U and Co Dual Single-Atom Doped MXene for Accelerating Electrocatalytic Hydrogen Evolution Activity.

A large amount of radioactive waste is accumulated in the process of nuclear fuel preparation, causing serious pollution to the environment and abundant depleted uranium resources to be abandoned. One of the key issues affecting the development of nuclear energy is how to make full use of depleted uranium resources efficiently. Here, U element with unique coordination mode of 5f electron is spacer bonded to transition metal with 3d orbit through the adsorption and anchoring effect of MXene, thus U and Co dual doped MXene catalyst is constructed along with the comprehensive utilization of depleted uranium resources. The as-prepared U-Co/MXene catalyst demonstrates excellent overpotential of only 184 mV at -10 mA cm-2 and excellent stability up to 150 h, significantly surpassing the bare MXene substrate. Theoretical calculations indicate that the U and Co dual doping optimizes the electronic structure of MXene catalyst by forming the U-O-Co network, thereby improving the thermodynamics of H* adsorption during the catalytic transition state. This research opens up a new path for the recovery of depleted uranium resources and the development of functional actinide catalysts.

Modeling of collision-induced excitation and quenching of atomic nitrogen.

Excited atomic nitrogen atoms play an important role in plasma formation in hypersonic shock-waves, as happens during spacecraft reentry and other high velocity vehicle applications. In this study, we have thoroughly studied collision induced excitation associated with two colliding nitrogen atoms in the N(4S), N(2D), and N(2P) states at collision energies up to 6 eV, using time-independent scattering calculations to determine cross sections and temperature-dependent rate coefficients. The calculations are based on potential curves and couplings determined in earlier multireference configuration interaction calculations with large basis sets, and the results are in good agreement with experiments where comparisons are possible. To properly consider the spin-orbit coupling matrix, we have developed a scaling method for treating transitions between different fine-structure components that only require calculations with two coupled states, and with this, we define accurate degeneracy factors for determining cross sections and rate coefficients that include all states. The results indicate that both spin-orbit and derivative coupling effects can play important roles in collisional excitation and quenching, and that although derivative coupling is always much stronger than spin-orbit, there are many transitions where only spin-orbit can contribute. As part of this, we identify two distinct pathways associated with N(2P) relaxation and one Auger-like mechanism leading to two N(2D) that could be important at high temperatures.

Total angular momentum conservation in Ehrenfest dynamics with a truncated basis of adiabatic states.

We show that standard Ehrenfest dynamics does not conserve linear and angular momentum when using a basis of truncated adiabatic states. However, we also show that previously proposed effective Ehrenfest equations of motion [M. Amano and K. Takatsuka, "Quantum fluctuation of electronic wave-packet dynamics coupled with classical nuclear motions," J. Chem. Phys. 122, 084113 (2005) and V. Krishna, "Path integral formulation for quantum nonadiabatic dynamics and the mixed quantum classical limit," J. Chem. Phys. 126, 134107 (2007)] involving the non-Abelian Berry force do maintain momentum conservation. As a numerical example, we investigate the Kramers doublet of the methoxy radical using generalized Hartree-Fock with spin-orbit coupling and confirm that angular momentum is conserved with the proper equations of motion. Our work makes clear some of the limitations of the Born-Oppenheimer approximation when using ab initio electronic structure theory to treat systems with unpaired electronic spin degrees of freedom, and we demonstrate that Ehrenfest dynamics can offer much improved, qualitatively correct results.

Linear and angular momentum conservation in surface hopping methods.

We demonstrate that, for systems with spin-orbit coupling and an odd number of electrons, the standard fewest switches surface hopping algorithm does not conserve the total linear or angular momentum. This lack of conservation arises not so much from the hopping direction (which is easily adjusted) but more generally from propagating adiabatic dynamics along surfaces that are not time reversible. We show that one solution to this problem is to run along eigenvalues of phase-space electronic Hamiltonians H(R, P) (i.e., electronic Hamiltonians that depend on both nuclear position and momentum) with an electronic-nuclear coupling Γ · P [see Eq. (25)], and we delineate the conditions that must be satisfied by the operator Γ. The present results should be extremely useful as far as developing new semiclassical approaches that can treat systems where the nuclear, electronic orbital, and electronic spin degrees of freedom altogether are all coupled together, hopefully including systems displaying the chiral-induced spin selectivity effect.

Comparison of LVIS and Enterprise stent-assisted coiling embolization for ruptured intracranial aneurysms: a propensity score-matched cohort study.

The role of a low-profile visualized intraluminal support stent (LVIS) and Enterprise in the treatment of unruptured intracranial aneurysms is well established. Although previous studies have investigated one single type of stent for the treatment of ruptured intracranial aneurysms (RIA), the safety and efficacy between the two types of stents has not been fully explored. Herein we conducted a study to compare the outcomes of the two stents for treatment of RIA. This is a prospective registry database of aneurysmal subarachnoid hemorrhage (aSAH) patients admitted to a single institution between 2018 and 2021. We collected patient baseline information, secondary complications, follow-up angiographic data, long-term prognostic outcomes, and conducted propensity score matching (PSM) analysis with 1:1 ratio and a multivariable logistic regression to compare the outcomes of the two types of stents. A total of 231 patients with RIAs were included in this study, with 108 treated using the LVIS device and 123 treated using the Enterprise device. Before PSM analysis, only the incidence of poor prognosis after 12 months was higher in the Enterprise group comparing to the LVIS group (20% vs. 10%, P = 0.049). After PSM analysis, there was a higher occurrence of delayed cerebral ischemia (DCI) in the Enterprise group compared to the LVIS group (odds ratio [OR] 3.95, 95% confidence interval [CI] [1.20-13.01], P = 0.024). However, no significant difference in prognosis was observed after PSM adjustment. Furthermore, subgroup analysis revealed that patients with female (P = 0.019), hypertension (P = 0.048), and anterior circulation aneurysms (P = 0.019) receiving the Enterprise device had a higher risk of DCI. The overall efficacy of LVIS and Enterprise in the treatment of RIA is comparable, while the incidence of DCI in the LVIS group is lower than that in the Enterprise group after PSM analysis. Registration number: NCT05738083 ( https://clinicaltrials.gov/ ).

A quantum-classical Liouville formalism in a preconditioned basis and its connection with phase-space surface hopping.

We revisit a recent proposal to model nonadiabatic problems with a complex-valued Hamiltonian through a phase-space surface hopping (PSSH) algorithm employing a pseudo-diabatic basis. Here, we show that such a pseudo-diabatic PSSH (PD-PSSH) ansatz is consistent with a quantum-classical Liouville equation (QCLE) that can be derived following a preconditioning process, and we demonstrate that a proper PD-PSSH algorithm is able to capture some geometric magnetic effects (whereas the standard fewest switches surface hopping approach cannot capture such effects). We also find that a preconditioned QCLE can outperform the standard QCLE in certain cases, highlighting the fact that there is no unique QCLE. Finally, we also point out that one can construct a mean-field Ehrenfest algorithm using a phase-space representation similar to what is done for PSSH. These findings would appear extremely helpful as far as understanding and simulating nonadiabatic dynamics with complex-valued Hamiltonians and/or spin degeneracy.

Surface hopping, electron translation factors, electron rotation factors, momentum conservation, and size consistency.

For a system without spin-orbit coupling, the (i) nuclear plus electronic linear momentum and (ii) nuclear plus orbital electronic angular momentum are good quantum numbers. Thus, when a molecular system undergoes a nonadiabatic transition, there should be no change in the total linear or angular momentum. Now, the standard surface hopping algorithm ignores the electronic momentum and indirectly equates the momentum of the nuclear degrees of freedom to the total momentum. However, even with this simplification, the algorithm still does not conserve either the nuclear linear or the nuclear angular momenta. Here, we show that one way to address these failures is to dress the derivative couplings (i.e., the hopping directions) in two ways: (i) we disallow changes in the nuclear linear momentum by working in a translating basis (which is well known and leads to electron translation factors) and (ii) we disallow changes in the nuclear angular momentum by working in a basis that rotates around the center of mass [which is not well-known and leads to a novel, rotationally removable component of the derivative coupling that we will call electron rotation factors below, cf. Eq. (96)]. The present findings should be helpful in the short term as far as interpreting surface hopping calculations for singlet systems (without spin) and then developing the new surface hopping algorithm in the long term for systems where one cannot ignore the electronic orbital and/or spin angular momentum.

Subdomain Adaptation Capsule Network for Partial Discharge Diagnosis in Gas-Insulated Switchgear.

Deep learning methods, especially convolutional neural networks (CNNs), have achieved good results in the partial discharge (PD) diagnosis of gas-insulated switchgear (GIS) in the laboratory. However, the relationship of features ignored in CNNs and the heavy dependance on the amount of sample data make it difficult for the model developed in the laboratory to achieve high-precision, robust diagnosis of PD in the field. To solve these problems, a subdomain adaptation capsule network (SACN) is adopted for PD diagnosis in GIS. First, the feature information is effectively extracted by using a capsule network, which improves feature representation. Then, subdomain adaptation transfer learning is used to accomplish high diagnosis performance on the field data, which alleviates the confusion of different subdomains and matches the local distribution at the subdomain level. Experimental results demonstrate that the accuracy of the SACN in this study reaches 93.75% on the field data. The SACN has better performance than traditional deep learning methods, indicating that the SACN has potential application value in PD diagnosis of GIS.

Chemical Species Transformation during the Dissolution Process of U3O8 and UO3 in the LiCl-KCl-AlCl3 Molten Salt.

In this work, we investigated the dissolution behavior of U3O8 and UO3 in the LiCl-KCl molten salt using 2.9 or 9.5 wt % AlCl3 as a chlorination agent under an argon atmosphere at 450 °C. Ultraviolet-visible/Ultraviolet-visible-near infrared absorption spectroscopy (UV-vis/UV-vis-NIR), fluorescence emission spectroscopy (FL), X-ray absorption fine structure (XAFS), and electrochemical techniques were used to systematically study the chemical species and the transformation of the dissolved products of U3O8 and UO3. It was found that with the aid of AlCl3, the initial products of U3O8 and UO3 dissolution were different. The initial products of U3O8 were UO2Cl42- and UCl62-, while the initial product of UO3 dissolution was UO2Cl42-. Interestingly, regardless of U3O8 or UO3, with the increase of AlCl3 content, the UO2Cl42- in their dissolved products showed a tendency to transform into UCl62-. In addition, UCl4 was produced by mixing 0.05 g of U3O8/UO3 powders with 10 times the amount of AlCl3 and heating them at 300 °C for 2 h. This work focuses on the pyrochemical reprocessing of spent oxide fuels, deepening the understanding of the dissolution of uranium oxides in higher oxidation states, and enriching the knowledge of uranium in the transformation of chemical species in molten salts.

Effect of Duschinskii Rotations on Spin-Dependent Electron Transfer Dynamics.

We investigate spin-dependent electron transfer in the presence of a Duschinskii rotation. In particular, we propagate dynamics for a two-level model system for which spin-orbit coupling introduces an interstate coupling of the form eiWx, which is both position(x)-dependent and complex-valued. We demonstrate that two-level systems coupled to Brownian oscillators with Duschinskii rotations (and thus entangled normal modes) can produce marked increases in transient spin polarization relative to two-level systems coupled to simple shifted harmonic oscillators. These conclusions should have significant relevance for modeling the effect of nuclear motion on chiral induced spin selectivity.

A phase-space semiclassical approach for modeling nonadiabatic nuclear dynamics with electronic spin.

Chemical relaxation phenomena, including photochemistry and electron transfer processes, form a vigorous area of research in which nonadiabatic dynamics plays a fundamental role. However, for electronic systems with spin degrees of freedom, there are few if any applicable and practical quasiclassical methods. Here, we show that for nonadiabatic dynamics with two electronic states and a complex-valued Hamiltonian that does not obey time-reversal symmetry (as relevant to many coupled nuclear-electronic-spin systems), the optimal semiclassical approach is to generalize Tully's surface hopping dynamics from coordinate space to phase space. In order to generate the relevant phase-space adiabatic surfaces, one isolates a proper set of diabats, applies a phase gauge transformation, and then diagonalizes the total Hamiltonian (which is now parameterized by both R and P). The resulting algorithm is simple and valid in both the adiabatic and nonadiabatic limits, incorporating all Berry curvature effects. Most importantly, the resulting algorithm allows for the study of semiclassical nonadiabatic dynamics in the presence of spin-orbit coupling and/or external magnetic fields. One expects many simulations to follow as far as modeling cutting-edge experiments with entangled nuclear, electronic, and spin degrees of freedom, e.g., experiments displaying chiral-induced spin selectivity.

Electron transfer and spin-orbit coupling: Can nuclear motion lead to spin selective rates?

We investigate a spin-boson inspired model of electron transfer, where the diabatic coupling is given by a position-dependent phase, eiWx. We consider both equilibrium and nonequilibrium initial conditions. We show that, for this model, all equilibrium results are completely invariant to the sign of W (to infinite order). However, the nonequilibrium results do depend on the sign of W, suggesting that photo-induced electron transfer dynamics with spin-orbit coupling can exhibit electronic spin polarization (at least for some time).

Semiclassical description of nuclear dynamics moving through complex-valued single avoided crossings of two electronic states.

The standard fewest-switches surface hopping (FSSH) approach fails to model nonadiabatic dynamics when the electronic Hamiltonian is complex-valued and there are multiple nuclear dimensions; FSSH does not include geometric magnetic effects and does not have access to a gauge independent direction for momentum rescaling. In this paper, for the case of a Hamiltonian with two electronic states, we propose an extension of Tully's FSSH algorithm, which includes geometric magnetic forces and, through diabatization, establishes a well-defined rescaling direction. When combined with a decoherence correction, our new algorithm shows satisfying results for a model set of two-dimensional single avoided crossings.

Modeling nonadiabatic dynamics with degenerate electronic states, intersystem crossing, and spin separation: A key goal for chemical physics.

We examine the many open questions that arise for nonadiabatic dynamics in the presence of degenerate electronic states, e.g., for singlet-to-triplet intersystem crossing where a minimal Hamiltonian must include four states (two of which are always degenerate). In such circumstances, the standard surface hopping approach is not sufficient as the algorithm does not include Berry force. Yet, we hypothesize that such a Berry force may be crucial as far as creating chiral induced spin separation, which is now a burgeoning field of study. Thus, this Perspective highlights the fact that if one can generate a robust and accurate semiclassical approach for the case of degenerate states, one will take a big step forward toward merging chemical physics with spintronics.

Chemical Reaction Rates for Systems with Spin-Orbit Coupling and an Odd Number of Electrons: Does Berry's Phase Lead to Meaningful Spin-Dependent Nuclear Dynamics for a Two State Crossing?

Within the context of a simple avoided crossing, we investigate the effect of a complex-valued diabatic coupling in determining spin-dependent rate constants and scattering states. We find that, if the molecular geometry is not linear and the Berry force is not zero, one can find significant spin polarization of the products. This study emphasizes that, when analyzing nonadiabatic reactions with spin orbit coupling (and a complex-valued Hamiltonian), one must consider how Berry force affects nuclear motion-at least in the context of gas phase reactions. Work is currently ongoing as far as extrapolating these conclusions to the condensed phase, where interesting spin selection has been observed in recent years.

Extracting the mechanisms and kinetic models of complex reactions from atomistic simulation data.

Determining reaction mechanisms and kinetic models, which can be used for chemical reaction engineering and design, from atomistic simulation is highly challenging. In this study, we develop a novel methodology to solve this problem. Our approach has three components: (1) a procedure for precisely identifying chemical species and elementary reactions and statistically calculating the reaction rate constants; (2) a reduction method to simplify the complex reaction network into a skeletal network which can be used directly for kinetic modeling; and (3) a deterministic method for validating the derived full and skeletal kinetic models. The methodology is demonstrated by analyzing simulation data of hydrogen combustion. The full reaction network comprises 69 species and 256 reactions, which is reduced into a skeletal network of 9 species and 30 reactions. The kinetic models of both the full and skeletal networks represent the simulation data well. In addition, the essential elementary reactions and their rate constants agree favorably with those obtained experimentally. © 2019 Wiley Periodicals, Inc.

Predicting Thermodynamic Properties of Alkanes by High-Throughput Force Field Simulation and Machine Learning.

Knowledge of the thermodynamic properties of molecules is essential for chemical process design and the development of new materials. Experimental measurements are often expensive and not environmentally friendly. In the past, studies using molecular simulations have focused on a specific class of molecules, owing to the lack of a consistent force field and simulation protocol. To solve this problem, we have developed a high-throughput force field simulation (HT-FFS) procedure by combining a recently developed general force field with a validated simulation protocol to calculate thermodynamic properties for large number of molecules. This procedure is applied to calculate liquid densities, heats of vaporization, heat capacities, vapor-liquid equilibrium curves, critical temperatures, critical densities and surface tensions for a wide range of alkanes. The predictions agree well with available experimental data in terms of accuracy and precision, demonstrating that HT-FFS is a valid approach to supplementing experimental measurements. Furthermore, the large amount of data generated by HT-FFS lays a foundation for machine learning. We have developed an artificial neural network that demonstrates the feasibility of expanding predictions beyond simulation using a machine learning model.

Liquid Exfoliation and Electrochemical Properties of WS2 Nanosheets.

Commercial WS2 powders were exfoliated in sodium dodecyl sulfate solution with a combination of ball-milling and sonication. WS2 nanosheets can be uniformly dispersed in the solution. The layers and thicknesses of WS2 nanosheets could be tailored via changing the ball-milling speed. The effects of the ball-milling speed on crystallinity and morphology of the samples were analyzed. The results show that the layer structure of WS2 nanosheets is destroyed and the crystallinity is decreased with increase of the ball-milling rate. The monolayer WS2 nanosheets at 200 rpm are obtained, which are mesoporous with the specific surface area as 5.419 m2 g-1. The specific capacitance and charge/discharge efficiency of WS2 nanosheets at 200 rpm are better than those of other samples. Its specific capacitance under the scanning rate of 20 mV s-1 and the current density of 0.5 A g-1 are 13.46 F g-1 and 22.50 F g-1, respectively. The charge/discharge curve of WS2 nanosheets at 200 rpm is a symmetrical triangle, which shows rapid charge and slow discharge. It means that WS2 nanosheets at 200 rpm has good electrochemical reversibility. The load transfer resistance and the internal series resistance of this sample are 84.60 Ω and 4.18 Ω, respectively.

Myosin phosphatase target subunit 1 (MYPT1) regulates the contraction and relaxation of vascular smooth muscle and maintains blood pressure.

Myosin light chain phosphatase with its regulatory subunit, myosin phosphatase target subunit 1 (MYPT1) modulates Ca(2+)-dependent phosphorylation of myosin light chain by myosin light chain kinase, which is essential for smooth muscle contraction. The role of MYPT1 in vascular smooth muscle was investigated in adult MYPT1 smooth muscle specific knock-out mice. MYPT1 deletion enhanced phosphorylation of myosin regulatory light chain and contractile force in isolated mesenteric arteries treated with KCl and various vascular agonists. The contractile responses of arteries from knock-out mice to norepinephrine were inhibited by Rho-associated kinase (ROCK) and protein kinase C inhibitors and were associated with inhibition of phosphorylation of the myosin light chain phosphatase inhibitor CPI-17. Additionally, stimulation of the NO/cGMP/protein kinase G (PKG) signaling pathway still resulted in relaxation of MYPT1-deficient mesenteric arteries, indicating phosphorylation of MYPT1 by PKG is not a major contributor to the relaxation response. Thus, MYPT1 enhances myosin light chain phosphatase activity sufficient for blood pressure maintenance. Rho-associated kinase phosphorylation of CPI-17 plays a significant role in enhancing vascular contractile responses, whereas phosphorylation of MYPT1 in the NO/cGMP/PKG signaling module is not necessary for relaxation.

Effect and its mechanism of potassium persulfate on aerobic composting process of vegetable wastes.

Vegetable waste (VW) is a potential organic fertilizer resource. As an important way to utilize vegetable wastes, aerobic composting of VW generally has the problems of long fermentation cycle and incomplete decomposition of materials. In this study, 0.3-1.2% of potassium persulfate (KPS) was added to promote the maturity of compost. The results showed that the addition of KPS promoted the degradation of materials, accelerated the temperature rise of compost. KPS also promoted the formation of humic substances (HS). Compared with the control, HS contents of treatments with KPS addition increased by 7.81 ~ 17.52%. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) analysis reveal the mechanism of KPS affecting the composting process: KPS stimulated the degradation of various organic substances such as lignin at high temperature stage, and the degradation of lignin could accelerate the release and decomposition of other components; KPS made the structure of the material looser, with more voids and pores, and more specific surface area of the material, which was more suitable for microbial degradation activities. Therefore, the addition of KPS can promote the decomposition of organic matter in the early stage of composting, accelerate the process of thermophilic phase, and shorten the composting process and improve product maturity.