Browse Articles

pH-dependent orientation of pyruvic acid and interfacial water at the air–water interface: Insights from sum-frequency generation spectroscopy and molecular dynamics

The molecular orientation and interfacial behavior of pyruvic acid at the air–water interface were investigated as a function of pH using phase-sensitive sum-frequency generation (SFG) spectroscopy combined with density functional theory molecular dynamics simulations. By performing polarization-resolved SFG measurements on both the protonated and deprotonated forms of pyruvic acid, we characterized the vibrational signatures of the carbonyl, carboxyl, and carboxylate groups, gaining insights into their relative orientations in each state. Our results reveal a pH-dependent shift in the deprotonation equilibrium at the interface, accompanied by distinct reorientations of pyruvic acid functional groups: the deprotonated COO− and C=O groups preferentially tilt toward the bulk aqueous phase. Furthermore, the orientation and hydrogen-bonding network of interfacial water molecules respond sensitively to pyruvic acid deprotonation, as evidenced by a reversal in the sign of the O–D stretching mode, indicating a reorientation of water dipoles. These findings offer detailed molecular-level insights into the structural dynamics of pyruvic acid at aqueous interfaces, with significant implications for understanding interfacial acid–base chemistry and solvation processes, which may serve as a foundational step toward unraveling pyruvic acid photochemistry.

Barrier impermeability is associated with migratory ungulate survival rates

Analytical analysis of the conformational and rheological properties of flexible active polar linear polymers under shear flow

The conformational and rheological properties of active polar linear polymers under linear shear flow are studied analytically. We describe a discrete active polar linear polymer as an inextensible flexible Gaussian bead–spring chain supplemented by active forces along the bonds. The linear, non-Hermitian equations of motion are solved by an eigenfunction expansion in terms of a biorthogonal basis set. The model reveals an intimate coupling between activity and shear flow, which implies activity-enhanced polymer conformational and rheological properties. Compared to a passive polymer, we find a significantly enhanced shrinkage transverse to the flow direction with increasing shear rate, with a power-law exponent of −4/3, compared to the passive value of −2/3. This conformational change is tightly linked with a strongly amplified shear-thinning behavior, where the shear viscosity exhibits the same power law. The characteristic shear rate for the onset of these effects is determined by the activity. In the asymptotic limit of large activities, the shear-induced features become independent of activity and equal to those of passive polymers.

Effects of rear-foot instability devices on lower-limb muscle activation during the Bulgarian split squat in male football players

Abstract Unilateral resistance exercises such as the Bulgarian Split Squat (BSS) are commonly used to develop lower-limb strength, postural control, and neuromuscular coordination, depending on training variables (e.g., load and intensity). Although instability training increases muscle activation, few studies have examined the effect of rearfoot instability on neuromuscular responses during BSS. This randomized crossover study investigated the acute effects of three rear-foot instability devices on muscle activation during the ascent and descent phases of the BSS in 23 trained male football players. Participants performed body-weight BSS under four conditions: stable platform, BOSU ball, Swiss ball (Swiss), and TRX suspension. Surface electromyography (sEMG) recorded activation of the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), semitendinosus (ST), and gluteus maximus (GM). Two‑way repeated‑measures ANOVA showed significantly greater activation during ascent for BF ( p  < 0.001), ST ( p  = 0.006), VL ( p  < 0.001), VM ( p  < 0.001), and GM ( p  < 0.001). Quadriceps activation during descent was highest on the Swiss: RF (Swiss vs. stable: p  = 0.002; Swiss vs. BOSU: p  < 0.001; Swiss vs. TRX: p  = 0.006), VL (Swiss vs. stable: p  = 0.017; Swiss vs. BOSU: p  = 0.001), and VM (Swiss vs. stable: p  = 0.024; Swiss vs. BOSU: p  = 0.046). TRX increased ST activation during the ascent compared to the Swiss ( p  = 0.034), and the BOSU showed higher ST activation than the Swiss during the descent ( p  = 0.004). Surface significantly affected activation (ST: p  = 0.018; RF: p  < 0.001; VL: p  < 0.001; VM: p  = 0.013; GM: p  = 0.042), and there was a significant surface × phase interaction for GM ( p  = 0.041). The findings highlight rearfoot instability as an effective programming variable to selectively enhance muscle activation without external loading, supporting its application in strength and rehabilitation programs.

An anomalous high-pressure phase and decompression-induced amorphization in dinitrotoluene

We investigate the high-pressure behavior of 2,4-dinitrotoluene (2,4-DNT), an energetic molecular solid, using in situ Raman spectroscopy (up to ∼19 GPa) and synchrotron x-ray diffraction (up to ∼12.3 GPa). Raman spectra reveal conformational rearrangements of the ortho-NO2 group near 1.5 GPa and a structural phase transition between 4 and 8 GPa. X-ray diffraction measurements corroborate this transition, showing the onset at ∼4.5 GPa and sluggish completion by ∼8.4 GPa. The ambient phase shows pronounced anisotropic compression, consistent with its layered crystal structure, while both phases display negative linear compressibility. In the high-pressure phase, only one-dimensional long-range order is preserved, accompanied by the formation of new hydrogen bonds. A larger phonon gap in 2,4-DNT (∼104 cm−1) indicates reduced impact sensitivity compared to trinitrotoluene [trinitrotoluene (TNT), ∼80 cm−1]. Upon decompression, two distinct recovery pathways are observed: samples released from P ≤ 10 GPa revert to the ambient phase with hysteresis, while those released from P ≥ 12.3 GPa undergo decompression-induced amorphization due to the changes in the hydrogen bonding network. The contrasting compression and recovery behavior of 2,4-DNT and TNT are also discussed, highlighting the critical role of functional-group interactions and pressure history in governing phase stability and amorphization in energetic molecular crystals.

GIS-integrated flood risk assessment for metro systems based on bayesian cosine maximization method: a case study in Beijing

Rotational relaxation of SH+ by collisions with He

The first two-dimensional potential energy surface for the interaction between He and SH+(3Σ−) has been calculated using CCSD(T)/aug-cc-pVXZ(X = T,Q,5) supplemented by a three-term extrapolation scheme. This surface is subsequently employed in close coupling calculations to investigate the collision dynamics of SH+ with He atoms. The collisional cross sections for fine structure energy levels are computed. The de-excitation rate coefficients for the lower fine structure levels of SH+ molecules due to collisions with He are determined over a temperature range of 10–500 K.

Novel structures of chaos-based parallel multiple image encryption and FPGA implementation

Abstract Image data has been generated massively by devices in medical imaging modalities, cameras, and even by artificial intelligence. Encryption is the powerful method to keep the image content confidential, in which an encryption algorithm must include the confusion and diffusion properties. For massive images, a efficient method of encryption must be chosen to meet the demands of encryption speed and confidentiality. So far, chaos-based image encryption has been an active topic of research because it is considered an effective method to remove the correlation in image data as well as to keep confidential by the involvement of chaotic system in the encryption process. Besides, multiple image encryption algorithms encrypt multiple images in parallel, and it provides highly efficient performance in term of speed if it is implemented on a parallel computing platform such as multiple core processing as well as digital hardware design. Chaos-based multiple image encryption is constructed by integrating a chaotic system into multiple image encryption. Recently, many algorithms of chaos-based multiple image encryption have been proposed, and they are proved to have high efficient in terms of both speed and confidentiality. However, all the existing algorithms of chaos-based multiple image encryption require images of the same size and of the same number of bits representing pixels. Further, they encrypt a cohort of plain images at the same time, and all ciphertext images of a cohort must also be decrypted at the same time. It means that if it does not allow to decrypt one or some selected ciphertext images from a cohort separately; and as a result, it wastes time and energy to decrypt unwanted images. In this paper, three novel structures of chaos-based multiple image encryption are proposed which overcome the drawbacks of existing algorithms. That is, the proposed cryptosystems accept cohort images of different sizes; pixels of images can be represented by different numbers of bits; and any selected ciphertext images from a cohort can be decrypted separately. The security is improved by using the session keys of image-content dependency. The proposed structures of multiple image encryption consist of permutation, substitution, and diffusion processes. The difference between three structures is the order of such processes. A perturbed chaotic map and a linear-feedback shift register are employed to generate pseudo-random bit sequences for session keys. The simulation results for the exemplar designs using the proposed structures show the effectiveness by means of the statistical analysis for the session keys using the NIST randomness test, information entropy, histogram, and correlation coefficients of adjacent pixels in ciphertext images, and security analysis by means of space and sensitivity of the secret key. The hardware implementation on the FPGA platform demonstrates the feasibility of the proposed structures by means of throughput and hardware efficiency.

Semiclassical analytic theory of multi-channel electronic energy transfer in nonadiabatic atomic collisions

The semiclassical theory of nonadiabatic energy transfer [Adamovich and Rich, J. Chem. Phys. 160, 194101 (2024)] is extended to include multi-channel electronic excitation and quenching in three-dimensional atomic collisions. The transition probabilities, cross sections, and rate coefficients predicted by the theory are compared with high-fidelity quantum scattering predictions for N + N, using state-of-the-art ab initio interaction potentials and nonadiabatic couplings, and with a few available experiments. The theory predictions are in good agreement with quantum scattering, both for conditions where the energy transfer is dominated by a single pair of adiabatic potentials and in cases where the energy transfer is affected by additional intermediate states. These cases include multiple curve crossings encountered during a single collision and pathways with the formation of closed channels, resulting in multiple resonances. The latter case is of particular interest, since it cannot be reduced to the interaction of individual potential pairs. Analytic expressions for the cross sections and rate coefficients are obtained using the same approach as in our previous work. The results quantify the effect of multi-channel interactions on the dynamics of energy transfer in atomic collisions. This approach can also be used to predict rate coefficients for electronic energy transfer in N + O and O + O collisions, as well as other atomic species collisions, such as involving Ar or He, over a wide range of temperatures. The fidelity of the theory predictions depends on the availability of accurate potentials for the interacting excited electronic states and their coupling (both spin–orbit and derivative). The results provide rate coefficients for the predictive simulation of low-temperature plasmas and plasmas generated behind hypersonic shock waves.

Natural talc: a basic, cost-effective, and available catalyst for the one-pot synthesis of dihydropyranochromenes and pyranopyrazoles, along with related DFT calculations

Abstract This study investigates environmentally friendly and efficient protocols for synthesizing two distinct heterocyclic scaffolds: pyranopyrazoles and dihydropyranochromenes. Dihydropyranochromenes were synthesized using talc in refluxing ethanol, while pyranopyrazoles were obtained from solvent-free under mixing conditions. The advantages of these methods include high yields, operability, and the use of an accessible, inexpensive, and non-toxic basic catalyst. The reaction conditions, including reaction time, molar ratios of reactants, and catalyst amount, were optimized for the synthesis of products, resulting in high yields of 97% for pyranopyrazoles and 95% for dihydropyranochromenes. The synthesized products were characterized using analytical techniques, including FTIR and NMR, which confirmed the successful synthesis. In this study, total energy and band gap energy calculations were performed for dihydropyranochromenes and pyranopyrazoles derivatives. This suggests that talc powder a natural catalyst, can enhance organic synthesis and offer a sustainable and environmentally friendly solution for modern organic chemistry.

Static and dynamic properties of a binary, symmetric mixture of ultrasoft particles in the vicinity of criticality

We investigate the static and the dynamic properties of a binary, equimolar, size-symmetric mixture of ultrasoft particles in the vicinity of the critical point of the system. Based on the generalized exponential potential (GEM) of order four for the particle interaction and using extensive molecular dynamics simulations in the canonical ensemble, we investigate the above-mentioned properties for various scenarios: we consider several supercritical and subcritical states, and we expose the system to rapid quenches and to external shearing forces. Based on an accurate determination of the phase diagram and of the location of the critical point, we study the static structure of the system in terms of particle-based radial distribution functions. As systems of GEM particles are prone to cluster formation, we complement these investigations with a detailed analysis of the composition of the clusters and of their spatial correlations for the different scenarios introduced above. Furthermore, we analyze the temperature dependence of the diffusivity of the particles and the shear viscosity of the system. All these data provide a detailed and profound insight into the properties of the system under phase separation conditions and near criticality.

Climate-driven flood hazard assessment in data-scarce mountainous basins using a GIS-based machine learning and hydrodynamic modelling under CMIP6 SSP scenarios

Non-equilibrium Trajectory Sampling (NETS) method for generating free-energy landscapes and steady-state distributions

This study presents a novel method for constructing free-energy profiles and steady-state distributions from either equilibrium or non-equilibrium trajectories along a defined reaction coordinate. The method works by tracking the final states of a swarm of short simulations launched under different initial conditions with no prior knowledge of the free energy landscape. Subsequently, this trajectory information is used to build a transition matrix whose primary eigenvector captures the steady-state occupation probability for each value of the reaction coordinate, yielding the free energy profile in equilibrium. This innovative method holds potential for many new materials and engineering applications where it is desired to know the free energy of rate-limiting configurations as may be relevant for transport processes (in, e.g., battery electrolytes and nano-filtration membranes), complexation (in, e.g., self-assembly and ligand-binding interactions), or in tuning properties such as adsorption. We illustrate the effectiveness of the method by capturing the free energy associated with a one-dimensional barrier potential modeling a separation membrane and the particle distribution associated with thermophoresis under a temperature gradient. Further extensions and applications of the method are also discussed.

Mechanistic insights into dissolution enhancement of co-spray dried meloxicam with chitosan and solubilization agent

Abstract This study presents a co-spray drying formulation approach to enhance the dissolution rate of meloxicam (MX), a poorly soluble model drug, by combining it with chitosan (CHIT) and sodium lauryl sulfate (SLS). Ternary formulations were prepared using both mini- and medium-scale spray dryers and compared with physical mixtures and RAW MX. In vitro dissolution testing revealed a significant increase in the release rate, with up to 80% of MX dissolved within 5 min. A comprehensive set of solid-state analytical techniques (XRPD, FTIR, and confocal Raman microscopy) revealed subtle changes in MX crystallinity and hydrogen-bonding interactions with both excipients. These findings support three key mechanisms contributing to enhanced dissolution: (i) reduced agglomeration of MX via adsorption onto the CHIT surface, (ii) improved wettability of products due to the presence of SLS, and (iii) increased matrix hydrophilicity facilitating drug–medium contact. The successful scale-up using a medium-scale spray dryer demonstrated the feasibility of this strategy for industrial application. The results highlight co-spray drying with functional excipients as a robust and scalable method for improving the biopharmaceutical performance of poorly soluble drugs. The simple co-spraying of the CHIT dispersion with the drug solution, without the need to dissolve the chitosan, is additional advantage.

A semi-focused multi-state variant of the mapping approach to surface hopping

The mapping approach to surface hopping (MASH) is one of the most promising methods for simulating nonadiabatic dynamics in molecular systems, in a mixed quantum/classical framework. In its original formulation, MASH is limited to the treatment of two-state systems. Here, we present a generalization of MASH to multiple electronic states, which we call semi-focused MASH (SMASH). A key distinguishing aspect of our approach is that only a selected subset of electronic states, identified through an appropriate clustering procedure, is initially populated. Test simulations of the ultrafast photodynamics of three molecular systems (spiropyran, thioguanine, and azobenzene) show that SMASH gives results closely matching those of decoherence-corrected fewest-switches surface hopping, while eliminating the need for the ad hoc decoherence correction.

Elevated liver enzyme trajectories in early adulthood and persistently high levels predict type 2 diabetes risk in Japanese adults

Fourier-transform infrared spectroscopy of hydrogen fluoride dimers in solid parahydrogen

We investigate the Fourier-transform infrared spectra of hydrogen fluoride dimers in solid parahydrogen, the detailed analysis of which has remained unexplored. We propose a plausible analysis based on concentration dependence, light polarization, annealing, and time evolution. The absorption lines exhibited multiple peaks, with intensity ratios significantly altered by annealing and by time evolution at a constant temperature. The spectral patterns and isotopic effects suggest that the dimers do not rotate freely in solid parahydrogen, while multiple peaks arise from different stable structures, including single and double substitution sites. Unlike in the gas phase and helium droplets, no tunneling splitting was observed. The broad ν1 band suggests that some dimer structures may exhibit axial rotation. Spectral changes due to annealing likely result from site conversion, while observed IR-induced changes indicate preferential dissociation of dimers in double substitution sites. These findings still remain tentative, necessitating further experimental and theoretical studies.

A denoising method for aeroengine gas path electrostatic signal of low signal-to-noise ratio based on IMFs optimized reconstruction and wavelet threshold

Relativistic Fock-space multireference coupled cluster theory with full iterative triples for the one-, two-, and three-hole sectors

The relativistic Fock-space coupled cluster method with full iterative inclusion of connected triple excitations (FS-CCSDT) for the 1h0p, 2h0p, and 3h0p Fock space sectors was presented and implemented. The newly developed methods were benchmarked in a series of calculations of both atomic (Ar1/2/3+, I0/1/2+) and molecular (Ar2+, HI+, HI2+) systems for which high-quality experimental data are available. Typical uncertainties in ionization potential and adiabatic excitation energy calculations for FS-CCSD and FS-CCSDT in the low sectors (1h0p and 2h0p) are ∼0.05–0.10 and 0.005–0.02 eV, respectively. The accuracy of the FS-CCSD model is quite similar to that of the relativistic third-order algebraic diagrammatic construction and the closely related equation-of-motion IP-EOM-CCSD and DIP-EOM-CCSD methods. The newly developed relativistic FS-CCSDT model is ∼3 to 5 times more accurate in these sectors. Models formulated for the 3h0p sector provide an acceptable accuracy in calculations of excitation energies of the Ar3+ and I2+ ions with average errors not exceeding 0.13 and 0.06 eV for FS-CCSD and FS-CCSDT, respectively.

AP-1 elements in the promoter and second intron mediate endoplasmic reticulum stress-induced expression of the GPAT3 gene

Abstract An excessive accumulation of hepatic lipids is a characteristic feature of metabolic dysfunction-associated steatotic liver disease (MASLD) and its severe form, metabolic dysfunction-associated steatohepatitis (MASH). Acyl-CoA:glycerol-sn-3-phosphate acyltransferase 3 (GPAT3) and other members of the GPAT family are enzymes which play an important role in glycerolipid synthesis. Previous articles have reported that GPAT3 mRNA and ER stress marker genes are upregulated in patients with MASH. Here, we study the regulatory mechanism of GPAT3 gene expression in human hepatoma cells suffering from ER stress. Transcriptome profiling showed that among the genes implicated in the formation of glycerolipids, GPAT3 is one of the most strongly activated genes in response to tunicamycin, an inducer of ER stress. CRISPR/Cas9-mediated disruption of activating transcription factor 4 ( ATF4 ) resulted in reduced GPAT3 expression under ER stress. Luciferase reporter assays of GPAT3 gene fragments encompassing ATF4 ChIP-seq peaks and mutational analysis revealed that activator protein-1 (AP-1) sites located in GPAT3 promoter and intron 2 mediate the activation of transcription in response to ER stress and ATF4. CRISPR/Cas9-mediated deletion of the region containing AP-1 sites from GPAT3 intron 2 caused a reduction of GPAT3 expression and triglyceride content in both unstressed cells and under ER stress. Thus, the results indicate that the induction of GPAT3 expression in response to ER stress is mediated by ATF4 via AP-1 elements in the promoter and second intron.