Non‐negative matrix factorization for the near real‐time interpretation of absorption effects in elemental distribution images acquired by X‐ray fluorescence imaging

Elemental distribution images acquired by imaging X‐ray fluorescence analysis can contain high degrees of redundancy and weakly discernible correlations. In this article near real‐time non‐negative matrix factorization (NMF) is described for the analysis of a number of data sets acquired from samples of a bi‐modal α+β Ti‐6Al‐6V‐2Sn alloy. NMF was used for the first time to reveal absorption artefacts in the elemental distribution images of the samples, where two phases of the alloy, namely α and β, were in superposition. The findings and interpretation of the NMF results were confirmed by Monte Carlo simulation of the layered alloy system. Furthermore, it is shown how the simultaneous factorization of several stacks of elemental distribution images provides uniform basis vectors and consequently simplifies the interpretation of the representation.     

Hydrothermal preparation and characterization of ZnFe2O4 magnetic nanoparticles as an efficient heterogeneous catalyst for the synthesis of multi‐substituted imidazoles and study of their anti‐inflammatory activity

Nanoparticles are key focus of research for a wide range of novel applications. As such, ZnFe₂O₄ magnetic nanoparticles were synthesized hydrothermally and characterized via scanning and transmission electron microscopies, powder X‐ray diffraction, energy‐dispersive X‐ray and infrared spectroscopies, thermogravimetric analysis and magnetic measurements. They were used as a robust catalyst for the synthesis of a series of biologically active multi‐substituted imidazoles using a multicomponent reaction by the reaction of benzil with various aromatic aldehydes, ammonium acetate and aliphatic amines (N,N‐dimethyl‐1,3‐propanediamine and 1‐amino‐2‐propanol) under solvent‐free conditions. The key advantages of this method are shorter reaction times, very high yield and ease of operation. The thermally and chemically stable, benign and economical catalyst was easily recovered using an external magnet and reused in at least five successive runs without an appreciable loss of activity. All of these novel synthesized compounds were characterized from spectral data and their purities were checked using thin‐layer chromatography, giving one spot. Furthermore, the prepared compounds were tested for their anti‐inflammatory activity.     

Donor–acceptor photovoltaic polymers based on 1,4‐dithienyl‐2,5‐dialkoxybenzene with intramolecular noncovalent interactions

Donor–acceptor (D–A) conjugated polymers bearing non‐covalent configurationally locked backbones have a high potential to be good photovoltaic materials. Since 1,4‐dithienyl‐2,5‐dialkoxybenzene ( TBT ) is a typical moiety possessing intramolecular S…O interactions and thus a restricted planar configuration, it was used in this work as an electron‐donating unit to combine with the following electron‐accepting units: 3‐fluorothieno[3,4‐b]thiophene ( TFT ), thieno‐[3,4‐c]pyrrole‐4,6‐dione ( TPD ), and diketopyrrolopyrrole ( DPP ) for the construction of such D–A conjugated polymers. Therefore, the so‐designed three polymers, PTBTTFT , PTBTTPD , and PTBTDPP , were synthesized and investigated on their basic optoelectronic properties in detail. Moreover, using [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as acceptor material, polymer solar cells (PSCs) were fabricated for studying photovoltaic performances of these polymers. It was found that the optimized PTBTTPD cell gave the best performance with a power conversion efficiency (PCE) of 4.49%, while that of PTBTTFT displayed the poorest one (PCE = 1.96%). The good photovoltaic behaviors of PTBTTPD come from its lowest‐lying energy level of the highest occupied molecular orbital (HOMO) among the three polymers, and good hole mobility and favorable morphology for its PC₇₁BM‐blended film. Although PTBTDPP displayed the widest absorption spectrum, the largest hole mobility, and regular chain packing structure when blended with PC₇₁BM, its unmatched HOMO energy level and disfavored blend film morphology finally limited its solar cell performance to a moderate level (PCE: 3.91%). © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 689–698     

On the Main Aspects of the Inverse Conductivity Problem

We consider a nonlinear inverse problem for an elliptic partial differential equation known as the Calder{\''o}n problem or the inverse conductivity problem. Based on several results, we briefly summarize them to motivate this research field. We give a general view of the problem by reviewing the available results for $C^2$ conductivities. After reducing the original problem to the inverse problem for a Schr\"odinger equation, we apply complex geometrical optics solutions to show its uniqueness. After extending the ideas of the uniqueness proof result, we establish a stable dependence between the conductivity and the boundary measurements. By using the Carleman estimate, we discuss the partial data problem, which deals with measurements that are taken only in a part of the boundary.     

Magnetic non‐volatile flip‐flop with spin‐Hall assistance

A novel multi‐bit non‐volatile flip‐flop (NVFF) written by spin‐Hall‐assisted spin‐transfer torque (STT) is proposed. This NVFF employs perpendicular‐anisotropy MTJs and requires an STT current combined with a spin‐Hall current to write the data. Thanks to the assistance of spin‐Hall effect (SHE), the incubation delay required by the conventional STT switching can be eliminated to achieve fast operation. Our proposed NVFF uses multi‐bit architecture and shows high‐density and low‐energy advantages over hybrid NV/volatile FFs in the application of the NV register file. Sim‐ulation results show that the proposed spin‐Hall‐assisted NVFF saves ～31% storage density and ～32% energy dissipation compared with the conventional STT‐NVFF. Moreover, the reliability of MTJ barrier is enhanced due to the reduction of the write voltage. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Characterisation of the different hands in the composition of a 14th century breviary by means of portable XRF analysis and complementary techniques

A 14th‐century breviary known as Breviario di San Michele della Chiusa, produced at the disposal of the monks of Sacra di San Michele abbey (near Turin, Italy) has been analysed in order to identify the different authors who contributed in its making. The study aimed at revealing how many scribes composed the text and the musical notations and how many artists worked for miniatures and for the decorations of initials. All inks and decorative features have been analysed by means of portable X‐ray fluorescence spectrometry for determining elemental distribution and by means of ultraviolet–Visible diffuse reflectance spectrophotometry with optic fibres and spectrofluorimetry for identifying colourants. The results on non‐invasive measurements highlighted that at least 11 persons (six scribes for the text, two scribes for the musical notations, two artists for initials and filigrees and one artist for the full‐page miniature at f. 208v) were at work at the Breviario. Moreover, the black inks used for text and notes have an anomalous composition, being iron gall inks with a larger than usual amount of zinc, possibly as a consequence of the use of vitriols made from goslarite; this suggests that the scribes could come from Northern Europe. The presence of traces of bismuth in blue paints also suggested the provenance of azurite from Central or Northern Europe. Copyright © 2017 John Wiley & Sons, Ltd.     

Mathematical models for the non‐isothermal Johnson–Segalman viscoelasticity in porous media: stability and wave propagation

We present a nonlinear model for Johnson–Segalman type polymeric fluids in porous media, accounting for thermal effects of Oldroyd‐B type. We provide a thermodynamic development of the Darcy's theory, which is consistent with the interlacement between thermal and viscoelastic relaxation effects and diffusion phenomena. The appropriate invariant convected time derivative for the flux vector and the stress tensor is discussed. This is performed by investigating the local balance laws and entropy inequality in the spatial configuration, within the single‐fluid approach. For constant parameters, our thermomechanical setting is of Jeffreys type with two delay time parameters, and hence, in the linear/linearized version, it is strictly related to phase‐lag theories within first‐order Taylor approximations. A detailed spectral analysis is carried out for the linearized version of the model, with a scrutiny to some significant limit situations, enhancing the stabilizing effects of the dissipative and elastic mechanisms, also for retardation responses. For polymeric liquids, rheological aspects, wave propagation properties and analogies with other theories with lagging are pointed out. Copyright © 2014 John Wiley & Sons, Ltd.