Browse Articles

Magnetic flux imaging in a 3D superconductor integrated circuit

Abstract We report on imaging magnetic flux distributions in a multilayered superconductor integrated circuit which emerge during magnetization and after field cooling of the circuit in the DC magnetic field. The obtained complicated field maps expose the flux propagation across the patterned superconducting ground planes sandwiching layers with Josephson junction-based logic cells, fine wire grid around the functional units, and multiple superconducting fill structures located in different inner layers. The observed intricate flux distributions are explained by specific patterns of Meissner screening currents and superconducting critical currents in different mutually interacting parts of the integrated circuit. Our results provide important insights into possible ways of improving the protection of superconductor integrated circuits from magnetic fields and their resilience against flux trapping.

Modeling high-order harmonic generation in quantum dots using a real-space tight-binding approach

Recently, the size-dependence of high-order harmonic generation (HHG) in quantum dots (QDs) has been investigated experimentally. In particular, for longer driving wavelengths and quantum dots smaller than 3 nm, HHG was strongly suppressed; however, there is no computational model capable of describing the strong-field response of such systems. In this work, we introduce a computationally efficient three-dimensional real-space tight-binding model specifically designed for the simulation of HHG in confined systems. The model parameters are meticulously derived from density functional theory calculations for the semiconductor bulk, followed by a process of Wannierization. Our findings demonstrate that the proposed model accurately captures the observed dependency of the HHG yield on the quantum dot size. In addition, we simulate the HHG yield for elliptically polarized pulses for different QD-sizes and driving wavelengths up to 5 μm. The proposed model fills the theoretical void in simulating HHG within medium-sized nanostructures, which cannot be described by methods applied for periodic solids, or small molecules or atoms.

Study on establishment of cardiovascular interventional disease database and prediction of postoperative mortality risk

Atom-centered electric multipole moments dynamically generated from QM/MM MD simulations

Atom-centered electric multipole moments can be extremely useful in chemistry, as they enable the systematic mapping of a complex electrostatic problem to a simpler model. However, since they do not correspond to physical observables, there is no unique way to define them. In this study, we present an extension of the dynamically generated RESP charges (D-RESP) method, referred to as xDRESP, where atom-centered multipoles are computed from mixed quantum mechanics/molecular mechanics molecular dynamics simulations. We compare the ability of xDRESP charges to reproduce the electrostatic potential, as well as molecular multipoles, against the performance of fixed point-charge models commonly used in force fields. Moreover, we highlight cases where xDRESP atomic multipoles can provide valuable information about chemical systems, such as indicating when polarization plays a significant role, and chemical reactions in which xDRESP atomic multipoles can be used as an on-the-fly analysis tool to track changes in electron density.

Social encapsulation of parasite eggs by honeybee colonies

Abstract Eusocial insect colonies can choose different behaviours to combat the same parasites. While honeybee (HB), Apis mellifera , colonies remove eggs and larvae of parasitic small hive beetles (SHB), Aethina tumida , they encapsulate adults in propolis. It is currently unknown whether there is flexibility in this system. Here, we show encapsulation of eggs by colonies as an alternative to removal. Oviposition sites with or without SHB eggs were introduced into HB field colonies of mixed European origin. After 24 h, sites were removed to measure the propolised area and to quantify the remaining eggs. Further, SHB egg laying depth, and HB worker proboscis length and thickness, were measured. Even though the proboscises were long enough to reach most eggs, the number of eggs before and after introduction did not differ. Instead, HB used more propolis on sites with eggs compared to controls. This suggests decision making by colonies for either egg removal or encapsulation and demonstrates considerable flexibility in social immunity. Such flexibility probably contributes to eusocial insect resilience and calls for efforts to understand colony decision making.

Precision ultranarrow-linewidth resonance excitation (PURE) preparation of a molecular beam of nitric oxide molecules for inelastic scattering with argon

We recently reported a novel technique that utilizes narrow-linewidth lasers to selectively excite molecules into a pure quantum state with a well-resolved, tunable distribution of velocities [O. A. Krohn and D. W. Chandler, J. Phys. Chem. Lett. 15(50), 12455–12463 (2024)]. We refer to the preparation of molecules by this technique as precision ultranarrow-linewidth resonant excitation (PURE) preparation. Here, we pair this PURE preparation methodology with active frequency stabilization of the quantum cascade laser that drives the excitation. In doing so, highly velocity-resolved packets of molecules are possible, with the limitations of this velocity resolution set by the stability of the laser locking and the spectral linewidth of the transition. We show that side-of-fringe locking to a Doppler-broadened absorption spectrum of our target molecule is sufficiently stable for PURE preparation of molecules for long timescales (several hours) with highly resolved velocity spreads (σ < 3 m/s). To demonstrate the scientific utility of this new capability, we present differential cross sections from scattering between a neat molecular beam of argon and a velocity-selected beam of nitric oxide (NO) in a pure quantum state. We observe well-resolved quantum diffraction oscillations in the forward-scattered collisions as well as general trends consistent with prior characterized collisions of NO + Ar.

Functional near-infrared spectroscopy identifies neural biomarkers of burnout in active-duty Police officers

Seeding and controlling colloidal self-assembly through focused ion beam deposition

To obtain high yields of a desired structure from self-assembly, one often needs a seed: a template that favors formation of the structure. The physical mechanisms of seeding have been studied in detail in micrometer-scale colloidal systems, but much of this prior work has focused on quasi-planar substrates. Our overarching aim is to seed colloidal self-assembly on curved surfaces, for which the orientation of a two-dimensional (2D) crystal nucleus—typically unimportant for assembly on a flat surface—determines whether defects form. Because existing methods lack the spatial control to seed colloidal crystals on curved surfaces, we develop a new method that can be applied to both flat and curved surfaces. Our method leverages the spatial precision of focused ion beam (FIB) deposition. We deposit perhaps the simplest nanostructures that can seed the growth of 2D crystals: triangular configurations of three wells. We then use confocal microscopy to monitor the dynamics of depletion-mediated colloidal self-assembly in the presence and absence of the FIB nanostructures. On flat surfaces, we find that nucleation can be either directly or indirectly controlled by the seeding nanostructure, depending on the supersaturation and the interaction strength, and we observe growth occurring by both particle attachment and oriented attachment. Based on these results, we extend our seeding method to control the crystal orientation on a highly curved 5 μm glass fiber. Our FIB-deposition approach to seeding might be useful not only for controlling assembly on geometrically frustrated systems but also for modifying functional devices such as optical fibers and neural probes.

Study on the impact of urban underground public space expansion on near-ground carbon monoxide concentrations

Photodissociation dynamics of the OCS + <i>hv</i> → CO(1Σ+) + S(3P <i>J</i> =2, 1, 0) in the first UV absorption band

The OCS photodissociation dynamics of the minor triplet S(3PJ=2, 1, 0) channels across the first UV absorption band (202–248 nm) have been studied using the time-sliced velocity-mapped ion imaging technique. Wavelength-dependent dynamical features are directly revealed from the sliced images of the S(3PJ=2, 1, 0) photofragments. The internal energy distributions of the counter CO fragments exhibit a vibrational progression, superimposed by a dominant high-energy feature characterized by low vibrational but high rotational excitation. In addition, a minor fraction of extremely high rotationally excited CO(v = 0, 1) is observed near the limitation of available energy. The relative populations of these components show pronounced dependences on both photolysis wavelength and spin–orbit state. The internal-energy-dependent anisotropy parameters β(Eint), combined with insights from potential energy surfaces, indicate distinct dissociation mechanisms. The large positive β(Eint) values for both the dominant highly rotationally excited CO and a substantial population of vibrationally excited CO support a dissociation mechanism dominated by intersystem crossing from the initially excited 21A′ (and minor 11A″) state to the dissociative triplet 23A″ state. In contrast, the minor component of extremely high rotationally excited CO is generated via a two-step nonadiabatic pathway involving internal conversion from the 21A′ state to the ground state followed by intersystem crossing to the triplet 13A′ or 13A″ state, which yields near-zero or small negative β(Eint) values due to the nonaxial recoil effect. Furthermore, an abrupt drop in β(Eint) for low vibrationally excited CO fragments near 223 nm suggests an additional contribution from direct excitation to the triplet 23A″ state and its subsequent nonadiabatic dissociation.

Extraction method shapes soil water-soluble organic matter composition as revealed by absorbance, fluorescence, and parallel factor analysis (PARAFAC)

Abstract Organic matter (OM) is central to biogeochemical processes in both soils and aquatic systems. Water-soluble organic matter (WSOM), leached from soil, is widely analyzed as a proxy for the mobile OM fraction, yet the chemical composition of extracts depends strongly on the extraction method used. We compared two WSOM extraction protocols—distilled water and 0.5 M K 2 SO 4 —across 217 soil samples from 83 depth profiles spanning four central European regions. Absorbance and fluorescence spectroscopy with PARAFAC modeling were used to characterize dissolved organic carbon (DOC) concentration and composition—approaches increasingly applied in soil science to trace soil organic matter dynamics. DOC generally declined with profile depth. K 2 SO 4 extracts consistently yielded higher DOC concentrations, dominated by humic-like fluorescence. Water extracts were more variable, with stronger protein-like signals—showing clearer depth-related trends, with deeper layers enriched in microbially-derived DOM. This higher variability likely reflects the dynamic nature of labile WSOM fractions. We highlight the importance of extraction chemistry: water-based methods capture reactive, microbially-produced WSOM—likely indicators of immediate inputs to aquatic systems, whereas salt-based methods emphasize more stable pools—acting as indicators of less bio-available, long-term terrestrial reservoirs. Extraction methodology selection should consider the study objectives and specific biological and physicochemical processes investigated.

Numerically exact quantum dynamics with tensor networks: Predicting the decoherence of interacting spin systems

Predicting the quantum dynamics of promising solid-state and molecular quantum technology candidates remains a formidable challenge. Yet, accessing these dynamics is key to understanding and controlling decoherence mechanisms—a prerequisite for designing better qubits, sensors, and memories. We leverage a matrix product state representation to introduce a numerically exact and scalable method to achieve this goal. We demonstrate that our method accurately predicts coherence and population dynamics of spin networks across a wide range of parameter regimes, encompassing nuclear spin sensors and qubits in solid-state semiconductors and molecular magnets. Our method further predicts spin dynamics under the influence of repeated light pulses, which are commonly used to mitigate decoherence and perform quantum sensing experiments. Our method thus provides reliable results for moderately sized spin platforms spanning molecular magnets and solid-state spins that can guide the development of approximate but efficient quantum dynamics methods and enable principled inquiry into decoherence mechanisms.

Primary dysmenorrhea and associated factors among female adolescents in Jinka town, Southern Ethiopia, 2024

Non-equivalent local excitations and conformation dependent charge transfer in N,N-dimethylethylenediamine

The discrimination of local excitation sites in multi-charge-center molecular systems remains a long-standing challenge and is rarely explored. Herein, non-equivalent local excitations of two distinct 3s Rydberg states (3s1 and 3s2, as excited from the N1 and N4 atoms, respectively) in two-charge-center N,N-dimethylethylenediamine and their ensuing conformation-dependent charge transfer dynamics have been observed by femtosecond time-resolved photoelectron spectra. In particular, following local excitation at N4, the 3s2 state structurally evolves away from the Franck–Condon region driven by charge redistribution from N1 to the hole of N4 via through-bond interaction, leading to the 3s1 and 3s2 states being energetically indistinguishable after 300 fs. The preferential charge stabilization at N4 is observed, exhibiting a new paradigm of charge localization. Concurrently, the 3p state undergoes internal conversion to 3s_h and 3s_l states and approaches a dynamic conformation equilibrium (3s_h/3s_l = 61%:39%) within about 1.1 ps. This work provides new insight into the understanding of charge localization and transfer phenomena in biologically relevant molecular systems with multiple charge centers.

Highly sensitive hierarchically structured Si-based UV sensor–photodetectors via optimized ZnO–Al2O3 nanocomposite architectures

Abstract The rapid and reliable detection of ultraviolet (UV) radiation is critical for applications ranging from environmental monitoring to optoelectronic security systems. This study presents an integrated theoretical and experimental investigation into highly sensitive, hierarchically structured Si-based UV sensor–photodetectors optimized via ZnO–Al 2 O 3 nanocomposite architectures. A combination of density functional theory (B3LYP/6-31G(d,p)) calculations and comprehensive materials characterization was employed to elucidate the interplay between electronic structure, surface morphology, and optical performance. Theoretical modeling provided detailed insights into band alignment, total and partial density of states, frontier molecular orbitals, and electrostatic potential distributions for pure and hybrid oxide systems, revealing that ZnO–Al 2 O 3 exhibits superior electronic coupling and enhanced carrier mobility pathways. Experimentally, ZnO and Al 2 O 3 nanoparticles were synthesized via hydrothermal routes, integrated into hybrid thin-film architectures on Si substrates, and structurally verified by XRD, FE-SEM, and EDX analyses. Surface roughness and apparent porosity measurements indicated that Al 2 O 3 incorporation increased roughness from 6.7 to 8.2 µm and porosity from 26 to 36%, fostering enhanced light scattering and active site density. Optical absorption spectroscopy (250–650 nm) revealed strong UV selectivity with calculated band gaps of 3.18 eV (ZnO), 3.11 eV (Al 2 O 3 ), and 3.26 eV (ZnO–Al 2 O 3 ), while electrochemical impedance spectroscopy confirmed reduced charge transfer resistance in the hybrid architecture. Electrical conductivity improved from 27.7 × 10 −2  S/m (ZnO) to 44.5 × 10 −2  S/m (ZnO–Al 2 O 3 ), correlating with faster response and recovery dynamics under UV illumination. These synergistic structural, optical, and electronic enhancements establish ZnO–Al 2 O 3 as a promising candidate for next-generation, high-performance UV photodetectors with superior sensitivity, stability, and spectral selectivity.

The second Gibbs paradox

Gibbs’s monumental article on the equilibrium of heterogeneous substances contains a paradoxical sentence stating that, for a crystallite in equilibrium with a fluid, the chemical potential of the solid will not be equal to that of the fluid if the surface free-energy density differs from the mechanical surface-tension. How can this be? After all, in chemical equilibrium, the chemical potential of any species should be the same throughout the system. This “second Gibbs paradox” has intrigued many authors. In the present paper, I sketch my interpretation of the approach of Gibbs and that of Mullins [J. Chem. Phys. 81, 1436–1442 (1984)], which accounts for the possibility of vacancies and interstitials. I argue that a consistent treatment of point defects in a critical nucleus is essential for clarifying the meaning of the chemical potential of the nucleus. My paper lacks the rigor of Gibbs or Mullins but will hopefully be more accessible for scientists who think primarily in terms of atoms and molecules. In my attempt, I am motivated by a quote that is sometimes attributed to Paul Valéry: “The glass must be absolutely transparent for one to perceive the mud at the bottom.”

Predictors of adult ICU mortality: a retrospective study at two government hospitals in Ethiopia

Abstract The number of life-threatening conditions requiring admission to intensive care units has increased substantially in low-income countries, partly due to the expansion of hospital services. In Ethiopia, ICU mortality rates vary across regions. However, evidence regarding the magnitude of ICU mortality and its associated predictors remains limited and inconclusive. To assess the magnitude of the mortality rate and its predictors among hospitalized adult patients A two-center retrospective cross-sectional study was conducted among patients admitted to the ICU between December 1, 2023, and May 30, 2024. Data were collected using a pretested, structured questionnaire. The completed data were gathered via a web link developed using Kobo Toolbox (kobtoolbox.org), then coded, manually verified for completeness, and exported to SPSS version 27 for analysis. Descriptive statistics and logistic regression analyses were performed to evaluate the data. A total of 309 patient charts were reviewed. The median ICU stay was 5 days. The leading causes of ICU admission were postoperative conditions, septic shock, stroke, and congestive heart failure. The most common causes of death were septic shock, stroke, head trauma, and acute respiratory distress syndrome (ARDS). The overall mortality rate among ICU-admitted patients was 46.3%. A higher Charlson Comorbidity Index score, the need for mechanical ventilation at admission, and the presence of hospital-acquired infections were significantly associated with ICU mortality. Compared with some developed countries, the observed mortality rate in this cohort was higher. The findings of the present study indicate that hospital-acquired infections, the Charlson Comorbidity Index, and the need for mechanical ventilation were all significantly associated with mortality among intensive care unit patients.

Water structure and dynamics under distinct microheterogeneity in DMSO–water and acetone–water mixtures

Dimethyl sulfoxide (DMSO) and acetone are water miscible structural analogs with sharply contrasting cryoprotective properties. These cosolvents perturb water structure and dynamics in different ways, leading to distinct molecular associations, hydration patterns, and solute-specific microheterogeneous environments. To explore these divergences, this work presents a comparative study of DMSO–water and acetone–water mixtures over a cosolvent mole-fraction range of 0.05–0.5, using classical molecular dynamics simulations combined with graph theoretical analysis, quantification of spatial inhomogeneity via the h-value, and analysis of water dynamics. DMSO integrates into the water network, locally disrupting tetrahedral order while minimizing DMSO–DMSO self-association and preserving connectivity through the formation of DMSO–water complex. In contrast, acetone promotes cohesive self-aggregation of acetone molecules and enhanced clustering of water molecules, creating a microheterogeneous environment. Correspondingly, water in acetone mixtures exhibits faster translational diffusion and rotational dynamics with shorter H-bond lifetimes, whereas DMSO mixtures slow water dynamics and lengthen H-bond lifetimes. Notably, the study on these differences in structural and dynamical properties in both aqueous mixtures could help rationalize DMSO’s established effectiveness in cryopreservation, owing to its relatively low microinhomogeneity, in contrast to the tendency of acetone to promote microinhomogeneity, thereby limiting its utility as a cryoprotectant.

AI driven dual constraint cooptimization of affective semantics and engineering parameters for biomimetic product design

Intermediate time sub-diffusion and stress relaxation in ring polymer melts

The slow dynamics of non-concatenated ring melts remains a frontier problem in polymer science with implications for many soft material environments including cellular biophysics. Here, we report large-scale simulations of model ring melts that analyze the monomer and center-of-mass (CM) mean square displacements (MSD) and stress relaxation function on intermediate time and length scales. The degree of dynamical slowing down is characterized by the maximally sub-diffusive fractional time scaling exponents. The data span an exceptionally wide range of ring degrees of polymerization and stiffnesses and are not successfully organized based on the classic measure linear chain entanglement, N/Ne. Rather, we find that the crossover degree of polymerization, ND, based on ring macromolecular caging that successfully allows master curves to be constructed for the long-time CM self-diffusion constant also collapses these temporal dynamic scaling exponents. Different properties display different exponents and exhibit one or two regimes of linear variation with the logarithm of ND/N. A distinct crossover of the CM-MSD and stress relaxation exponents emerges at sufficiently large N or stiffness that is not found for the monomer MSD, indicating a novel form of dynamic decoupling. This crossover aligns with the predicted critical degree of polymerization for transitioning from a weak to strong caging regime, indicative of activated transport. The latter may reflect the emergence of an intermolecular collective contribution to stress in analogy with dense soft colloidal matter. Suggestions are made for future theoretical work to address the rich patterns of behavior discovered.