Materials Sciences (United States)

Aurivillius structured Bi6Ti3Fe1.5Mn0.5O18 (B6TFMO) has emerged as a rare room temperature multiferroic, exhibiting reversible magnetoelectric switching of ferroelectric domains under cycled magnetic fields. This layered oxide presents exceptional avenues for advancing data storage technologies owing to its distinctive ferroelectric and ferrimagnetic characteristics. Despite its immense potential, a comprehensive understanding of the underlying mechanisms driving multiferroic behavior remains elusive. Herein, we employ atomic resolution electron microscopy to elucidate the interplay of octahedral tilting and atomic-level structural distortions within B6TFMO, associating these phenomena with functional properties. Fundamental electronic features at varying bonding environments within this complex system are scrutinized using electron energy loss spectroscopy (EELS), revealing that the electronic nature of the Ti4+ cations within perovskite BO6 octahedra is influenced by position within the Aurivillius structure. Layer-by-layer EELS analysis shows an ascending crystal field splitting (Δ) trend from outer to center perovskite layers, with an average increase in Δ of 0.13 ± 0.06 eV. Density functional theory calculations, supported by atomic resolution polarization vector mapping of B-site cations, underscore the correlation between the evolving nature of Ti4+ cations, the extent of tetragonal distortion and ferroelectric behavior. Integrated differential phase contrast imaging unveils the position of light oxygen atoms in B6TFMO for the first time, exposing an escalating degree of octahedral tilting toward the center layers, which competes with the magnitude of BO6 tetragonal distortion. The observed octahedral tilting, influenced by B-site cation arrangement, is deemed crucial for juxtaposing magnetic cations and establishing long-range ferrimagnetic order in multiferroic B6TFMO.

Abstract The first demonstration of converse piezoelectricity in 3D fluids is presented by measuring a linear electromechanical effect in ferroelectric nematic liquid crystals. The observed piezoelectric coupling constant below 6 kHz electric field is larger than 1 nC/N, comparable to, or better than, values for the strongest solid piezoelectric materials. Symmetry considerations indicate that the alignment of the ferroelectric nematic liquid crystal in the experimental study is not optimized, so the observed signal is likely only a fraction of the theoretically achievable signal. Understanding the electromechanical response of ferroelectric nematics will enable mechanical energy harvesting and open up a new avenue for developing fluid actuators, micro positioners, and electrically tunable optical lenses.

A novel contact–separation triboelectric generatorconceptis proposed in this paper, which consists of a limestone-based mountingputty and a metallized polyester (PET/Al) sheet. This is an attemptto explore tacky materials for power generation and extend the operationalfrequency bandwidth compared to existing TriboElectric NanoGenerators(TENGs). Moreover, the proposed design is very cost-effective andeasy to build. Unlike traditional TENGs, which generate power solelydue to a charge developing on the surface, the putty also replieson charge developed inside the material. Parametric study was conductedto determine the optimal putty thickness in a shaker test at 40 Hz.It was found that a putty layer at 0.6 mm thick yielded maximum powergeneration. During the separation phase, the electrical breakdownbetween triboelectric layers allows most existing electrons to flowback from the ground due to rapid charge removal at the interface.We are able to achieve a peak power of 16 mW in a shaker test at 40Hz with an electrical load of 8 MΩ, which corresponds to a powerdensity of 25.6 W/m2. A peak power of 120 mW in a manualprototype generator is achieved, which operates at approximately 2Hz. Since putty material has less tackiness than double-sided tape,we are able to expand the frequency bandwidth up to 80 Hz, which issignificantly higher than a TENG (typically <10 Hz). The mountingputty material contains limestone with approximate 31 nm of mean grainsize mixed with synthetic rubber materials. Elasticity from rubberand the nanohardness of calcite crystallites allow us to operate aputty generator repeatedly without the concern of grain fracture.Also, a durability test was conducted with up to 250,000 contact–separationcycles. In summary, comparable performance is achieved in the proposedputty generator to benefit energy harvesting and sensor applications.

Field-induced domain wall dynamics in ferroelectric materials underpins multiple applications ranging from actuators to information technology devices and necessitates a quantitative description of the associated mechanisms including giant electromechanical couplings, controlled non-linearities, or low coercive voltages. While the advances in dynamic Piezoresponse Force Microscopy measurements over the last two decades have rendered visualization of polarization dynamics relatively straightforward, the associated insights into the local mechanisms have been elusive. Here we explore the domain dynamics in model polycrystalline materials using a workflow combining deep learning-based segmentation of the domain structures with non-linear dimensionality reduction using multilayer rotationally-invariant autoencoders (rVAE). The former allows unambiguous identification and classification of the ferroelectric and ferroelastic domain walls. The rVAE discover the latent representations of the domain wall geometries and their dynamics, thus providing insight into the intrinsic mechanisms of polarization switching, that can further be compared to simple physical models. The rVAE disentangles the factors affecting the pinning efficiency of ferroelectric walls, offering insights into the correlation of ferroelastic wall distribution and ferroelectric wall pinning.

Despite its limited analytical specificity and ruggedness, the thiobarbituric acid reactive substances (TBARS) assay has been widely used as a generic metric of lipid peroxidation in biological fluids. It is often considered a good indicator of the levels of oxidative stress within a biological sample, provided that the sample has been properly handled and stored. The assay involves the reaction of lipid peroxidation products, primarily malondialdehyde (MDA), with thiobarbituric acid (TBA), which leads to the formation of MDA-TBA2 adducts called TBARS. TBARS yields a red-pink color that can be measured spectrophotometrically at 532 nm. The TBARS assay is performed under acidic conditions (pH = 4) and at 95 °C. Pure MDA is unstable, but these conditions allow the release of MDA from MDA bis(dimethyl acetal), which is used as the analytical standard in this method. The TBARS assay is a straightforward method that can be completed in about 2 h. Preparation of assay reagents are described in detail here. Budget-conscious researchers can use these reagents for multiple experiments at a low cost rather than buying an expensive TBARS assay kit that only permits construction of a single standard curve (and thus can only be used for one experiment). The applicability of this TBARS assay is shown in human serum, low density lipoproteins, and cell lysates. The assay is consistent and reproducible, and limits of detection of 1.1 μM can be reached. Recommendations for the use and interpretation of the spectrophotometric TBARS assay are provided.

We show that a doped spin-1/2 ladder with antiferromagnetic intra-chain and ferromagnetic inter-chain coupling is a symmetry protected topologically non-trivial Luttinger liquid. Turning on a large easy-plane spin anisotropy drives the system to a topologically-trivial Luttinger liquid. Both phases have full spin gaps and exhibit power-law superconducting pair correlation. The Cooper pair symmetry is singlet $d_{xy}$ in the non-trivial phase and triplet $S_z=0$ in the trivial phase. The topologically non-trivial Luttinger liquid exhibits gapless spin excitations in the presence of a boundary, and it has no non-interacting or mean-field theory analog even when the fluctuating phase in the charge sector is pinned. As a function of the strength of spin anisotropy there is a topological phase transition upon which the spin gap closes. We speculate these Luttinger liquids are relevant to the superconductivity in metalized integer spin ladders or chains.

We have investigated the association interactions between the fluorescent dyes TAMRA, Cy3B and Alexa-546 and the DNA deoxynucleoside monophosphates by means of fluorescence quenching and fluorescence correlation spectroscopy (FCS). The interactions of Cy3B and TAMRA with the nucleotides produce a decrease in the apparent diffusion coefficient of the dyes, which result in a shift toward longer times in the FCS autocorrelation decays. Our results with Cy3B demonstrate the existence of Cy3B-nucleotide interactions that do not affect the fluorescence intensity or lifetime of the dye significantly. The same is true for TAMRA in the presence of dAMP, dCMP and dTMP. In contrast, the diffusion coefficient of Alexa 546 remains practically unchanged even at high concentrations of nucleotide. These results demonstrate that interactions between this dye and the four dNMPs are not significant. The presence of the negatively charged sulfonates and the bulky chlorine atoms in the phenyl group of Alexa 546 possibly prevent strong interactions that are otherwise possible for TAMRA. The characterization of dye-DNA interactions is important in biophysical research because they play an important role in the interpretation of energy transfer experiments, and because they can potentially affect the structure and dynamics of the DNA.

در این تحقیق طی یک روش ساده و مؤثر تخلخل?های درشت در ساختار شیشه از طریق ایجاد گاز در ترکیب شیشه در دمای بالا به دست آمد. پس از تهیه شیشه از روش ذوب، ماده حاصل به صورت پودر آسیاب شده و با مقادیر مختلف کربنات کلسیم مخلوط گردید و به صورت قرص پرس گردید. نمونه ها در دمای ˚C1150 قرار داده شدند که در آن دما در اثر تجزیه کربنات کلسیم و تولید گاز دی اکسید کربن و به دلیل نرم بودن شیشه ساختار متخلخل ایجاد می گردد. مورفولوژی تخلخل ها کروی شکل بوده و مقدار و سایز آنها بستگی به مقدار کربنات کلسیم مورد استفاده دارد. در این روش با استفاده از 8/1 درصد وزنی کربنات کلسیم حدود 60 درصد تخلخل در شیشه ایجاد شد که تخلخل�هایی با ابعاد حدود 60 میکرومتر نیز در آنها وجود داشت. عملیات حرارتی برای ایجاد تخلخل باعث تبلور شیشه گردید ولی در زیست فعالی آن تأثیری نداشت.

Cancer cell line bioassay-guided separation of an extract from the fungus Aspergillus phoenicis collected in Saskatchewan, Canada, resulted in the isolation of three new constituents designated asperlactone (1), aspergillol A (2), and aspergillol B (3), accompanied by four previously known constituents: asperic acid (4), hexylitaconic acid (5), methyl 2-hydroxyphenylacetate (6), and methyl 4-hydroxyphenylacetate (7). The structure of each was determined by analyses of high-resolution mass spectra and high-field NMR data. Asperic acid (4) was found to inhibit growth of the murine lymphocytic leukemia P388 (ED 50 0.18 μg/mL) and a panel of human cancer cell lines (GI 50 1.7-2.0 μg/mL; pancreas, breast, CNS, lung, colon, and prostate), while aspergillol A (2) showed moderate inhibition against the breast adenocarcinoma MCF-7 (GI 50 7.2 μg/mL).