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Boroxol ring dissolution in molten and glassy B2O3 by neutron and x-ray diffraction difference methods
The structure of 11B2O3 boron oxide glass and its liquid have been measured over a wide temperature range by pulsed neutron diffraction, from T = 14 K up to 1500 K. Contrary to prior neutron scattering results in the literature, thermal expansion of the B–O bond is resolved, with a coefficient of αBO = 4.1(3) ppm K−1, in quantitative agreement with the result previously derived by high-energy x-ray diffraction. Exploiting the scattering contrast between neutrons and x rays, difference functions are derived that eliminate contributions due to O–O pairs, revealing, for the first time, the nearest-neighbor B–B peak in the pair distribution function. This peak occurs at rBB = 2.430(1) Å in B2O3 glass, consistent with a mean B–O–B bond angle β ≃ 124° and a large boroxol ring fraction. In the liquid, a much larger rBB ≃ 2.54 Å and β ≃ 134° are indicative of either a much lower ring fraction f, a larger non-ring B–O–B bond angle, βNR, or a combination of both. The latter scenario is supported by comparison to a range of molecular dynamics models with varying boroxol ring fractions.
Excited states of mono- and biruthenium(II) complexes adsorbed on nanocrystalline titanium dioxide studied by electroabsorption spectroscopy
Abstract Comprehensive characterization of the lowest energy electronic excited states for mono- and binuclear Ru(II) complexes containing bipyridine ligands has been performed by electroabsorption (EA) spectroscopy. The EA spectra of Ru complexes sensitizing a TiO2 semiconductor were compared with the spectra of these complexes in the form of solid neat films, both of which parametrized within the Liptay theory. The extracted values of relevant parameters, relating to molecular dipoles after optical MLCT (metal-to-ligand-charge-transfer) excitation, exhibit a clearly noticeable increase for Ru complexes adsorbed on TiO2, but they are too small to be attributed to excitation associated with the direct transfer of an electron from the dye adsorbate to the TiO2 semiconductor. Due to the difficulties arising from standard analysis based on Liptay formalism, we have for the first time successfully reproduced the EA spectra of the Ru/TiO2 systems using the time-dependent density functional (TDDFT) calculations, incorporating into the Hamiltonian a term describing the interaction of a molecule with the local electric field it experiences from the TiO2 structure and the neighboring Ru complex molecules, without additional assumptions about the lineshape of the EA signal. The implications of these results are briefly discussed in the context of dye-sensitized solar cells.
Photoionization-induced charge separation for efficient solar energy conversion
The most important primary process in solar energy conversion systems is photo-induced charge separation. This Perspective summarizes our current understanding of the photoionization-induced charge separation process, which involves the transfer of an electron from a discrete to a continuous electronic state with particular emphasis on the threshold energy and efficiency of photoionization. Based on our understanding of alkane solutions and in aromatic organic crystals, the charge separation mechanism in dye-sensitized solar cells is discussed as a photoionization-induced solar energy conversion system.
Silent magnetic resonance angiography diagnostic value of intracranial unruptured aneurysms
Oxygen K-edge inner-shell calculations of polymers in solutions realized by the extraction of local structures from molecular dynamics simulations
Inner-shell quantum chemical calculations of large molecular systems, such as polymers and soft matter in solution, were performed to understand the phase transition dynamics of these systems using soft x-ray absorption spectroscopy (XAS). The molecular structures of 40-mer poly(N-isopropylacrylamide) (PNIPAM) chains in solutions were obtained using molecular dynamics simulations. The 5-mer PNIPAM chains with terminated H atoms, including the second coordination shells of the solvent methanol and water molecules, were extracted from the 40-mer PNIPAM chains in solutions. The O K-edge inner-shell spectra of the 5-mer PNIPAM chains were obtained by averaging the inner-shell spectra of 9700 extracted polymer structures. This calculation method can be used to precisely evaluate the energy shifts of the C=O π* peaks of PNIPAM caused by the structural changes of the polymer chains, the substitutions of the hydrogen bonds of the C=O groups in PNIPAM from methanol to water molecules, and the increase in the coordination numbers of solvent molecules with the C=O groups, which were observed in the O K-edge XAS experiments.
To construct and validate a risk score model of angiogenesis-related genes to predict the prognosis of hepatocellular carcinoma
On the performance of QTP functionals applied to second-order response properties
Correlated orbital theory (COT) is an exact one-particle treatment that adds essential electron correlation into its molecular orbitals, potentially reducing correlated treatments of response properties to one-particle coupled-perturbed Hartree–Fock- or Kohn–Sham-like calculations. Such a computation is vastly simpler than the usual ab initio correlated approach that would add correlation typically with EOM-CC after a perturbed mean-field solution. The question then is, how well can this be accomplished via the Quantum Theory Project (QTP) exchange–correlation (XC) functionals that are meant to emulate the rigorous COT framework? This paper addresses this question for response properties by making comparisons between such orbital-specific calculations and those from well-correlated EOM-CC solutions for static polarizabilities, nuclear magnetic resonance coupling constants, and chemical shifts. The simple orbital-specific version provides an accurate realization of the correlated EOM-CC results, but now in a mode that facilitates an orbital-by-orbital interpretation. Here, we compare 33 XC functionals from the different Jacob’s ladder rungs always against the EOM-CCSD results. Thus, the smallest mean absolute deviation for the static polarizability comes from LC-QTP XC, 0.28 a.u. Regarding the total nuclear spin–spin coupling constants, QTP01 performs best, %Error = 10.63% (QTP02 and LC-QTP are second and third best). Finally, the XC that stood out in the chemical shift analysis was TPSS0, which presented the best result for the majority of the chemical shifts. However, considering the overall performances based on linear fitting of all isotope data points, five functionals are recommended for a chemical shift study: TPSS0, ωB97X, QTP00, QTP01, and QTP02, all presenting R2 = 0.96.
Direct current electrical fields inhibit cancer cell motility in microchannel confinements
Abstract The capability of cells to sense and respond to endogenous electrical fields plays a crucial role in processes like nerve regeneration, wound healing, and development. In vitro, many cell types respond to electrical fields by migrating along the corresponding electrical field vectors. This process is known as galvano- or electrotaxis. Here we report on the combined impact of micro-confinements and direct current electrical fields (dcEFs) on the motility of MDA-MB-231 human breast cancer cells using a self-developed, easy-to-use platform with microchannels ranging from 3 $$\upmu$$ μ m to 11 $$\upmu$$ μ m in width and 11 $$\upmu$$ μ m height. We found that MDA-MB-231 cells respond to exogenous electrical fields ranging from 100 mV mm $$^{-1}$$ - 1 to 1000 mV mm $$^{-1}$$ - 1 with altered cell motility depending on the confinement size. Our data show an overall inhibited galvanotaxis in confinements, while in contrast an enhancing effect in unconfined galvanotaxis is found. The application of direct current electrical fields to microchannels not only caused a reduction in migration speed but also decreased the number of permeating cells. By applying 1000 mV mm $$^{-1}$$ - 1 , single-cell permeation could be prevented in confinements of 5 $$\upmu$$ μ m and smaller.
State selective preparation and nondestructive detection of trapped O2+
The ability to prepare molecular ions in selected quantum states enables studies in areas such as chemistry, metrology, spectroscopy, quantum information, and precision measurements. Here, we demonstrate (2 + 1) resonance-enhanced multiphoton ionization (REMPI) of oxygen, both in a molecular beam and in an ion trap. The two-photon transition in the REMPI spectrum is rotationally resolved, allowing ionization from a selected rovibrational state of O2. Fits to this spectrum determine spectroscopic parameters of the O2d1Πg state and resolve a discrepancy in the literature regarding its band origin. The trapped molecular ions are cooled by co-trapped atomic ions. Fluorescence mass spectrometry nondestructively demonstrates the presence of the photoionized O2+. We discuss strategies for maximizing the fraction of ions produced in the ground rovibrational state. For (2 + 1) REMPI through the d1Πg state, we show that the Q(1) transition is preferred for neutral O2 at rotational temperatures below 50 K, while the O(3) transition is more suitable at higher temperatures. The combination of state-selective loading and nondestructive detection of trapped molecular ions has applications in optical clocks, tests of fundamental physics, and control of chemical reactions.
Examining tolerability, safety, and blinding in 1032 transcranial electrical stimulation sessions for children and adolescents with neuropsychiatric and neurodevelopmental disorders
Development of interatomic potential suitable for molecular dynamics simulation of Ni oxidation and Ni–NiO interface
Large-scale molecular dynamics (MD) simulations enabled by computationally efficient semiempirical potentials are an invaluable tool for materials modeling. In the case of metallic alloys, embedded atom method (EAM) and Finnis–Sinclair (FS) potentials are a reasonable choice based on their good balance of quality and computational cost. However, these semiempirical potentials are not suitable for simulating ionic systems, which prevents their use in studying many technologically relevant metal–oxide systems. The charge transfer ionic potential (CTIP), which can utilize EAM/FS potentials available in the literature together with a variable charge representation of electrostatic interactions, should be a reasonable choice for performing reliable and computationally efficient MD simulations of such systems. However, only a few such potentials are available in the literature, and their computational cost is much higher compared to EAM/FS potentials. In the present work, we have attempted to remedy these deficiencies by combining several modifications to the CTIP model proposed in the literature and efficiently implementing them into the widely used Large-scale Atomic/Molecular Massively Parallel Simulator MD code. Using these modifications, we have developed a new Ni–O CTIP parameterization, which has been tested in several different scenarios of interest. First, the early stages of Ni surface oxidation were simulated, demonstrating the nucleation and growth of a crystalline NiO film across the surface. Second, solidification and vitrification in the Ni–O system were investigated, demonstrating that the new CTIP parameterization provides reasonable agreement with the experimentally determined equilibrium phase diagram. Finally, we studied the interaction of dislocations in a Ni matrix with a NiO inclusion using a simulation cell with an unprecedented number of atoms for a variable charge MD simulation. Thus, the approach utilized in the present study is an efficient method to simulate large scale atomic mechanisms in metal–oxide systems.
Models based on dietary nutrients predicting all-cause and cardiovascular mortality in people with diabetes
Autonomous walking dynamics of a nanorobot on a nanopore track driven by salt concentration gradients
The walking of a nanorobot with DNA legs requires a preset track to serve as footholds for the DNA legs and a track-matched driving mechanism to propel the nanorobot. Recently, a newly suggested track formed by multiple nanopores has garnered attraction due to its chemical stability. The nanorobot can be powered by biased leg-nanopore interactions along the walking direction. Here, we propose utilizing a salt concentration gradient along the nanopore track to induce an interaction bias based on different local ion screening effects on the nanopore charges. The nanorobot walking behaviors under different salt concentration gradients are studied through a combination of computational simulations and theoretical analyses. We find that the walking properties (such as velocity and directionality) highly depend on the local interactions experienced by the lagging leg. Under strong leg-nanopore attraction, the lagging leg needs a drag force provided by the leading leg to leave from the nanopore, while under weak attraction, the lagging leg can leave the nanopore without the assistance of the leading leg. Therefore, different walking modes can be observed under various ion conditions, leading to the complicated walking dynamics of the nanorobot driven by the salt concentration gradients.
Author Correction: Finite element analysis of restoring length with multiple internal fixations in calcaneal body fracture
RADE: A reduced approach to density-functional expansion
Density-functional theory (DFT) has become an extensively and successfully used tool in the studies of molecules and materials. However, DFT remains computationally expensive, especially for exploring the conformational space of molecular systems comprising a few hundred atoms. Here, we present a Reduced Approach to Density-functional Expansion (RADE), devised to substantially reduce the computational cost of standard DFT methods. RADE can be implemented fully non-empirically as an efficient first-principles electronic structure method. Preliminary results for molecules containing elements H, C, N, and O indicate that this method can, in general, reproduce well the results from standard DFT calculations.
Predictive modeling and optimization of SI engine performance and emissions with GEM blends using ANN and RSM
‘We are a target’: scientific society under pressure after Trump DEI crackdown
Correlating the low-temperature photoluminescence with electron transport properties in cerium oxide thin film
The complex interaction between the intrinsic and extrinsic state variables of strongly correlated insulator thin films is drawing interest as it shows memristive behavior that may be applicable to neuromorphic computing. Cerium oxide is an interesting material as its band structure is modified due to the formation of oxygen vacancy defects. The polaron formation that results from the reduction of the Ce4+ state to the Ce3+ state through oxygen vacancies is crucial for the electron transport in cerium oxide and is strongly influenced by temperature. In this work, we examined the relationship between the change in band structure and the associated conductivity at lower temperatures when ceria is exposed to light. Following light excitation, the creation of oxygen vacancies results in electron localization in the Ce 4f state, followed by the electron transition from 4f1 to 4f0, generating the PL spectra. With decreasing temperature, the lattice vibration decreases, and the splitting in the PL peak at a particular energy state validates the weaker electron–phonon interaction with an exciton trap. This reduces the carrier mobility of the film as observed from the resistance vs temperature curve of ceria under dark conditions. When excited by a particular energy of light, the electrons move more easily from the defect state to the conduction band, increasing conductivity at much lower temperatures than the conductivity under dark conditions.