Skew trapezoidal bipyramidal distortion in MoS6 unit stabilizing distorted phases of 1T-MoS2 single layer

The exceptional electrocatalytic performance of the 1T phase of MoS2 in the hydrogen evolution reaction has motivated researchers to design methods for enhancing the stability of this phase. Herein, the electronic origin of the stability of 1T-MoS2 and its distorted phases: 1T' (zig-zag), 1T′′ (diamond chain), and 1T′′′ (triangle) was elucidated using first-principles calculations. The phase stability can be altered by the repeating MoS6 units that play a significant role in the generation of metal clusters. A novel skew trapezoidal bipyriamidal (STB) distortion was observed in the MoS6 unit, which increased the stability of the distorted 1T phases in MoS2. The highly distorted STB unit was found in the stable 1T' phase with an enhanced dyz orbital population. The short edges of the distorted STB increase the electron density fraction of the Mo atoms, promoting Mo-Mo bond formation. The 1T' phase exhibited superior stability due to stronger electron delocalization in the Mo-Mo bond compared to that in the 1T′′ and 1T′′′ phases. The nature of Mo-Mo bonding varied on different metal clusters for 1T' (σ, π, and δ), 1T′′ (π and σ), and 1T′′′ (σ) bond types. Therefore, the stability of the 1T'-MoS2 phase depends on the extent of distortion in the MoS6 unit, Mo-Mo bond nature, and layer thickness.11Nsciescopu

Activated somatostatin interneurons orchestrate memory microcircuits

Despite recent advancements in identifying engram cells, our understanding of their regulatory and functional mechanisms remains in its infancy. To provide mechanistic insight into engram cell functioning, we introduced a novel local microcircuit labeling technique that enables the labeling of intraregional synaptic connections. Utilizing this approach, we discovered a unique population of somatostatin (SOM) interneurons in the mouse basolateral amygdala (BLA). These neurons are activated during fear memory formation and exhibit a preference for forming synapses with excitatory engram neurons. Post-activation, these SOM neurons displayed varying excitability based on fear memory retrieval. Furthermore, when we modulated these SOM neurons chemogenetically, we observed changes in the expression of fear-related behaviors, both in a fear-associated context and in a novel setting. Our findings suggest that these activated SOM interneurons play a pivotal role in modulating engram cell activity. They influence the expression of fear-related behaviors through a mechanism that is dependent on memory cues. © 2023 Elsevier Inc.11Nsciescopu

Limit of Bergman kernels on a tower of coverings of compact Kähler manifolds

We prove the convergence of the Bergman kernels and the L2-Hodge numbers on a tower of Galois coverings { Xj} of a compact Kähler manifold X converging to an infinite Galois (not necessarily universal) covering X~. We also show that, as an application, sections of canonical line bundle KXj for sufficiently large j give rise to an immersion into some projective space, if so do sections of KX~. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.11Nsciescopu

Rational Molecular Design of Redox-Active Carbonyl-Bridged Heterotriangulenes for High-Performance Lithium-Ion Batteries

Carbonyl aromatic compounds are promising cathode candidates for lithium-ion batteries (LIBs) because of their low weight and absence of cobalt and other metals, but they face constraints of limited redox-potential and low stability compared to traditional inorganic cathode materials. Herein, by means of first-principles calculations, a significant improvement of the electrochemical performance for carbonyl-bridged heterotriangulenes (CBHTs) is reported by introducing pyridinic N in their skeletons. Different center atoms (B, N, and P) and different types of functionalization with nitrogen effectively regulate the redox activity, conductivity, and solubility of CBHTs by influencing their electron affinity, energy levels of frontier orbitals and molecular polarity. By incorporating pyridinic N adjacent to the carbonyl groups, the electrochemical performance of N-functionalized CBHTs is significantly improved. Foremost, the estimated energy density reaches 1524 Wh kg−1 for carbonyl-bridged tri (3,5-pyrimidyl) borane, 50% higher than in the inorganic reference material LiCoO2, rendering N-functionalized CBHTs promising organic cathode materials for LIBs. The investigation reveals the underlying structure-performance relationship of conjugated carbonyl compounds and sheds new lights for the rational design of redox-active organic molecules for high-performance lithium ion batteries (LIBs).11Nsciescopu

Random-singlet-like state emergent in s = 5/2 frustrated cubic lattice

We employ thermodynamic and electron spin resonance (ESR) techniques to elucidate the effects of quenched disorder on a ground state of s= 5 / 2 frustrated cubic antiferromagnet La 3 Sb 3 Mn 2 O 14 . We observe the development of multiple ESR lines for temperatures below 80 K. Concomitantly, the ESR linewidth exhibits a power-law increase, accompanied by an intriguing shift in resonance fields. These observations point to the occurrence of inhomogeneous magnetism. Additionally, ac magnetic susceptibility and magnetization data obey a scaling relation of χ′(H, T) and M(H, T) in μBH/ kBT with the scaling exponent α= 0.53 . This scaling behavior alludes to the formation of a random-singlet-like state and the presence of abundant low-lying excitations. Our results highlight the concerted interplay of strong disorder and frustration to stabilize a putative random-singlet state even in classical and high-dimensional spin systems. © 2024, The Korean Physical Society.11Nscopuskc

Quantum spin nematic phase in a square-lattice iridate

Spin nematic is a magnetic analogue of classical liquid crystals, a fourth state of matter exhibiting characteristics of both liquid and solid 1,2. Particularly intriguing is a valence-bond spin nematic 3–5, in which spins are quantum entangled to form a multipolar order without breaking time-reversal symmetry, but its unambiguous experimental realization remains elusive. Here we establish a spin nematic phase in the square-lattice iridate Sr2IrO4, which approximately realizes a pseudospin one-half Heisenberg antiferromagnet in the strong spin–orbit coupling limit 6–9. Upon cooling, the transition into the spin nematic phase at T C ≈ 263 K is marked by a divergence in the static spin quadrupole susceptibility extracted from our Raman spectra and concomitant emergence of a collective mode associated with the spontaneous breaking of rotational symmetries. The quadrupolar order persists in the antiferromagnetic phase below T N ≈ 230 K and becomes directly observable through its interference with the antiferromagnetic order in resonant X-ray diffraction, which allows us to uniquely determine its spatial structure. Further, we find using resonant inelastic X-ray scattering a complete breakdown of coherent magnon excitations at short-wavelength scales, suggesting a many-body quantum entanglement in the antiferromagnetic state 10,11. Taken together, our results reveal a quantum order underlying the Néel antiferromagnet that is widely believed to be intimately connected to the mechanism of high-temperature superconductivity 12,13. © 2023, The Author(s), under exclusive licence to Springer Nature Limited.11Nsciescopu

Symmetrically pulsating bubbles swim in an anisotropic fluid by nematodynamics

Swimming in low-Reynolds-number fluids requires the breaking of time-reversal symmetry and centrosymmetry. Microswimmers, often with asymmetric shapes, exhibit nonreciprocal motions or exploit nonequilibrium processes to propel. The role of the surrounding fluid has also attracted attention because viscoelastic, non-Newtonian, and anisotropic properties of fluids matter in propulsion efficiency and navigation. Here, we experimentally demonstrate that anisotropic fluids, nematic liquid crystals (NLC), can make a pulsating spherical bubble swim despite its centrosymmetric shape and time-symmetric motion. The NLC breaks the centrosymmetry by a deformed nematic director field with a topological defect accompanying the bubble. The nematodynamics renders the nonreciprocity in the pulsation-induced fluid flow. We also report speed enhancement by confinement and the propulsion of another symmetry-broken bubble dressed by a bent disclination. Our experiments and theory propose another possible mechanism of moving bodies in complex fluids by spatiotemporal symmetry breaking. © The Author(s) 2024.11Ysciescopu

Efficient and Inexpensive Synthesis of 15N-Labeled 2-Azido-1,3-dimethylimidazolinium Salts Using Na15NO2 Instead of Na15NNN

N-15-Labeled azides are important probes for infrared and magnetic resonance spectroscopy and imaging. They can be synthesized by reaction of primary amines with a N-15-labeled diazo-transfer reagent. We present the synthesis of N-15-labeled 2-azido-1,3-dimethylimidazolinium salts 1 as a N-15-labeled diazo-transfer reagent. Nitrosation of 1,3-dimethylimidazolinium-2-yl hydrazine (2) with (NaNO2)-N-15 under acidic conditions gave 1 as a 1:1 mixture of alpha- and gamma-N-15-labeled azides, alpha- and gamma-1, rather than gamma-1 alone. The isotopomeric mixture thus obtained was then subjected to the diazo-transfer reaction with primary amines 3 to afford azides 4 as a 1:1 mixture of beta-N-15-labeled azides beta-4 and unlabeled ones 4'. The efficient and inexpensive synthesis of 1 as a 1:1 mixture of alpha- and gamma-1 using (NaNO2)-N-15 instead of (NaNNN)-N-15 facilitates their wide use as a N-15-labeled diazo-transfer reagent for preparing N-15-labeled azides as molecular probes.11Ysciescopu

Recognizing the G 2-horospherical Manifold of Picard Number 1 by Varieties of Minimal Rational Tangents

Pasquier and Perrin discovered that the G2-horospherical manifold X of Picard number 1 can be realized as a smooth specialization of the rational homogeneous space parameterizing the lines on the 5-dimensional hyperquadric; in other words, it can be deformed nontrivially to the rational homogeneous space. We show that X is the only smooth projective variety with this property. This is obtained as a consequence of our main result that X can be recognized by its VMRT, namely, a Fano manifold of Picard number 1 is biregular to X if and only if its VMRT at a general point is projectively isomorphic to that of X. We employ the method the authors developed to solve the corresponding problem for symplectic Grassmannians, which constructs a flat Cartan connection in a neighborhood of a general minimal rational curve. In adapting this method to X, we need an intricate study of the positivity/negativity of vector bundles with respect to a family of rational curves, which is subtler than the case of symplectic Grassmannians because of the nature of the differential geometric structure on X arising from VMRT. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.11Nsciescopu

Bioengineering toolkits for potentiating organoid therapeutics

Organoids are three-dimensional, multicellular constructs that recapitulate the structural and functional features of specific organs. Because of these characteristics, organoids have been widely applied in biomedical research in recent decades. Remarkable advancements in organoid technology have positioned them as promising candidates for regenerative medicine. However, current organoids still have limitations, such as the absence of internal vasculature, limited functionality, and a small size that is not commensurate with that of actual organs. These limitations hinder their survival and regenerative effects after transplantation. Another significant concern is the reliance on mouse tumor-derived matrix in organoid culture, which is unsuitable for clinical translation due to its tumor origin and safety issues. Therefore, our aim is to describe engineering strategies and alternative biocompatible materials that can facilitate the practical applications of organoids in regenerative medicine. Furthermore, we highlight meaningful progress in organoid transplantation, with a particular emphasis on the functional restoration of various organs. © 2024 Elsevier B.V.11Nsciescopu