Browse Articles

Isovalent substitution-induced pseudodoping in ZrxTi1−xSe2 transition metal dichalcogenides

The crystal and electronic structure of ZrxTi1−xSe2 (0 < x < 1) compounds and their electrical resistivity have been studied in detail for the first time. A combination of soft x-ray spectroscopic methods (XPS, XAS, and ResPES) was used to investigate the electronic structure. The lattice parameters as a function of the metal concentration x obey Vegard’s law. It was shown that the substitution of Ti by Zr results in an increase in the Fermi energy, attributed to the lower binding energy of Zr 4d compared to Ti 3d in the ZrxTi1−xSe2 valence band. Given that the oxidation states of both Ti and Zr are +4, and the concentration of free charge carriers remains unchanged upon substitution, the observed effect is explained by a reduced density of electronic states near the Fermi level. The influence of temperature on the Ti 2p–3d and Zr 3p–4d ResPES spectra is interpreted in terms of pseudodoping occurring with the substitution of Ti by Zr.

Adenosine diphosphate stimulates VEGF-independent choroidal endothelial cell proliferation: A potential escape from anti-VEGF therapy

We hypothesized that a strategy employing tissue-specific endothelial cells (EC) might facilitate the identification of tissue- or organ-specific vascular functions of ubiquitous metabolites. An unbiased approach was employed to identify water-soluble small molecules with mitogenic activity on choroidal EC. We identified adenosine diphosphate (ADP) as a candidate, following biochemical purification from mouse EL4 lymphoma extracts. ADP stimulated the growth of bovine choroidal EC (BCEC) and other bovine or human eye-derived EC. ADP induced rapid phosphorylation of extracellular signal-regulated kinase in a dose- and time-dependent manner. ADP-induced BCEC proliferation could be blocked by pretreatment with specific antagonists of the purinergic receptor P2Y1 but not with a vascular endothelial growth factor (VEGF) inhibitor, indicating that the EC mitogenic effects of ADP are not mediated by stimulation of the VEGF pathway. Intravitreal administration of ADP expanded the neovascular area in a mouse model of choroidal neovascularization. Single-cell transcriptomics from human choroidal datasets show the expression of P2RY1, but not other ADP receptors, in EC with a pattern similar to VEGFR2. Although ADP has been reported to be a growth inhibitor for vascular EC, here we describe its growth-stimulating effects for BCEC and other eye-derived EC.

Preliminary evidence of immune infiltration and neutrophil degranulation in peripheral blood of non-obese OSA patients related to cognitive decline

Erratum: “Exciton and biexciton transient absorption spectra of CdSe quantum dots with varying diameters” [J. Chem. Phys. 160, 014708 (2024)]

Effective doses received by the gastrointestinal tract compartments of adults due to food intake in Egypt

Abstract 226Ra, 232Th, and 40K levels in various foods frequently consumed by Egyptians were determined using a gamma-ray spectrometer based on the germanium detector (HPGe). Activity concentrations of 226Ra, 232Th, and 40K were in the range of < 0.10 to 0.79 ± 0.07, < 0.09 to 0.42 ± 0.04, and < 1.96 to 89.73 ± 2.96 Bq/kg, respectively. The gastrointestinal tract (GIT) model was employed to estimate the effective doses received by the different parts of the adult’s gastrointestinal tract, i.e., stomach (ST), small intestine (SI), upper large intestine (ULI), and lower large intestine (LLI), due to the ingestion of the analyzed foods. This estimation was based on mathematical calculations of the energy absorbed by organs due to transformations of ingested radionuclides. The effective doses (μSv/y) received by each compartment were 8.86 (ST), 8.76 (SI), 66.90 (ULI), and 176.76 (LLI). The results do not exceed the safe thresholds set by global organizations UNSCEAR and WHO, 290 and 250–400 μSv/y, respectively. Therefore, radionuclide intakes due to investigated food consumption do not pose any significant radiological impact.

Slowly quenched, high pressure glassy B2O3 at DFT accuracy

Modeling inorganic glasses requires an accurate representation of interatomic interactions, large system sizes to allow for intermediate-range structural order, and slow quenching rates to eliminate kinetically trapped structural motifs. Neither first principles-based nor force field-based molecular dynamics (MD) simulations satisfy these three criteria unequivocally. Herein, we report the development of a machine learning potential (MLP) for a classic glass, B2O3, which meets these goals well. The MLP is trained on condensed phase configurations whose energies and forces on the atoms are obtained using periodic quantum density functional theory. Deep potential MD simulations based on this MLP accurately predict the equation of state and the densification of the glass with slower quenching from the melt. At ambient conditions, quenching rates larger than 1011 K/s are shown to lead to artifacts in the structure. Pressure-dependent x-ray and neutron structure factors from the simulations compare excellently with experimental data. High-pressure simulations of the glass show varied coordination geometries of boron and oxygen, which concur with experimental observations.

Argonaute2 modulates megakaryocyte development and sex-specific control of platelet protein expression and reactivity

Analysis of intramolecular modes of liquid water in two-dimensional spectroscopy: A classical hierarchical equations of motion approach

Two-dimensional (2D) vibrational spectroscopy is a powerful means of investigating the structure and dynamics of complex molecules in condensed phases. However, even in theory, analysis of 2D spectra resulting from complex inter- and intra-molecular motions using only molecular dynamics methods is not easy. This is because molecular motions comprise complex multiple modes and peaks broaden and overlap owing to various relaxation processes and inhomogeneous broadening. On the basis of an anharmonic multimode Brownian oscillator model with nonlinear system–bath coupling, we have developed an approach that simulates 2D spectra, taking into account arbitrary modes of intermolecular and intramolecular vibrations simultaneously. Although only two-mode quantum calculations are feasible with this model, owing to high computational costs, here we restrict ourselves to the classical case and perform three-mode calculations. We demonstrate the applicability of our method by calculating 2D correlation infrared spectra of water for symmetric stretching, antisymmetric stretching, and bending modes. The quantum effects of these results are deduced by comparing 2D quantum spectra previously obtained for two intramolecular modes with those obtained using our classical approach under the same physical conditions. The results show that the 2D spectra calculated by separating the stretching modes into symmetric and asymmetric modes provide better descriptions of peak profiles, such as the splitting of cross-peaks.

Evaluation of ampicillin plus ceftobiprole combination therapy in treating Enterococcus faecalis infective endocarditis and bloodstream infection

Multiple and transforming vibrational identities of atoms in amorphous solids

Identifying the diverse roles of disorderly packed atoms inside an amorphous solid has been a highly pursued but daunting task in glass physics. By analyzing the full-frequency vibrational modes of a model Cu50Zr50 glass, here, we classify the internal atoms into low-, subhigh-, and high-frequency ones that have different tendencies for rearrangements upon excitations. We find that low-frequency atoms are structurally unfavored and tend to aggregate. High-frequency atoms originating from compressed atomic pairs are also mechanically unstable. As yield approaches, shear-transformation rearrangements shift from low-frequency to high-frequency atoms. Subhigh-frequency atoms play the role of stable backbones. Given that atoms can have different identities, multiple identities are observed to overlap in space. Atoms with one vibrational identity often transform to another one, showing different preferences in transformation routes. Our results deepen the understanding of atomic structures for amorphous plasticity beyond the simplified picture of soft vs hard spots.

Triaxial behavior and microstructural insights of loose sandy soil stabilized with alkali activated slag

How to correct Ehrenfest nonadiabatic dynamics in open quantum systems: Ehrenfest plus random force (E + <i>σ</i>) dynamics

One key challenge in the study of nonadiabatic dynamics in open quantum systems is to balance computational efficiency and accuracy. Although Ehrenfest dynamics (ED) is computationally efficient and well-suited for large complex systems, ED often yields inaccurate results. To address these limitations, we improve the accuracy of the traditional ED by adding a random force (E + σ). In this work, the construction of random forces is considered in Markovian and non-Markovian scenarios, and we ensure the dynamics satisfy the detailed balance in both scenarios. By comparing our E + σ with existing methods such as the electronic friction model and surface hopping, we furthermore validate its reliability. In addition, the E + σ model still retains the high efficiency of ED and does not incur much additional computation. We believe that this method provides an alternative to accurately describe the mixed quantum–classical dynamics in open quantum systems, particularly for large complex systems.

Short-term airborne ultrasound induced cell death in tobacco cells and changed their wall components

Structural evolution of particle configurations: Zero-temperature phases under increasing confinement

In this study, we investigate the phase behavior and structural organization of colloidal particles in a two-dimensional (2D) system under isotropic harmonic confinement using overdamped Langevin dynamics simulations. We employ a modified mermaid potential, which introduces an additional short-distance term resulting in a null-force region, distinct from the conventional mermaid potential. This modification facilitates a richer exploration of self-assembled structures, revealing a variety of phases influenced by the interplay between confinement strength V0 and the interaction potential. Our analysis spans a wide range of parameters, resulting in a detailed phase diagram that captures transitions from dispersed clusters to well-ordered patterns, including square, triangular, rhomboidal, and mixed configurations, as the confinement strength increases. The findings underscore the intricate balance of forces governing the self-assembly of colloidal systems and offer valuable insights for future experimental realizations.

Insulator–metal transition in VO2 film on sapphire studied by broadband dielectric spectroscopy

Mixed atomistic–implicit quantum/classical approach to molecular nanoplasmonics

A multiscale quantum mechanical (QM)/classical approach is presented that is able to model the optical properties of complex nanostructures composed of a molecular system adsorbed on metal nanoparticles. The latter is described by a combined atomistic–continuum model, where the core is described using the implicit boundary element method (BEM) and the surface retains a fully atomistic picture and is treated employing the frequency-dependent fluctuating charge and fluctuating dipole (ωFQFμ) approach. The integrated QM/ωFQFμ-BEM model is numerically compared with state-of-the-art fully atomistic approaches, and the quality of the continuum/core partition is evaluated. The method is then extended to compute surface-enhanced Raman scattering within a time-dependent density functional theory framework.

Biomechanical analysis of a newly designed and 3D printed plate-locking interbody cage: an observational study of finite element analysis

Low-energy electron driven reactions in 2-bromo-5-nitrothiazole

Thiazole derivatives are biologically relevant molecules, used also in pharmaceutical applications. Herein, we report results for electron attachment to 2-bromo-5-nitrothiazole (BNT) in the gas phase. Employing two crossed electron–molecule beam experiments, we determined the efficiency curves of various fragment anions as a function of the initial electron energy between about 0 and 10 eV as well as the emission angle and kinetic energy distributions of Br− and NO2− ions formed from a resonance near 4 eV. The experiments were supported by quantum chemical calculations, exploring possible dissociation pathways along with their reaction energies. We also compared the electron attachment characteristics of BNT with those of the native thiazole molecule by performing electron attachment experiments and calculations for this molecule as well. Compared to thiazole, which is primarily degraded only by electrons with kinetic energies between about 5 and 10 eV, BNT is susceptible to low-energy electrons near 0 eV with enhanced cross section for (dissociative) electron attachment. However, although BNT offers two localization sites with high electron affinity (Br and NO2 moieties), we do not find the corresponding anions as the dominant negatively charged species formed upon electron attachment. Instead, the reaction channels with an abstraction of Br and NO2 as neutral radicals prevail, accompanied by the opening of the thiazole ring due to the relatively weak C–S bond.

Association between ethylene oxide exposure and cognitive function in older adults from NHANES data

Exploring low barrier quantum tunneling and structural planarity in 3-methylstyrene conformers: Insights from microwave spectroscopy

The first ground-state rotational spectrum of 3-methylstyrene (3MS) was measured by Fourier transform microwave spectroscopy under supersonic jet-cooled conditions. Transitions were assigned for two conformers: cis-3MS and trans-3MS. In the cis conformer, the vinyl group is oriented toward the methyl group, while in the trans conformer, it is positioned away from the methyl. The energy difference between the two conformers was calculated to be only 2.1 cm−1, with the cis conformer having lower energy. Significant tunneling splitting, caused by the low-barrier internal rotation of the methyl group, was observed and analyzed using the XIAM and BELGI-Cs codes. The BELGI results show that the V3 barrier is 30.6688(87) cm−1 for the cis conformer and 11.0388(88) cm−1 for the trans conformer. The experimental rotational and torsional parameters are compared to their density functional theory counterparts. The planarity of the molecular geometry of cis- and trans-3MS is discussed, contributing to the long-standing topic of discussion about the planarity of styrene derivatives.