Browse Articles

Potential of CoMn2O4 spinel as soot oxidation catalyst and its kinetics thereof

AbstractEfficient catalysts for soot oxidation are critical for mitigating environmental pollution. In this study, CoMn2O4 spinel catalysts were synthesised using reverse co-precipitation and co-precipitation methods to evaluate their performance in soot oxidation and kinetic behaviour. All samples exhibited a tetragonal phase (XRD) and spherical morphology with rough surfaces (SEM). Raman spectroscopy confirmed structural disorder and oxygen vacancies, while XPS analysis revealed the presence of low-valence Mn ions, facilitating oxygen vacancy formation critical for soot oxidation. Additionally, the co-existence of Co and Mn ions contributed to a synergistic effect, enhancing the catalytic properties of the spinel structure. The reverse co-precipitation method produced a catalyst with a higher concentration of oxygen vacancies and active oxygen species among the samples. This sample demonstrated superior catalytic performance, achieving a T50% of 424 °C, low activation energy (153 kJ/mol) and pre-exponential factor (25 min− 1). Soot TPR analysis highlighted the role of catalyst reducibility, while thermogravimetric analysis revealed that activation energy and pre-exponential factors were influenced by surface composition. These findings provide valuable insights into the design of efficient catalysts for soot oxidation, emphasising the importance of synthesis methods and surface characteristics.

Solvatochromic charge model of isonitrile probes for investigating hydrogen-bond dynamics with 2DIR spectroscopy

Isonitrile-derivatized amino acids are emerging as highly effective infrared (IR) probes for investigating the structures and dynamics of hydrogen (H)-bonds. These probes enable the quantification of chemical exchange processes in solute–solvent complexes via two-dimensional IR spectroscopy and hold significant promise for site-specific dynamic studies within proteins. Despite their potential, theoretical models that elucidate the solvatochromism of isonitriles remain underdeveloped. Here, we present the development and validation of a solvatochromic charge model for isonitrile (N≡C) probes. Using density functional theory calculations, we parameterized solvatochromic charges for isonitrile and integrated them into classical molecular dynamics (MD) simulations of β-isocyanoalanine in various solvents, including water and fluorinated alcohols. The model incorporates solvent-induced frequency shifts and accurately reproduces complex experimental line shapes, including asymmetric features from non-Gaussian dynamics. The model successfully reproduced the bimodal distribution of frequency shifts corresponding to free and H-bonded species in alcohols, as well as cross-peaks due to chemical exchange. Achieving reproducibility required long MD trajectories, which were computationally demanding. To manage this, we implemented graphics processing unit acceleration, drastically reducing the computational time and enabling the efficient processing of extensive MD data. While some discrepancies in population ratios suggest the need for refined solvent force field parameters and modeling transition dipole moment variations, the developed solvatochromic model is a reliable tool for studying the solvation dynamics. The model enables more detailed investigations of ultrafast dynamics in solute–solvent complexes and represents important steps toward modeling site-specific dynamics of biomolecules with isonitrile probes.

Analysis of the relationships between the degree of migraine with right-to-left shunts and changes in white matter lesions and brain structural volume

A composite hydrogel of porous gold nanorods and gelatin: Nanoscale structure and rheomechanical properties

Incorporating nanomaterials into hydrogels allows for the creation of versatile materials with properties that can be precisely tailored by manipulating their nanoscale structures, leading to a wide range of bulk properties. Investigating the structural and property characteristics of composite hydrogels is crucial in tailoring their performance for specific applications. This study focuses on investigating the correlation between the structural arrangement and properties of a composite hydrogel of thermoresponsive polymer, gelatin, and light-responsive antimicrobial porous gold nanorods (PAuNRs). The rheomechanical properties of the composite hydrogels are correlated with their nanoscale structural characteristics, investigated using small-angle neutron scattering (SANS). Analysis of SANS data reveals a decrease in the fractal dimension of PAuNRs incorporated hydrogel matrix, as compared to pure gelatin. Incorporating PAuNRs results in the formation of a softer composite hydrogel, as evident from the decrease in viscoelastic moduli, critical yield strain, denaturation temperature, and swelling ratio. Our results demonstrate that the structural modulation at the nanoscale can be precisely controlled through adjusting PAuNRs concentration and temperature, providing a fabrication mechanism for hydrogels with desired elastic properties. The reduced elasticity of the composite hydrogel and light-sensitive/antimicrobial property of the PAuNRs make this system suitable for specific biomedical applications, such as tissue engineering, device fabrication, and stimuli-based controlled drug delivery devices.

Usage of double injector for efficient mixing of the fuel behind the ramp injector at supersonic combustion chamber

Effects of quenched disorder on the kinetics and pathways of phase transition in a soft colloidal system

Although impurities are unavoidable in real-world and experimental systems, most numerical studies on nucleation focus on pure (impurity-free) systems. As a result, the role of impurities in phase transitions remains poorly understood, especially for systems with complex free energy landscapes featuring one or more intermediate metastable phases. In this study, we employed Monte Carlo simulations to investigate the effects of static impurities (quenched disorder) of varying length scales and surface morphologies on the crystal nucleation mechanism and kinetics in the Gaussian core model system—a representative model for soft colloidal systems. We first explored how the nucleation free energy barrier and critical cluster size are influenced by the fraction of randomly pinned (or, static) particles (fp) and the size (np) of the pinned region or cluster. Both the nucleation free energy barrier and critical cluster size increase sharply with increasing fp but decrease as np grows for a given fraction of pinned particles, eventually approaching the homogeneous nucleation limit. On examining the impact of impurity’s surface morphology on nucleation kinetics, we observed that the nucleation barrier significantly decreases with increasing the impurity (or, seed) size with crystalline surface morphologies with body-centered cubic showing the greatest facilitation. Interestingly, seeds with random surface roughness had little effect on nucleation kinetics. In addition, the polymorphic identity of particles in the final crystalline phase is influenced by both the seed’s surface morphology and system size. This study further provides crucial insights into the intricate relationship between surface-induced local structural fluctuations and the selection of the polymorphic identity in the final crystalline phase, which is essential for understanding and controlling crystallization processes in experiments.

Online comments of tourist attractions combining artificial intelligence text mining model and attention mechanism

The alchemical integral transform revisited

We recently introduced the Alchemical Integral Transform (AIT), enabling the prediction of energy differences, and guessed an ansatz to parameterize space r in some alchemical change λ. Here, we present a rigorous derivation of AIT’s kernel K and discuss the parameterization r(λ) in n dimensions, i.e., necessary conditions, mathematical freedoms, and additional constraints when obtaining it. Analytical expressions for changes in energy spectra and densities are given for a number of systems. Examples include homogeneous potentials such as the quantum harmonic oscillator, hydrogen-like atom, and Dirac well, both for one- and multiparticle cases, and a multiparticle system beyond coordinate scaling for harmonic potentials.

Evaluation of an acne lesion detection and severity grading model for Chinese population in online and offline healthcare scenarios

Electride transition in liquid aluminum under high pressure and high temperature

Despite the conventional view of liquid aluminum (l-Al) as a simple metal governed by the free-electron model, it exhibits unique bonding characteristics. This study uncovers a gradual transition from free electron to electride behavior in l-Al at high pressure and temperature, forming a type of two-component liquid where atomic and electride states coexist. The proportion of electride increases with pressure and temperature until reaching saturation, leading to notable changes in the pair-correlation function and coordination number of l-Al at saturation pressure. Furthermore, this electride transition was found to profoundly impact the thermodynamic and dynamic properties, as evidenced by anomalous crossovers in the isothermal bulk modulus, thermal expansivity, heat capacity, sound speed, and self-diffusion coefficient correlated with varying pressure and temperature. The finding of the anomalous behavior of l-Al described in this work will deepen our understanding of the electronic structure and also lay ground work for interpreting and predicting new physical and chemical behavior under extreme conditions.

Machine learning-based estimation of crude oil-nitrogen interfacial tension

Observing quantum coherent oscillations in a three-level atom via electromagnetically induced transparency by two-dimensional spectroscopy

Two-dimensional electronic spectroscopy (2DES) has high spectral resolution and is a useful tool for studying atomic dynamics. In this paper, we show a smallest unit of electromagnetically induced transparency (EIT) for 2DES, i.e., a three-level system. It is found that the original main peak is split into four small ones due to the introduction of EIT. It suggests that the homogeneous broadening of 2DES can be effectively reduced by EIT. Moreover, in sharp contrast to a constant height, the height of the peaks will manifest a damped oscillation with respect to the population time. It seems that the quantum-beat phenomenon appears. These findings may help us obtain more information about the dynamics of excited states.

Impact of early initiation of renal replacement therapy in patients on venoarterial ECMO using target trial emulation with Japanese nationwide data

AbstractWhile renal replacement therapy (RRT) allows for precise fluid management as well as addressing electrolyte imbalances and the removal of other necessary compounds, its early initiation has not shown benefit in the general critically ill population. Moreover, the effects of early RRT initiation specifically in patients on venoarterial extracorporeal membrane oxygenation (VA-ECMO) also remain unclear. This retrospective study investigated adult patients who underwent VA-ECMO between April 2018 and March 2022 and used the clone-censor-weight method to emulate a hypothetical target trial and compare two groups: patients who initiated RRT within 2 days of VA-ECMO initiation (Early) and those who did not (Late). The primary outcomes were 28-day and 90-day hospital mortality analyzed by Cox proportional hazards models and the secondary outcome was 90-day RRT dependence by pooled logistic regression models. Inverse probability censoring weights were applied to adjust the models. A total of 2,513 VA-ECMO patients were cloned into both groups. The 28-day and 90-day mortalities were lower in the Early group (HR 0.59 [95% CI 0.53–0.68] and 0.67 [0.61–0.75]). However, the early group experienced greater RRT dependence at 90 days than the late group (OR 2.58 [1.94–3.46]). In conclusion, early initiation of RRT (within 2 days of VA-ECMO) was associated with lower hospital mortality but with a higher likelihood of 90-day RRT dependence in adult patients on VA-ECMO.

h-CMD: An efficient hybrid fast centroid and quasi-centroid molecular dynamics method for the simulation of vibrational spectra

Developing efficient path integral (PI) methods for atomistic simulations of vibrational spectra in heterogeneous condensed phases and interfaces has long been a challenging task. Here, we present the h-CMD method, short for hybrid centroid molecular dynamics, which combines the recently introduced fast quasi-CMD (f-QCMD) method with fast CMD (f-CMD). In this scheme, molecules that are believed to suffer more seriously from the curvature problem of CMD, e.g., water, are treated with f-QCMD, while the rest, e.g., solid surfaces, are treated with f-CMD. To test the accuracy of the newly introduced scheme, the infrared spectra of the interfacial D2O confined in the archetypal ZIF-90 framework are simulated using h-CMD compared to a variety of other PI methods, including thermostatted ring-polymer molecular dynamics (T-RPMD) and partially adiabatic CMD as well as f-CMD and experiment as reference. Comparisons are also made with classical MD, where nuclear quantum effects are neglected entirely. Our detailed comparisons at different temperatures of 250–600 K show that h-CMD produces O–D stretches that are in close agreement with the experiment, correcting the known curvature problem and redshifting of the stretch peaks of CMD. h-CMD also corrects the known issues associated with too artificially dampened and broadened spectra of T-RPMD, which leads to missing the characteristic doublet feature of the interfacial confined water, rendering it unsuitable for these systems. The new h-CMD method broadens the applicability of f-QCMD to heterogeneous condensed phases and interfaces, where defining curvilinear coordinates for the entire system is not feasible.

Out-of-distribution generalization for segmentation of lymph node metastasis in breast cancer

Simulating anharmonic vibrational polaritons beyond the long wavelength approximation

In this work, we investigate anharmonic vibrational polaritons formed due to strong light–matter interactions in an optical cavity between radiation modes and anharmonic vibrations beyond the long-wavelength limit. We introduce a conceptually simple description of light–matter interactions, where spatially localized cavity radiation modes couple to localized vibrations. Within this theoretical framework, we employ self-consistent phonon theory and vibrational dynamical mean-field theory to efficiently simulate momentum-resolved vibrational-polariton spectra, including effects of anharmonicity. Numerical simulations in model systems demonstrate the accuracy and applicability of our approach.

Longitudinal growth of the Saccharina kelp embryo depends on actin filaments that control the formation of a corset-like structure composed of alginate

A sum-frequency generation vibrational spectroscopy studies on buried liquid/liquid interfaces of CCl4/[C<i>n</i>mim][TFSA] (<i>n</i> = 4 and 8) hydrophobic ionic liquids

The liquid/liquid interfaces of room-temperature ionic liquids (RTILs) play a pivotal role in chemical reactions owing to their characteristic microscopic structure, yet the structure of hydrophobic liquid/RTIL interfaces remains unclear. We studied the structure at the liquid/liquid interfaces of carbon tetrachloride (CCl4) and 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([Cnmim][TFSA]; n = 4 and 8) RTILs using infrared–visible sum frequency generation (SFG) vibrational spectroscopy. A comparison of the SFG spectra of the CCl4/RTIL and air/RTIL interfaces revealed that the solvation of the alkyl chains of the [Cnmim]+ cations by CCl4 reduces the number of gauche defects in the alkyl chain and the interface number density of the cation at the CCl4 interface. The orientational change of the [TFSA]− anion and concomitant increase in the area it occupies at the CCl4 interface was observed to be greater than that at the air interface. This is accompanied by the expansion of the space among the alkyl chains of the cations to be solvated by CCl4. The structural change of the CCl4 interface from the air interface can be attributed to the solvophilic effect of CCl4 on the alkyl chains of the cations at the CCl4/[Cnmim][TFSA] interface. This is in contrast with the solvophobic effect of CCl4 on the Langmuir film at the CCl4/water interface. This phenomenon is caused by the loosely packed alkyl chains of the cations at the RTIL surface and the flexible anion–cation arrangement owing to the weak basicity and acidity of the ions in the RTILs.

Antitumor immunostimulatory effect via cell-killing action of a novel extracorporeal blood circulating photodynamic therapy system using 5-aminolevulinic acid

Magic-NOVEL: Suppressing electron–electron coupling effects in pulsed DNP

Pulsed dynamic nuclear polarization (DNP) enhances the nuclear magnetic resonance sensitivity by coherently transferring electron spin polarization to dipolar coupled nuclear spins. Recently, many new pulsed DNP techniques such as NOVEL, TOP, XiX, TPPM, and BEAM have been introduced. Despite significant progress, numerous challenges remain unsolved. The electron–electron (e–e) interactions in these sequences can severely disrupt the efficiency of electron–nuclear (e–n) polarization transfer. In order to tackle this issue, we propose the magic-NOVEL DNP method, utilizing Lee–Goldburg decoupling to counteract e–e coupling effects. Our theoretical analysis and quantum mechanical simulations reveal that magic-NOVEL significantly improves the transfer efficiency of DNP, even at shorter e–e distances. This method offers a new perspective for advancing pulsed DNP techniques in systems with dense electron spin baths. Furthermore, we demonstrate the effectiveness of phase-modulated Lee–Goldburg sequences in improving pulsed DNP transfer.