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Incorporating the effect of spin–orbit interaction in Auger decay spectra: Theory and examples

A theoretical framework for computing Auger spectra that include spin-orbit interaction is presented. The framework is based on the state-interaction approach using equation-of-motion coupled-cluster wave-functions. The working equations for Auger decay rates are derived within the Feshbach–Fano formalism. The capabilities of the theory are illustrated by the calculation of L-edge Auger spectra of H2S and Ar using the Feshbach–Fano and complex basis function (CBF) approaches. The quality of the Feshbach–Fano results depends critically on the treatment of the free-electron state. In contrast to the K-edge spectra for which both plane wave and Coulomb wave treatments yield reasonable results, the Feshbach–Fano calculations yield accurate results for L-edges only when using Coulomb wave (FF-CW). The FF-CW and CBF calculations of Auger spectra in H2S and Ar agree well with each other and with the available experimental data. The results highlight the importance of spin–orbit interactions for modeling L-edge Auger spectra.

Pseudo-grand canonical molecular dynamics via volumetrically controlled osmotic pressure

Molecular dynamics simulations are typically constrained to have a fixed number of particles, which limits our capability to simulate chemical and physical processes where the composition of the system changes during the simulation time. Typical examples are the calculation of nucleation and crystal growth rates in heterogeneous solutions where the driving force depends on the composition of the fluid. Constant chemical potential molecular dynamics simulations would instead be required to compute time-independent growth and nucleation rates. While this can, in principle, be achieved through the addition and deletion of particles using the grand canonical partition function, this is very inefficient in the condensed phase due to the low acceptance probability of these events. Adaptive resolution schemes, which use a reservoir of non-interacting particles that can be transformed into solute particles, circumvent this problem, but at the cost of relatively complicated code implementations. In this work, a simpler approach is proposed that uses harmonic volumetric restraints to control the solute osmotic pressure, which can be considered a proxy for the system’s chemical potential. The osmotic pressure regulator is demonstrated to reproduce the expected properties of ideal gases and ideal solutions. Using the mW water model, the osmotic pressure regulator is shown to provide a constant growth rate for ice in the presence of an electrolyte solution, unlike what standard molecular dynamics simulations would produce.

Strong field quantum control of bimolecular reactions

We present a strategy for the quantum control of polyatomic bimolecular reactions using moderately intense, long-pulse laser fields. Bimolecular reactions pose a challenge to quantum control, not encountered in the unimolecular case, due to their complex scattering dynamics and the averaging of their observables over a thermal distribution of reactant states. Our approach bypasses these hurdles; it involves the interaction of a nonresonant, polarized field with the molecular coordinate-dependent polarizability tensor to generate spatially nonuniform Stark shifts of the potential energy surfaces. We focus on the commonly encountered case where the reaction dynamics involve complicating features such as several coupled electronic states, deep potential wells, a high density of vibronic states, and several transition states en route from reactants to products. We consider highly averaged observables, including the canonical and microcanonical rate constants. It is shown that the complexities of polyatomic bimolecular reactions introduce new opportunities for reaction enhancement and control. In particular, the occurrence of one or more potential wells combines with the spatial structure of the polarizability tensor to introduce a vast enhancement that is subject to control by the choice of field parameters. Our results are based on a quantum mechanical theory and ab initio calculations of the potential energy and polarizability tensor. As a model system, we consider the CH(X2Π)+N2(XΣg+1)→HCN(XΣ+1)+N(S4) reaction, but our results and conclusions are general.

On the vibrational excitation of shock-heated air. I. CO/O2/Ar mixtures

This series of papers aims to investigate the vibrational excitation behaviors of shock-heated high-temperature air using the CO rovibrational thermometry. The present part of this series serves as a prerequisite for the work. The time-dependent rovibrational temperatures of CO were measured during the vibrational excitation process of CO/O2/Ar mixtures within the temperature range of 1680–2970 K and pressures of 1.37–2.43 bar to investigate the vibrational energy transfer between CO and O2. The state-to-state (StS) approach was employed in the simulations, where the vibrational energy levels of CO and O2 are treated as pseudo-species. The datasets of vibrational state-specific reactive and inelastic rate coefficients for CO + O2, O2 + Ar, and CO + O collisions were generated in this paper. The present StS simulations agreed well with the experimental data, whereas the Schwartz–Slawsky–Herzfeld (SSH) formula predicted faster CO vibrational temperatures. A sensitivity analysis was then performed and highlighted that the vibration–vibration (V–V) energy transfer between CO and O2 (τV−VCO−O2) is the key item inducing the discrepancies observed between the SSH results and experimental data. Therefore, a new expression was summarized for calculating τV−VCO−O2 based on the present experiments, and it also agreed well with the measured data in the literature at 100–700 K. In addition, the oxidation of CO and the effects of vibrational energy transfer between CO and O2 were discussed. Since differences in vibrational temperatures between CO and O2 were observed during the relaxation process, the refined rate of vibrational energy transfer between CO and O2 paves the way for the investigations in Part II.

Molecular dynamics characterization of structural properties of <i>ɛ</i>-phase syndiotactic polystyrene

The structure of ɛ-phase syndiotactic polystyrene was investigated, based on geometrical analysis and diffusion paths of light gases, to determine the shape and size of its channels (porous). Pore size distribution and empty volume fraction were determined using PoreBlazer v4.0. Diffusion trajectory paths DA of gases such as H2, D2, He, CO2, N2, CH4, C2H4, and C2H6 were calculated by molecular dynamics at temperatures T = 298, 313, 333, and 353 K; additionally, diffusion coefficients were also determined. For the smaller gases (H2, D2, and He), quantum corrections were also considered using a Wigner–Kirkwood approximation applied to the Lennard-Jones effective potential. It was observed that in some cases, gases such as He, H2, D2, and CO2 could percolate across the channels in the crystal at T = 353 K. These gases also showed the highest diffusion coefficients along the Z axis. Interestingly, CO2, which was the heaviest molecule of all gases in this study and showed the lowest diffusion coefficient, could also percolate through the structure.

Does covalency decrease with coordination number?

It is traditionally believed that the degree of covalency of chemical bonds decreases with increasing coordination number, while the degree of ionicity increases. Using Bader charge analysis and our novel definition of atomic charges based on Wannier functions, we demonstrate that this expectation does not hold for zinc oxide (ZnO), carbon dioxide (CO2) and sodium chloride (NaCl). The low-pressure wurtzite phase of ZnO (with fourfold coordination of Zn and O) and the high-pressure rock salt phase (with sixfold coordination) exhibit nearly identical degrees of ionicity. For CO2, covalency slightly increases in the high-pressure β-cristobalite phase (where the carbon atom is fourfold coordinated) compared to its low-pressure molecular cubic phase (where it is twofold coordinated). Thus, contrary to the common belief, the degree of covalency of chemical bonds is governed primarily by the chemical nature of the atoms and their stoichiometric ratio, rather than by the coordination number.

Revealing exciton energy structure and interactions in quantum dots by 25 kHz shot-to-shot phase-cycling 2D electronic spectroscopy

The use of spectroscopic techniques to resolve the energy level structure of excitonic excited states and to elucidate the interaction mechanisms between excitons in quantum dots is of vital importance for the development and application of such materials. However, various static and dynamic one-dimensional spectroscopic techniques are limited by inhomogeneous broadening effects, making it challenging to directly observe the fine-level energy structure of quantum dots. We developed a 25 kHz shot-to-shot phase-cycling two-dimensional (2D) electronic spectroscopy technique to investigate the excitonic energy structure and exciton–exciton interactions in a quantum dot aggregate. Using CdTe/CdSe/ZnS core–shell–shell quantum dots as a model system, we implemented a 36-step phase-cycling scheme to acquire rephasing 2D spectra at zero waiting time under varying excitation powers. In these spectra, both diagonal and off-diagonal features reveal spectral components that are otherwise obscured in one-dimensional spectroscopy due to inhomogeneous broadening. The presence of off-diagonal peaks in the 2D spectra indicates non-negligible interactions between excitons with different transition energies. Power-dependent 2D spectroscopy reveals that, with increasing excitation power, high-energy states exhibit greater resistance to Auger recombination. The experimental method developed in this work may contribute to advancing the theory of excited-state structures and dynamics in quantum dots and other low-dimensional materials.

Thermodynamics of a compressible lattice gas crystal: Generalized Gibbs–Duhem equation and adsorption

Compressible lattice gas models are used in material science to understand the coupling between composition and strain in alloys. The seminal work in this field is the 1973 Larché–Cahn paper [F. C. Larché and J. W. Cahn, Acta Metall. 21, 1051–1063 (1973)]. Single-phase crystals in Larché–Cahn theory are stable under open constant pressure, constant temperature conditions. The Gibbs free energy does not have to match the product μN of the number of particles N and their chemical potential μ. Similarly, the grand potential and the product pV of pressure and volume V may not add up to zero. Discrepancies already arise under hydrostatic stress. The elastic energy is not proportional to volume and the Gibbs–Duhem relation valid for liquids is violated. Extensivity is recovered by treating the number of lattice sites M as an additional thermodynamic variable. The difference G − μN can be identified with νM where ν is the thermodynamic force conjugate to M. The reinstated Gibbs–Duhem equation can be cast in the form of an adsorption equation and applied to quantify the tendency to vacancy creation under isothermal isobaric conditions. We have worked this out for a uniform one-component compressible lattice gas crystal. Shear stress is omitted. The coupling between composition and strain is implemented by decomposing pressure in a mechanical component depending on deformed density N/V and an elastic term linear in the volume strain as determined by V/M. Various μ,p,T response functions are compared to the μ,V,T counterparts.

On Boltzmann averaging in <i>ab initio</i> thermodynamics

Ab initio thermodynamics is a widespread, computationally efficient approach to predict the stable configuration of a surface in contact with a surrounding (gas or liquid) environment. In a prevalent realization of this approach, this stable configuration is simply equated with the structure in a considered candidate pool that exhibits the lowest surface free energy. Here, we discuss the possibility to consider the thermal accessibility of competing, higher-energy configurations through Boltzmann averaging when extended surface configurations and their energetics are computed within periodic boundary condition supercells. We show analytically that fully converged averages can be obtained with a candidate pool derived from exhaustive sampling in a surface unit-cell exceeding the system’s correlation length. In contrast, averaging over a small pool of ad hoc assembled structures is generally ill-defined. Enumerations of a lattice-gas Hamiltonian model for on-surface oxygen adsorption at Pd(100) are employed to illustrate these considerations in a practical context.

Hotly anticipated US vaccine meeting ends with confusion — and a few decisions

Multiple lines of evidence for a hypervelocity impact origin for the Silverpit Crater

Abstract An impact origin for Silverpit Crater, on the UK continental shelf, has been contested over the last two decades, with a lack of definitive evidence – traditionally petrographic evidence of shock metamorphism – to resolve the debate. Here we present 3D seismic, petrographic and biostratigraphic data, and numerical impact simulations to test the impact hypothesis. The seismic data provide exceptional imaging of the entire structure, confirming the presence of a central uplift, annular moat, damage zone and numerous secondary craters on the contemporaneous seabed. The distribution of normal and reverse faults in the brim, and curved radial faults around the central uplift suggest a low-angle impact from the west. The pitted, flat-topped central uplift at the top chalk horizon may indicate significant devolatilization of chalk immediately following impact. Biostratigraphic data confirm that this event occurred during the middle Eocene, between 43-46 million years ago. Petrographic analysis from the reworked ejecta sequence in the nearby 43/25-1 well reveals two grains with shock lamellae, indicating shock pressures of ~10-13 GPa, consistent with results from our numerical models. This combination of data and modelling provide compelling evidence that Silverpit Crater is an exceptionally preserved hypervelocity impact structure.

Transient ligand contacts of the intrinsically disordered N-terminus of neuropeptide Y2 receptor regulate arrestin-3 recruitment

Abstract Previous efforts in delineating molecular mechanisms of G protein-coupled receptor (GPCR) activation have focused on transmembrane regions and ligand-receptor contacts of the extracellular loops. The role of the highly flexible N-termini of rhodopsin-like GPCRs have not been well characterized to date. We hypothesize that transient contacts between the peptide ligand and the intrinsically disordered N-terminus (NT) of the neuropeptide Y (NPY) receptor Y2 (Y2R) will affect receptor signaling. We employ cross-linking mass spectrometry to capture ligand-receptor contacts including transient binding modes. A photo-reactive NPY analogue allows mapping the interaction between NPY and Y2R NT resulting in a total number of 40 cross-links. The cross-links provide distance constraints for deriving structural models of the interaction. Molecular dynamics simulations highlight the structural flexibility and rapid interconversion of ligand-receptor contacts. Mutagenesis of Y2R and functional characterization suggest that the cross-linking hotspots in the NT electrostatically control its conformational ensemble. The NT engages in transient contacts to the peptide and prolongs ligand residence time, which is required for efficient interaction of Y2R with arrestin-3, but not Gi. We delineate structure-function relationships for the intrinsically disordered Y2R NT and propose a functional role for transient binding modes involving the NT of a peptide-binding receptor.

Are videos uploaded by dental professionals on lip repositioning surgery of higher quality? A youtube video analysis

Lip repositioning surgery is a minimally invasive procedure used in the treatment of gummy smile. With the increasing demand for aesthetic dental procedures, platforms like YouTube™ have become popular sources for visual health information. This study aimed to evaluate the quality, reliability, and educational value of YouTube™ videos related to lip repositioning surgery and to identify factors influencing video quality. This research was conducted on YouTube™ using the term “lip repositioning” on February 20, 2025. The first 150 videos sorted by relevance were screened. According to the inclusion criteria, 53 videos were recorded. Data such as video duration, upload source, view count, comments, likes/dislikes, and country of origin were recorded. Viewer engagement was analyzed through interaction index and viewing rate. Content was evaluated using the Video Content Quality (VCQ) score, Global Quality Scale (GQS) and DISCERN tool. Statistical analyses were performed with a significance level of P &lt; 0.05. Most videos were uploaded by dentists (64.2%), and 71.7% were educational. The mean VCQ score was 9.98 ± 3.95, indicating low-to-moderate content quality. Videos uploaded by professionals had higher quality scores (p &lt; 0.001), while 56.6% were of poor content quality. Although YouTube™ is a widely used source for health information, videos on lip repositioning surgery lack sufficient educational value and reliability. Professional content creation should be encouraged.

Impact of middle leaders’ competencies on teachers’ technology acceptance in Malaysian TS25 schools

This study examines how middle leaders’ competencies influence teachers’ technology acceptance in Malaysian TS25 primary schools. The research combines the Middle Leaders’ Competency Model for Education 4.0 (MLCMEdu4.0) and the Teachers’ Technology Acceptance Model (TTAM). Using a cross-sectional survey, data were gathered from 302 teachers in TS25 schools in Kuala Lumpur and analyzed using Structural Equation Modeling (SEM). Results show a significant positive relationship (β = 0.599, p &lt; .001), with middle leaders’ competency accounting for 36% of the variance (R² = .36) in teachers’ technology acceptance. Critical thinking was identified as the most vital middle leadership competency in Education 4.0, followed by entrepreneurial skills and collaboration. Among factors influencing teachers’ technology acceptance, perceived ease of use, perceived usefulness, and facilitation conditions were most impactful. This study highlights the critical role of middle leaders in supporting technology acceptance, especially in Malaysia’s educational reform context. It highlights the need for targeted professional development programs and clear role definitions for middle leaders to enhance their influence on technology acceptance. Future studies should explore these dynamics across varied educational contexts and adopt longitudinal designs to assess the long-term effects of middle leadership on technology acceptance.

PDK1, associated with glycolytic metabolism, is a potential prognostic biomarker in osteosarcoma

The study explores the prognostic significance and therapeutic potential of 3-phosphoinositide dependent protein kinase-1 (PDK1) in osteosarcoma. Using bioinformatics analysis and experimental validation, we analyzed PDK1 expression and its correlation with patient prognosis from GEPIA and UCSCXena databases. High PDK1 expression was found to be significantly associated with reduced survival in osteosarcoma patients, suggesting its value as a prognostic biomarker. Functional assays were performed to investigate the biological processes influenced by PDK1. Gene Ontology (GO) analysis indicated that PDK1 is involved in metabolism and cell proliferation. KEGG enrichment analysis revealed that genes related to PDK1 are enriched in pathways associated with metabolism, cell proliferation, and immune escape. In vitro experiments demonstrate that silencing PDK1 impairs glycolysis, reduces proliferation, and induces apoptosis in 143B osteosarcoma cells. Pan-cancer analysis confirms PDK1’s overexpression and poor prognosis association in multiple malignancies. Pan-cancer analysis extended the findings to other cancer types, confirming that PDK1 is overexpressed in multiple malignancies and generally associated with poor prognosis. This reinforces the potential of PDK1 as a universal biomarker and therapeutic target in oncology. The findings suggest PDK1 as a critical regulator of glycolytic metabolism and a potential therapeutic target in osteosarcoma. Targeting PDK1 could provide a novel therapeutic strategy for treating osteosarcoma and possibly other cancers.

The influence of somatostatin analogues on the incidence of pancreatic fistulas and postoperative morbidity in patients undergoing pancreatic resection: A Bayesian network meta-analysis

Background Pancreatic resection is a critical treatment for pancreatic cancer and other pancreatic diseases. Somatostatin analogs are commonly used to prevent complications following pancreatic resection, but their efficacy and safety remain debated. Methods Following PRISMA guidelines, a systematic search was conducted across multiple databases, including PubMed, EMBASE, Scopus, Cochrane Library, Ovid, ClinicalTrials.gov, Web of Science, CNKI, and WanFang Data. The search focused on studies comparing the use of somatostatin analogs after pancreatic surgery. Key outcomes included postoperative pancreatic fistula (POPF), clinically relevant POPF (CR-POPF), mortality, and morbidity. Statistical analysis was performed using a consistency model, calculating relative risk ratios (RR) with 95% confidence intervals (CI), and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) tool was used to assess the quality of evidence. Results In the absence of stratification based on the surgical procedure, For POPF prevention, pasireotide showed a relative risk (RR) of 0.46 (95% CI: 0.23, 0.87, Low) compared to placebo, and octreotide had an RR of 0.76 (95% CI: 0.66, 0.88, Moderate). Somatostatin and vapreotide showed no significant differences. In preventing CR-POPF, pasireotide had an RR of 0.46 (95% CI: 0.23, 0.86, Low), somatostatin had an RR of 0.60 (95% CI: 0.36, 0.99, Moderate), and octreotide had an RR of 0.61 (95% CI: 0.39, 0.94, Moderate). Regarding postoperative mortality, vapreotide showed an RR of 0 (95% CI: 0.00, 0.29, Low), while octreotide, somatostatin and pasireotide did not demonstrate significant effects. For reducing morbidity, octreotide had an RR of 0.74 (95% CI: 0.66, 0.82, Moderate), somatostatin had an RR of 0.76 (95% CI: 0.66, 0.87, Moderate), vapreotide and pasireotide showed no significant effect.In Pancreaticoduodenectomy subgroup, somatostatin showed an RR of 0.22(95% CI: 0.03, 0.84, Moderate) for preventing CR-POPF.For all the other outcomes, neither somatostatin nor octreotide proved effective. Conclusion While robust evidence confirms the efficacy of octreotide in preventing POPF, a critical concern regarding its inconsistent efficacy within the PD subgroup persists. This variability indicates that the overall clinical benefit of octreotide may be predominantly attributable to its utility in non-PD pancreatic resections.

A Chinese AI tool can manage chronic disease — could it revolutionize health care?

Melatonin agonist tasimelteon (HETLIOZ®) improves sleep in patients with primary insomnia: A multicenter, randomized, double-blind, placebo-controlled trial

Background Tasimelteon is a dual melatonin 1 and melatonin 2  receptor agonist. Tasimelteon is the first and only approved medicine to treat a circadian rhythm disorder. In this Phase III trial, the efficacy and safety of tasimelteon was studied in primary insomnia characterized by difficulty falling asleep. Trial design A randomized, double-blind, placebo-controlled, multi-center study investigated 20 mg or 50 mg tasimelteon vs placebo in 322 patients with primary insomnia over a 5-week double-blind treatment interval using polysomnography(PSG) measures of sleep. Methods Patients underwent PSGs on Nights 1, 8, 22 and 29. Entry criteria emphasized enrollment of primary insomnia patients with a confirmed difficulty falling asleep. Subjective sleep latency was ≥ 45 minutes based on sleep history and sleep diary and, patients had a mean latency to persistent sleep (LPS) of ≥30 minutes on two consecutive screening PSG nights with no night having an LPS less than 20 minutes. Findings On the primary end point, the mean improvement in LPS from baseline to the average of Nights 1 and 8 was 44.9 minutes (20 mg) and 46.3 minutes (50 mg) versus 28.2 minutes (placebo) (p &lt; 0.001). Improvements in LPS persisted through the follow-up time points (Nights 22 and 29, p &lt; 0.01). Tasimelteon use was not associated with cognitive or mood changes, and neither rebound nor withdrawal effects were observed after discontinuation. Conclusion Tasimelteon improved sleep from the first night of treatment, and the effect continued for the duration of the study. Tasimelteon was well-tolerated with no adverse next-day residual effects observed. The results of the study strongly suggest that tasimelteon may be an effective therapeutic tool in the treatment of individuals with chronic sleep onset insomnia.

Apocalypse then: how cataclysms shaped human societies

Can flavoprotein monooxygenases functionalize long-chain n-alkanes?

Long-chain n-alkane functionalization is relevant for industrial and environmental applications, but it remains a significant challenge due to the inherent stability of their covalent bonds. Biocatalytic approaches offer promising strategies due to their potential for selective, efficient, and environmentally friendly processes. Among the enzyme families known to functionalize long-chain n-alkanes, one iron-binding protein, AlkB, has been characterized. Additionally, two distinct metal-free flavin-dependent enzymes, LadA and AlmA, are presumed to perform this function. Unlike the membrane-bound AlkB, LadA and AlmA are soluble proteins, making them more amenable to engineering and scalable industrial applications. In this study, we attempted to reproduce and optimize the n-alkane monooxygenase activity of LadA. We tested the functionality of this enzyme, an optimized variant, and four novel homologs under in vitro conditions. Despite extensive efforts, we were unable to detect any long-chain n-alkane hydroxylation. Analysis of LadA’s protein superfamily and the reported experimental evidence indicate that LadA may be involved in the metabolism of long-chain n-alkanes. However, its role in the first oxo-functionalization step could not be corroborated. Similar conclusions were published regarding AlmA’s activity. Altogether, these findings challenge the current understanding of flavoprotein monooxygenases as long-chain n-alkane monooxygenases and underscore the need for further investigation into their biochemical role.