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Isomers and band assignments in the cryogenic vibrational spectrum of the binary complex between water and protonated formic acid using two color, IR–IR photobleaching and H/D isotopic substitution

Protonated formic acid (PFA) is purported to be the active species in the catalytic activation of condensation reactions at the acidic interface of microdroplets. Here, we investigate the fundamental interaction between PFA and water with cryogenic ion vibrational spectroscopy of the binary PFA–H2O complexes generated via electrospray ionization followed by buffer gas cooling to about 20 K. The patterns displayed by the isomer-specific IR spectra of D2-tagged PFA–H2O indicate that two distinct, non-interconverting rotamers are present at low temperatures based on the cis and trans structures of the HCO2H2+ core ion. Both of these occur with the water molecule attached to the OH that is in a cis-configuration relative to the CH group (denoted E), but differ in the E vs Z (cis vs trans relative to the CH group) orientation of the spectator OH. This assignment scheme corrects a previous theoretical analysis that invoked a scenario in which structures with E- and Z-bound water molecules interconvert at low (20 K) temperatures. Isomer-specific bands arising from the OH stretches and water bending modes are deconvoluted using isotopomer-specific spectroscopy of the complexes with partial H/D exchange. The dependence of the nominal shared proton OH stretch frequency on the deuteration of the tethered water confirms strong coupling between this mode and the water bending fundamental.

Dynamic fluctuations in a highly cross-linked polybutadiene rubber

Using a combined approach of different neutron scattering techniques that allows experimental separation of the self and collective dynamics, we investigated the various types of motion in a highly cross-linked 1,2-polybutadiene rubber. As a reference, the neat, fully deuterated melt was also studied. In the latter, the collective segmental relaxation around the structure factor peak S(Qmax) exhibits pronounced de Gennes narrowing, with a collective relaxation time τc(Q) that increases without plateauing toward lower momentum transfers Q. Apparently, due to the very bulky monomer structure, the correlation length ξc for the crossover to viscoelastic homogeneity is unusually large. In the highly cross-linked d1,2-PB rubber, the original structure factor peak of the pure d1,2-PB is significantly reduced. Instead, a strong low-Q peak emerges, which we attribute to correlations between the hydrogen-containing cross-linkers. Both the collective d1,2-PB relaxation rates around the former S(Qmax) and the relaxation around the new crosslink correlation peak are significantly slowed down compared to the neat melt. Finally, the cross-linking strands exhibit their own fast dynamics, which is well described by diffusion within a spherical Gaussian well, with a corresponding radius R ≅ 4 Å.

Static and dynamic theory of polarization under internal and directing electric fields: Fixed-charge and fixed-potential conditions

We present a continuum theory on statics and dynamics of polar fluids, where the orientational polarization p1 and the induced polarization p2 are governed by the Onsager directing field Ed and the Lorentz internal field F, respectively. We start with a dielectric free energy functional F with a cross term ∝∫drp1 · p2, which was proposed by Felderhof [J. Phys. C: Solid State Phys. 12, 2423 (1979)]. With this cross-coupling, our theory can yield the theoretical results by Onsager and Kirkwood. We also present dynamic equations using the functional derivatives δF/δpi to calculate the space-time correlations of pi. We then obtain analytic expressions for various frequency-dependent quantities, including the Debye formula. We find that the fluctuations of the total polarization drastically depend on whether we fix the electrode charge or the applied potential difference between parallel metal electrodes. In the latter fixed-potential condition, we obtain a nonlocal (long-range) polarization correlation inversely proportional to the cell volume V, which is crucial to understanding the dielectric response. It is produced by nonlocal charge fluctuations on the electrode surfaces and is sensitive to the potential drops in the Stern layers in small systems. These nonlocal correlations in the bulk and on the surfaces are closely related due to the global constraint of fixed potential difference. We also add some results in other boundary conditions, including the periodic one, where nonlocal correlations also appear.

Brownian motion of snowman-shaped colloidal particles

We investigate the Brownian motion of isolated snowman-shaped particles consisting of pairs of large and small spheres by video microscopy. Our observations reveal that the particle exhibits varying degrees of anisotropic translational diffusion depending on the reference point used for tracking. In particular, when tracking the snowman’s geometrical center, the diffusion coefficient along the particle’s long axis (Da) is greater than that along the short axis (Db). When tracking the large sphere’s center, Da and Db are identical, while tracking the small sphere’s center results in Da being smaller than Db. Since Da remains constant across these geometrical centers, the higher Db thus leads to the fastest diffusion for the small sphere’s center. These differences in diffusion arise from the varying coupling between translational and rotational motions, determined by the tracking points relative to the center of hydrodynamic stress (CoH). The CoH has been experimentally confirmed to be the geometrical center of the snowman-shaped particle. Our findings are consistent with the Langevin theory for the Brownian motion of anisotropic particles.

Higher order relationships in the canonical ensemble for local reactivity indices

In this paper, higher order relations derived from the canonical ensemble N,νr⃗ are presented in the framework of Density Functional Theory (DFT), with a focus on the Fukui function [f(r⃗)], dual descriptor [f2(r⃗)], and the function t(r⃗) introduced by Fuentealba and Parr. These relationships extend existing theoretical models, providing a more detailed understanding of local and non-local chemical reactivity. The equations developed establish direct connections between higher order reactivity indices, such as hyperhardness (γ), the fourth order energy function f3r⃗, and non-local response functions, offering new insights into the activation and deactivation of molecular systems under external perturbations. These findings are particularly relevant in the study of activation processes by the presence of n bodies generating external perturbations. The results highlight the fundamental role of higher-order kernels in describing changes in reactivity, contributing to the development of a more refined theoretical framework in conceptual DFT.

Depicting a neoteric family of biocompatible ionic liquids: A look through a molecular dynamics prism

The organization of Ionic Liquids (ILs) at the nanoscale has been demonstrated to be invaluable knowledge to understand and even rationally develop novel applications. In this line, this work aims at the deeper structural comprehension of five model ionic solvents from the recently presented family of biocompatible ILs based on cholinium cation ([Ch]+) and peptide anions ([Pep]−). To do this, a molecular dynamics approach was employed. The use of different [Pep]− allowed us to evaluate the influence of (i) incrementing an oligopeptide chain through the glycyl (Gly) unit and (ii) employing a more complex functionalization based on the phenylalanyl (Phe) group. The simulations show that the additional peptide group from [Ch][Pep] adds a new anchoring point for inter-anionic association through H-bonding, and while the peptide hydrogen is interacting with other anions, the peptide oxygen seems to approach cation charged centers. This stronger H-bonding grid may explain the boost in viscosity observed when transitioning from [Ch][AA] to [Ch][Pep]. On the other hand, the nano-segregation of ILs built with Phe is distinguished by two continuous mesophases, polar and apolar. Both these networks have their impact on each other since, when the peptide chain is incremented from 1 to 2 Phe residues, (i) the polar domain is slightly less continuous and (ii) the apolar one presents different phenyl ring (Pher) solvation profiles depending on their position in the peptide chain. In addition, the edge-to-face configurations dominate the Pher–Pher aggregation, suggesting an electrostatic influence in the internal organization of this domain, and π–cation complexes appear to disturb apolar accumulation.

Spin-polarized alkali-metal trimers revisited

Homonuclear spin-polarized alkali-metal trimers in their lowest-lying electronic state are investigated theoretically. Their equilibrium geometries and binding energies are determined with the state-of-the-art quantum chemical methods at three levels of approximation. The equilibrium geometries obtained Req(Li3) = 3.100 Å, Req(Na3) = 4.353 Å, Req(K3) = 4.996 Å, Req(Rb3) = 5.391 Å, and Req(Cs3) = 5.730 Å are compared to the other theoretical results and also to the very recent experimental results obtained through the laser-induced Coulomb explosion. Further theoretical studies are proposed, which could help with better interpretation of the experimental results for the sodium and cesium trimers.

From all-atom to rigid monomer treatment of molecular clusters

Given a system of M molecular monomers, represented with a presumably accurate all-atom potential energy surface (PES), V(r), we partition the configuration space by setting a one-to-one correspondence r ↔ (R, q), where R describes the centers and orientations of all the M monomers and q describes all the vibrational intra-molecular degrees of freedom. We then define a temperature-dependent free-energy surface of the corresponding rigid monomer system, F(R;T), by averaging over the intra-molecular degrees of freedom. F(R;T) is here estimated directly using the local harmonic approximation. While conceptually simple and numerically inexpensive, the coarse-grained PES defined in this manner turns out to be surprisingly accurate for the model systems considered, namely water and ammonia clusters. The proposed framework can be used in a more general context for local rigidification of other molecular systems in non-uniform environments.

Trump wants to put humans on Mars: what scientists think of the plan

‘Integrity index’ flags universities with high retraction rates

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Second ispace craft has probably crash-landed on Moon

How Trump’s budget cuts could derail global science collaborations

Randomised active controlled trial examining effects of aerobic exercise, cognitive and music interventions on depression, balance and mobility in schizophrenia

Abstract Schizophrenia significantly impairs daily functioning, requiring innovative, cost-effective treatments beyond standard antipsychotics, and cognitive interventions. This study examined the individual and combined effects of cognitive, music, and aerobic exercise interventions on depression, balance, and mobility in patients with schizophrenia and severe depression. Eighty-four male patients with schizophrenia and severe depression from an inpatient psychiatric centre participated in a 12-week, single-blind, randomised active-controlled trial. Participants were systematically assigned to one of seven equal groups (n = 12 each): aerobic exercise (AerG), cognitive rehabilitation/treatment-as-usual (CogG), music intervention (MusG), aerobic exercise + music intervention (A&MG), aerobic exercise + cognitive intervention (A&CG), cognitive intervention + music intervention (C&MG), and a comprehensive combination of all three modalities (ACMG). Each intervention was delivered over 60 min, three times weekly for 12 weeks. The study employed the Beck Depression Inventory Short Form, Stork Balance Test, and modified Timed Up and Go Test to assess improvements in depression, balance, and mobility. Statistical analyses were conducted using paired t-tests for within-group comparisons and ANCOVA with Bonferroni post hoc tests for between-group differences, with significance set at p ≤ 0.05. Results showed significant improvements in depression, balance, and mobility across all treatment groups. The CogG group outperformed both AerG and MusG in all outcomes, establishing it as the gold-standard comparator. A&CG yielded greater benefits than other single or dual-modality groups, while the multimodal ACMG group demonstrated the most substantial improvements across all measures. These findings highlight the practical value of incorporating multimodal interventions into standard care to improve both mental health and physical function, offering a scalable, cost-effective approach to addressing the diverse needs of this population of patients with schizophrenia and severe depression. Implementing such interventions in psychiatric care settings could lead to more comprehensive and effective treatment strategies for improving patient outcomes.

Therapeutic efficacy of BSA formulated hydrogels in corneal wound healing and epithelial cell regeneration: an ex vivo study

The value of intratumoral and peritumoral ultrasound radiomics model constructed using multiple machine learning algorithms for non-mass breast cancer

Effects of staking techniques on growth and yield of tomato varieties in northwestern Ethiopia

Machine learning of automatic hierarchical multi-label classification method for identifying metal failure mechanisms

Universal and economical experimental platform for colloidal mixing lab-on-chip in parabolic flight

Abstract This study presents an economical experimental platform designed to investigate colloid and emulsion mixing under parabolic flight conditions. The compact 20 kg system integrates a modular fluidic device with real-time imaging capabilities to enable the observation of fluid interactions at the millimeter scale. The platform focuses on safety, like a double containment system, while remaining accessible for quick experimental modifications. Experiments using four distinct colloids, Thailand Lunar Simulant (TLS-01A), emulsions with Span 80 (50% v/v) and Tween 80 (10% v/v), and a control without additives, enabled analysis of surface tension and particle effects on mixing behavior. Through 29 experimental trials during parabolic flight cycles, each with approximately 20 s of microgravity, the system captured fluid dynamics at 240 frames per second. The platform enables future research to observe effects of surfactant and mixer geometry in real-world scale, with potential for improvements in automation and imaging capabilities. Using a simple measure of color distribution entropy, the Span 80 sample exhibited the highest degree of mixing, with a 24.2% improvement over the microgravity control and a 19.4% increase relative to ground-based Span sample.

Impact of perinatal factors on breast milk composition and volume in preterm infants