Browse Articles

Automated search of minimum-energy conical intersections with projected metadynamics

We present a new method for the automated search of minimum-energy conical intersections (MECIs) based on metadynamics. In this method, two independent forces are constructed and projected into the minimization subspace and the constraint subspace, respectively. One force is directed toward the minimum-energy point, while the other is directed toward the conical intersection seam. The root-mean-square deviation based bias potential is added to the potential energy surface to force the structure escape from the already explored regions. The additional constraint function is used to enable the structure reach different intersection seams. This method can be used for systematically and automatically searching MECIs or exploring conical intersection seams. Compared to the penalty function-based metadynamics method, this new method is more effective and stable in searching MECIs. Furthermore, this method can be combined with any kind of constraint, whether geometric or non-geometric, making it a generalized tool for the automated search of constrained minimum.

FoxA1 knockdown promotes BMSC osteogenesis in part by activating the ERK1/2 signaling pathway and preventing ovariectomy-induced bone loss

From viral variants to devastating storms, how names shape the public's reaction to science

Fast passage effect in cw-ODMR of an ensemble of NV− centers

A rapid scan technique of the magnetic field has been developed to improve excitation efficiency in continuous wave (cw)-electron spin resonance. The resulting passage effects induce significant responses of magnetizations, most notably an inversion of longitudinal magnetization. The change in longitudinal magnetization can be observed in optically detected magnetic resonance (ODMR), but the passage effect has not been investigated in cw-ODMR spectroscopy. In this study, we combine the ODMR technique with the rapid scan of the magnetic field to demonstrate the impact of fast passage effects on the field-swept cw-ODMR. An ensemble of negatively charged nitrogen-vacancy (NV−) centers in a diamond crystal is used as a model system. By selecting the fast passage adiabatic region among six distinct passage regions, efficient ODMR detection is achieved through the macroscopic control of longitudinal magnetization. Experimental results are explained by the numerical analyses of classical time-dependent Bloch equations and related rate equations under an optical cycle. This knowledge paves the way for the facilitation of versatile applications of ODMR for quantum sensors.

Study on the stability of excavation process of permafrost subgrade slope in Alpine region

Nonlinear Kondo transport through serially coupled double quantum dots

We study the transport property through the serially coupled double quantum dots (DQDs) system with Kondo resonance based on the dissipation equation of motion theory. A nonlinear behavior of the transport current is exhibited due to the competition between the interdot coupling strength of the two QDs and the Kondo effect. With the increase in interdot coupling strength, the transport current first increases at low interdot couplings and then decreases with the strong interdot couplings. The reason is that the interdot coupling strength will result in a continuous evolution from the Kondo singlet state of individual QDs to the spin singlet state forming between the two QDs. Moreover, we define the physical quantity ∂G/∂t as the differential function of differential conductance G with respect to interdot coupling strength t. The nonlinear transport behavior and the physical quantity ∂G/∂t with differential conductance at different bias voltages can be used to detect the potential Kondo resonance in the nonequilibrium transport experiments.

Panoramic analysis of 2D dirubidium telluride monolayer benchmarking the DFT approach

Abstract Through the DFT computations, the structural, vibrational, electronic, elastic, optical and thermal (thermoelectric, thermodynamic) properties of the two-dimensional Rb2Te monolayer are briefly contemplated. The Perdew-Bruke-Ernzerhof (PBE) form of generalized gradient approximation (GGA) functional in WIEN2k was deployed for the analysis of all these material properties. The trigonally crystallizing monolayer with an indirect band gap of 1.72 eV may be an upright single-layer that suffices distinct applications. ‘No negative’ phonon bands confirm the dynamical stability of the monolayer. The Rb2Te monolayer has large indirect band gap than Rb2S and Rb2Se. It exhibits mechanical stability with positive elastic constants satisfying the Born-Huang criterion for two-dimensional materials. The absorption coefficient spanning largely in the ultra-violet range makes the monolayer a congruous material for UV applications. Also, the thermoelectric figure of merit for p-type Rb2Te single-layer at room temperature is high (0.67) compared to the analogous series of compounds, that makes the monolayer a viable one for thermoelectric flexibility and experimental synthesis. The monolayer has high hole effective mass and D ratio. The obtained results aids in revealing the outstanding properties and excellent stability of the monolayer. Based on these findings the Rb2Te monolayer paves the way for promising applications in the fields of photovoltaics, thermoelectrics and UV-based applications.

Theoretical study of the structure and vibrational sum frequency generation spectroscopy of liquid–vapor interface of aqueous acetic acid

We have investigated the liquid–vapor interface of aqueous acetic acid solution through calculations of the structure and vibrational sum frequency generation (VSFG) spectra of the interfaces for varying concentrations of the acetic acid (AA). Our findings reveal the surface propensity of the AA molecules. As the concentration of AA increases, more AA molecules are found to be present in the interfacial region. The AA molecules at the interface are found to be oriented in a manner where the hydrophobic part (methyl chain) is oriented toward the vapor phase and the hydrophilic part is pointed toward the liquid phase. The total VSFG spectrum reveals that the intensity of the peak of dangling OH groups of water around 3750 cm−1 decreases when the concentration of AA increases, while the intensity of the peak around 3550 cm−1 due to OH groups having hydrogen bonds between water and AA molecules increases. Furthermore, the latter peak is redshifted as the AA concentration increases, which is due to the partial cancellation between the positive response of water OH modes and the negative response of the OH modes of AA molecules. It is also noted that the AA molecules make the interfacial water more structured by making hydrogen bonds with its otherwise dangling OH modes at the surface.

First-in-human exploratory trial assessing safety, feasibility, and efficacy of artificial protein (silk-elastin) in promoting healing in patients with meniscus injuries

Abstract Meniscal tears, especially those in avascular regions, pose a significant risk for osteoarthritis if repair fails. While meniscal repair is the preferred method for preserving knee function, it often has a high failure rate in avascular zones. This study aimed to evaluate the safety and potential efficacy of silk-elastin (SE), an artificial protein with wound-healing properties, for enhancing meniscal repair. Eight patients with meniscal tears in avascular areas underwent arthroscopic repair followed by SE application, including cases of lateral and medial tears, discoid lateral meniscus, and bucket-handle tears. No adverse events or reactions were attributed to SE. At 3 months post-surgery, clinical outcomes and repair sites were evaluated using MRI and arthroscopy. Significant improvements were observed in Lysholm and visual analog scale scores ( P  < 0.05), with the knee injury and osteoarthritis outcome scores showing significant improvement in the symptom subscale. MRI findings indicated one patient with grade 1 healing, three with grade 2, and four with grade 3 (unhealed). Arthroscopically, six patients demonstrated completely healed menisci, while two showed incomplete healing; none were classified as “unhealed.” These findings suggest that SE is safe and may support meniscal healing in avascular zones, indicating its potential to improve repair outcomes.

Considerable spin asymmetry of deep valence states induced by partial neutralization of charged SrTiO3(011) surfaces

Recently, spin asymmetry in O 2p related deep valence states was evidenced in SrTiO3(001) [Popescu et al., Phys. Scr. 99(10), 105925 (2024)]. In this work, we report the detection of a much higher (about four times) spin asymmetry in SrTiO3(011) by spin resolved photoelectron spectroscopy, with samples characterized also by core level x-ray photoelectron spectroscopy and low energy electron diffraction. The explanation of a so important spin asymmetry is related to the partial neutralization of O2(4−) or SrTiO(4+) end layers. Missing electrons from O 2p states in the case of O2 terminations enable robust atomic spins, according to Hund’s rule. The parallel analysis of core level shifts for surface atoms and the amplitude of spin asymmetry suggests that 50% of the oxygens from the surface SrO layer of SrTiO3(001) have a 2p5 configuration with an unpaired electron (the rest are in a 2p6 configuration), while in the case of O2 terminated SrTiO3(011), about 50% of surface oxygens have a 2p5 configuration and 50% of surface oxygens are neutral (2p4), yielding a net charge per O2 surface unit cell of (−1) instead of (−4). The magnetization is oriented along the rows formed by the (4 × 1) reconstruction in the 01̄1 in-plane direction.

Determination of 5-fluorouracil anticancer drug solubility in supercritical CO2using semi-empirical and machine learning models

How my research focus exposed me to threats and harassment

Shock compression of liquefied gases: Molecular dissociation and radiance change at the sample/LiF interface

This study investigates the behavior of nitrogen and other liquefied gases under shock compression, with a focus on temperature variations and molecular dissociation. Through dynamic compression experiments on liquefied Ar, O2, CO, and N2, we aimed to understand shock-induced cooling and radiance changes at the sample/lithium fluoride (LiF) interface. The experiments were conducted using a setup involving a Doppler pin system and pyrometer to measure shock velocities, pressures, and temperatures across the interface between shocked liquids and LiF. Under the first-shock, molecular liquids experienced partial dissociation due to a rapid rise in pressure, density, and temperature within nanoseconds. Upon re-shocking at the sample/LiF interface, a radiance drop was observed for all liquids except Ar. Our data analysis suggests that the cooling effect is likely due to a chemical reaction occurring at the interface between reactive species, produced during the initial shock, and the layer of LiF at the surface under re-shock conditions. One probable interpretation is that this reaction formed a thin, partially transparent layer on the LiF, which absorbed a significant portion of the radiation emitted by the shocked fluid. Thus, the observed temperature drop in re-shocked liquid nitrogen is likely attributable to radiation reduction.

Focal adhesion kinase promotes aerobic glycolysis in hepatic stellate cells via the cyclin D1/c-Myc/MCT-1 pathway to induce liver fibrosis

Polyampholyte sequence controls the type of electrostatic coil-globule transition in good solvent

Coarse-grained molecular dynamics simulations are employed to explore the conformational behavior of globally neutral polyampholytes under good solvent conditions. The interplay between non-Coulomb repulsions and sequence-dependent Coulomb attractions of monomers results in qualitatively different types of electrostatically driven chain contraction for diblock, random, and alternating statistics. At increasing the solution Bjerrum length lb, diblock and random polyampholytes exhibit a smooth coil-globule crossover, with the globule size continuously decreasing with lb according to the theoretical power laws. This confirms the scaling picture of the globule interior consisting of oppositely charged blobs attracting each other via long-range electrostatic forces and repelling via short-range two-body interactions. In contrast, alternating polyampholytes collapse completely analogously to neutral chains because Coulomb interactions in them are effectively dipole–dipole short-range. The transition region shrinks with increasing chain length, implying phase transition behavior in the limit of infinitely long chains. These collapse curves fall on the universal master curve, which is well-fitted by the theory of coil-globule transitions and demonstrates that Coulomb interactions in alternating polyampholytes renormalize (reduce) the dimensionless second virial coefficient by δB∝−lb2. This study highlights the profound impact of primary sequence on the conformational behavior of charge-balanced polyampholytes in good solvents, particularly the nature of the electrostatically driven coil-globule transition they undergo.

Towards autonomous robotic THz-based in vivo skin sensing: the PicoBot

Abstract Terahertz (THz) light has the unique properties of being very sensitive to water, non-ionizing, and having sub-millimeter depth resolution, making it suitable for medical imaging. Skin conditions including eczema, psoriasis and skin cancer affect a high percentage of the population and we have been developing a THz probe to help with their diagnosis, treatment and management. Our in vivo studies have been using a handheld THz probe, but this has been prone to positional errors through sensorimotor perturbations and tremors, giving spatially imprecise measurements and significant variations in contact pressure. As the operator tires through extended device use, these errors are further exacerbated. A robotic system is therefore needed to tune the critical parameters and achieve accurate and repeatable measurements of skin. This paper proposes an autonomous robotic THz acquisition system, the PicoBot, designed for non-invasive diagnosis of healthy and diseased skin conditions, based on hydration levels in the skin. The PicoBot can 3D scan and segment out the region of interest on the skin’s surface, precisely position (± 0.5/1 mm/degrees) the probe normal to the surface, and apply a desired amount of force (± 0.1N) to maintain firm contact for the required 60 s during THz data acquisition. The robotic automation improves the stability of the acquired THz signals, reducing the standard deviation of amplitude fluctuations by over a factor of four at 1 THz compared to hand-held mode. We show THz results for skin measurements of volunteers with healthy and dry skin conditions on various parts of the body such as the volar forearm, forehead, cheeks, and hands. The tests conducted validate the preclinical feasibility of the concept along with the robustness and advantages of using the PicoBot, compared to a manual measurement setup.

Have Trump’s anti-DEI orders hit private funders? HHMI halts inclusive science programme

Data-driven signal-to-noise enhancement in scattering near-field infrared microscopy

This study introduces a machine-learning approach to enhance signal-to-noise ratios in scattering-type scanning near-field optical microscopy (s-SNOM). While s-SNOM offers a high spatial resolution, its effectiveness is often hindered by low signal levels, particularly in weakly absorbing samples. To address these challenges, we utilize a data-driven “patch-based” machine learning reconstruction method, incorporating modern generative adversarial neural networks (CycleGANs) for denoising s-SNOM images. This method allows for flexible reconstruction of images of arbitrary sizes, a critical capability given the variable nature of scanned sample areas in point-scanning probe-based microscopies. The CycleGAN model is trained on unpaired sets of images captured at both rapid and extended acquisition times, thereby modeling instrument noise while preserving essential topographical and molecular information. The results show significant improvements in image quality, as indicated by higher structural similarity index and peak signal-to-noise ratio values, comparable to those obtained from images captured with four times the integration time. This method not only enhances image quality but also has the potential to reduce the overall data acquisition time, making high-resolution s-SNOM imaging more feasible for a wide range of biological and materials science applications.

Active frequency support capability evaluation of photovoltaic stations based on bi-level evaluation method

Superoxide anion (O2−) collisions with CO2 molecules in the energy range of 50–950 eV

A novel gas-phase molecular scattering study is reported for O2− collisions with CO2 for impact energies ranging from 50 to 950 eV in the lab frame. The absolute total electron detachment, relative total, and partial ionization cross sections have been measured within this energy range together with the positive ion yields. The primary anionic beam projectile is produced in a pulsed hollow cathode discharge induced plasma, and its interactions with the neutral molecular target occur in a gas cell at a well-known constant pressure. For impact energies above 500 eV, high mass (m > 44 u) charged complexes have been detected. With the aid of a theoretical study using ab initio methods, we propose a mechanism to infer the formation of these cationic species, which have been assigned to projectile–target stable compounds (CO3+ and CO4+).