Possible Persistence of Multiferroic Order down to Bilayer Limit of van der Waals Material NiI2.

Realizing a state of matter in two dimensions has repeatedly proven a novel route of discovering new physical phenomena. Van der Waals (vdW) materials have been at the center of these now extensive research activities. They offer a natural way of producing a monolayer of matter simply by mechanical exfoliation. This work demonstrates that the possible multiferroic state with coexisting antiferromagnetic and ferroelectric orders persists down to the bilayer flake of NiI2. By exploiting the optical second-harmonic generation technique, both magnitude and direction of the ferroelectric order, arising from the cycloidal spin order, are successfully traced. The possible multiferroic state's transition temperature decreases from 58 K for the bulk to about 20 K for the bilayer. Our observation will spur extensive efforts to demonstrate multifunctionality in vdW materials, which have been tried mostly by using heterostructures of singly ferroic ones until now.

Production of trans-cinnamic acid by whole-cell bioconversion from L-phenylalanine in engineered Corynebacterium glutamicum.

BACKGROUND: trans-cinnamic acid (t-CA) is a phenylpropanoid with a broad spectrum of biological activities including antioxidant and antibacterial activities, and it also has high potential in food and cosmetic applications. Although significant progress has been made in the production of t-CA using microorganisms, its relatively low product titers still need to be improved. In this study, we engineered Corynebacterium glutamicum as a whole-cell catalyst for the bioconversion of L-phenylalanine (L-Phe) into t-CA and developed a repeated bioconversion process. RESULTS: An expression module based on a phenylalanine ammonia lyase-encoding gene from Streptomyces maritimus (SmPAL), which mediates the conversion of L-Phe into t-CA, was constructed in C. glutamicum. Using the strong promoter PH36 and ribosome binding site (RBS) (in front of gene 10 of the T7 phage), and a high-copy number plasmid, SmPAL could be expressed to levels as high as 39.1% of the total proteins in C. glutamicum. Next, to improve t-CA production at an industrial scale, reaction conditions including temperature and pH were optimized; t-CA production reached up to 6.7 mM/h in a bioreactor under optimal conditions (50 °C and pH 8.5, using NaOH as base solution). Finally, a recycling system was developed by coupling membrane filtration with the bioreactor, and the engineered C. glutamicum successfully produced 13.7 mM of t-CA (24.3 g) from 18.2 mM of L-Phe (36 g) and thus with a yield of 75% (0.75 mol/mol) through repetitive supplementation. CONCLUSIONS: We developed a highly efficient bioconversion process using C. glutamicum as a biocatalyst and a micromembrane-based cell recycling system. To the best of our knowledge, this is the first report on t-CA production in C. glutamicum, and this robust platform will contribute to the development of an industrially relevant platform for the production of t-CA using microorganisms.

Real-time dynamics of angular momentum transfer from spin to acoustic chiral phonon in oxide heterostructures.

Chiral phonons have recently been explored as a novel degree of freedom in quantum materials. The angular momentum carried by these quasiparticles is generated by the breaking of chiral degeneracy of phonons, owing to the chiral lattice structure or the rotational motion of ions of the material. In ferromagnets, a mechanism for generating non-equilibrium chiral phonons has been suggested, but their temporal evolution, which obeys Bose-Einstein statistics, remains unclear. Here we report the real-time dynamics of thermalized chiral phonons in an artificial superlattice composed of ferromagnetic metallic SrRuO3 and non-magnetic insulating SrTiO3. Following the photo-induced ultrafast demagnetization in the SrRuO3 layer, we observed the appearance of a magneto-optic signal in the superlattice, which is absent in the SrRuO3 single films. This magneto-optic signal exhibits thermally driven dynamic properties and a clear correlation with the thickness of the non-magnetic SrTiO3 layer, implying that it originates from thermalized chiral phonons. We use numerical calculations considering the magneto-elastic coupling in SrRuO3 to validate our experimental observations and the angular momentum transfer mechanism between the lattice and spin systems in ferromagnetic systems and also to the non-magnetic system.

Deterministic Orientation Control of Ferroelectric HfO2 Thin Film Growth by a Topotactic Phase Transition of an Oxide Electrode.

The scale-free ferroelectricity with superior Si compatibility of HfO2 has reawakened the feasibility of scaled-down nonvolatile devices and beyond the complementary metal-oxide-semiconductor (CMOS) architecture based on ferroelectric materials. However, despite the rapid development, fundamental understanding, and control of the metastable ferroelectric phase in terms of oxygen ion movement of HfO2 remain ambiguous. In this study, we have deterministically controlled the orientation of a single-crystalline ferroelectric phase HfO2 thin film via oxygen ion movement. We induced a topotactic phase transition of the metal electrode accompanied by the stabilization of the differently oriented ferroelectric phase HfO2 through the migration of oxygen ions between the oxygen-reactive metal electrode and the HfO2 layer. By stabilizing different polarization directions of HfO2 through oxygen ion migration, we can gain a profound understanding of the oxygen ion-relevant unclear phenomena of ferroelectric HfO2.

Giant Enhancement of Electron-Phonon Coupling in Dimensionality-Controlled SrRuO3 Heterostructures.

Electrons in crystals interact closely with quantized lattice degree of freedom, determining fundamental electrodynamic behaviors and versatile correlated functionalities. However, the strength of the electron-phonon interaction is so far determined as an intrinsic value of a given material, restricting the development of potential electronic and phononic applications employing the tunable coupling strength. Here, it is demonstrated that the electron-phonon coupling in SrRuO3 can be largely controlled by multiple intuitive tuning knobs available in synthetic crystals. The coupling strength of quasi-2D SrRuO3 is enhanced by ≈300-fold compared with that of bulk SrRuO3 . This enormous enhancement is attributed to the non-local nature of the electron-phonon coupling within the well-defined synthetic atomic network, which becomes dominant in the limit of the 2D electronic state. These results provide valuable opportunities for engineering the electron-phonon coupling, leading to a deeper understanding of the strongly coupled charge and lattice dynamics in quantum materials.

Higher Fat-Related Body Composition Measurement and Lower Resting-State Inter-Network Functional Connectivity of APOE ε4 Carrier in Mild Cognitive Impairment Patients With Aß Deposition.

OBJECTIVE: We aimed to evaluate the impact of interaction between APOE ε4 carrier status and body composition measurements on intra- and inter-regional functional connectivity (FC) in mild cognitive impairment (MCI) patients with Aß deposition. METHODS: MCI patients with and without APOE ε4 allele (carrier, n=86; non-carrier, n=95) underwent neuropsychological battery, resting-state functional magnetic resonance imaging scans, positron emission tomography scans with [18F]flutemetamol, and bioelectrical impedance analysis for measuring body composition. We employed a priori defined regions of interest to investigate the intra- and inter-network FC profiles of default mode network (DMN), central executive network (CEN), and salience network. RESULTS: There was a significant interaction of APOE ε4 carrier status with body fat mass index, visceral fat area, and waist-hip circumference ratio for inter-network FC between DMN and CEN, contributing higher fat-related body composition measurements in the APOE ε4 carrier with lower DMN-CEN FC. CONCLUSION: The present results highlight the detrimental effect of APOE ε4 carrier status on the associations between the fat-related body composition measurements and FC in the MCI patients with Aß accumulation.

Production of Cinnamaldehyde through Whole-Cell Bioconversion from trans-Cinnamic Acid Using Engineered Corynebacterium glutamicum.

Cinnamaldehyde (CAD) has various applications in foods and pharmaceuticals and has gained prominence as a potent nematicide in agricultural research owing to its nematicidal activity. However, conventional methods of CAD production, including extraction from plants or organic chemical synthesis, are environmentally hazardous and limit its utilization for downstream applications. Here, we engineered Corynebacterium glutamicum as a whole-cell biocatalyst for the efficient bioconversion of trans-cinnamic acid (t-CA) into CAD. An expression module of Mycobacterium phlei carboxylic acid reductase was constructed for the conversion of t-CA to CAD. Additionally, the putative dehydrogenase-related genes (dkgA, adhC, and cg1176) responsible for the conversion of CAD to cinnamyl alcohol were deleted from the engineered C. glutamicum strain to prevent the loss of CAD. Furthermore, as the conversion is NADPH-dependent, we investigated the conversion efficiency by exchanging the putative promoter region for the zwf gene, which encodes glucose-6-phosphate dehydrogenase, with a strong promoter to increase the NADPH pool. Finally, a bioconversion platform using C. glutamicum as a whole-cell biocatalyst was developed by deleting the vdh gene, which is involved in the reverse conversion of CAD to t-CA. Taken together, a 100% conversion yield of 1.1 g/L CAD from 1.2 g/L t-CA was obtained within 30 min.

Alkali fusion using sodium carbonate for extraction of vanadium and tungsten for the preparation of synthetic sodium titanate from spent SCR catalyst.

Alkali fusion method to extract vanadium and tungsten from spent SCR catalyst and to simultaneously prepare synthetic sodium titanate for the purpose of preparation of feedstock for TiO2 manufacturing by hydrometallurgical processing was investigated. Based on the Na2O-TiO2 phase diagram and experimentally obtained results, appropriate alkali-fusion temperature and molar ratio (MOx/Na2O + MOx) were determined to prepare soluble vanadium, tungsten salts, and sodium titanate. As results, the extraction efficiency of vanadium and tungsten was >99% and sodium titanate as feedstock for making TiO2 was obtained under the following alkali fusion conditions: Temperature, 950 °C; reaction time, 20 min; molar ratio, 0.5. When the molar ratio (MOx/Na2O + MOx) was less than 0.5, complete liquidized product (eutectic melt of the feedstock and Na2CO3) was obtained at the given conditions. This method, compared to conventional alkali roasting, is advantageous for rapid synthesis of water-soluble compounds for leaching of vanadium and tungsten, and for use as feedstock for the preparation of TiO2 by hydrometallurgical route.