Double Group Research Articles

Nano-structured and High-performance Mn-based Positive Electrode Materials for Lithium-ion Batteries

Towards widespread adoption of electric vehicles, Co/Ni-free and high energy density positive electrode materials for lithium-ion batteries are necessary. Among the various positive electrode materials, stoichiometric “zigzag”-type layered LiMnO2 with orthorhombic space-group symmetry has been extensively studied as potential high-energy and low-cost positive electrode materials. Although orthorhombic LiMnO2 delivers a large reversible capacity of over 200 mA h g-1 thorough a phase transition from layered to spinel-like phase during charging and discharging, over 30 cycles are required to obtain such a large reversible capacity due to the sluggish phase transition kinetics. In this study, nanostructured LiMnO2 with both orthorhombic and monoclinic layered domains is synthesized, and its electrochemical performance as positive electrode materials is examined. The nanostructured LiMnO2 delivers a maximum reversible capacity of >200 mA h g-1 within 5 cycles, indicating that the phase transition kinetics to the spinel-like phase upon electrochemical cycling are faster when compared with orthorhombic LiMnO2. Moreover, a significant improvement of cycle performance, i.e., ~90% retention after 100 cycles, is achieved by using a highly concentrated electrolyte solution coupled with lithium phosphate coating through suppression of Mn dissolution into electrolyte. From these results, the feasibility of practical Co/Ni-free high-energy positive electrode materials will be discussed in detail.

Comparison of fusion rate, radiologic and clinical outcome between CaO-SiO2-P2O5-B2O3 bioactive glass-ceramics 7 (BGS-7) spacer and allograft spacer with iliac bone graft in multilevel ACDF.

CaO-SiO2-P2O5-B2O3 bioactive glass-ceramics7 (BGS-7) are known for their strong integration with bone and stability and are commonly used in spinal fusions. This study aimed to compare fusion rates and radiological and clinical outcomes between BGS-7 and allograft spacers with iliac bone grafts (IBG) in multilevel anterior cervical discectomy and fusion (ACDF) surgeries. This retrospective study was conducted at BRM Medical Center. We included patients who underwent multilevel ACDF at BRM Medical Center between January 2012 and December 2023. The patients had symptoms such as cervical radiculopathy and myelopathy due to cervical disc herniation, stenosis, and spondylosis. We evaluated the preoperative and postoperative Japanese Orthopedic Association (JOA) scores, neck disability index (NDI), functional rating index (FRI), and visual analog scale (VAS) scores for the neck, shoulder, and upper extremities at 6 months and 1 year after surgery. Fusion rates were assessed using dynamic radiography and computed tomography (CT) scans at 1 year postoperatively. Radiological measurements were obtained from preoperative and postoperative plain radiographs. At the 1-year follow-up, the fusion rates were 89.5% for BGS-7 and 92.2% for the allograft cage on dynamic radiographs (p=0.156) and 93.4% and 90.4%, respectively, on CT scans (p=0.319), confirming both internal and external osseointegration. Subsidence rates were 4% for BGS-7 and 10% for the allograft spacer group. Both groups showed increased cervical lordosis (CL), segmental lordosis (SL), and segmental height postoperatively, with maintained lower segmental height (LSH) in the BGS-7 group than in the allograft spacer group at postoperatively 1 year. No adjacent segmental disease (ASD) occurred in either group. The JOA, NDI, and FRI showed significant improvements in both groups. The VAS scores decreased significantly in both groups, indicating improved clinical outcomes. In multilevel ACDF, BGS-7 demonstrated fusion rates comparable to those of the allograft spacer with IBG, experiencing fewer instances of subsidence and cage fracture. Therefore, BGS-7 spacer can be safely utilized in multilevel ACDF as a substitute for traditional allograft spacers, without the need for additional IBG.

Moving Groups in the Solar Neighborhood with Gaia, APOGEE, GALAH, and LAMOST: Dynamical Effects Gather Gas and the Ensuing Star Formation Plays an Important Role in Shaping the Stellar Velocity Distributions

With Gaia, APOGEE, GALAH, and LAMOST data, we investigate the positional, kinematic, chemical, and age properties of nine moving groups in the solar neighborhood. We find that each moving group has a distinct distribution in the velocity space in terms of its metallicity, α abundance, and age. Comparison of the moving groups with their underlying background stars suggests that they have experienced the enhanced, prolonged star formation. We infer that any dynamical effects that gathered stars as a moving group in the velocity space also worked for gas. We propose for the first time that the ensuing newborn stars from such gas inherited the kinematic feature from the gas, shaping the current stellar velocity distributions of the groups. Our findings improve the understanding of the origins and evolutionary histories of moving groups in the solar neighborhood.

Unveiling the role of temperature on structural, compositional, morphological, thermal and optical properties of hydrothermally synthesized SnS2 nanostructures

Recently, the layered metal dichalcogenides (LMDs) such as tin disulfide (SnS2) has engrossed significant attention because of their n-type semiconducting tunable properties. A hydrothermal method was employed for the synthesis of SnS2 nanostructures by varying reaction temperatures i.e. 160, 170 and 180 °C. To determine the crystallographic, micro-structural, morphological, elemental compositions, thermal and optical properties of the prepared samples, various characterizations such as XRD, Raman spectroscopy, FTIR, FESEM, EDS XPS, TGA, PL and UV spectroscopy were employed. The structural analysis revealed the hexagonal phase formation of prepared SnS2 nanostructures with space group symmetry of P63mc (layer group no.: 186) in all the prepared samples. The sample prepared at 160 °C also exhibit orthorhombic crystal phase of SnS along with SnS2 crystal phase. The intensity of diffraction peaks increased with rise in growth temperature which infers the crystallinity improvement and crystallite size growth. Raman and FTIR spectroscopy also confirm the formation of SnS2 phase in synthesized samples. FESEM analysis showed the development of hexagonal shaped nanostructures for all the prepared samples. Elemental analysis showed the improvement of stoichiometry of SnS2 with increase in reaction temperature. XPS results inferred the existence of Sn and S with +4 and −2 energy states respectively, confirmed the formation of SnS2. The optical property analysis shows the emission in visible region. Furthermore, the band gap values get decreased i.e. 2.42 eV–2.34 eV with increase in growth temperature. Also, the refractive index of the synthesized samples was determined by various empirical models. The improvement of linear optical susceptibility (χ(1)), nonlinear refractive index (n2) and nonlinear optical susceptibility (χ(3)) suggest the usefulness of synthesized nanostructures in optical and photonic applications. Engineering of different properties of SnS2 nanostructures with reaction temperatures suggests the potential usage of these nanostructures for optoelectronic applications.

Fabrication and characterization of Nd-doped BiFeO₃-KNbO₃ solid solution

The polycrystalline Bi0.35Nd0.15K0.5Fe0.5Nb0.5O3 (BNKF) ceramic was fabricated by the solid-state reaction method. Room temperature structural analysis using X-ray diffraction and Rietveld’s analysis confirmed the crystallization of ceramic in the double-phase Tetragonal and Rhombohedral (P4mm+R3c space group) symmetry. The microstructure analysis by field-emission scanning electron microscopy (FESEM) reveals the densely packed grain distribution with different shapes and sizes. The temperature and frequency dependent dielectric parameters were studied over a broad range of temperature and frequency. The complex impedance analysis reveals a non-Debye type relaxation process and NTCR behavior of BNKF. The frequency-dependent ac conductivity curve follows the universal Jonscher power law. The optimum values of polarization at zero electric field and coercivity are 0.193 µC/cm2 and 6.532 kV/cm respectively. The room-temperature weak ferromagnetism found in the material may be due to the breakage of the spiral spin structure in BNKF.

Computing the homology of universal covers via effective homology and discrete vector fields

Effective homology techniques allow us to compute homology groups of a wide family of topological spaces. By the Whitehead tower method, this can also be used to compute higher homotopy groups. However, some of these techniques (in particular, the Whitehead tower) rely on the assumption that the starting space is simply connected. For some applications, this problem could be circumvented by replacing the space by its universal cover, which is a simply connected space that shares the higher homotopy groups of the initial space. In this paper, we formalize a simplicial construction for the universal cover, and represent it as a twisted Cartesian product.As we show with some examples, the universal cover of a space with effective homology does not necessarily have effective homology in general. We show two independent sufficient conditions that can ensure it: one is based on a nilpotency property of the fundamental group, and the other one on discrete vector fields.Some examples showing our implementation of these constructions in both SageMath and Kenzo are shown, together with an approach to compute the homology of the universal cover when the group is Abelian even in some cases where there is no effective homology, using the twisted homology of the space.

Interlayer-Functionalized Graphene with Phosphorus–Silicon-Containing Elements for Improving Thermal Stability and Flame Retardance of Polyacrylonitrile

Highly-effective non-halogenated flame retardants have received widespread attention because they are environmentally friendly, with low toxicity and low smoke density. In this work, interlayer-functionalized graphene (fRGO) containing silicon and phosphorus elements was synthesized via hydrolytic condensation with 3-(methacryloyloxy)propyltrimethoxysilane and addition reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Interlayer spacing and oxygen-containing groups of reduced graphene oxide (RGO) were regulated by controlling the hydrazine hydrate dosage. Then, phosphorus–silicon-containing organic molecules were inserted into RGO interlayers; this was verified by FTIR, XPS, TEM, etc. The fRGO was added to a polyacrylonitrile (PAN) matrix using a solution blending method to prepare polyacrylonitrile (PAN) composites. The fRGO addition caused the significant decrease in cyclization heat and the considerable increase in char residues, indicating improved thermal stability. Importantly, PAN composites exhibited outstanding flame-retardant properties, with the peak heat release rate reduced by 45%, which is ascribed to the dense graphitic carbon layers induced by phosphorus–silicon-containing organics and the 2D barrier effect of RGO layers to prevent the heat and mass transfer.

Biomechanical Effects of Different Spacing Distributions Between the Cemented Superior Boundary and Surgical Vertebral Superior Endplates After Percutaneous Vertebroplasty for Osteoporotic Vertebral Compression Fractures: A Three-Dimensional Finite Element Analysis.

Patients with osteoporotic vertebral compression fractures (OVCF) treated with vertebroplasty (PVP) are experiencing an increasing number of problems such as pain recurrence, mainly due to recompression fractures of the operated vertebral body within a certain period of time after the operation, which is closely related to the distribution of intraoperative bone cement. The aim of this study is to investigate the effect of different spacing distributions between the upper boundary of the cement and the upper endplate of the operated vertebra on the biomechanics of the operated vertebra after percutaneous vertebroplasty for OVCF using finite element analysis (FEA). One patient with L1 vertebral body OVCF was selected, and computed tomography (CT) of the thoracolumbar segment was performed. The CT data were extracted to establish an FEA model of the T12-L2 vertebral bodies. Bone cement was injected into the L1 vertebral body. Based on the spacing between the upper boundary of the bone cement and the vertebral body's upper endplates, the model vertebrae were divided into 0, 2, 4, and 6 mm spacing groups, and the human body's upright, flexion-extension, lateral flexion, and rotational positions were simulated. The biomechanical effects of different spacing distributions on the postoperative L1 vertebral body and the injected bone cement were evaluated. In this paper, we found that the Von Mises stress of the L1 vertebrae was the smallest when the spacing between the upper boundary of the bone cement and the vertebral body's upper endplates was 0 mm. The larger the spacing in a certain range between the upper boundary of the bone cement and the vertebral body's upper endplates, the greater the Von Mises stress of the L1 vertebrae. However, in the stress comparison of the injected bone cement, the Von Mises stress of the bone cement was greatest when the spacing between the upper boundary of the bone cement and the upper endplate of the vertebral body was 0 mm; the larger the spacing, the smaller the Von Mises stress. When the contact spacing between the upper boundary of the bone cement and the upper endplate of the vertebral body is 0 mm, it can effectively eliminate and transfer the pressure caused by the load, thus reducing the stress on the cancellous bone and further reducing the risk of vertebral refracture after surgery.

Same same but Different - Definition and Explicit Notation of an Orientation in MTEX vs. Quasi-Standard

Even though the descriptive definition of orientation is the same in both settings, the explicitnotation of a crystallographic orientation as (3 3) matrix in terms of Euler angles featuredby the popular MATLAB toolbox MTEX differs by an inversion from the quasi-standard notation datedback to the early days of quantitative texture analysis championed by H.-J. Bunge. The origin of thisdiscrepancy is revealed by an enlightening view provided in algebraic terms of a change of basis.Understanding the effect of inversion is instrumental to do proper computations with crystallographicorientations and rotations, e.g. when multiplying with elements of a crystallographic symmetry group,and to compare results of texture analyses accomplished in different settings.

Random walks and contracting elements II: Translation length and quasi-isometric embedding

Continuing from Choi (2022), we study random walks on metric spaces with contracting elements. We prove that random subgroups of the isometry group of a metric space are quasi-isometrically embedded into the space. We discuss this problem in two ways, namely in the sense of random walks and counting problem. We also establish the genericity of contracting elements and the central limit theorem and its converse for translation length.

A Novel Machine Learning Model and a Web Portal for Predicting the Human Skin Sensitization Effects of Chemical Agents.

Skin sensitization is a significant concern for chemical safety assessments. Traditional animal assays often fail to predict human responses accurately, and ethical constraints limit the collection of human data, necessitating a need for reliable in silico models of skin sensitization prediction. This study introduces HuSSPred, an in silico tool based on the Human Predictive Patch Test (HPPT). HuSSPred aims to enhance the reliability of predicting human skin sensitization effects for chemical agents to support their regulatory assessment. We have curated an extensive HPPT database and performed chemical space analysis and grouping. Binary and multiclass QSAR models were developed with Bayesian hyperparameter optimization. Model performance was evaluated via five-fold cross-validation. We performed model validation with reference data from the Defined Approaches for Skin Sensitization (DASS) app. HuSSPred models demonstrated strong predictive performance with CCR ranging from 55 to 88%, sensitivity between 48 and 89%, and specificity between 37 and 92%. The positive predictive value (PPV) ranged from 84 to 97%, versus negative predictive value (NPV) from 22 to 65%, and coverage was between 75 and 93%. Our models exhibited comparable or improved performance compared to existing tools, and the external validation showed the high accuracy and sensitivity of the developed models. HuSSPred provides a reliable, open-access, and ethical alternative to traditional testing for skin sensitization. Its high accuracy and reasonable coverage make it a valuable resource for regulatory assessments, aligning with the 3Rs principles. The publicly accessible HuSSPred web tool offers a user-friendly interface for predicting skin sensitization based on chemical structure.

Unveiling the Monoclinic Phase in CsPbBr3-xClx Perovskite Crystals, Phase Transition Suppression and High Energy Resolution γ-Ray Detection.

All-inorganic CsPbBr3 and CsPbCl3 perovskites are promising materials for high-performance solar cells and advanced radiation detection technologies with high stability. Here we report that CsPbBr3-xClx (x = 0-3) crystals exhibit eutectoid behavior for the melting points and phase transition temperatures. The well-known halide perovskite cubic phase transition temperature shifts near room temperature (∼37 °C for CsPbBr2Cl). We conducted an extensive crystallographic analysis on single crystals of 7 different compositions, including the end members CsPbBr3 and CsPbCl3. Contrary to previous beliefs, we discovered they exhibit a monoclinic structure with space group symmetry P21/m at room temperature, rather than the orthorhombic Pnma. This new structural model is more precise and features a unit cell volume that is four times larger than that of the orthorhombic model. From high-quality single crystals of CsPbBr2Cl, grown by the Bridgman method, we constructed γ-ray detectors achieving an energy resolution of 7.2% at 200 V for 57Co radiation. Thermally stimulated current spectroscopy of the CsPbBr2Cl samples revealed that the defect densities in crystals from different regions of the ingot were relatively uniform, with values of ∼4.72 × 1012 and ∼5.09 × 1012 cm-3. These findings indicate that low deep-level defect densities can be achieved that are consistent with the notable performance of the CsPbBr2Cl perovskite as a high-energy γ radiation detector.

Dual-Modality Accurate Visualization of Drug Synergy Based on Mass Spectrometry and Fluorescence Imaging.

There is a potential synergistic effect between nonsteroidal anti-inflammatory drugs and hydrogen sulfide (H2S), but direct evidence for the study is lacking. With a single fluorescence detection method, it is difficult to accurately confirm the effectiveness of the synergistic effect. In this study, the fluorescent probe and the nonsteroidal anti-inflammatory drug naproxen were combined via different self-immolative spacer groups to obtain a diagnostic and therapeutic integrated fluorescent probe Nap-NP-NSB, which can release H2S. The quantitative release of H2S by Nap-NP-NSB was evaluated in vitro and in cells, and the synergistic effect of H2S and naproxen was confirmed by monitoring the treatment process of cellular inflammation and oxidative damage of gastric mucosa cells. Finally, in vivo fluorescence imaging and mass spectrometry imaging of the liver and stomach tissues and their sections were performed in the mouse model of acute hepatitis. The dual-modal detection method not only confirmed that Nap-NP-NSB had better anti-inflammatory activity and less gastric mucosal damage, but also enabled a more accurate visualization of the drug synergistic effect of naproxen and H2S. This work provides a dual visualization imaging method combining fluorescence and mass spectrometry imaging and develops a new idea for studying drug synergies based on self-immolative structures.

Architecture of transit spaces

The problem of modern cities is considered - the need to ensure efficient and comfortable movement of people and goods. With the development of transport, the issue of maintaining an attractive pedestrian environment arises. The concept of “architecture of transit spaces” and the role of transit routes in the planning structure of the city are revealed, and their diversity is examined. These spaces include various elements of urban infrastructure, pedestrian streets, boulevards, squares, underground passages, passages that provide connections between different parts of the city. The study identified four main groups of transit spaces: streets, bridges, covered walkways and temporary structures. Using the example of real objects, factors influencing the formation of transit routes, their scale and geometry, functional content and, as a result, the architecture itself are studied.

Topological signatures of triply degenerate fermions in Heusler alloys: an ab initio study

Triply degenerate nodal point (TP) fermions, lacking elementary particle counterparts, have been theoretically anticipated as quasiparticle excitations near specific band crossing points constrained by distinct space-group symmetries instead of Lorentz invariance. Here, based onfirst-principlescalculations and symmetry analysis, we demonstrate the presence of TP fermions in Heusler alloys. Furthermore, we predict that these Heusler alloys are dynamically stable, exhibiting TP fermions along four distinctC3axes in the F-43m space group. We show thatα-LiCaPdSb harbours peculiar Fermi arcs and surface states on the (111) and (001) crystal facets, owing to the coexistence of threefold rotational and time reversal symmetry. More interestingly, a modest tensile strain can increase the distance of fermions along the Γ-Lhigh symmetric line by as much as 21.10%, which give rise to measurable Fermi arcs. Furthermore, we investigate non-trivial topological insulator phase inβ-LiCaPdSb, by changing the chemical environment through placing transition metal atoms at various Wyckoff positions. Theβ-LiCaPdSb harbour a semi-metallic nature, and by breaking cubic symmetry, it undergoes a transition from semi-metal to a non-trivial topological insulator. In addition, for the first time, rare-earth LaPtBi half-Heusler alloy is examined under strain to uncover multiple band inversions associated with the TP fermionic phase. The observed multiple band inversion is entirely unaffected by spin-orbit coupling. We show that the LaPtBi compound hosts TP fermions, which are linked to aZ2topological invariant. Remarkably, with clear band crossings and multiple band inversion, we point out the possibilities of the LaPtBi for displaying a rich topological phase diagram. Our work provides a prototype material platform for experimental detection through angle-resolved photoemission spectroscopy or scanning tunnelling spectroscopy and practical spintronic applications.

The Crystal Chemistry of Boussingaultite, (NH4)2Mg(SO4)2·6H2O, and Its Derivatives in a Wide Temperature Range

The crystal structure, thermal behavior, and vibrational spectra of the anthropogenic analogue of boussingaultite, (NH4)2Mg(SO4)2·6H2O, and its dehydrated counterpart efremovite, (NH4)2Mg2(SO4)3, were studied in detail. The sample from the Chelyabinsk burning coal dumps has the composition of (NH4)1.92(Mg1.02Mn0.01Fe0.01)∑1.04(SO4)2·6H2O and crystallizes in the space group P21/a, with a = 9.3183(4), b = 12.6070(4), c = 6.2054(3) Å, β = 107.115(5)°, V = 696.70(5) Å3 (at 20 °C), Z = 2. The thermal evolution steps are as follows: boussingaultite (NH4)2Mg(SO4)2·6H2O (25–90 °C) → X-ray amorphous phase (100–150 °C) → efremovite (NH4)2Mg2(SO4)3 (160–340 °C) → MgSO4 Cmcm + Pbnm (340–580 °C) → MgSO4 Pbnm (580–700 °C). Thermal expansion is anisotropic, with the coefficients (×106 °C−1) α11 = 52(2), α22 = 68(2), α33 = –89(3), and αv = 31(3) at T = –123 °C; and α11 = 53(2), α22 = 67(2), α33 = 15(1), and αv = 136(3) at T = 60 °C. The maximal thermal expansion is along the b-axis and is due to straightening of corrugated pseudolayers (within the ab plane) of Mg(H2O)6 octahedra and SO4 tetrahedra with NH4 groups in the interlayer space. Vibrational spectroscopy outlines the general trend of dehydration and deammonization as the difference in the temperature intervals of these transformation steps allows separation of O–H and N–H vibrations in the process of dehydration by infrared and Raman spectroscopy. The intermediate partially dehydrated modification of boussingaultite was detected by in situ Raman spectroscopy at 110 °C that may correspond to ammonium leonite.

A space level light bulb theorem in all dimensions

Given a d -dimensional manifold M and a knotted sphere s\colon \mathbb{S}^{k-1}\hookrightarrow \partial M with 1\leq k\leq d , for which there exists a framed dual sphere G\colon \mathbb{S}^{d-k}\hookrightarrow \partial M , we show that the space of neat embeddings \mathbb{D}^{k} \hookrightarrow M with boundary s can be delooped by the space of neatly embedded (k-1) -disks, with a normal vector field, in the d -manifold obtained from M by attaching a handle to G . This increase in codimension significantly simplifies the homotopy type of such embedding spaces, and is of interest also in low-dimensional topology. In particular, we apply the work of Dax to describe the first interesting homotopy group of these embedding spaces, in degree d-2k . In a separate paper we use this to give a complete isotopy classification of 2-disks in a 4-manifold with such a boundary dual.

Minimal Nonsolvable Bieberbach Groups

Several authors have shown that there exist nonsolvable Bieberbach groups of dimension 15. In this paper, we show that this is, in fact, a minimal dimension for such groups.

Symmetry adaptation for self-consistent many-body calculations

The exploitation of space group symmetries in numerical calculations of periodic crystalline solids accelerates calculations and provides physical insight. We present results for a space-group symmetry adaptation of electronic structure calculations within the finite-temperature self-consistent GW method along with an efficient parallelization scheme on accelerators. Our implementation employs the simultaneous diagonalization of the Dirac characters of the orbital representation. Results show that symmetry adaptation in self-consistent many-body codes results in substantial improvements of the runtime, and that block diagonalization on top of a restriction to the irreducible wedge results in additional speedup.

Electronic and Optical Properties of 2D Heterostructure Bilayers of Graphene, Borophene and 2D Boron Carbides from First Principles.

In the present work the atomic, electronic and optical properties of two-dimensional graphene, borophene, and boron carbide heterojunction bilayer systems (Graphene-BC3, Graphene-Borophene and Graphene-B4C3) as well as their constituent monolayers are investigated on the basis of first-principles calculations using the HSE06 hybrid functional. Our calculations show that while borophene is metallic, both monolayer BC3 and B4C3 are indirect semiconductors, with band-gaps of 1.822 eV and 2.381 eV as obtained using HSE06. The Graphene-BC3 and Graphene-B4C3 bilayer heterojunction systems maintain the Dirac point-like character of graphene at the K-point with the opening of a very small gap (20-50 meV) and are essentially semi-metals, while Graphene-Borophene is metallic. All bilayer heterostructure systems possess absorbance in the visible region where the resonance frequency and resonance absorption peak intensity vary between structures. Remarkably, all heterojunctions support plasmons within the range 16.5-18.5 eV, while Graphene-B4C3 and Graphene-Borophene exhibit a π-type plasmon within the region 4-6 eV, with the latter possessing an additional plasmon at the lower energy of 1.5-3 eV. The dielectric tensor for Graphene-B4C3 exhibits complex off-diagonal elements due to the lower P3 space group symmetry indicating it has anisotropic dielectric properties and could exhibit optically active (chiral) effects. Our study shows that the two-dimensional heterostructures have desirable optical properties broadening the potential applications of the constituent monolayers.