Pohang University of Science and Technology

Dopamine (DA) is an essential neuromodulator that underlies critical aspects of cognitive processes, motor function, and reward systems. Disruptions in DA signaling contribute to various neurodegenerative diseases, including Parkinson's disease (PD). Despite its important role in neuronal function, the impact of DA release/uptake on neurochemical imbalances during neuronal development remains unclear. We propose a novel application of near-infrared catecholamine nanosensor (NIRCat) for real-time visualization of DA neurotransmission among neurodegenerative disease cells. The near-infrared fluorescence (900–1400 nm) of NIRCat allows the semi-quantitative measurement of DA release in living neurons and offers insights into cellular dynamics and neuropathological development. In this study, we applied NIRCat to elucidate DA release in human induced pluripotent stem cells (hiPSCs)-derived dopaminergic neurons from both healthy control and PD patient carrying GBA1 mutations. We accurately quantified electrically stimulated DA release events, identifying distinct ‘hotspots’ of activity across DA neuronal cells. Our findings present a significantly enhanced spatial and temporal resolution of DA signaling, providing a deeper understanding of the role and balance of DA release in the progression of neurodegenerative disease.

In this paper we formalize in rewriting logic the intended discrete-event semantics of the Lingua Franca coordination language for cyber-physical systems in the simplified setting where each reaction has exactly one trigger. We then show how such Lingua Franca models can be simulated and model checked using Maude, and provide functionality that should make the formal analysis easy to perform also for the Maude non-expert. We illustrate such Maude verification on a number of existing Lingua Franca models, including of a car driver assistance system and of train door controllers. To the best of our knowledge, this is the first verification framework for Lingua Franca that captures the intended semantics of the language, and which therefore provides correct (and state-space efficient) model checking analysis for Lingua Franca.

Nonlinear microscopy provides excellent depth penetration and axial sectioning for 3D imaging, yet widespread adoption is limited by reliance on expensive ultrafast pulsed lasers. This work circumvents such limitations by employing rare‐earth doped upconverting nanoparticles (UCNPs), specifically Yb³⁺/Tm³⁺ co‐doped NaYF4 nanocrystals, which exhibit strong multimodal nonlinear optical responses under continuous‐wave (CW) excitation. These UCNPs emit multiple wavelengths at UV (λ ≈ 450 nm), blue (λ ≈ 450 nm), and NIR (λ ≈ 800 nm), whose intensities are nonlinearly governed by excitation power. Exploiting these properties, multi‐colored nonlinear emissions enable functional imaging of cerebral blood vessels in deep brain. Using a simple optical setup, high resolution in vivo 3D imaging of mouse cerebrovascular networks at depths up to 800 µmm is achieved, surpassing performance of conventional imaging methods using CW lasers. In vivo cerebrovascular flow dynamics is also visualized with wide‐field video‐rate imaging under low‐powered CW excitation. Furthermore, UCNPs enable depth‐selective, 3D‐localized photo‐modulation through turbid media, presenting spatiotemporally targeted light beacons. This innovative approach, leveraging UCNPs' intrinsic nonlinear optical characteristics, significantly advances multimodal nonlinear microscopy with CW lasers, opening new opportunities in bio‐imaging, remote optogenetics, and photodynamic therapy.

Li1+xFe1‐xPO4 (Li‐rich LFP) has been proposed as an alternative to address low ionic and electronic conductivity of stoichiometric LiFePO4 (LFP). However, comprehensive studies investigating the impact of the carbon coating process on crystal structure and electrochemical performance during the synthesis of Li‐rich LFP are still lacking. In particular, the characteristics of carbon precursor and calcination atmosphere significantly influence formation of crystal structure and electrochemical properties of the Li‐rich LFP, underlining the necessity for further investigation. In this study, we compare two synthesis process: introducing carbon precursor before formation of LFP crystal structure (C/BLF) and adding it an additional calcination step after structure has formed (C/ALF). The C/ALF process sample has a larger unit cell volume and denser coating layer. As a result, the C/ALF sample exhibits a lower overpotential (0.54 V) and a higher discharge capacity (~134.13 mAhg‐1) than C/BLF sample. These findings elucidate the influence of carbon coating process sequence on crystal structure and electrochemical performance during the synthesis of Li‐rich LFP.

Antiferromagnetic spin fluctuations are the most promising candidate as the pairing glue of high critical temperature (Tc) superconductivity in cuprates. However, many-body states and intertwined orders have made it difficult to determine how electrons couple with fluctuating spins to form Cooper pairs. Recent experimental and theoretical studies have suggested spin fluctuation-driven quasiparticle band folding, but the relationship between the resultant Fermi pockets and superconductivity remains unclear. Here, using angle-resolved photoemission spectroscopy and numerical simulations, we show a proportional relationship between Tc and the quasiparticle weight of the incipient hole pocket near the nodal point in electron-doped Pr1−xLaCexCuO4±δ. Through complementary muon spin spectroscopy measurements, we uncover that the hole pocket forms only in the regime of the fluctuating antiferromagnetic ground state around a presumed quantum critical point. Our observations highlight the significance of the electron-spin fluctuation interaction in enhancing the hole pocket and consequently driving superconductivity.

We report the influence of microstructural disorder, introduced by varying nitrogen content, on the vortex dissipation mechanisms of molybdenum nitride thin films grown by reactive sputtering at room temperature. The 22 nm-thick films were deposited at a total pressure of 0.66 Pa using (Ar+N2) mixtures with nitrogen concentrations of 7.5%, 10%, 15%, and 20%. Under these conditions, the superconducting critical temperature (Tc) gradually decreases from approximately 7.6 K to 6.4 K as the N2 concentration in the reactive mixture increases. This reduction in Tc is attributed to increased disorder induced by interstitial nitrogen and amorphous phases, affecting the microstructure of the films. Using current–voltage curves, we investigated vortex instability and the corresponding vortex velocities as functions of temperature and magnetic field. While inhomogeneities and pinning centers are expected to reduce vortex velocities due to localized heating in the bridge, we observed that the velocity plateau at moderate and high fields—typically indicative of a uniform quasiparticle distribution—depends on the microstructure of the samples (linked to Tc) and scales with the absolute temperature at which measurements were conducted. For comparison, nitrogen-doped W thin films with Tc ≈ 4.6 K, and a plateau in the vortex velocities at T = 3 K, show a good match with the values observed in molybdenum nitride samples at higher temperatures. This finding suggests that, in addition to the disorder and intrinsic superconducting properties of the films, thermally activated phonons, potentially associated with the silicon substrate, contribute to the enhancement of vortex velocities within the analyzed temperature range.

Herein, we report the impact of thermal annealing on the metal (Fe-3d)-oxygen (O-2p) hybridization in zinc ferrite thin films using the angle-dependent near-edge X-ray absorption fine structure (NEXAFS) technique. Zinc ferrite thin films of thickness ~ 100 nm are grown on MgO (200) substrates using radio frequency sputtering. Further, these as-grown films are annealed at temperatures 200, 400, and 600 °C in an air atmosphere to improve the crystallinity of the films. NEXAFS studies on Fe L2,3-edge and O K-edge reveal the importance of thermal annealing on the modification of the electronic structure of zinc ferrite films. Angle-dependent NEXAFS studies on Fe L2,3-edge suggest that the variation in electronic structure caused by the metal–oxygen hybridization in Zinc Ferrite is influenced by the film’s crystallinity through the annealing process. Further, the nature of metal–oxygen hybridization in zinc ferrite is confirmed by the O K pre-edge angle-dependent NEXAFS studies.

Akkermansia muciniphila, a promising candidate for next-generation probiotics, exhibits significant genomic diversity, classified into several distinct clades (AmI to AmIV). Notably, a single Akkermansia clade tends to predominate within individual hosts, with co-occurrence of different clades being rare. The mechanisms driving such clade-specific exclusion remain unclear. Here, we show that extracellular vesicles (EVs) derived from AmII clade inhibit the growth of clade I (AmI), conferring a competitive advantage to AmII. Moreover, we observe clade-specific immunoglobulin A (IgA) responses, where AmII clade-specific IgAs, induced by EVs from AmII, facilitate niche occupancy and competitive exclusion of AmI. These findings provide insights into the competitive dynamics of A. muciniphila clades and suggest that future personalized microbiome interventions could be optimized by considering the clade composition of A. muciniphila in individual hosts.

Electrochemical random-access memory devices are promising for analog cross-point array-based artificial intelligence accelerators due to their high stability and programmability. However, understanding their switching mechanism is challenging due to complex multilayer structures and the high resistivity of oxide materials. Here, we fabricate multi-terminal Hall-bar devices and conduct alternating current magnetic parallel dipole line Hall measurements to extract transport parameters. Through variable-temperature Hall measurements, we determine the oxygen donor level at approximately 0.1 eV in tungsten oxide and reveal that conductance potentiation even at low temperatures results from increased mobility and carrier density. This behavior is linked to reversible electronic and atomic structure changes, supported by density functional theory calculations. Our findings enhance the understanding of electrochemical random-access memory switching mechanisms and provide insights for improving high-performance, energy-efficient artificial intelligence computation in analog hardware.

The stacking sequence of two-dimensional hexagonal boron nitride (hBN) is a critical factor that determines its polytypes and its distinct physical properties. Although most hBN layers adopt the thermodynamically stable AA′ stacking sequence, achieving alternative stacking configurations has remained a long-standing challenge. Here we demonstrate the scalable synthesis of hBN featuring unprecedented AA stacking, where atomic monolayers align along the c axis without any translation or rotation. This previously considered thermodynamically unfavourable hBN polytype is achieved through epitaxial growth on a two-inch single-crystalline gallium nitride wafer, using a metal–organic chemical vapour deposition technique. Comprehensive structural and optical characterizations, complemented by theoretical modelling, evidence the formation of AA-stacked multilayer hBN and reveal that hBN nucleation on the vicinal gallium nitride surface drives the unidirectional alignment of layers. Here electron doping plays a central role in stabilizing the AA stacking configuration. Our findings provide further insights into the scalable synthesis of engineered hBN polytypes, characterized by unique properties such as large optical nonlinearity.

Cyclic polymers are very attractive due to their unique properties; however, so far, they have simple and less reactive backbone structures due to synthetic limitations, restricting their further post‐modification. Notably, allenes present a potentially useful platform in polymer chemistry due to their well‐established toolbox in organic chemistry. Nevertheless, the biggest challenge remains in synthesizing poly(allenamer)s with high allene contents or polymerization efficiency, as well as synthesizing different types of cyclic poly(allenamer)s. Herein, we synthesized linear and cyclic poly(allenamer)s via ring‐opening metathesis polymerization (ROMP) and ring‐expansion metathesis polymerization (REMP), employing highly efficient cyclic–alkyl–amino–carbene (CAAC) ruthenium catalysts. Mechanistic studies suggested CAAC ligands enhanced stability of propagating Ru vinylidene, enabling various linear and cyclic poly(allenamer)s with turnover number up to 1360 and molecular weight reaching 549 kDa. Their cyclic architecture was thoroughly characterized by multiangle light scattering size‐exclusion chromatography (MALS SEC) with viscometer. Moreover, controlled ROMP of a highly reactive α‐substituted cyclic allene was achieved using third‐generation Grubbs' catalyst. Finally, we demonstrated highly efficient and selective post‐modifications on poly(allenamer)s with primary and secondary alcohols. This broadens the scope of cyclic polymers with improved efficiency and structural control, affording a practical platform for diverse macromolecules.

To extend the lifespan of Ni‐rich layered oxide cathodes, doping, coating, and particle‐morphology optimization strategies have been explored, though these approaches often result in reduced reversible capacity. In this study, a novel LiNi0.92Co0.04Mn0.04O2 cathode is introduced featuring gradients in Li concentration and particle size at the secondary‐particle level. By controlling the oxygen partial pressure during synthesis, enhanced cycle stability is achieved without compromising the capacity of this unique structure. Contrary to common knowledge, the superior performance of cathode materials synthesized under oxygen‐deficient conditions is reported, delivering a remarkable capacity of 226.7 mAh g⁻¹ and robust cycle retention of 87.23% after 200 cycles. These electrodes achieve 85.08% capacity retention at 2 C/0.1 C, demonstrating excellent rate performance. Comprehensive diffraction and microscopy analyses identify secondary particles with Li‐excess structures on their surfaces (characterized by larger primary particles) and stoichiometric structures in the core (featuring smaller primary particles). This dual‐gradient structure enhances performance by suppressing surface reactions and stabilizing the bulk. Furthermore, the electrodes retain pristine microstructure during electrochemical cycling, minimize lattice contraction (3.86%), and suppress H2‐to‐H3 transitions. This study highlights the potential of using Li concentration gradients to mitigate surface side reactions, paving the way for the development of durable, high‐capacity, and cost‐effective cathodes.

Cascade enzymatic reactions in living organisms are fundamental reaction mechanisms in coordinating various complex biochemical processes such as metabolism, signal transduction, and gene regulation. Many studies have attempted to mimic cascade reactions using nanoparticles with enzyme-like activity; however, precisely tuning each reaction within complex networks to enhance the catalytic activity remains challenging. Here, we present enzyme-like chiral plasmonic nanoparticles for optically tunable catalytic cancer therapy. We create chiral plasmonic nanoparticles with glucose oxidase (GOD) and peroxidase (POD) activities, followed by introducing circularly polarized light (CPL). By sequentially activating GOD and POD reactions with right-handed CPL (RC) followed by left-handed CPL (LC), we achieve 1.25- and 1.9-fold enhanced catalytic performance (overall 1.3 times enhancement) compared to non-controlled cascade reactions by creating an optimal acidic environment for the subsequent reaction. Moreover, the D-Au nanoparticle shows a 2-fold higher binding selectivity to D-glucose substrates, attributed to chirality matching. In both cell studies and male mouse models, sequentially irradiated groups (RC followed by LC) exhibit the highest radical generation and the most efficient treatment outcomes compared to the other systems under different irradiation conditions. We believe that our system holds strong potential for medical applications, suggesting a promising platform for catalytic therapy.

Despite the recent advancement, Matteson‐type reactions are almost exclusively used to construct linear molecules. Herein we report an iterative boron‐homologation approach to construct various carbocycles from a single precursor. This method utilizes an electron‐withdrawing group (EWG) as a handle to enable intramolecular Matteson‐type couplings, leading to diastereoselective and enantioselective ring formation. An intriguing role of the Lewis acid additive is identified. This approach proves to be general for preparing carbocycles with different ring sizes and multiple stereocenters. The annulation processes are also scalable, and the products can undergo various transformations to provide synthetically valuable structural motifs. In addition, this method can be extended to the preparation of diverse hard‐to‐make spirocyclic compounds from simple cyclic ketones. Moreover, an iterative approach to synthesize double spirocycles is also demonstrated.

Despite the recent advancement, Matteson‐type reactions are almost exclusively used to construct linear molecules. Herein we report an iterative boron‐homologation approach to construct various carbocycles from a single precursor. This method utilizes an electron‐withdrawing group (EWG) as a handle to enable intramolecular Matteson‐type couplings, leading to diastereoselective and enantioselective ring formation. An intriguing role of the Lewis acid additive is identified. This approach proves to be general for preparing carbocycles with different ring sizes and multiple stereocenters. The annulation processes are also scalable, and the products can undergo various transformations to provide synthetically valuable structural motifs. In addition, this method can be extended to the preparation of diverse hard‐to‐make spirocyclic compounds from simple cyclic ketones. Moreover, an iterative approach to synthesize double spirocycles is also demonstrated.

I briefly review the canonical vorticity theoretical framework and its applications in collisionless, magnetized plasma physics. The canonical vorticity is a weighted sum of the fluid vorticity and the magnetic field and is equal to the curl of the canonical momentum. By taking this variable as the primary variable instead of the magnetic field, various phenomena that require non-MHD effect in their scrutiny can be simplified. Two examples are given, namely magnetic reconnection and magnetogenesis, and exactly how the canonical vorticity framework simplifies their analyses is described. Suggestions for future work are also delineated.

The objective of this study is to propose a bulged bottom process as a means of reducing the amount of springback from a U-shaped channel in advanced high-strength steel sheets. The recently proposed method is based on the U-bending process, but it employs modified tooling, specifically a punch head with a shallow groove and a bottom die plate with a bulgy shape. Two distinct types of steel sheets, each exhibiting an ultimate tensile strength of 980 MPa and a thickness of 1.2 mm, were subjected to investigation. The efficacy of the process in reducing springback was examined by comparing it to the springback observed in the conventional U-bending process. A finite element analysis was conducted to evaluate the proposed processing technique, considering the effects of plastic anisotropy and the elastic modulus degradation with increased plastic deformation. Furthermore, the anisotropic hardening law was employed to account for the Bauschinger effect and the associated strain hardening behavior during loading path changes. The results of the experiments and simulations were evaluated and examined to gain insight into the effect of anisotropic hardening on springback under specific loading conditions and to interpret the mechanisms of springback reduction.