We introduce a computationally simple algorithm for sampling open-chain distributions within the framework of imaginary-time Feynman path integration. The present method is based on the staging algorithm introduced by Pollock and Ceperley [Phys. Rev. B 30, 2555 (1984)] originally developed for computing position-dependent observables. Here, we sample off-diagonal elements of the density matrix, formulated as a distribution describing a linear polymer-like chain of beads, each connected via nearest-neighbor springs to calculate momentum-dependent quantities. This is achieved using a Monte Carlo scheme that ensures efficient and unbiased sampling of all beads along the chain from the free-particle distribution via a staging transformation; we refer to this approach as staging open path integral Monte Carlo (OPIMC). The proposed algorithm is straightforward to implement, as it only involves sampling Gaussian distributions through a transformation defined by a set of recursion relations, followed by a standard Metropolis acceptance/rejection step. The staging OPIMC method accurately reproduces end-to-end and momentum distributions for quantum systems ranging from coupled harmonic oscillators to liquid water.

A new kinetics calculation method using factorization and proper orthogonal decomposition (POD) is proposed. In the present method, discretized neutron balance equations that have fine and coarse time resolutions are derived using the factorization of the neutron flux. Then dimensionality reduction using POD is applied to the fine time-step calculation. The orthogonal basis for POD is constructed from the flux distributions at the current and previous coarse time steps on the fly. The fine time dependence captured in the fine time-step POD calculation is reflected in the coarse time-step calculation to accurately span the solution space around the next time step. The accuracy and performance of the present method are verified in the TWIGL benchmark problem. The calculation results show that the present method achieved a 26% speedup while maintaining accuracy compared to the conventional multigrid amplitude function method in the present calculation conditions.

Development of micro-Raman spectroscopy for determination of 18O/16O ratio of forsterite (Mg2SiO4).

We present an analytic gradient method for divide-and-conquer (DC)-based nonlocal excited-state calculations, enabling efficient geometry optimization of large molecular systems exhibiting delocalized or charge-transfer excitations. Transition density matrices are extracted from response densities near polarizability poles, and subsystem Z-vector equations are solved independently, reducing the dominant computational scaling from O(N3.55) in standard time-dependent Hartree-Fock/density functional theory to O(N1.60). Applications to push-pull polyenes and [9]cycloparaphenylene ([9]CPP) demonstrate that the DC-based gradients systematically converge toward standard results with increasing buffer size and accurately reproduce excited-state structural relaxation, including the pronounced quinoid distortion and large Stokes shift in [9]CPP. These results establish the present method as a practical and scalable approach for excited-state geometry optimization in systems beyond the feasible range of conventional excited-state techniques.

This paper presents a high-order generalized differential quadrature element (GDQE)-thermal lattice Boltzmann flux solver (TLBFS) for simulating incompressible thermal flows. The GDQE method partitions the computational domain into multiple elements, within which the GDQ technique is applied to approximate solution gradients and flux divergences via high-order polynomial interpolations. The TLBFS is then utilized to reconstruct the distribution functions of density and internal energy, enabling the simultaneous evaluation of inviscid and viscous fluxes. Numerical examples confirm that the present method is well-suited for handling thermal flow problems with curved boundaries and complex geometry on arbitrary meshes, while achieving good solution accuracy and computational efficiency. The good performance also suggests the great potential in solving practical thermal flow problems.

A simple HPLC method for selective determination of hydrogen sulfide and bound sulfane sulfur in human plasma.

Ultrasound assisted extraction combined with NH2-MIL-101(Cr)/ polysulfone thin film-μSPE for determination of pesticides in food samples.

A simple one-pot protocol is described for the synthesis of dispiro[fluorene-9,3'-pyrazole-5',4″-pyrazolidines] via a [3 + 2] cycloaddition reaction between 9-diazo-9H-fluorene (DF) and a series of (E/Z)-4-arylidene-1-phenylpyrazolidine-3,5-diones (APPs). In all cases, the cycloaddition proceeds with complete regioselectivity, affording a single regioisomeric framework as a pair of diastereomers through an endo approach. The structures and regiochemical outcomes of the cycloadducts were established by comprehensive 1D and 2D NMR spectroscopic analyses (1H, 13C, DEPT-135, COSY, 1H-HSQC, HMBC, and ROESY). The regiochemistry and mechanism of the cycloaddition reaction were investigated using density functional theory (DFT) calculations at the B3LYP/cc-pVTZ level of theory, supported by analysis of global and dual local electrophilicity and nucleophilicity descriptors. To rationalize the observed stereoselectivity, the relevant transition-state structures were located and optimized using a QST3-based transition-state search at the same level of theory. Global electron density transfer (GEDT) analysis revealed that the cycloaddition reactions are highly polar, with electron density flowing from 9-diazo-9H-fluorene (DF) toward the (E/Z)-4-arylidene-1-phenylpyrazolidine-3,5-dione (APP) framework. Consistently, molecular electrostatic potential surface (MESP) analysis showed that, in the energetically favored transition states, the reacting partners approach through regions of opposite electrostatic potential, leading to stabilizing electrostatic interactions between the two fragments. The computational results are consistent with the experimental observations and support a polar, synchronous one-step cycloaddition mechanism. The developed protocol affords the desired dispiro compounds in good to excellent yields (59-91%) with complete regioselectivity, providing a single regioisomeric framework as a pair of diastereomers. This work provides valuable insights into diazo-based cycloaddition chemistry and is expected to stimulate further research in the synthesis of structurally complex spiroheterocycles. Compared to previously reported approaches, the present method offers a simple one-pot strategy with high efficiency, complete regioselectivity, and operational simplicity.

Two-trace two-dimensional correlation spectroscopy (2T2D-COS) approach to analyze Fourier transform infrared (FTIR) spectroscopic data of melamine adulterated milk powder: A quantitative approach.

Complex, powerful, and representative fractional SDDMs are used to model fractional-order systems of stochasticity and time delays. This study aims to construct an approximate spectral collocation scheme, numerically solving certain types of these models. Specifically, a suitable model of conformable fractional operator sense where the stochastic term is of the standard one-dimensional SBM type, and the time delay is discrete and constant, is established and solved. The proposed scheme is based on the spectral collocation method, with SLP basis functions and SLGL collocation points. To obtain the desired approximate solutions utilizing the present method, the domain under consideration is discretized into steps, and at each step, the solution is approximated using the spectral collocation technique. Simply, complicated problems are evolved into a system of algebraic equations where the unknowns are the Legendre coefficients. These equations are solved utilizing an appropriate numerical method executed by MATHEMATICA. For convenience, the convergence analysis under Lipschitz properties is presented. To validate the reality of the method, some applications of linear and nonlinear types of the suggested model are solved, and the errors are computed. Moreover, the Log-Log plots are sketched to confirm the efficiency of the presented method when more collocation points are used. The results formulated in tables, figures, and discussions illustrate the high accuracy and capability of the proposed methodology. Final remarks and future work are reviewed and debated, too.

Direct carboxylation of C(sp 3 )H bonds with carbon dioxide (CO 2 ) offers an attractive route to value‐added carboxylic acids but remains challenging due to the inertness of both reaction partners. Here, we report a fundamentally distinct electrochemical strategy that enables carboxylation of dibenzylic C(sp 3 )H bonds using hydrogen atom transfer (HAT) species reductively generated at the cathode. This represents a rare example of C(sp 3 )H bond functionalization mediated by cathodically generated HAT species. In contrast to anodic HAT systems that require interelectrode diffusion of reactive intermediates, the present method allows all the elementary steps (HAT species generation, C(sp 3 )H bond cleavage, and CO 2 incorporation) to occur at the same cathode. Consequently, the reaction proceeds efficiently under mild conditions (room temperature, 1 atm CO 2 ) without requiring an external sacrificial redox reagent, affording carboxylation products in good yields (up to 69%) within a short reaction time (2 h). Mechanistic studies support a pathway involving sequential electron transfer‐chemical reaction (EC) and CO 2 ‐coupled electron transfer processes for HAT species generation. This work establishes a mechanistically defined platform for electrochemical dibenzylic C(sp 3 )H bond functionalization.

Polarity‐inversion S N Ar offers a useful solution to the electronic limitations of classical two‐electron nucleophilic aromatic substitution. Here, we report a hydrogen peroxide‐initiated S N Ar of halophenols with carboxylic acids using commercially available 30% aqueous H 2 O 2 as a simple initiator. Under operationally straightforward conditions, this method converts readily available halophenols into para ‐acyloxy arenes, accommodates a broad range of carboxylic acids, and is readily scalable to gram scale. The electrophile scope, however, shows a clear dependence on ortho substitution adjacent to the phenolic OH group. Overall, the present method provides a practical and complementary H 2 O 2 ‐initiated option for thermally driven carboxylate coupling of halophenols.

Planar multi-loop mechanisms often generate a large number of non-isomorphic candidate topological graphs during automatic synthesis, making it difficult to efficiently identify configurations that satisfy engineering-oriented functional requirements. To address this issue, a loop-constrained connectivity calculation method and a connectivity-based localization and screening procedure are proposed. The proposed connectivity calculation is directly formulated for general planar non-fractionated kinematic chains (NFKCs), including those with multiple joints. For planar fractionated kinematic chains (FKCs), however, the present method is not applied directly at the full-system level, but only to decomposed non-fractionated subchains after system-level decomposition. Starting from a structurally admissible set of candidate topological graphs, a connectivity matrix is established for automatic localization of the base and the end-effector (EE). Functional screening is then performed by combining the connectivity criterion with object-oriented rules on hydraulic driving-pair arrangement and driving-redundancy patterns. The method was validated using the 10-link, 3-DOF single-joint equivalent of the KC1 subchain of a mine scaler manipulator arm. Under the prescribed structural and functional constraints, 249 admissible configurations were obtained. The results indicate that the proposed method provides an effective basis for application-oriented topological screening and subsequent dimensional synthesis.

Abstract This paper presents a robust Wide Strip Transition Matrix (WSTM) method for analyzing the vibration behavior of a restrained orthotropic plate subjected to in-plane compression and resting on Winkler-Pasternak foundations. This study highlights the complexity of the mathematical analysis of this advanced plate, which has significant applications across various engineering fields, including aerospace panels, composite bridge decks, pavements, and machine foundations. WSTM integrates analytical nodal lines and wide strips into transition matrices via Winkler-Pasternak foundation coupling, yielding a lower-order eigenvalue problem across a limited number of wide strips. This process achieves superior modal accuracy compared to other advanced analytical and numerical methods, while significantly reducing computational costs and processor memory. The innovation of the WSTM lies in integrating the wide strip concept with a precise transition matrix derived directly from the modal ordinary differential equations, based on the plate's partial differential equation of motion. The numerical results are obtained by employing the WSTM method as an initial value algorithm that utilizes an improved transition matrix operating on panels divided into wide strips. Compared to numerical methods like finite element, finite difference, or finite strip methods, the proposed approach eliminates the need for extensive element formulation and the solution of large systems of algebraic equations. The advantages of the present method are discussed, and its convergence, stability, and accuracy are demonstrated. The findings strengthen the reliability of predicting dynamic responses and stability limits. This evidence, in turn, enables the optimized design of plate-like structural components in engineering applications. .

The transformation of readily available materials into high-value-added chemicals through rearrangement processes has always been a hot topic and a significant challenge in organic synthesis. Herein, we report a Cu-catalyzed divergent rearrangement reaction of propargyl ethers to access indenes and benzofurans via the 1,4-aryl migration-cyclization reaction and [3,3]-σ-rearrangement, respectively. Without the use of an excessive reductant and strong protic acid, the present method exhibits excellent functional group compatibility and therefore has diverse chemical transformations. Furthermore, the atom and step economical protocol, readily accessible starting materials, and mild reaction conditions give this novel method potential for applications in organic synthesis.

Decellularized bovine and porcine pericardia are the most extensively used biological substitutes in clinical settings as self-regenerating replacements for treating cardiovascular anomalies. Despite advancements, these substitutes undergo early deterioration and degeneration if not crosslinked. The chemical crosslinking of these scaffolds, aimed at addressing their weak mechanical strength, hinders their long-term performance and regenerative efficacy. The present method describes the systematic evaluation of an alkaline-catalyzed, low-temperature mediated citric acid crosslinking strategy to incorporate silk fibroin (SF) for enhancing the biomechanical properties and stability of decellularized porcine pericardia (DPP) . Decellularization was performed using the tridecyl alcohol (ATE) method. Silk fibroin reinforced porcine pericardium (SFDPP) was systematically analyzed for successful incorporation of SF using histology, Confocal Raman microscopy, and SEM. Thermal analysis, biomechanical properties, suturability, and resistance to collagenase degradation has demonstrated increased strength and durability. In vitro cytocompatibility and toxicological studies further confirmed that SFDPP is biocompatible and non-toxic, making it suitable for cardiovascular applications. Rat subcutaneous implantation has proven SFDPP to be associated with significantly reduced inflammation and mineralization compared to the commercially available SJM Biocor pericardial patch. Results from rat abdominal wall defect and pig aortic vascular defect models demonstrated that SFDPP patch promoted structural restoration by site-appropriate constructive remodelling in both the defects. All these evidences confirmed its efficacy as a potential patch for treating cardiovascular defects.

Abstract We propose an enhanced machine learning method to calculate the ground state of two-body systems. By extending the original method [Phys. Rev. Res. 5 , 033189 (2023)], the present method enables consideration of the spin and isospin degrees of freedom by employing a non-fully connected deep neural network and unsupervised machine learning technique. The validity of this method is verified by calculating the unique bound state of the deuteron.

Spectroscopic probing of ultrafast chiral molecular dynamics gives deep insight into the mechanism of biomolecular reactions, since the three-dimensional molecular structure plays crucial roles in the selectivity and efficiency of the reactions. Here, we demonstrate a practical method for tracking the change of the absolute configuration of photoexcited biomolecules by combining ultrafast and broadband time-resolved circular dichroism (TRCD) spectroscopy with exciton coupling theory. A proof-of-principle experiment on bilirubin-human serum albumin (BR-HSA) complexes reveals that the excited-state CD spectra show sign inversion with a time constant of ∼5 ps. Instead of a complete chirality inversion across a high energy barrier, we attribute this sign reversal to a structural change from the stable ridge-tile conformation to a stretched conformation based on exciton coupling theory. These results show that the present method is a useful tool for probing excited-state molecular dynamics accompanying structural changes on a real-time basis.

Krokinobacter eikastus rhodopsin 2 (KR2) is a microbial light-driven ion pump that transports Na+ out of the cell. The active transport is coupled to a photocycle of the retinal chromophore, covalently attached to the protein via a Schiff base linkage. In this work, we have employed time-resolved pump-probe resonance Raman (TR RR) spectroscopy to characterize the operational switches of KR2 that control Na+ uptake from the cytosol and release to the exterior. The analysis was based on a comprehensive spectroscopic investigation of the parent state using different excitation lines. Two substates were identified in which the Asp116 counterion and water positions differ with respect to the Schiff base. In line with published crystallographic data, one of the substates was ascribed to the active configuration that binds Na+ after deprotonation of the Schiff base. The main advantage of the present TR RR method is that chromophore structures of the photocycle intermediates and their kinetics can be determined. Thus, we identified two redshifted intermediates O1 and O2 formed within ca. 2 and 5-7 ms after illumination, in which the chromophore adopts a protonated 13-cis and all-trans configuration, respectively. This isomerization is ascribed to be the switch for Na+ release.

The elastic moduli of recycled carbon fiber nonwoven reinforced polymer (rCFRP) plates are studied using statistical methods to account for the curved, aligned, and entangled fibers. The effect of these fibers on elastic properties is quantified by introducing a joint expected fiber length cumulative distribution function (JELCDF) per unit area with respect to an orientation angle and curvature. The curvatures and orientation angles of the fibers are measured at the crossing point with the reference line. The explicit polynomial functions of the JELCDF are determined from experimental results using the least-squares method. The joint expected fiber length density function is used to estimate the orthotropic elastic moduli of the rCFRP plate, based on a self-consistent scheme where the curvature effect is neglected. The estimated results show good agreement with the experimental results and the present probabilistic method can be an effective method to estimate the performance of the rCFRP laminates.