Browse Articles

Crystallization and particle size distribution of hydrothermally synthesized SAPO-34: an experimental and population balance study

Large magnetoresistance induced by monolayer ScV2S4 with interlayer antiferromagnetic coupling between two V atomic layers

Antiferromagnetic spintronic devices are ideal candidates for next-generation picosecond-response and high-density information carriers, and the discovery of van der Waals (vdW) antiferromagnets provides a new platform for exploring antiferromagnet-based spintronic devices. Here, we propose monolayer ScV2S4 antiferromagnet with two magnetic V atomic layers and investigate the influence of strain on the electronic structure, magnetic property, and in-plane spin-dependent transport of the proposed monolayer ScV2S4 using first-principles calculations. It is found that the proposed monolayer ScV2S4 is an antiferromagnetic (AFM) metal with the interlayer AFM coupling between two V atomic layers, and the interlayer AFM coupling can be switched to ferromagnetic coupling by a compressive strain of −2.2%. Moreover, a large magnetoresistance of about 114–120% is achieved in the proposed monolayer ScV2S4 using a compressive strain of −2.5%. The electrical control of the interlayer magnetic coupling in monolayer ScV2S4 clamped by piezoelectric material can be achieved by combining the strain-induced change in interlayer magnetic coupling of monolayer ScV2S4 with the inverse piezoelectricity of piezoelectric materials. Our work presents a promising avenue for developing low-dissipation vdW spintronic devices based on antiferromagnets.

The Manhattan exciton size: A physically tractable delocalization measure

Delocalized excitations, denoted excitons, play an important role in many systems in chemical physics. The characterization of their extent of delocalization is a crucial element in understanding these quasiparticles. In this paper, I will revisit the most common delocalization measures applied to Frenkel-type excitons. Based on this analysis, I propose to use a so-far ignored measure. The key advantage of this measure, which I will denote as the Manhattan exciton size, is that it directly connects with the oscillator strength of the excitons. It provides a strict upper bound on the oscillator strength of any given exciton for linear aggregates. Finally, I demonstrate that this exciton delocalization measure is more sensible for analyzing super-radiant states compared to, for example, the most commonly applied measure, i.e., the (inverse) participation ratio. However, these two measures together provide insight into the degree of exciton confinement.

Communication skills, understanding intellectual coordination and marital satisfaction on childbearing motivation in reproductive-age Iranian couples

Cu interconnect lifetime estimation in the presence of thermal gradients

Through physical and electrical analysis, the impact of thermal gradients on mass transport in Cu interconnects is studied using a dedicated test structure. The key physical parameter for thermomigration (TM), the heat of transport (Q∗), is evaluated experimentally to be 0.21 eV. Furthermore, an analytical model based on existing 1D physics-based models [M. A. Korhonen et al., J. Appl. Phys. 73, 3790–3799 (1993); H. Zahedmanesh et al., Microelectron. Reliab. 111, 113769 (2020)] is proposed to predict the time to void nucleation, the void growth rate (νgrowth), and the time to failure (TTF) due to TM. Also, their dependence on temperature (T), temperature gradient (dTdx), and second derivative of the temperature (d2Tdx2) is derived. This analytical model calibrated using experimental data predicts a TTF of 38 years for a 1μm wide Cu interconnect under specific stress conditions: an operating temperature of 100°C, a local temperature increase of 67°C, and a d2Tdx2=−2.9°C/μm2 induced by an external heat source.

On the complex hydrogen-bond network structural dynamics of liquid methanol: Chains, rings, bifurcations, and lifetimes

Solvation plays a pivotal role in chemistry to effectively steer chemical reactions. While liquid water has been extensively studied, our molecular-level knowledge of other associated liquids capable of forming H-bond networks, such as liquid methanol, remains surprisingly scarce. We use large-scale ab initio molecular dynamics simulations to comprehensively study the structural, dynamical, and electronic properties of bulk methanol under ambient conditions. Methanol is an interesting species in the liquid state since it can only donate one H-bond while a significant fraction accepts two H-bonds, which imprints one-dimensional linear and cyclic H-bonding patterns subject to significant bifurcations. After validation of radial distribution functions and the self-diffusion coefficient with respect to experimental data, we carried out detailed analyses of the H-bond network topology in terms of chain-like, ring-like, and branched H-bonded aggregates, including lifetime assessment. The analysis revealed that nearly all methanol molecules are actively engaged in filamentary H-bonding, predominantly forming branched linear chains with a significant contribution arising from tetrameric to hexameric rings—in stark contrast to the compact three-dimensional H-bond network of water. Five-membered rings turned out to be the most long-lived cyclic structures with an intermittent lifetime of 4 ps, while rings consisting of only three methanol molecules as well as very large cyclic structures are merely transient motifs. Detailed analyses of the effective electric molecular dipoles disclose a pronounced sensitivity of non-additive polarization and charge transfer effects of the individual methanol molecules to the particular H-bond network structure they are a member of, including its topology, be it linear or cyclic.

The PRECISION study protocol: Can cervical stiffness in the second trimester predict preterm birth in high-risk singleton pregnancies? A feasibility, cohort study

Background Preterm birth (PTB) is a leading cause of neonatal morbidity and mortality. More than 13 million babies are affected globally every year and PTB will contribute to over 900,000 deaths. In the UK, PTB affects 8% of pregnancies and costs more than £260 million annually in neonatal care. Identifying those at risk of this devastating complication of pregnancy and implementing preventative treatment remains a maternal health priority. The mainstay of PTB prevention has been assessment of cervical length (CL) in women at high-risk of PTB. However, CL has limitations, namely it is invasive, user dependent and varies over time through pregnancy. Importantly, not all those who are high-risk with a short CL will subsequently deliver preterm and CL screening doesn’t identify a sub-set of women who have a spontaneous PTB without a short cervix. Therefore, existing care pathways for managing PTB can potentially benefit from additional assessments of risk. Novel ways of assessing cervical structure and function may improve our ability to predict spontaneous PTB and refine preventative intervention. This feasibility study will explore the use of a new antenatal test of cervical stiffness for assessing risk of spontaneous PTB in a high-risk singleton population. Methods PRECISION is a single site prospective, feasibility, cohort study of asymptomatic women with singleton pregnancies at high risk for spontaneous PTB attending an inner-city tertiary maternity hospital in the UK. All study participants will be undergoing routine screening and management of PTB as per local guidance (NICE/Saving Babies Lives guidance) including CL screening with transvaginal ultrasound. Cervical stiffness will be assessed using the Pregnolia System; a novel, licensed, CE-marked, aspiration-based device. A measurement is obtained by applying the device directly to the anterior lip of the cervix, visualised via placement of a speculum, and gives a quantitative assessment of cervical stiffness represented as the Cervical Stiffness Index (CSI, in mbar). Participants will undergo cervical stiffness assessments at up to three timepoints in the second trimester between 14+0 weeks and 25+6 weeks gestation. The cervical stiffness index data will be paired with routine PTB clinic CL measurements taken at the same time points. The primary outcome will focus on the feasibility of using this novel antenatal test in this high-risk population and explore any association between cervical stiffness and PTB. Discussion This is an exploratory study to assess the use of this novel device in clinical practice. Direct comparison between cervical stiffness assessment using the Pregnolia System and CL assessment will determine the acceptability of this new assessment in this population, as well as explore its potential association with PTB. Our findings from this feasibility study will provide data on the potential of this novel device to impact PTB screening and evaluate acceptability of use in a high-risk population. Data on eligibility, recruitment rates and participant feedback will help inform future study design using the device. Trial registration ClinicalTrials.gov NCT05837390

Decoding carbon pathways of Shanghai megacity through historical land use patterns and urban ecosystem transitions

The Zintl pnictides Yb10CdSb9 and Yb14CdSb11: New candidate thermoelectric materials

The synthesis of new materials is the lifeline of solid-state science, and it continues to offer us unique opportunities for testing various theoretical formulations and models on a practical material. Such an avenue, therefore, provides a breeding ground for technological innovations and advancements that can completely revolutionize our world. Here, we report the results of our exploratory syntheses in the Yb–Cd–Sb compositional space that lead to the identification of two new Zintl antimonides, namely, Yb10CdSb9 and Yb14CdSb11. Their crystal structures were established via single-crystal X-ray diffraction methods; the basic electronic and transport properties of the new materials were also characterized. Yb10CdSb9 crystallizes in a disordered variant of the tetragonal Ca10LiMgSb9 structure type with unit cell parameters a = 11.8473(8) Å and c = 17.1302(12) Å (space group P42/mnm). Yb14CdSb11 crystallizes in the tetragonal Ca14AlSb11 structure type with unit cell parameters: a = 16.605(3) Å and c = 12.144(7) Å (space group I41/acd). Although the structures of both compounds can be rationalized within the framework of the Zintl formalism, based on the partitioning of the valence electrons in the much disordered Yb10CdSb9 phase, the charge is indicative of a slightly electron-rich composition. Electronic structure calculations in both cases support the notion of intrinsic semiconductor behavior, as expected for a Zintl phase. The temperature dependence of the electrical resistivity of a single crystal of Yb10CdSb9 is in line with that, and the evolution of the Seebeck coefficient indicates an electron-dominated transport mechanism, and a respectable power factor of 0.71 μW/cm K2 at 460 K can be calculated for Yb10CdSb9. The electrical resistivity of Yb14CdSb11, however, evolves in a semimetallic manner, which could suggest an overdoped sample or degenerate semiconducting behavior.

Nonlinear optical spectroscopy of open quantum systems

The development of experimental techniques at the nanoscale has enabled the performance of spectroscopic measurements on single-molecule current-carrying junctions. These experiments serve as a natural intersection for the research fields of optical spectroscopy and molecular electronics. We present a pedagogical comparison between the perturbation theory expansion of standard nonlinear optical spectroscopy and the (non-self-consistent) perturbative diagrammatic formulation of the nonequilibrium Green’s functions method (which is widely used in molecular electronics), highlighting their similarities and differences. By comparing the two approaches, we argue that the optical spectroscopy of open quantum systems must be analyzed within the more general Green’s function framework.

Colombian centenarians: A Geohealth approach to longevity study

Introduction Population longevity is a global phenomenon influenced by various factors including social, economic transitions, and medical advancements. The study focused on the population over 95 years old, adopting an approach that integrates data from the 2018 Census and geospatial analysis techniques. Methods An ecological study was conducted using anonymized microdata from the 2018 National Population and Housing Census (CNPV). Geographic analysis, choropleth maps, and Kernel density estimation were employed to identify clusters of individuals aged over 95 years. Results The study identified 43,427 individuals aged 95 years or older in Colombia, with concentrations observed in departments such as Antioquia and Bogotá. Analysis by department and municipality revealed variations in rates and sex distribution. Kernel density analysis highlighted clusters in the Valle de Tenza area and other regions. Conclusion This study sheds light on the geographical distribution of centenarians in Colombia, emphasizing clusters in certain regions. More research is needed to understand the individual and contextual factors underlying successful aging in Colombia and to inform policies to improve the quality of life of older populations.

Cognitive and sensorimotor benefits of moderate- and high-intensity exercise are associated with specific expression of neurotrophic markers in older rats

Nanoscale electrical conductance and leakage currents in etched and selective-area regrown GaAs pn junctions

Analysis and mitigation of junction leakage currents are central to the engineering of vertical semiconductor diode structures. We have used scanning capacitance microscopy and conductive atomic force microscopy to characterize, with nanoscale spatial resolution, charge carrier distributions and local current distributions at the edges of mesa-etched and selective-area regrown vertical GaAs pn junction diodes grown by molecular-beam epitaxy. These studies indicate that wet etch-induced defect states are present on the etched surfaces of mesa structures, leading to increased local electrical conductivity that could contribute to sidewall leakage. For selective-area regrown structures, we observe an annular low-conductivity region in the vicinity of the GaAs–SiO2 interface at the edge of regrown pn junction structures that could act to suppress current flow at the edges of pn junction diodes fabricated from selective-area regrown material. Together, these studies provide new insights into the origin of sidewall leakage currents in mesa-etched GaAs pn junction diodes and their suppression in selective-area regrown devices.

A new interaction potential for Cl−, Li+, Na+, and Ca+2 in methanol solutions using the scaled charges concept

The Madrid-2019 intermolecular potential was developed for use in molecular simulations of salty aqueous solutions. The selection of the accurate TIP4P/2005 potential for water and the adoption of scaled charges for ions, ±0.85e for monovalent ions and ±1.70e for divalent ions, are the key features of the model. The use of scaled charges enhances the description of several properties, including solubility, transport properties, the density maximum, and the water activity in ionic solutions. In this study, we will investigate the performance of scaled charges in describing the properties of inorganic salts containing Cl−, Li+, Na+, and Ca+2 in another polar solvent, methanol. The ion charges and ion–ion interactions were taken from the Madrid-2019 potential, while the accurate OPLS/2016 model was selected for methanol. The protocol used in the development of the Madrid-2019 model, particularly regarding the selection of target properties in the fitting procedure, was applied to create this potential using LiCl, NaCl, and CaCl2 as inorganic salts. Its predictive ability was evaluated by calculating the density, dielectric constant, self-diffusion coefficients of methanol and ions, and viscosity for methanolic solutions of these three salts. As will be shown, the experimentally observed effects of salt addition are reproduced by the new model, not only qualitatively but also quantitatively. Furthermore, since the interaction potential is compatible with the Madrid-2019 model, we also demonstrated its accurate predictive ability in the ternary system methanol + water + NaCl.

Preparation and properties of isocyanate self-healing microcapsule cement-based material

Self-healing microcapsule cement-based materials autonomously repair microcracks within the matrix. This study utilized the interfacial polymerization method to prepare isocyanate microcapsules, incorporating montmorillonite to enhance the wall material. The optimized synthesis conditions were established as follows: a reaction time of 2 hours at 50°C, using 3g of wall material, 13.5g of core material, and 1% montmorillonite, achieving a core material content of 61.5%. Both micro and macro analyses confirm the microcapsules’ excellent alkaline resistance and compatibility with cement-based materials. The ideal microcapsule concentration was determined to be 4%, which increased the compressive strength recovery rate of the self-healing mortar to 117.38%.

Metabolic dysfunction associated steatotic liver disease is associated with atrial fibrillation recurrence following cryoballoon ablation

Unstable instantaneous normal modes and diffusion in supercooled liquids

At supercooled temperatures, liquid fluidity requires barrier crossing on the multidimensional potential energy surface or landscape. However, most equilibrium quantities are then dominated by configurations close to the local minima and do not contain information about the barriers. Thus, they are not indicated as the basis of a theory for long-time dynamics, specifically, for the self-diffusion constant, D(T). By contrast, the unstable instantaneous normal modes (INMs) are well-defined equilibrium properties with contributions only from configurations with some downward curvature of the potential, primarily, regions above the inflection points and the barriers. They are uniquely well suited to describe long-time dynamics, and the results of pursuing that idea are described herein: (1) The well developed and successful INM theory of self-diffusion. (2) The theory and functional form of the unstable density of states, which contains information about the topography of the landscape, a significant factor in the nature of supercooled dynamics. (3) A random energy model and the soft potential model provide simplification and add additional insight. (4) Despite the focus on dynamics, the configurational entropy is expressed in terms of the unstable INM, and the heat capacity has unstable INM contributions.

Coacervation drives morphological diversity of mRNA encapsulating nanoparticles

The spatial arrangement of components within an mRNA encapsulating nanoparticle has consequences for its thermal stability, which is a key parameter for therapeutic utility. The mesostructure of mRNA nanoparticles formed with cationic polymers has several distinct putative structures: here, we develop a field theoretic simulation model to compute the phase diagram for amphiphilic block copolymers that balance coacervation and hydrophobicity as driving forces for assembly. We predict several distinct morphologies for the mesostructure of these nanoparticles, depending on salt conditions and hydrophobicity. We compare our predictions with cryogenic-electron microscopy images of mRNA encapsulated by charge altering releasable transporters. In addition, we provide a graphics processing unit-accelerated, open-source codebase for general purpose field theoretic simulations, which we anticipate will be a useful tool for the community.

Velocities of hippocampal traveling waves are proportional to their coherence frequency

Cortical traveling waves, defined by their spatial, temporal, and frequency characteristics, provide key insights into active brain regions, timing, frequency, and the direction of activity propagation. Emerging evidence suggests that the directionality and spatiotemporal extent of these waves encode cognitive processes. However, the relationship between frequency and this encoding mechanism remains unclear. We investigate the hypothesis that coherence frequency determines wave propagation velocity. By employing both bivariate linear and multivariate nonlinear coherence analyses, we demonstrate that coherence frequency encodes propagation velocity. Unlike linear analyses, which may overestimate velocities due to bidirectional flow when assessing multiple pair coherences, our nonlinear approach—calculating propagation along four-node pathways—treats pathways as holistic units with net unidirectional flow, making it more appropriate for calculating wave velocities. We extracted pairwise coherence and four-node pathways from local field potentials recorded via intracranial electrodes positioned along the hippocampal longitudinal axis in patients with drug-resistant epilepsy. Our findings reveal that average coherence values and contact pair distances calculated by the multivariate analysis are more consistent across frequencies compared to pairwise coherence. The average coherence values are higher, and the average pair distances and wave velocities are lower in the multivariate analysis than in the pairwise approach. Propagation velocities along the hippocampus at low frequencies (<~35 Hz) exhibit a linear dependence on frequency in the alpha and beta bands, with a steeper slope in the gamma band, indicating distinct mechanisms for velocity-frequency dependence across oscillation bands. While observed within the hippocampus, these findings suggest that the relationship between frequency and wave velocity may extend to other cortical areas. Our nonlinear multivariate analysis appears better suited than pairwise coherence for investigating brain network dynamics. Further research is needed to elucidate the role of conduction velocity in brain function.

County-to-county migration is associated with county-level racial bias in the United States

Abstract Millions of people move within the U.S. each year. We propose that people function as proxies for their locations, bringing the culture of their previous residence to their new homes. As a result, migration might systematically influence regional biases across geographic units over time. Using county-to-county migration data from the U.S. census and county-level racial attitude estimates from Project Implicit, the present research examined the impact of people relocating from one U.S. county to another on racial attitudes in their new county. Consistent with our prediction, the bias brought by the migrants positively predicts county-level racial bias after migration, even after controlling for county-level racial bias before migration. This finding remains robust across various sample inclusion criteria and spans three time periods (2006–2010, 2011–2015, and 2016–2020). These results highlight the significant role of migration in spreading and shaping regional racial attitudes, emphasizing the importance of considering macro-societal processes such as migration when studying changes in regional racial attitudes.