Magnetic Resonance Elastography and Its Application in Brain Diseases

Magnetic resonance elastography (MRE) is a method to estimate biomechanical properties of soft tissues by recording shear wave propagation using MR imaging. The wave excitation is produced by an external actuator and the properties are inversely calculated based on the wave equation. Biomechanical properties of brain tissue, especially the viscoelastic properties, are closely related to the growth, aging, and disease of brain. This review first introduces the theoretical background of MRE, followed by the physical meaning of the viscoelastic parameters and wave equations used for inversion. Scanning protocols for MRE, along with a specific example focusing on brain MRE, are also described. The paper presents various clinical applications of brain MRE, with a specific emphasis on brain tumors and neurodegenerative diseases. The application of viscoelastic properties as biomarkers in fundamental scientific research, disease diagnosis, and prognosis is discussed. We further highlight the current trends in brain MRE research covering both technical and clinical aspects, providing a reference for future neuroscience research and clinical applications

Sequential Doping of Ladder-Type Conjugated Polymers for Thermally Stable n-Type Organic Conductors

Doping of organic semiconductors is a powerful tool to optimize the performance of various organic (opto)electronic and bioelectronic devices. Despite recent advances, the low thermal stability of the electronic properties of doped polymers still represents a significant obstacle to implementing these materials into practical applications. Hence, the development of conducting doped polymers with excellent long-term stability at elevated temperatures is highly desirable. Here, we report on the sequential doping of the ladder-type polymer poly-(benzimidazobenzophenanthroline) (BBL) with a benzimidazole-based dopant (i.e., N-DMBI). By combining electrical, UV-vis/infrared, X-ray diffraction, and electron paramagnetic resonance measurements, we quantitatively characterized the conductivity, Seebeck coefficient, spin density, and microstructure of the sequentially doped polymer films as a function of the thermal annealing temperature. Importantly, we observed that the electrical conductivity of N-DMBI-doped BBL remains unchanged even after 20 h of heating at 190 degrees C. This finding is remarkable and of particular interest for organic thermoelectrics.Funding Agencies|Swedish Research CouncilSwedish Research Council [2016-03979]; AForsk [18-313, 19310]; Olle Engkvists Stiftelse [204-0256]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Finnish Cultural FoundationFinnish Cultural Foundation; Finnish Foundation for Technology Promotion; Knut and Alice Wallenberg FoundationKnut &amp; Alice Wallenberg Foundation; Knut and Alice Wallenberg FoundationKnut &amp; Alice Wallenberg Foundation [Dnr KAW 2014.0041]</p

Monolithically-grained perovskite solar cell with Mortise-Tenon structure for charge extraction balance

Abstract Although the power conversion efficiency values of perovskite solar cells continue to be refreshed, it is still far from the theoretical Shockley-Queisser limit. Two major issues need to be addressed, including disorder crystallization of perovskite and unbalanced interface charge extraction, which limit further improvements in device efficiency. Herein, we develop a thermally polymerized additive as the polymer template in the perovskite film, which can form monolithic perovskite grain and a unique “Mortise-Tenon” structure after spin-coating hole-transport layer. Importantly, the suppressed non-radiative recombination and balanced interface charge extraction benefit from high-quality perovskite crystals and Mortise-Tenon structure, resulting in enhanced open-circuit voltage and fill-factor of the device. The PSCs achieve certified efficiency of 24.55% and maintain >95% initial efficiency over 1100 h in accordance with the ISOS-L-2 protocol, as well as excellent endurance according to the ISOS-D-3 accelerated aging test