Segment Anything in Optical Coherence Tomography: SAM 2 for Volumetric Segmentation of Retinal Biomarkers.

Optical coherence tomography (OCT) is a non-invasive imaging technique widely used in ophthalmology for visualizing retinal layers, aiding in the early detection and monitoring of retinal diseases. OCT is useful for detecting diseases such as age-related macular degeneration (AMD) and diabetic macular edema (DME), which affect millions of people globally. Over the past decade, the area of application of artificial intelligence (AI), particularly deep learning (DL), has significantly increased.

From a humorous post to a detailed quantum-chemical study: isocyanate synthesis revisited.

Isocyanates play an essential role in modern manufacturing processes, especially in polyurethane production. There are numerous synthesis strategies for isocyanates both under industrial and laboratory conditions, which do not prevent searching for alternative highly efficient synthetic protocols. Here, we report a detailed theoretical investigation of the mechanism of sulfur dioxide-catalyzed rearrangement of phenylnitrile oxide into phenyl isocyanate, which was first reported in 1977.

Diamond surface functionalization via visible light-driven C-H activation for nanoscale quantum sensing.

Nitrogen-vacancy (NV) centers in diamond are a promising platform for nanoscale NMR sensing. Despite significant progress toward using NV centers to detect and localize nuclear spins down to the single spin level, NV-based spectroscopy of individual, intact, arbitrary target molecules remains elusive. Such sensing requires that target molecules are immobilized within nanometers of NV centers with long spin coherence.

The Role of Electrolytes in the Relaxation of Near-Surface Spin Defects in Diamond.

Quantum sensing with spin defects in diamond, such as the nitrogen vacancy (NV) center, enables the detection of various chemical species on the nanoscale. Molecules or ions with unpaired electronic spins are typically probed by their influence on the NV center's spin relaxation. Whereas it is well-known that paramagnetic ions reduce the NV center's relaxation time (), here we report on the opposite effect for diamagnetic ions.

Benchmarking DFT Functionals for Excited-State Calculations of Donor-Acceptor TADF Emitters: Insights on the Key Parameters Determining Reverse Inter-System Crossing.

The importance of intermediate triplet states and the nature of excited states has gained interest in recent years for the thermally activated delayed fluorescence (TADF) mechanism. It is widely accepted that simple conversion between charge transfer (CT) triplet and singlet excited states is too crude, and a more complex route involving higher-lying locally excited triplet excited states has to be invoked to witness the magnitude of the rate of reverse inter-system crossing (RISC) rates. The increased complexity has challenged the reliability of computational methods to accurately predict the relative energy between excited states as well as their nature.

Controlled Surface Modification to Revive Shallow NV Centers.

Near-surface negatively charged nitrogen vacancy (NV) centers hold excellent promise for nanoscale magnetic imaging and quantum sensing. However, they often experience charge-state instabilities, leading to strongly reduced fluorescence and NV coherence time, which negatively impact magnetic imaging sensitivity. This occurs even more severely at 4 K and ultrahigh vacuum (UHV, = 2 × 10 mbar).

Training a neural network to predict dynamics it has never seen.

Neural networks have proven to be remarkably successful for a wide range of complicated tasks, from image recognition and object detection to speech recognition and machine translation. One of their successes lies in their ability to predict future dynamics given a suitable training data set. Previous studies have shown how echo state networks (ESNs), a type of recurrent neural networks, can successfully predict both short-term and long-term dynamics of even chaotic systems.

Toward Large-Scale Restricted Active Space Calculations Inspired by the Schmidt Decomposition.

We present an alternative, memory-efficient, Schmidt decomposition-based description of the inherently bipartite restricted active space (RAS) scheme, which can be implemented effortlessly within the density matrix renormalization group (DMRG) method via the dynamically extended active space procedure. Benchmark calculations are compared against state-of-the-art results of C and Cr, which are notorious for their multireference character. Our results for ground and excited states together with spectroscopic constants demonstrate that the proposed novel approach, dubbed as DMRG-RAS, which is variational and free of uncontrolled method errors, has the potential to outperfom conventional methods for strongly correlated molecules.

Dielectric control of reverse intersystem crossing in thermally activated delayed fluorescence emitters.

Thermally activated delayed fluorescence enables organic semiconductors with charge transfer-type excitons to convert dark triplet states into bright singlets via reverse intersystem crossing. However, thus far, the contribution from the dielectric environment has received insufficient attention. Here we study the role of the dielectric environment in a range of thermally activated delayed fluorescence materials with varying changes in dipole moment upon optical excitation.

Modeling of Multiresonant Thermally Activated Delayed Fluorescence Emitters─Properly Accounting for Electron Correlation Is Key!

With the surge of interest in multiresonant thermally activated delayed fluorescent (MR-TADF) materials, it is important that there exist computational methods to accurately model their excited states. Here, building on our previous work, we demonstrate how the spin-component scaling second-order approximate coupled-cluster (SCS-CC2), a wavefunction-based method, is robust at predicting the Δ (i.e.

Ultraviolet Quantum Emitters in Hexagonal Boron Nitride from Carbon Clusters.

Ultraviolet (UV) quantum emitters in hexagonal boron nitride (hBN) have generated considerable interest due to their outstanding optical response. Recent experiments have identified a carbon impurity as a possible source of UV single-photon emission. Here, on the basis of first-principles calculations, we systematically evaluate the ability of substitutional carbon defects to develop the UV color centers in hBN.

Ozone destruction due to the recombination of oxygen atoms.

Kinetics of ozone destruction due to the recombination of oxygen atoms produced by pulsed 266 nm laser photolysis of O/M (M = CO and/or N) mixtures was studied using the absorption and emission spectroscopy to follow time evolutions of O and electronically excited molecules O* formed in the recombination process 2O(P) + M → O* + M. An unexpected high ozone destruction rate was observed when O* was present in the system. The kinetic model developed for the oxygen nightglow on the terrestrial planets was adapted to interpret the detected temporal profiles of the ozone number density and the O* emission intensities.

The role of charge recombination to triplet excitons in organic solar cells.

The use of non-fullerene acceptors (NFAs) in organic solar cells has led to power conversion efficiencies as high as 18%. However, organic solar cells are still less efficient than inorganic solar cells, which typically have power conversion efficiencies of more than 20%. A key reason for this difference is that organic solar cells have low open-circuit voltages relative to their optical bandgaps, owing to non-radiative recombination.

Lanthanide-doped inorganic nanoparticles turn molecular triplet excitons bright.

The generation, control and transfer of triplet excitons in molecular and hybrid systems is of great interest owing to their long lifetime and diffusion length in both solid-state and solution phase systems, and to their applications in light emission, optoelectronics, photon frequency conversion and photocatalysis. Molecular triplet excitons (bound electron-hole pairs) are 'dark states' because of the forbidden nature of the direct optical transition between the spin-zero ground state and the spin-one triplet levels. Hence, triplet dynamics are conventionally controlled through heavy-metal-based spin-orbit coupling or tuning of the singlet-triplet energy splitting via molecular design.

Interlayer Bonding in Two-Dimensional Materials: The Special Case of SnP and GeP.

Stacked two-dimensional (2D) heterostructures are evolving as the "next-generation" optoelectronic materials because of the possibility of designing atomically thin devices with outstanding characteristics. However, most of the existing 2D heterostructures are governed by weak van der Waals interlayer interactions that, as often is the case, exert limited impact on the resulting properties of heterostructures relative to their constituting components. In this work, we investigate the optoelectronic properties of a novel class of 2D MP (M = Ge and Sn) materials featuring strong interlayer interactions, applying a robust theoretical framework combining density functional theory and many-body perturbation theory.

Computational investigation of energy transfer and line broadening for Ar + He collisions.

Potential energy curves for all states arising from the interaction of He with the 3p, 3p4s, and 3p4p configurations of Ar have been determined using high-level electronic structure calculations. The results have been used to examine collisional energy transfer probabilities and spectral line shape parameters (shifting and broadening rate coefficients). The main focus has been on states and transitions that are of relevance to optically pumped He/Ar laser systems.

A Long-Term Study of the Biological Properties of ASF Virus Isolates Originating from Various Regions of the Russian Federation in 2013-2018.

Biological properties of the African swine fever (ASF) virus isolates originating from various regions of the Russian Federation (2013-2018) were studied in a series of experimental infections. Comparative analysis allowed us to establish the differences in the key characteristics of the infection, such us the duration of the incubation periods, disease, and the onset of death. The incubation period averaged 4.

Intramolecular Borylation via Sequential B-Mes Bond Cleavage for the Divergent Synthesis of B,N,B-Doped Benzo[4]helicenes.

New symmetric and unsymmetric B,N,B-doped benzo[4]helicenes 3-6 a/b have been achieved in good yields, using a three-step process, starting from N(tolyl) in a highly divergent manner (7 examples). A borinic acid functionalized 1,4-B,N-anthracene 1 was found to display unprecedented reactivity, acting as a convenient and highly effective precursor for selective formation of bromo-substituted B,N,B-benzo[4]helicenes 2 a/2 b via intramolecular borylation and sequential B-Mes bond cleavage in the presence of BBr . Subsequent reaction of 2 a/2 b with Ar-Li provided a highly effective toolbox for the preparation of symmetrically/unsymmetrically functionalized B,N,B-helicenes.

Highly emissive excitons with reduced exchange energy in thermally activated delayed fluorescent molecules.

Unlike conventional thermally activated delayed fluorescence chromophores, boron-centered azatriangulene-like molecules combine a small excited-state singlet-triplet energy gap with high oscillator strengths and minor reorganization energies. Here, using highly correlated quantum-chemical calculations, we report this is driven by short-range reorganization of the electron density taking place upon electronic excitation of these multi-resonant structures. Based on this finding, we design a series of π-extended boron- and nitrogen-doped nanographenes as promising candidates for efficient thermally activated delayed fluorescence emitters with concomitantly decreased singlet-triplet energy gaps, improved oscillator strengths and core rigidity compared to previously reported structures, permitting both emission color purity and tunability across the visible spectrum.

Rate constants for collision-induced emission of O(aΔ) with He, Ne, Ar, Kr, N, CO and SF as collisional partners.

Rate constants for singlet oxygen collision induced emission of the a1Δg-X3Σ-g transition at 1.27 μm were measured for CO2, N2, SF6, and rare gases as collisional partners. Photolysis of ozone by 266 nm laser radiation produced singlet oxygen.

Engineering Chemically Active Defects in Monolayer MoS Transistors via Ion-Beam Irradiation and Their Healing via Vapor Deposition of Alkanethiols.

Irradiation of 2D sheets of transition metal dichalcogenides with ion beams has emerged as an effective approach to engineer chemically active defects in 2D materials. In this context, argon-ion bombardment has been utilized to introduce sulfur vacancies in monolayer molybdenum disulfide (MoS ). However, a detailed understanding of the effects of generated defects on the functional properties of 2D MoS is still lacking.

Luminescence of the (O2(a(1)Δ(g)))2 collisional complex in the temperature range of 90-315 K: Experiment and theory.

Experimental and theoretical studies of collision induced emission of singlet oxygen molecules O2(a(1)Δg) in the visible range have been performed. The rate constants, half-widths, and position of peaks for the emission bands of the (O2(a(1)Δg))2 collisional complex centered around 634 nm (2) and 703 nm (3) have been measured in the temperature range of 90-315 K using a flow-tube apparatus that utilized a gas-liquid chemical singlet oxygen generator. The absolute values of the spontaneous emission rate constants k2 and k3 are found to be similar, with the k3/k2 ratio monotonically decreasing from 1.

Improving the Accuracy of the Charge Transfer Integrals Obtained by Coupled Cluster Theory, MBPT(2), and TDDFT.

Theoretical modeling of the charge transport in organic materials in the diabatic representation requires an accurate evaluation of the charge transfer integrals. In this paper, we show that the coupled cluster and MBPT(2) approaches are the methods of choice for performing the benchmark calculations of this quantity, in contrast to some recently published results. We demonstrate that a proper treatment of the involved ionized states, achieved by applying the continuum-orbital strategy, reduces the error of the transfer integrals by one order of magnitude, which in the case of the CC2 method corresponds to a lowering of the mean relative unsigned error (MRUE) from 39.

Development of highly accurate approximate scheme for computing the charge transfer integral.

The charge transfer integral is a key parameter required by various theoretical models to describe charge transport properties, e.g., in organic semiconductors.