Browse Articles

Quantum tunneling and anti-tunneling across entropic barriers

We study the dynamics of a quantum particle in a constricted two-dimensional channel and analyze how the onset of quantum corrections impacts the (semi-)classical high-temperature behavior as temperature is lowered. We characterize both equilibrium and non-equilibrium (transport) properties of the system, considering the case of a narrow and disorder-free channel. Counterintuitively, we find that quantum corrections do not monotonically enhance the particle current as the temperature is lowered, as naively expected from the activation of coherent tunneling, but they rather inhibit transport at intermediate temperatures, increasing the effective free-energy barrier. We illustrate this “anti-tunneling” effect numerically by computing the non-equilibrium steady-state of a quantum master equation describing the system and confirm it analytically by adopting the quantum Smoluchowski limit.

Utilizing alkaline solid waste for low-carbon construction material via in-situ calcium phase design

Photochemistry of ClClS and ClSCl isomers

The photochemistry of chlorine–sulfur species is central to Venus’s atmospheric chemistry, particularly concerning the unidentified near-UV absorber. This study investigates the electronic structure, spectroscopy, and photochemistry of the ClSCl and ClClS isomers, with implications for their potential role as near-UV absorbers in Venus’ atmosphere. High-level CCSD(T) and MRCI+Q calculations indicate that ClSCl is the global minimum, but ClClS is 2.34 eV higher in energy. For ClSCl, the photo-absorption cross-section displays a strong deep-UV peak at 197 nm and a much weaker band centered near 370 nm. In contrast, ClClS shows two comparatively intense near-UV bands at 350 and 271 nm. Potential energy surface analyses show that ClSCl’s excited states undergo non-adiabatic coupling upon near-UV irradiation, with deep-UV excitation leading to rapid ClS + Cl formation. Although both isomers absorb in the same near-UV spectral range as the unknown Venus absorber, these isomers are photochemically unstable under the actinic UV radiation and so are unable to play major roles.

Structural insights into polymerase-catalyzed FAD capping of hepatitis C virus RNA

Spin and charge control in conjugated ionic oligomers: DFT and EPR study

The initial oxidized trans-polyacetylene and polythiophene-based conjugated oligomers, as well as their composites with polycyclic aromatic hydrocarbons, were studied by density functional theory (DFT) and electron paramagnetic resonance methods. The relative electronic density and spin population of each oligomer atom are obtained within the framework of different formalisms. The stabilization of different spin charge carriers in different poly(3-alkylthiophene)-based oligomers is shown. The role of the hybridization of the molecular orbitals of oligomers in stabilizing these charge carriers on an oligomer chain is analyzed. The main parameters of the spin Hamiltonian of spin charge carriers formed in compounds with various structures and morphologies are determined. A significant change in the electronic and magnetic properties of these charge carriers is shown to occur upon the modification of oligomers with graphene-like polycyclic aromatic hydrocarbons owing to hyperfine coupling of their extended π-conjugated structures. Magic numbers of some graphene-like additives with stabilized structural and electronic parameters were determined. This interaction is initiated by spin polarization, depends on the polycyclicity of the aromatic additive, and is characterized by several extremes. This effect was assumed to arise as a result of cross-coupling of oligomers and graphene-like subsystems with enhanced stability and electronic or/and magnetic properties. It enhances their hyperfine exchange coupling, and it affects a barrier for the spin magnetization switching. Such composite spin-filter functionality can be used in fully organic spin‒controlled molecular devices. This should have an impact on the wide fields of fully organic spintronics, nanotechnology, and quantum devices by controlling and manipulating spin and charge.

Ribosome biogenesis in plants requires the nuclear envelope and mitochondria localized OPENER complex

Abstract Eukaryotic ribosome biogenesis proceeds from nucleolus to cytosol assisted by various assembly factors. The process is evolutionarily conserved across eukaryotes but differences between the kingdoms are emerging. Here, we describe how the OPENER (OPNR) protein complex is required for 60S ribosome assembly in the model plant Arabidopsis thaliana. The complex is observed on both nuclear envelope and mitochondria, and contains OPNR, OPENER ASSOCIATED PROTEIN 1 (OAP1), OAP2, Cell Division Cycle 48 D (CDC48D) and Calmodulin-interacting protein 111 (CIP111). Depletion of the OPNR complex components results in reproductive lethality and cytoplasmic retention of assembly factors on 60S ribosomes. Subsequent biochemical analyses and structural modelling suggest that OPNR, OAP1 and OAP2 form a claw-like trimer which grabs the ribosome assembly factor RIBOSOMAL PROTEIN L24C (RPL24C) on the pre-60S ribosome. Our results reveal previously unrecognised subcellular complexity of ribosome biogenesis in plants, and point to mitochondria association as a feature to ensure sufficient translational capacity.

Fluctuations in the <i>μpT</i> ensemble

We work out the statistical ensemble of an equilibrium macroscopic system composed of particles interacting via short-range forces in a completely open situation in which heat, mechanical work, and matter can be exchanged with the surroundings. Attention is focused on variances and covariances of extensive properties, with particular emphasis on their connection with thermodynamic response functions like the isothermal compressibility or the isobaric thermal expansivity. The exact formulas we derive prove that, with full generality, response functions quantify variances and covariances of ratios between extensive properties such as the number density, the enthalpy per particle, or the “Hill energy” per unit volume. Results for grand canonical or isothermal–isobaric ensembles are recovered when either the volume or the number of particles are fixed, while consistency with Einstein’s thermodynamic theory is also encountered. A water-like Ising model illustrates how the standard mean-field approach proceeds in the ensemble, while it validates the correctness of our fluctuation formulas numerically. A potential usefulness of the ensemble to deepen on the phenomenological pattern of behavior of thermodynamic systems shows up.

Frontline acalabrutinib, lenalidomide and rituximab for advanced stage follicular lymphoma with high tumor burden: phase II trial

Length scales in electrolytes

The elusive presence of an anomalously increasing screening length at high ionic concentrations hampers a complete image of interactions in electrolytes. Theories that extend the diluted Debye–Hückel framework to higher concentrations predict, in addition to the expected decreasing Debye length, an increasing significant scale of the order of at most a few ionic diameters. More recent surface force balance experiments with different materials succeeded in measuring increasing length scales that, however, turned out to extend over tenths or even hundreds of ionic diameters. While simulation work has managed to characterize the former, the latter still avoids detection, generating doubts about its true origin. Here, we provide a step forward in the clarification of such a conundrum. We have studied by extensive molecular dynamics simulation the properties of a generic model of electrolyte, lithium tetrafluoroborate dissolved in ethylene-carbonate, in a vast range of salt concentrations continuously joining the Debye non-interacting limit to the opposite overcharged solvent-in-salt states. On one side, we have accurately determined the macroscopic concentration-induced structural, dielectric, and transport modifications; on the other, we have quantified the resulting nanoscale ion organization. Based only on the simulation data, without resorting to any uncontrolled hypotheses or phenomenological parameters, we identify a convincing candidate for the measured anomalously increasing length, whose origin has possibly been misinterpreted.

Compact eye camera with two-third wavelength phase-delay metalens

Förster resonance energy transfer in inhomogeneous and absorptive environment

We present an analytical model for Förster resonance energy transfer (FRET) between a donor and an acceptor placed in an inhomogeneous and absorptive environment characterized by a complex dielectric function, e.g., near a metal–dielectric structure. By extending the standard approach to FRET to include energy transfer (ET) channel to the environment, we show that, in the absence of plasmonic enhancement effects, the Förster radius, which defines the characteristic distance for efficient FRET, is reduced due to a competing ET process. We demonstrate that the reduction in the Förster radius can dramatically affect fluorescence from large ensemble of molecules whose emission kinetics is dominated by FRET-induced concentration quenching. In particular, we perform numerical calculations for dye-doped polymer films deposited on top of a metallic substrate to find that, at high dye concentrations, the emission kinetics slows down considerably as compared to the same films on a glass substrate, in sharp contrast to acceleration of single-molecule fluorescence near the metal. Furthermore, the effective fluorescence decay rate exhibits a non-monotonic behavior with varying film thickness, consistent with the experiment, indicating a non-trivial interplay between the metal quenching and concentration quenching mechanisms.

Lithium intercalated FeSe as a high-temperature superconducting ferromagnet

Abstract Merging superconductivity and ferromagnetism in a single material may promise unparalleled quantum properties for next-generation devices. Here, we bring together the two antagonistic phenomena at a record-high temperature via electric-field controlled lithiation of FeSe. The in-situ gating allows us to switch the simple compound of FeSe between a nonmagnetic superconductor and a superconducting ferromagnet. In the latter state, itinerant ferromagnetism persists from above 200 K to a temperature well below the superconducting transition temperature (45 K), as demonstrated not only by magneto-transport but also via scanning superconducting quantum interference device (sSQUID) microscopy. Interestingly, applying certain in-plane magnetic fields enhances superconductivity, reflecting the intimate interplay between high-temperature superconductivity and ferromagnetism. Density-functional theory calculations further reveal the instability of FeSe toward ferromagnetism at a moderate lithium concentration. These findings open up fresh opportunities in iron-based superconductors that interface dissipationless electronics and spintronics.

Modeling CO2 adsorption in flexible MOFs with open metal sites via fragment-based neural network potentials

Metal–organic frameworks (MOFs) with open metal sites (OMS) are among the most promising porous materials for gas adsorption and separation, owing to their strong and selective interactions with guest molecules. However, simulating adsorption in such systems with high accuracy and efficiency remains a key challenge due to the need to model complex guest–MOF interactions and framework flexibility. Classical force fields often lack the precision to capture these effects, while ab initio methods are computationally prohibitive for large-scale, long-timescale simulations. In this work, we developed a neural network potential (NNP) trained on highly accurate density functional theory (PBE-D4/def2-TZVP) level data derived from a single representative fragment of the Mg-MOF-74 framework, a prototypical OMS-containing MOF, with CO2 molecules. Despite the limited training domain, the NNP accurately captured both intra- and inter-molecular interactions in the CO2–Mg-MOF-74 system, including those involving the open metal sites. We integrated this NNP into a hybrid molecular dynamic and grand canonical Monte Carlo simulation workflow, enabling accurate modeling of CO2 adsorption in flexible MOFs. This approach allows accounting for both framework dynamics and complex host–guest interactions with chemical accuracy and computational efficiency. Our results highlight the crucial role of framework flexibility in adsorption behavior and demonstrate that fragment-based NNP, when combined with advanced simulation techniques, offer a powerful and efficient approach for realistically modeling adsorption processes in MOFs with open metal sites.

Unprecedented large-scale aquifer recovery through human intervention

Taming the virtual space for incremental full configuration interaction

Incremental full configuration interaction (iFCI) closely approximates the FCI limit with polynomial cost through a many-body expansion of the correlation energy, providing highly accurate total energies within a given basis set. To extend iFCI beyond previous basis set limitations, this work introduces a novel natural orbital (NO) screening approach, incremental NO full configuration interaction (iNO-FCI). By consideration of the importance of virtual orbital selection in the convergence of iFCI, iNO-FCI maximizes the consistency between orbitals selected for each correlated body. iNO-FCI employs a principle of cancellation of errors and ensures that the same set of virtual NOs is used for interdependent terms. This strategy significantly reduces computational cost without compromising precision. Computational savings of up to 95% are demonstrated, allowing access to larger basis sets that were previously computationally prohibitive. iNO-FCI is herein introduced and benchmarked for several difficult test cases involving double-bond dissociation, biradical systems, conjugated π systems, and the spin gap of a Cu-based transition metal complex.

Light-driven modulation of proximity-enhanced functionalities in hybrid nano-scale systems

Abstract Advancing quantum information and communication technology requires smaller and faster components with actively controllable functionalities. This work presents an all-optical strategy for dynamically modulating magnetic properties via proximity effects controlled by light. We demonstrate this concept using hybrid nanoscale systems composed of C₆₀ molecules proximitized to a cobalt metallic ferromagnetic surface, where proximity interactions are particularly strong. Our findings show that by inducing excitons in the C60 molecules with resonant ultrashort light pulses, we can significantly modify the interaction at the Cobalt/C60 interface, leading to a remarkable 60% transient shift in the frequency of the Co dipolar ferromagnetic resonance mode. This effect, detected via a specifically designed time-resolved Magneto-Optical Kerr Effect (tr-MOKE) experiment, persists on a timescale of hundreds of picoseconds. Since this frequency shift directly correlates with a transient change in the anisotropy field—an essential parameter for technological applications—our findings establish a new material platform for ultrafast optical control of magnetism at the nanoscale.

Functional amyloid proteins confer defence against predatory bacteria

Inverted perovskite solar cells via multifunctional potassium sorbate to etch PEDOT:PSS and modify the PEDOT:PSS/perovskite interface

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely used as a hole transport layer in inverted perovskite solar cells (PSCs). However, the PSS chains on the surface of PEDOT:PSS can absorb water molecules in humid environments, which accelerates the degradation of the perovskite at the PEDOT:PSS/perovskite interface (hereafter referred to as the PP interface). In addition, the mismatched valence band levels between PEDOT:PSS and perovskite result in a high defect density at the PP interface, leading to significant open-circuit voltage loss. To address these issues, inspired by semiconductor etching processes, we employed an ethanol solution of potassium sorbate to etch the surface of PEDOT:PSS. After etching with ethanol, the sorbate anion and potassium ions from potassium sorbate fill the positions left by the etched PEDOT and PSS chains, forming new electrostatic interactions. This not only improves the conductivity of PEDOT:PSS but also improves the energy level matching between PEDOT:PSS and perovskite, facilitating hole transport at the PP interface. As a result, the open-circuit voltage of the device increased from 1.085 to 1.144 V, and the power conversion efficiency improved from 17.54% to 21.10%. The –C=O group of potassium sorbate also acts as a Lewis base, forming a Lewis adduct with the uncoordinated Pb2+ ions at the PP interface, significantly reducing the defect density and enhancing the stability of the PSCs. This approach provides new insights and methods for improving both the efficiency and stability of inverted PSCs.

One-hour extraction-free loop-mediated isothermal amplification HPV DNA assay for point-of-care testing in Maputo, Mozambique

Abstract Human papillomavirus (HPV) is responsible for nearly all cases of cervical cancer. Affordable point-of-care DNA testing is needed for cervical cancer screening in low- and middle-income countries, where most cervical cancer cases occur. HPV DNA testing typically requires complex lab infrastructure and trained personnel. In this work, we develop a loop-mediated isothermal amplification (LAMP)-based HPV DNA test, which targets three of the most oncogenic HPV types (HPV16, HPV18, HPV45) and a cellular control and achieves analytical sensitivity comparable to gold standard methods. Our extraction-free sample preparation strategy permits adding sample lysate directly to the LAMP reaction. We utilize a low-cost benchtop heater/fluorimeter, delivering results in less than one hour. We analytically evaluate our assay with clinical samples in Houston, Texas ( n  = 38) and Maputo, Mozambique ( n  = 191). Results show 100% and 93% concordance, respectively, with a reference test widely used in low-resource settings. This sensitive and specific four-step assay can potentially expand cervical cancer screening in resource-limited settings.

The COVID-19 pandemic transformed this scientist into a research-integrity sleuth