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Based on the ab initio molecular dynamic simulations, for LiBa12(BO3)7F4and NaBa12(BO3)7F4, the transition into a dynamically disordered state was established. In LiBa12(BO3)7F4, the [BO3] groups and Li atoms located in the channels pass into the dynamically disordered state above ∼700 K. In NaBa12(BO3)7F4, the dynamic disorder of the [BO3] groups occurs at the lower temperature, ∼500 K. Na atoms, in contrast to Li atoms, do not pass into the dynamically disordered state at any temperature. It was shown that the dynamic disorder of the [BO3] groups increases the symmetry of the structure from ordered P42bcto P42/mbcand I4/mcm.

The migration of an electron-loss center (hole) in calf thymus DNA to bisbenzimidazole ligands bound in the minor groove is followed by pulse radiolysis combined with time-resolved spectrophotometry. The initially observed absorption spectrum upon oxidation of DNA by the selenite radical is consistent with spin on cytosine (C), as the GC•pair neutral radical, followed by the spectra of oxidized ligands. The rate of oxidation of bound ligands increased with an increase in the ratio (r) ligands per base pair from 0.005 to 0.04. Both the rate of ligand oxidation and the estimated range of hole transfer (up to 30 DNA base pairs) decrease with the decrease in one-electron reduction potential between the GC•pair neutral radical of ca. 1.54 V and that of the ligand radicals (E0′, 0.90–0.99 V). Linear plots of log of the rate of hole transfer versus rgive a common intercept at r= 0 and a free energy change of 12.2 ± 0.3 kcal mol–1, ascribed to the GC•pair neutral radical undergoing a structural change, which is in competition to the observed hole transfer along DNA. The rate of hole transfer to the ligands at distance, R, from the GC•pair radical, k2, is described by the relationship k2= k0exp(constant/R), where k0includes the rate constant for surmounting a small barrier.

Industrial 2G HTS wires optimized for low-temperature application are studied using XRD. We aim at understanding the origin of noticeable variation of the lift factor LF = Jc(20K, 8T)/Jc(77 K, sf) with the final goal of narrowing down the statistical scatter of the performance in production wires. Two approaches are used - (1) the direct characterization of Y123 defect state through analysis of diffuse scattering effects and (2) quantification of YBCO nanostructure (contents of Y2O3 precipitates, their size, strain state of Y2O3 precipitates and Y123 matrix). Only weak correlations between the parameters extracted from XRD patterns and Jc(20K, 8T) have been found. A rather complex strain state of Y123 with out-of-plane tension, anisotropic in-plane compression, and (likely) overall contraction is observed. Further plans are discussed.

Noble-metal nanoparticles for photocatalysis have become a major research object in recent years due to their plasmon-enhanced strong light–matter interaction. The dynamics of the hot electrons in the noble metal is crucial for the efficiency of the photocatalysis and for the selective control of reactions. In this work, we present a kinetic description of the nonequilibrium electron distribution created by photoexcitation based on full energy-resolved Boltzmann collision integrals for the laser excitation as well as for the electron–electron thermalization. The laser-induced electronic nonequilibrium and the inherently included secondary electron generation govern the dynamics of nonthermal electrons. Applying our method to gold, we show a significant dependence of hot electron dynamics on the kinetic energy. Specifically, the time scales of the relaxation as well as the qualitative behavior are dependent on the evaluated energy window. During the thermalization processes, there are cases of increasing electron density as well as of decreasing electron density. Studying the influence of excitation parameters, we find that the photon energy and the fluence of the exciting laser can be tuned to influence not only the initial excitation but also the subsequent characteristics of the time-resolved electronic spectral density dynamics. The electronic thermalization including secondary electron generation leads to time-dependent spectral densities, which differ from their specific final equilibrium values for picoseconds after irradiation ended.

The production of second-generation high-temperature superconductors (2G HTS) greatly simplifies the construction of electrical devices based on them. In turn, the performance of 2G HTS is highly dependent on the manufacturing process, architecture, and materials on which they are produced. Particularly important in the process of industrial 2G HTS development is the addition of doping additives to reduce the anisotropy of the current-carrying capacity. In this work, the current-carrying capacity Ic (T, B, θ) of industrial 2G HTS samples with different deposition rate and concentration of BaSnO3 - 6 mol.% doping additives were measured in fields up to 9 T and at temperatures 65 and 77 K. Experimental measurements were carried out at various orientations of an external magnetic field of up to 1 T relative to the sample plane. It was found that the change of sputtering velocity leads to the decrease of current-carrying capacity at 77 K. The influence of the microstructural characteristics of the artificial pinning centers on the electrophysical parameters was considered.

In the present study, we use the crystal structure prediction technique to reveal the new high-pressure structures of PbCO3, SrCO3, and BaCO3. As a result, we found the new calcite-like R3mstructure thermodynamically stable for PbCO3, SrCO3, and BaCO3. Without consideration of the temperature effect, PbCO3-R3mis stable in the pressure range of 15–30 GPa. With increasing temperature, the stability field of PbCO3-R3min P–Tcoordinates reduces, and above 2000 K, the aragonite phase directly transforms into the post-aragonite phase without the formation of R3m. SrCO3-R3mis thermodynamically stable at pressures 10–20 GPa and temperatures above 750 K. BaCO3-R3mis dynamically stable at ambient pressure and the available experimental data indicate its appearance at temperatures above 1086 K. By analogy with KNO3, we assume the possibility of the appearance of BaCO3-R3mduring rapid quenching of high-temperature dynamically disordered phases of BaCO3, as well as metastable crystallization of the R3mphase at ambient pressure.

The transition from structures with classical [CO3] triangles to structures with [CO4] tetrahedra, corresponding to the transition from sp2to sp3hybridization of carbon atoms, is quite well established for alkaline earth carbonates CaCO3and MgCO3. Here, using a crystal structure prediction technique, we show that alkali carbonates Na2CO3and K2CO3follow the same trend. Both compounds form isostructural sp3-hybridized phases, Na2CO3–C2/mand K2CO3–C2/m, which became thermodynamically stable at pressures above 125 and 150 GPa, respectively. The automated topological search through ICSD has shown that the found C2/mstructures, as well as sp3-structures of CaCO3and MgCO3do not have topological analogs among silicates and phosphates. Transitions of Na2CO3and K2CO3to C2/mstructures are realized without sufficient perturbation of the initial Na2CO3–P21/mand K2CO3–P1̅ structures and require relatively small atomic displacements of carbon and oxygen atoms. These transitions are realized through simple energy optimization. This indicates the absence or low height of the energy barrier. In the wide interval of pressures before the transition to the sp3structures, carbon atoms of [CO3] triangles are gradually displaced from the plane defined by three oxygen atoms due to the interaction with the fourth oxygen atom. In the case of Na2CO3, the dihedral angle C–O–O–O describing the degree of this displacement increases from 5 to 12°, when the pressure increases from 60 to 127 GPa. At pressures above 130 GPa, the angle abruptly increases to the value of 31°, which corresponds to the formation of the sp3-hybridized phase Na2CO3–C2/m. Based on the examples of alkali and alkaline earth carbonates, we show that the transition from a sp2-hybridized [CO3] triangle to a sp3-hybridized [CO4] tetrahedron is realized when the fourth oxygen atom approaches the carbon atom at a distance less than 2.0 Å, which is usually realized at pressures of around 100 GPa. The stable structures with sp3-hybridized carbon atoms have not been found for Li2CO3in the considered pressure range up to 200 GPa, and we show that the P63/mcmstructure of this compound is stable in sp2form up to a pressure of 700 GPa or even higher. This indicates that not all the structures of carbonates adopt sp3form even at extreme pressures.

Gas breakthrough is becoming an increasingly common problem, with a growing number of gas-and-oil fields being developed. Gas-and-oil fields are usually characterized by a complex geological structure, high reservoir heterogeneity, low net-pay thickness, and large gas cap, which lead to gas breakthrough, especially in horizontal production wells. Chemical gas-blocking methods lately have gained more scientific interest and are becoming more applicable in the fields, the reason being the potential for adjusting the type and properties of chemical gas-blocking agents (GBA) to increase blocking selectivity. It is hard to numerically simulate the gas-blocking properties of GBA due to the complexity of their structure and behavior. Flooding experiments of GBA injection and blocking ability in zones with different permeabilities and saturations can provide reliable data to choose the right GBA. However, there are no studies with an experimental comparison of the several GBA with a variation of reservoir core permeability and saturation. In this work, blocking ability and selectivity of three hydrolyzed polyacrylamide-based GBA in the coreflooding experiments were compared: polymer-foam, foam-gel, and gel. East-Messoyakhskoye gas-and-oil field fluid and core material were used. This field faced a gas breakthrough in middle-stage development through high-permeability zones into long horizontal production wells. Coreflooding experiments were carried out in two stages (injection and breakthrough of GBA) with the simulation of four common reservoir zones: oil-saturated low permeability, gas-saturated high permeability, oil-saturated high permeability, and gas-saturated low permeability. Results show that polymer-foam achieved low injection and medium blocking selectivity. The gel showed higher damaging risks due to the lowest selectivity in both the injection and breakthrough stages. The best blocking selectivity and blocking efficiency were achieved by foam-gel due to low initial viscosity and the in situ generation of a rigid gas-blocking structure.

General synthetic approach toward phenols with a polyfunctional side-chain is described. It is based on two subsequent [3,3]-sigmatropic rearrangements, in particular, Johnson–Claisen and aromatic Claisen. Facilitation of the reaction sequence is achieved by the separation of steps and discovery of the efficient catalysts for aromatic Claisen rearrangement. The best performance was achieved by the combination of rare earth metal triflate with 2,6-di-tert-butylpyridine. The reaction scope was established on 16 examples with 17–80% yield (on two steps). Synthetic equivalents for the related Ireland–Claisen and Eschenmoser Claisen/Claisen rearrangements were proposed. Further versality of the products was demonstrated by a number of post-modification transformations.

The artificial olfaction units (or e-noses) capable of room-temperature operation are highly demanded to meet the requests of society in numerous vital applications and developing Internet-of-Things. Derivatized 2D crystals are considered as sensing elements of choice in this regard, unlocking the potential of the advanced e-nose technologies limited by the current semiconductor technologies. Herein, we consider fabrication and gas-sensing properties of On-chip multisensor arrays based on a hole-matrixed carbonylated (C-ny) graphene film with a gradually changed thickness and concentration of ketone groups of up to 12.5 at.%. The enhanced chemiresistive response of C-ny graphene toward methanol and ethanol, of hundred ppm concentration when mixing with air to match permissible exposure OSHA limits, at room-temperature operation is signified. Following thorough characterization via core-level techniques and density functional theory, the predominant role of the C-ny graphene-perforated structure and abundance of ketone groups in advancing the chemiresistive effect is established. Advancing practice applications, selective discrimination of the studied alcohols is approached by linear discriminant analysis employing a multisensor array’s vector signal, and the fabricated chip’s long-term performance is shown.

•A demonstration of a new derivatization reagent PG-Cl for amino acids presented.•A comparison of LOD and LOQ with the commonly used derivatization using DNS-Cl provided.•LOQs in the range of 0.5–500 µg/mL were obtained for amino acids with PG-Cl.•The possibility of PG-Cl usage for non-target screening applications was discussed.

An efficient access to novel families of cyano‐containing polyheteroaromatic D−A molecules with extended π‐conjugation, including dibenzo[c,h][1,6]naphthyridine derivatives, has been elaborated. The synthetic strategy is based on the sequence of metal‐catalyzed annulation and cross‐coupling reactions starting from available 4‐ethynyl‐5,6‐difluoro‐7‐(p‐methoxyphenyl)‐2,1,3‐benzothiadiazole to get a new series of isoquinoline‐linked BTD‐based D−A compounds, which further undergo a selective cyanation to afford the corresponding mono‐CN‐ or di‐CN‐BTD derivatives depending on the reaction conditions. In course of the investigation of cyanation process, a new type of intramolecular heterocyclization included the transformation of the benzothiadiazole core into hardly accessible dibenzo[c,h][1,6]naphthyridine framework has been unexpectedly discovered. The protocols developed tolerate a wide range of donor blocks such as diphenylamine, carbazole, dibenzoazepine and dihydroacridine. New type of intramolecular heterocyclization included the transformation of the benzothiadiazole core into hardly accessible dibenzo[c,h][1,6]naphthyridine framework has been developed.

Carbonates in the system Na2CO3-CaCO3are nowadays suggested as having a wide stability field at conditions of the mantle transition zone. Our structural analysis of nyerereite, which has limited stability fields at ambient conditions, and its similarities with already known carbonates that are stable at high-pressure conditions, allowed us to propose that nyerereite likely undergoes phase transitions at both high-pressure and high-temperature conditions. This supports the hypothesis that nyerereite takes part in carbon transportation from the mantle/deep crust toward the surface, with important implications for the deep carbon cycle associated with carbonatites.

Intermetallic compounds formed by two or more metals are characterized by wide structural diversity. The design of complex intermetallics, such as quasicrystals or their approximants, is a challenging scientific problem. We present a hybrid computational approach for searching for new stable 1/1 Mackay-type quasicrystal approximants in Sc-rich intermetallics. For the Sc-Rh, Sc-Pd, Sc-Ir, and Sc-Pt systems, we developed a routine for the generation of simplified composition/configuration spaces that contain up to 2107 configurations each. Using the density functional theory (DFT) for the evaluation of their thermodynamic properties, we rationalized extended search spaces consisting of 3942 configurations each. Random Forest and graph neural network (GNN) regression models were trained on the simplified sets and utilized as inference machines for enhanced search spaces. Among the systems studied, more than 20 potentially new Sc-Pt and Sc-Pd approximants were predicted and confirmed within DFT calculations. A comparative analysis shows that GNN performance depends on the target energy type─relaxed energy, formation energy, and energy above the convex hull. Nevertheless, GNN-based solutions may provide a higher recall of predictions depending on architecture modifications and target energy chosen.

Background: The aim of the study was to assess the prevalence of seropositive status for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-IgA, -IgM, and -IgG; its dynamics in connection with restrictive measures during the coronavirus disease (COVID-19) pandemic; and the quantitative dynamics of antibody levels in the population of St. Petersburg, Russia. Methods: From May to November 2020, a retrospective analysis of Saint Petersburg State University Hospital laboratory database was performed. The database included 158,283 test results of 87,067 patients for SARS-CoV-2 detection by polymerase chain reaction (PCR) and antibody detection of SARS-CoV-2-IgA, -IgM, and -IgG. The dynamics of antibody level was assessed using R v.3.6.3. Results: The introduction of a universal lockdown was effective in containing the spread of COVID-19. The proportion of seropositive patients gradually decreased; approximately 50% of these patients remained seropositive for IgM after 3–4 weeks; for IgG, by follow-up week 22; and for IgA, by week 12. The maximum decrease in IgG and IgA was observed 3–4 months and 2 months after the detection of the seropositive status, respectively. Conclusions: The epidemiological study of post-infection immunity to COVID-19 demonstrates significant differences in the dynamics of IgA, IgM, and IgG seropositivity and in PCR test results over time, which is linked to the introduction of restrictive measures. Both the proportion of seropositive patients and the level of all antibodies decreased in terms of the dynamics, and only approximately half of these patients remained IgG-positive 6 months post-infection.

NaSrR(BO3)2(R = Ho–Lu, Y, Sc) compounds were obtained for the first time. Their structures exhibit disordered positions of Sr2+and Na+atoms while RO6polyhedra are connected through the BO3groups. Large distances between R atoms and high transparency in the range of 250–900 nm make them promising for phosphor applications. A pathway to obtain single crystals was shown by growing NaSrY(BO3)2and NaSrYb(BO3)2by the top seeded solution growth method with Na2O-B2O3-NaF flux.

Photobleaching is one of the basic chemical processes that occur naturally in organic molecules. In this work, we investigate the quantum dynamics of Cy 7.5 dye molecules optically coupled to Au nanorod particles and experimentally demonstrate the decrease of the photobleaching rate in this hybrid system. We discover the effect of a resonance-like behavior not observed before for any type of emitter─the photobleaching rate of the dye molecules reaches a minimum for a suitable number of molecules coupled to the nanoparticle. The manifestation of the effect is the consequence of shifts in the energy levels in the hybrid system caused by the change in the number of molecules coupled to a nanoparticle. The energy shifts are the prerequisite for the effective depopulation of the triplet level, which is responsible for the photodegradation mechanism. The discovered effect paves the way for increasing the efficiency of optoelectronic and photovoltaic devices.

Sleep apnea is a common disorder that represents a global public health burden. KCNK3encodes TASK-1, a K+channel implicated in the control of breathing, but its link with sleep apnea remains poorly understood. Here we describe a new developmental disorder with associated sleep apnea (developmental delay with sleep apnea, or DDSA) caused by rare de novo gain-of-function mutations in KCNK3. The mutations cluster around the ‘X-gate’, a gating motif that controls channel opening, and produce overactive channels that no longer respond to inhibition by G-protein-coupled receptor pathways. However, despite their defective X-gating, these mutant channels can still be inhibited by a range of known TASK channel inhibitors. These results not only highlight an important new role for TASK-1 K+channels and their link with sleep apnea but also identify possible therapeutic strategies.

Understanding the mechanisms and controlling the possibilities of surface nanostructuring is of crucial interest for both fundamental science and application perspectives. Here, we report a direct experimental observation of laser-induced periodic surface structures (LIPSS) formed near a predesigned gold step edge following single-pulse femtosecond laser irradiation. Simulation results based on a hybrid atomistic-continuum model fully support the experimental observations. We experimentally detect nanosized surface features with a periodicity of ∼300 nm and heights of a few tens of nanometers. We identify two key components of single-pulse LIPSS formation: excitation of surface plasmon polaritons and material reorganization. Our results lay a solid foundation toward simple and efficient usage of light for innovative material processing technologies.

The manipulation of the quality of laser ablation of solids can be of crucial importance from fundamental and industrial perspectives. Here we have studied the effect of an external magnetic field on the micromaterial processing of silicon by ultrashort laser pulses. It was found experimentally that such a field directed along the laser beam improves the quality and efficiency of the material removal. Additionally, we observe that the formation of laser-induced periodic surface structures in a multi-pulse regime is affected by the external magnetic field. Our results open a route toward efficient and controllable ultrafast laser micromachining.

In the present work, based on the density functional theory and crystal structure prediction algorithms, we found novel structures of alkali metal orthocarbonates Li4CO4-C2/c, Na4CO4-C2/c, and K4CO4-P21/c. The pressure of thermodynamic stabilization of the obtained orthocarbonates with respect to decomposition into the corresponding carbonate and oxide ranges from 21 GPa (for K4CO4) to 25 GPa (for Li4CO4). All obtained structures contain isolated groups of [CO4]tetrahedra. The structures of lithium and sodium orthocarbonates were found to be isotypic. As well as alkaline earth orthocarbonates, orthocarbonates of alkali metals are structurally similar to orthosilicates of the same metal. Na4CO4-C2/cwas found to be dynamically stable at ambient pressure, while all other structures are destabilized on decompression. In addition, the P–Tphase diagrams of lithium, sodium, and potassium oxides have been calculated for the first time. All oxides have a high-pressure phase transition from the Fm3̅m(anti-fluorite) structure to the Pnma(anti-cotunnite) structure at 34 GPa for Li2O, at 10 GPa for Na2O, and at 5 GPa for K2O at low temperatures. In the Na2O and K2O systems, high-temperature phase transition to the P6̅2m(barringerite) structure was revealed at temperatures above 1300 and 650 K, respectively.

The DNA interaction with cis-isomers of photosensitive azobenzene-containing surfactants was studied by both experimental methods and computer simulation. It was shown that before the organization of micelles, such surfactants in the cis-conformation form associates of only a single type with a disordered orientation of molecules. In contrast, for trans-isomers, there exist two types of associates with head-to-head or head-to-tail orientations of molecules in dependence on salt concentration in a solution. The comparison of cis- and trans-isomer binding to DNA and the influence of salt concentration on the formation of their complexes with DNA were studied. It was shown that cis-isomers interact with phosphate groups of DNA and that their molecules were also located along the minor groove of DNA.

We have synthesized the orthocarbonate Sr3[CO4]O in a laser-heated diamond anvil cell at 20 and 30 GPa by heating to ≈3000 (300) K. Afterward, we recovered the orthocarbonate with [CO4]4–groups at ambient conditions. Single-crystal diffraction shows the presence of [CO4]4–groups, i.e., sp3-hybridized carbon tetrahedrally coordinated by covalently bound oxygen atoms. The [CO4]4–tetrahedra are located in a cage formed by corner-sharing OSr6octahedra, i.e., octahedra with oxygen as a central ion, forming an antiperovskite-type structure. At high pressures, the octahedra are nearly ideal and slightly rotated. The high-pressure phase is tetragonal (I4/mcm). Upon pressure release, there is a phase transition with a symmetry lowering to an orthorhombic phase (Pnma), where the octahedra tilt and deform slightly.

To increase the likelihood of finding a causative genetic variant in patients with a focal segmental glomerulosclerosis (FSGS) lesion, clinical and histologic characteristics were analyzed.

When did you start investigating diamond as a stationary phase--and why? Our group started investigating diamond as a potential stationary phase for chromatography in 2005, following a discussion about the [...]

SPTBN1encodes βII-spectrin, the ubiquitously expressed β-spectrin that forms micrometer-scale networks associated with plasma membranes. Mice deficient in neuronal βII-spectrin have defects in cortical organization, developmental delay and behavioral deficiencies. These phenotypes, while less severe, are observed in haploinsufficient animals, suggesting that individuals carrying heterozygous SPTBN1variants may also show measurable compromise of neural development and function. Here we identify heterozygous SPTBN1variants in 29 individuals with developmental, language and motor delays; mild to severe intellectual disability; autistic features; seizures; behavioral and movement abnormalities; hypotonia; and variable dysmorphic facial features. We show that these SPTBN1variants lead to effects that affect βII-spectrin stability, disrupt binding to key molecular partners, and disturb cytoskeleton organization and dynamics. Our studies define SPTBN1variants as the genetic basis of a neurodevelopmental syndrome, expand the set of spectrinopathies affecting the brain and underscore the critical role of βII-spectrin in the central nervous system.

Orthocarbonates of alkaline earth metals are the newly discovered class of compounds stabilized at high pressures. Mg-orthocarbonates are the potential carbon host phases, transferring oxidized carbon in the Earth’s lower mantle up to the core–mantle boundary. Here, we demonstrate the possibility for the formation of Mg2CO4in the lower mantle at pressures above 50 GPa by ab initiocalculations. Mg2CO4is formed by the reaction MgCO3+ MgO = Mg2CO4, proceeding only at high temperatures. At 50 GPa, the reaction starts at 2200 K. The temperature decreases with pressure and drops down to 1085 K at the pressure of the Earth’s core–mantle boundary, approximately 140 GPa. Two stable structures, Mg2CO4-Pnmaand Mg2CO4-P21/c, were revealed using a crystal structure prediction technique. Mg2CO4-Pnmais isostructural to mineral forsterite (Mg2SiO4), while Mg2CO4-P21/cis isostructural to mineral larnite (β-Ca2SiO4). Transition pressure from Mg2CO4-Pnmato Mg2CO4-P21/cis around 80 GPa. Both phases are dynamically stable on decompression down to the ambient pressure and can be preserved in the samples of natural high-pressure rocks or the products of experiments. Mg2CO4-Pnmahas a melting temperature more than 16% higher than the melting temperature of magnesite (MgCO3). At 23.7, 35.5, and 52.2 GPa, Mg2CO4-Pnmamelts at 2661, 2819, and 3109 K, respectively. Acoustic wave velocities Vpand Vsof Mg2CO4-Pnmaare very similar to that of magnesite, while universal anisotropy of Mg2CO4-Pnmais stronger than that of magnesite, as well as the coefficient AUis larger for orthocarbonate. The obtained Raman spectra of Mg2CO4-Pnmawould help its identification in high-pressure experiments.

The reaction between simple pyridines, Michael acceptors (cyclopentenone, N-methylmaleimide), and monoalkyl-3,3-difluorocyclopropenes affords 3-(1-hydroxyindolizin-3-yl)-succinimides or 3-(1-hydroxyindolizin-3-yl)-cyclopentanones in good yields. These air-sensitive products regenerate double bond in the incorporated Michael acceptors by selective and near-quantitative aerobic dehydrogenation, yielding intensively colored dyes. The purple 3-(1-hydroxyindolizin-3-yl)-maleimides are highly electrophilic and react smoothly with N-, S-, and P-nucleophiles at the maleimide double bond, which is again easily restored by aerobic dehydrogenation. In the particular case of hydrazine and hydroxylamine nucleophiles, their Michael adducts with the 3-(1-hydroxyindolizin-3-yl)-maleimides afford the novel pyrimido[6,1,2-cd]indolizin-5-one (5-aza[2.3.3]cyclazin-1-one) heterocyclic core by the proposed double-dehydrogenation–6π-electrocyclization−β-elimination reaction sequence. O-Protected 3-(1-hydroxyindolizin-3-yl)-succinimides are air-stable and not electrophilic. Deprotection returns the ability of the succinimides for aerobic dehydrogenation, yielding the appropriate electrophilic maleimides. This property may be employed in design of the switchable covalent-binding tool, activated by chemical or enzymatic cleavage of the O-protective group. Electron-withdrawing group at the C7 position of the indolizine core directly affects the dehydrogenation rate; hence, it can be used for kinetic tuning. Additionally, new stable indolizinium-based zwitterionic 3-oxo-3H-indolizin-4-ium-1-olate (1-oxo-1H-indolizin-4-ium-3-olate) was accessed by TEMPO oxidation of the C3-free indolizin-1-ol, generated by 3-hydroxypyrrole ring annulation with monoalkylcyclopropenone in situ.

Using molecular dynamics simulation and evolutionary metadynamic calculations, a series of structures were revealed that possessed enthalpies and Gibbs energies lower than those of aragonite but higher than those of calcite. The structures are polytypes of calcite, differing in the stacking sequence of close-packed (cp) Ca layers. The two- and six-layered polytypes have hexagonal symmetry P6322 and were named hexaragand hexite, respectively. Hexarag is similar to aragonite, but with all the triangles placed on the middle distance between the cp layers. On the basis of the structures found, a two-step mechanism for the transformation of aragonite to calcite is suggested. In the first step, CO3triangles migrate to halfway between the Ca layers with the formation of hexarag. In the second step, the two-layered cp (hcp) hexarag structure transforms into three-layered cp (fcc) calcite through a series of many-layered polytypes. The topotactic character of the transformation of aragonite to calcite, with [001] of aragonite being parallel to [0001] of calcite, is consistent with the suggested mechanism. High-temperature X-ray powder diffraction experiments did not reveal hexarag reflections. To assess the possibility of the formation of the polytypes found in nature or experiments, a TEM analysis of ground aragonite was performed. A grain was found that had six superstructure reflections in a direction perpendicular to the plane of the cp layer. This grain is believed to correspond to one of the predicted polytypes, with the diffuse character of the diffraction spots indicating a partial disordering of the cp layer stacking. A topological analysis was also performed, along with energy calculations, of the metastable high-pressure polymorphs CaCO3-II, -III, -IIIb, and -VI. The similarity of CaCO3-II, -II, and -IIIb to the calcite structure and the small energy difference explain the metastable formation of these polymorphs during the cold compression of calcite. On the basis of the performed analysis, the evolution of the CaCO3cation array at calcite to a post-aragonite transformation is described.

A new three-component reaction leading to 1-α-(pyridyl-2-[1,2,4]triazolyl)-2-alkyl-ethanones has been discovered while studying the reactivity of monosubstituted 3,3-difluorocyclopropenes in an inverse electronic demand Diels–Alder (IEDDA) cycloaddition–cycloreversion sequence with s-tetrazines. The reaction involving the above-mentioned reactants and (benzo)pyridine as a third component results in a complex transformation proceeding in mild conditions in a stoichiometric ratio of reactants and has high functional group tolerance (phenols, amides, ethers, carboxylic acids, ketones, and acrylic esters). As a result, simple pyridines are selectively functionalized at the α-position in good isolated yields. The reaction mechanism includes a rare azaphilic [4 + 2]-cycloaddition step between s-tetrazine and intermediate 1-hydroxyindolizine, suggested after byproduct identification and tracked with a deuterium label. To date, it is only the third known example of skewed azaphilic cycloaddition of tetrazine. The reaction is truly three-component and cannot be effectively performed stepwise.

Phases of CaCO3stabilized at high pressures and temperatures are the potential agents of the global carbon cycle, transferring oxidized carbon in deep Earth’s interiors and thus are of special interest for the Earth sciences. Here, we report finding of the new phase, named disarag, which is dynamically disordered aragonite with freely rotating CO3groups, similar to that in the CaCO3-V phase with a calcite-like structure. Disarag has a stability field expanding from 3 to 10 GPa and from 1600 to 2000 K. Consideration of twinned structure enlarges this field, decreasing the transition temperature from aragonite to disarag at 100–300 K. At P–Tparameters corresponding to the transition from aragonite to disarag, the marked disappearance of the diffraction peaks is observed in in situexperiments. We show that, among known phases of CaCO3, disarag is the best candidate for the explanation of this reconstruction of diffraction pattern. Also, for the first time, using ab initiomolecular dynamics technique, we determine equilibrium curves between calcite and its disordered phases CaCO3-IV and CaCO3-V. We show that the transitions of alkaline-earth carbonates CaCO3, SrCO3, and BaCO3to the disordered states start when the critical angle of librations of the CO3group about the axis perpendicular to the molecular three-fold axis exceeds 45°. The calcite-like structure of CaCO3is characterized by more intense librations than the aragonite-like structure of this compound and reaches the critical angle at lower temperatures. As a result, calcite transforms into the disordered state at lower temperatures than aragonite.

A set of structures of homomolecular organic crystals with information on the solvent utilized for crystallization was extracted from the Cambridge Structural Database in order to identify possible general relationships between changes in the crystal structure characteristics of polymorphs and changes in the properties of solvents from which they were crystallized. Feature descriptions of crystal structures and solvents were introduced, which are based on various types of numerical descriptors reflecting different aspects of crystal structures (molecular packing characteristics, lattice energy) and solvent properties (polarity, acid–base behavior, bulk characteristics, etc.). A statistical analysis of the studied set of compounds revealed that the crystal structures of polymorphs obtained from different solvents tend to differ slightly more from each other than the crystal structures of polymorphs crystallized from the same solvent, though these differences in crystal structure properties are not statistically significant. By analyzing the subset of polymorphs obtained from different solvents, we have discovered positive correlations between changes in the tightness of molecular packing and the solvent’s descriptors related to polarity (Spearman’s correlation coefficients ρ = 0.28–0.33). Notably, the more similar the molecular conformations in crystals of polymorphs and the more polar the compound, the more pronounced are the identified correlations (moderate correlations with ρ = 0.5–0.6). At the same time, the expected correlations between changes in the conformation-related properties of a molecule in a crystal and changes in the solvent properties were not found.

We describe the performance of a superconductor–insulator–superconductor (SIS) mixer operating in the frequency range of 780–950 GHz. Unlike most SIS mixers, the tunnel junction employs two different superconductors, a niobium nitride top and a niobium bottom electrode sandwiching an aluminum nitride barrier layer, fabricated on a niobium titanium nitride ground plane. The mixer was tested in a pulse tube cryostat, with all the optical components, in the signal path, mounted inside the vacuum environment to avoid attenuation of the RF signal as it propagates from the hot/cold loads to the mixer. With this setup, we have measured an RF-corrected noise temperature of $\sim$220 K. In this article, we focus on investigating the influence of local oscillator (LO) power heating on the performance of the terahertz mixer. The increase in the junction's physical temperature can be observed experimentally by noting the suppression of the gap voltage in the pumped current–voltage ($I\text{--}V$) curve as the LO pumping level is increased. Similar observation has already been reported, and attempts were made to estimate the effective temperature of the device using equations of heat transfer between the mixer chip layers. Here, we present an experimental method of quantifying this effect by recovering the effective temperature of the junction through comparing the pumped $I\text{--}V$ curves at different pumping levels and fixed bath temperature, with the unpumped $I\text{--}V$ curves obtained at varying bath temperatures. We also estimate, for the first time, the effect of heating on the noise temperature as a function of bath temperature and frequency. We show that for typical experimental parameters, the LO heating can increase the double-sideband receiver noise temperature by as much as 20%, and that in the frequency range of the measurements, the effective temperature of the junction at fixed LO power increases linearly with frequency at a rate of 0.5 K/100 GHz.

There has been one previous report of a cohort of patients with variants in Chromodomain Helicase DNA-binding 3 (CHD3), now recognized as Snijders Blok-Campeau syndrome. However, with only three previously-reported patients with variants outside the ATPase/helicase domain, it was unclear if variants outside of this domain caused a clinically similar phenotype. We have analyzed 24 new patients with CHD3variants, including nine outside the ATPase/helicase domain. All patients were detected with unbiased molecular genetic methods. There is not a significant difference in the clinical or facial features of patients with variants in or outside this domain. These additional patients further expand the clinical and molecular data associated with CHD3variants. Importantly we conclude that there is not a significant difference in the phenotypic features of patients with various molecular disruptions, including whole gene deletions and duplications, and missense variants outside the ATPase/helicase domain. This data will aid both clinical geneticists and molecular geneticists in the diagnosis of this emerging syndrome.

Spaser nanoparticles, with ultranarrow spectral line width, small size and good biocompatibility, offer a bright prospect as potential biological probes. Sadly, over 10 years since the first demonstration, how the structure components determine their optical performance has not been clarified. Here the effects of gain layer thickness and dye emitter density on the lasing behavior and photostability of spaser nanoparticles are theoretically and experimentally addressed. Results show that for a 16 nm gold-core cavity, gain layer of 10–15 nm is adequate to maximize the spaser emission. For this type of nanoparticle–spaser system, the minimal number of dye emitters per particle, referred to as “dye threshold”, is also vital to spasing action besides the “pump threshold” of laser power. Moreover, dye emitter distribution within the gain layer could be another approach to further improve spaser performance. These contributions give us an opportunity to profoundly understand the physical essence of spaser nanoparticles and to optimize their performance for further biology application.

Spiro[imidazol-5-one-4,1′-cyclopropanes] behave as donor–acceptor (D–A) cyclopropanes in a formal cycloaddition reaction with aldehydes. The activation of such type of cyclopropanes is achieved with an equivalent of Brønsted acid. The reaction proceeds in high yields of 51–92% and demonstrates moderate diastereoselectivity at the quaternary stereocenter, which is determined by the electron-donating nature of the aldehyde partner. The ease of separation of stereoisomers allowed the creation of a library of 44 spiroannulated tetrahydrofurans with various substitution patterns.

The data processing workflow for LC-MS based metabolomics study is suggested with signal drift correction, univariate analysis, supervised learning, feature selection and unsupervised modelling. The proposed approach requires only an annotation-free peak table and produces an extremely reduced set of the most relevant features together with validation viaReceiver Operating Characteristic analysis for selected predictors, cross-validation and unsupervised projection. The presented study was initially optimised by its own experimental set and then was successfully tested by using 36 datasets from 21 publicly available metabolomics projects. The suggested workflow can be used for classification purposes in high dimensional metabolomics studies and as a first step in exploratory analysis, data projection, biomarker selection, data integration and fusion.

We present a comprehensive study on the influence of Ti doping on K+migration in the K1–xFe1–xTixO2solid electrolyte. A novel approach is proposed which is based on modeling of configurational spaces (CSs) and full sets of inequivalent migration pathways by means of density functional theory (DFT) calculations and machine learning (ML) techniques. A 2 × 1 × 1 supercell (32 formula units) of a low-temperature polymorph of the KFeO2compound with space group symmetry Pbcawas used. For the three lowest Ti contents (x= 0.03, 0.06, and 0.09), all symmetrically inequivalent configurations of atomic arrangements (CSs) and K+migration pathways (total numbers: 128, 59520, and 8630400) were generated. With the DFT-derived energetics of K+migration at the lowest doping level (x= 0.03), the ML models were trained to predict ionic transport properties by using geometrical descriptors for the pathway-dopant arrangement. The trained ML models were then used to evaluate the K+migration properties for pathways at higher doping levels. The computational results obtained are in good agreement with the results of a previous experimental study of the title compound. This demonstrates the applicability of the proposed approach for modeling and predicting effects of doping in crystalline solids, such as solid electrolytes and intercalation cathodes. Brief recommendations are given on the application of the proposed combined approach.

To execute a large-scale, decentralized, clinical-grade whole exome sequencing study, coined Tapestry, for clinical practice, research discovery, and genomic education.

Here we have combined topological analysis, density functional theory (DFT) modeling, operandoneutron diffraction, and machine learning algorithms within the comparative analysis of the known widely LiNiO2(LNO) and LiNi0.8Co0.15Al0.05O2(NCA) cathode materials. Full configurational spaces of the mentioned materials during delithiation were set using the topological approach starting from the 2 × 2 × 1 supercell (12 formula units in total) of the LNO structure (space group R3̅m). Several types of the DFT models were applied for the structural relaxation of entries of the LNO configurational space (87 configurations) demonstrating a strong dependence of the results of optimization on the initial structure guess (at the latter delithiation stages) and on the Hubbard correction application (for the whole range of delithiation). Within the computationally easiest model considered for LNO, subsequent modeling of the NCA configurational space (20760 configurations) results in structural changes of the model cell that are well-consistent (relative errors <1.5% with respect to the lattice parameter values) with data of operandoneutron diffraction experiments during charge–discharge cycling. In the scope of the machine learning approach, topology of Li layers and relative disposition of Li and Al in NCA structure are found to be the most important descriptors during the energy balance estimations.

A novel three-dimensional coordination network 1in a new 4,5,6-connected topology (4,5,6T115) built from linear CuII4Cl3(H2O)2clusters and tetrahedral tetrakis(3-pyridyl)vinylsilane ligands is reported. Utilizing a similar tetrahedral ligand, tetrakis(3-pyridyl)ethylsilane, a different framework 2having CuII2Cl(H2O)2clusters is obtained in tcstopology. The activated sample of 1shows an excellent and reversible uptake of I2in solid as well as in solution phases owing to the presence of uncoordinated chloride ions and electron rich vinylic groups in it. The I2uptake studies on the anion-exchanged samples, of bromide, iodide, and nitrate ions, show a progressive decrease in the adsorption capacity with the sample containing uncoordinated Cl–ion showing a maximum uptake of 48.5% and the one with the NO3–ions exhibiting the lowest uptake of 24.0%. These observations suggest that the halide counterions interact better with I2in comparison with nitrate ions and the better I2uptake in the presence of Cl–ions over the other two halides is due to its smaller size that offers a larger surface area for adsorption. Also, both these compounds were shown to be useful catalysts for the solvent-free syntheses of bis(indolyl)methanes via Friedel–Crafts alkylation reaction.

DNA integration with silver and gold nanoparticles was carried out by the chemical reduction of silver and gold ions after the formation of their complexes with high molecular DNA in solution. It is shown that, for a good association of DNA with nanoparticles, the ions of silver and gold should be linked with DNA bases rather strongly. The proposed model of gold interaction with DNA is the coordination of gold to N7 guanine in a major groove followed by the transformation of the GC pair to Hoogsteen’s type pairing, in which the gold atom is located between the bases and is bonded simultaneously to N7 guanine and N3 cytosine. For gold and silver nanoparticles associated with DNA, the peak of plasmon resonance shifts relative to that of free nanoparticles in solution. AFM (atomic force microscopy) images of both free and associated with DNA nanoparticles were obtained. Binding of high molecular DNA to gold and silver nanoparticles leads to a decrease in the size of its molecular coil in solution, but the bending rigidity of DNA helix (persistent length) does not change. The almost 3-fold increase in the optical anisotropy of DNA was observed when DNA was associated with gold nanoparticles. This result was obtained with the flow birefringence method using a light source with a wavelength of 550 nm, which is close to the peak of the plasmon resonance of gold nanoparticles. For DNA associated with silver nanoparticles, a similar result was obtained when using a light source with a wavelength of about 410 nm.