possible photo-protective agents by evaluating cis-resveratrol isomer and THP formation under different UV-light exposure conditions with the aim of enhancing resveratrol photostability and inhibiting THP production. Our results demonstrate a marked photoprotective effect exerted by glycerol-containing NaDES, and in particular by proline/glycerol NaDES, which exerts a strong inhibitory effect on the photochemical isomerization of resveratrol and significantly limits the formation of the toxic derivative THP. Considering the presence of resveratrol in various commercial products, these results are of note in view of the potential genotoxic risk associated with its photochemical degradation products and in view of the need for the development of green, eco-sustainable and biocompatible resveratrol photo-stable formulations.