Stereodivergent 1,3-difunctionalization of alkenes by charge relocation.

Alkenes are indispensable feedstocks in chemistry. Functionalization at both carbons of the alkene-1,2-difunctionalization-is part of chemistry curricula worldwide1. Although difunctionalization at distal positions has been reported2-4, it typically relies on designer substrates featuring directing groups and/or stabilizing features, all of which determine the ultimate site of bond formation5-7. Here we introduce a method for the direct 1,3-difunctionalization of alkenes, based on a concept termed 'charge relocation', which enables stereodivergent access to 1,3-difunctionalized products of either syn- or anti-configuration from unactivated alkenes, without the need for directing groups or stabilizing features. The usefulness of the approach is demonstrated in the synthesis of the pulmonary toxin 4-ipomeanol and its derivatives.

Isothiouronium-Mediated Conversion of Carboxylic Acids to Cyanomethyl Thioesters.

We report the development of an isothiouronium salt as a reagent for the operationally simple synthesis of cyanomethyl thioesters with high functional group tolerance and avoiding the use of thiols. Additionally, we show that the products can be engaged in amide synthesis in either a two-step or one-pot fashion.

Indirect bandgap MoSe2 resonators for light-emitting nanophotonics.

Transition metal dichalcogenides (TMDs) are promising for new generation nanophotonics due to their unique optical properties. However, in contrast to direct bandgap TMD monolayers, bulk samples have an indirect bandgap that restricts their application as light emitters. On the other hand, the high refractive index of these materials allows for effective light trapping and the creation of high-Q resonators. In this work, a method for the nanofabrication of microcavities from indirect TMD multilayer flakes, which makes it possible to achieve pronounced resonant photoluminescence enhancement due to the cavity modes, is proposed. Whispering gallery mode (WGM) resonators are fabricated from bulk indirect MoSe2 using resistless scanning probe lithography. A micro-photoluminescence (µ-PL) investigation revealed the WGM spectra of the resonators with an enhancement factor up to 100. The characteristic features of WGMs are clearly seen from the scattering experiments which are in agreement with the results of numerical simulations. It is shown that the PL spectra in the fabricated microcavities are contributed by two mechanisms demonstrating different temperature dependences. The indirect PL, which is quenched with the temperature decrease, and the direct PL which almost does not depend on the temperature. The results of the work show that the suggested approach has great prospects in nanophotonics.

Photon Drag Currents and Terahertz Generation in α-Sn/Ge Quantum Wells.

We have fabricated α-Sn/Ge quantum well heterostructures by sandwiching nano-films of α-Sn between Ge nanolayers. The samples were grown via e-beam deposition and characterized by Raman spectroscopy, atomic force microscopy, temperature dependence of electrical resistivity and THz time-resolved spectroscopy. We have established the presence of α-Sn phase in the polycrystalline layers together with a high electron mobility µ = 2500 ± 100 cm2 V-1 s-1. Here, the temperature behavior of the resistivity in a magnetic field is distinct from the semiconducting films and three-dimensional Dirac semimetals, which is consistent with the presence of linear two-dimensional electronic dispersion arising from the mutually inverted band structure at the α-Sn/Ge interface. As a result, the α-Sn/Ge interfaces of the quantum wells have topologically non-trivial electronic states. From THz time-resolved spectroscopy, we have discovered unusual photocurrent and THz radiation generation. The mechanisms for this process are significantly different from ambipolar diffusion currents that are responsible for THz generation in semiconducting thin films, e.g., Ge. Moreover, the THz generation in α-Sn/Ge quantum wells is almost an order of magnitude greater than that found in Ge. The substantial strength of the THz radiation emission and its polarization dependence may be explained by the photon drag current. The large amplitude of this current is a clear signature of the formation of conducting channels with high electron mobility, which are topologically protected.

Clinical and echocardiographic predictors of the anterior mitral leaflet repair failure.

BACKGROUND: Anterior mitral leaflet prolapse repair is a highly effective procedure, but despite excellent operative results still has an inferior long-term durability when compared to posterior leaflet repair. METHODS: We analysed mitral repair durability in 74 consecutive patients operated for anterior leaflet prolapse between 2010 and 2021. Their pre- and postoperative clinical, echocardiographic data and repair durability as well, were compared with 74 randomly assigned posterior leaflet prolapse patients who underwent valve repair during the same period. RESULTS: While groups were of similar age, patients with anterior leaflet prolapse had an inferior preoperative status in terms of functional reserve, atrial fibrillation, operative risk, ejection fraction and had more dilated left heart chambers as well. 1, 5, and 10-year freedom from repair failure was 87.1 ± 4.6%, 79.8 ± 6.5% and 50.7 ± 12.5% in the anterior, and 98.5 ± 1.5% respectively in the posterior leaflet group. Atrial fibrilation (hazard ratio [HR] 5.365; 95%; confidence interval [CI] 1.093-26.324 p = .038) and left ventricle end-systolic diameter (HR 1.160 95%; CI 1.037-1.299 p = .010) independently predicted anterior leaflet repair failure. Receiver Operating Curve analysis established left ventricle end-systolic diameter ≤42 mm as a cut-off value associated with improved anterior leaflet repair durability. Accordingly, 10-year repair durability in a subset of patients, with preserved left ventricle end-systolic diameter (≤42 mm) was 86.4 ± 7.8%. CONCLUSION: Better long-term repair durability in patients with anterior mitral leaflet prolapse and preserved sinus rhytm and left-ventricle diameters justifies early reconstructive approach.

MoS2 flake as a van der Waals homostructure: luminescence properties and optical anisotropy.

We investigated multilayer plates prepared by exfoliation from a high-quality MoS2 crystal and revealed that they represent a new object - a van der Waals homostructure consisting of a bulk core and a few detached monolayers on its surface. This architecture comprising elements with different electron band structures leads to specific luminescence, when the broad emission band from the core is cut by the absorption peaks of strong exciton resonances in the surface monolayers. The exfoliated flakes exhibit strong optical anisotropy. We have observed linear to circular polarization conversion that reaches 15% for normally incident light in transmission geometry. This background effect is due to the fluctuations of the c axis relative to the normal, whereas the pronounced resonance contribution is explained by the polarization anisotropy of the excitons localized in the stripes of the dissected surface monolayers.

Baseline brain function in the preadolescents of the ABCD Study.

The Adolescent Brain Cognitive Development (ABCD) Study® is a 10-year longitudinal study of children recruited at ages 9 and 10. A battery of neuroimaging tasks are administered biennially to track neurodevelopment and identify individual differences in brain function. This study reports activation patterns from functional MRI (fMRI) tasks completed at baseline, which were designed to measure cognitive impulse control with a stop signal task (SST; N = 5,547), reward anticipation and receipt with a monetary incentive delay (MID) task (N = 6,657) and working memory and emotion reactivity with an emotional N-back (EN-back) task (N = 6,009). Further, we report the spatial reproducibility of activation patterns by assessing between-group vertex/voxelwise correlations of blood oxygen level-dependent (BOLD) activation. Analyses reveal robust brain activations that are consistent with the published literature, vary across fMRI tasks/contrasts and slightly correlate with individual behavioral performance on the tasks. These results establish the preadolescent brain function baseline, guide interpretation of cross-sectional analyses and will enable the investigation of longitudinal changes during adolescent development.

Stable and easily available sulfide surrogates allow a stereoselective activation of alcohols.

Isothiouronium salts are easily accessible and stable compounds. Herein, we report their use as versatile deoxasulfenylating agents enabling a stereoselective, thiol-free protocol for synthesis of thioethers from alcohols. The method is simple, scalable and tolerates a broad range of functional groups otherwise incompatible with other methods. Late-stage modification of several pharmaceuticals provides access to multiple analogues of biologically relevant molecules. Performed experiments give insight into the reaction mechanism.

Effect of crystal structure on the Young's modulus of GaP nanowires.

Young's modulus of tapered mixed composition (zinc-blende with a high density of twins and wurtzite with a high density of stacking faults) gallium phosphide (GaP) nanowires (NWs) was investigated by atomic force microscopy. Experimental measurements were performed by obtaining bending profiles of as-grown inclined GaP NWs deformed by applying a constant force to a series of NW surface locations at various distances from the NW/substrate interface. Numerical modeling of experimental data on bending profiles was done by applying Euler-Bernoulli beam theory. Measurements of the nano-local stiffness at different distances from the NW/substrate interface revealed NWs with a non-ideal mechanical fixation at the NW/substrate interface. Analysis of the NWs with ideally fixed base resulted in experimentally measured Young's modulus of 155 ± 20 GPa for ZB NWs, and 157 ± 20 GPa for WZ NWs, respectively, which are in consistence with a theoretically predicted bulk value of 167 GPa. Thus, impacts of the crystal structure (WZ/ZB) and crystal defects on Young's modulus of GaP NWs were found to be negligible.

Accuracy of Three-Dimensional (3D) Printed Dental Digital Models Generated with Three Types of Resin Polymers by Extra-Oral Optical Scanning.

Digital impression devices are used alternatively to conventional impression techniques and materials. The aim of this study was to evaluate the precision of extraoral digitalization of three types of photosensitive resin polymers used for 3D printing with the aid of a digital extraoral optical scanner. The alignment of the scans was performed by a standard best-fit alignment. Trueness and precision were used to evaluate the models. The trueness was evaluated by using bias as a measure and the standard deviation was used to evaluate the precision. After assessing the normality of the distributions, an independent Kruskal-Wallis test was used to compare the trueness and precision across the material groups. The Mann-Whitney test was used as a post-hoc test for significant differences. The result of the analysis showed significant differences (U = 66, z = -2.337, p = 0.019) in trueness of mesiodistal distances. Upon visual inspection of the models, defects were noticed on two out of nine of the models printed with a photosensitive polymer. The defects were presented as cavities caused by air bubbles and were also reflected in the scans. Mean precision did not vary too much between these three photosensitive polymer resins, therefore, the selection of 3D printing materials should be based on the trueness and the required precision of the clinical purpose of the model.

Study of local anodic oxidation regimes in MoSe2.

Scanning probe microscopy is widely known not only as a well-established research method but also as a set of techniques enabling precise surface modification. One such technique is local anodic oxidation (LAO). In this study, we investigate the LAO of MoSe2 transferred on an Au/Si substrate, focusing specifically on the dependence of the height and diameter of oxidized dots on the applied voltage and time of exposure at various humidities. Depending on the humidity, two different oxidation regimes were identified. The first, at a relative humidity (RH) of 60%-65%, leads to in-plane isotropic oxidation. For this regime, we analyze the dependence of the size of oxidized dots on the oxidation parameters and modify the classical equation of oxidation kinetics to account for the properties of MoSe2 and its oxide. In this regime, patterns with a maximum spatial resolution of 10 nm were formed on the MoSe2 surface. The second is the in-plane anisotropic oxidation regime that arises at a RH of 40%-50%. In this regime, oxidation leads to the formation of triangles oxidized inside the zigzag edges. Based on the mutual orientation of zigzag and armchair directions in successive oxidized layers, the stacking type and phase of MoSe2 flakes were determined. These results allow LAO to be considered not only as an ultra-high-resolution nanolithography method, but also as a method for investigating the crystal structure of materials with strong intrinsic anisotropy, such as transition metal dichalcogenides.

Effect of the Uniaxial Compression on the GaAs Nanowire Solar Cell.

Research regarding ways to increase solar cell efficiency is in high demand. Mechanical deformation of a nanowire (NW) solar cell can improve its efficiency. Here, the effect of uniaxial compression on GaAs nanowire solar cells was studied via conductive atomic force microscopy (C-AFM) supported by numerical simulation. C-AFM I-V curves were measured for wurtzite p-GaAs NW grown on p-Si substrate. Numerical simulations were performed considering piezoresistance and piezoelectric effects. Solar cell efficiency reduction of 50% under a -0.5% strain was observed. The analysis demonstrated the presence of an additional fixed electrical charge at the NW/substrate interface, which was induced due to mismatch between the crystal lattices, thereby affecting the efficiency. Additionally, numerical simulations regarding the p-n GaAs NW solar cell under uniaxial compression were performed, showing that solar efficiency could be controlled by mechanical deformation and configuration of the wurtzite and zinc blende p-n segments in the NW. The relative solar efficiency was shown to be increased by 6.3% under -0.75% uniaxial compression. These findings demonstrate a way to increase efficiency of GaAs NW-based solar cells via uniaxial mechanical compression.

Synthesis, Structure, and Reactivity of Binaphthyl Supported Dihydro[1,6]diazecines.

A short approach to chiral diaza-olefines from protected 2,2'-diamino-1,1'-binaphthyl is presented. Cis- and trans-olefines can be selectively obtained by twofold N-allylation followed by RCM or by bridging a 2,2'-diamino-1,1'-binaphthyl precursor with trans-1,4-dibromo-2-butene. Deprotection afforded cis- and trans-dihydro[1,6]diazecines 1 in 58 and 64% overall yield. The reactivity of the but-2-ene-1,4-diyl fragment was investigated yielding corresponding epoxides, diols, and mono- and dibromo products. In several cases rearrangements and participation of the proximate N-Boc group was observed. In no case could allylic substitution be accomplished. From 13 compounds X-ray structure analyses could be obtained.

Ectodermal and ectomesenchymal marker expression in primary cell lines of complex and compound odontomas: a pilot study.

BACKGROUND: Odontomas are odontogenic tumors with hamartoma features that are classified as compound or complex. Our objective was to characterize the proliferation of ectodermal and ectomesenchymal profile markers of primary cell cultures of complex and compound odontomas. METHODS: Four samples of compound odontomas (OdCm) and three of complex odontomas (OdCx) were obtained from patients attending the Oral Pathology and Medicine Clinic of the Graduate Dental School, National Autonomous University of Mexico for primary culture generation. MTT, immunocytochemistry and RT-PCR assays of CD34, Sox2, Amel, Ambn, p21, EDAR, Msx1, Msx2, Pax9, RUNX2, BSP, OPN, Barx1 and GAPDH (control) were performed. Additionally, six paraffin-embedded odontomas were obtained for immunocytochemistry and RT-PCR validation assays. The mean and standard deviation were determined, and ANOVA and Kruskall-Wallis tests were performed. RESULTS: Cultured compound odontoma exhibited higher proliferation, and an ectomesenchymal immunocytochemistry profile with predominant expression of Amel, BSP, Pax9, EDAR, Barx and Msx2; in complex cultured odontoma Sox2, CD34, RUNX2 and OPN predominated. Our statistical analysis showed a significant difference in PCR analysis (P<0.05) for OPN and CD34. Paraffin-embedded odontomas showed similar pattern with difference for NGFR and Sox2 for immunohistochemistry and EDAR, BARX1 and PAX9 for RT-PCR assays. CONCLUSIONS: The results suggested heterogeneous behavior for both odontoma cell lines, because in compound odontomas predominant biomarkers are related to the enamel knot, late-stage odontogenesis and ectomesenchymal interactions; and in complex odontoma the significant expression of CD34 and OPN could be responsible for the difference behavior and mineralized amorphous structure.

On the formation of seven-membered rings by arene-ynamide cyclization.

ABSTRACT: A Brønsted acid-catalyzed selective arene-ynamide cyclization is described. This reaction proceeds via a keteniminium intermediate and enables the preparation of seven-membered ring enamide products. Mechanistic studies uncover an unusual product inhibition behavior.

Current Correlations in a Quantum Dot Ring: A Role of Quantum Interference.

We present studies of the electron transport and circular currents induced by the bias voltage and the magnetic flux threading a ring of three quantum dots coupled with two electrodes. Quantum interference of electron waves passing through the states with opposite chirality plays a relevant role in transport, where one can observe Fano resonance with destructive interference. The quantum interference effect is quantitatively described by local bond currents and their correlation functions. Fluctuations of the transport current are characterized by the Lesovik formula for the shot noise, which is a composition of the bond current correlation functions. In the presence of circular currents, the cross-correlation of the bond currents can be very large, but it is negative and compensates for the large positive auto-correlation functions.

Chemoselective Activation of Diethyl Phosphonates: Modular Synthesis of Biologically Relevant Phosphonylated Scaffolds.

Phosphonates have garnered considerable attention for years owing to both their singular biological properties and their synthetic potential. State-of-the-art methods for the preparation of mixed phosphonates, phosphonamidates, phosphonothioates, and phosphinates rely on harsh and poorly selective reaction conditions. We report herein a mild method for the modular preparation of phosphonylated derivatives, several of which exhibit interesting biological activities, that is based on chemoselective activation with triflic anhydride. This procedure enables flexible and even iterative substitution with a broad range of O, S, N, and C nucleophiles.

Two-qubit logical operations in three quantum dots system.

We consider a model of two interacting always-on, exchange-only qubits for which controlled phase (CPHASE), controlled NOT (CNOT), quantum Fourier transform (QFT) and SWAP operations can be implemented only in a few electrical pulses in a nanosecond time scale. Each qubit is built of three quantum dots (TQD) in a triangular geometry with three electron spins which are always kept coupled by exchange interactions only. The qubit states are encoded in a doublet subspace and are fully electrically controlled by a voltage applied to gate electrodes. The two qubit quantum gates are realized by short electrical pulses which change the triangular symmetry of TQD and switch on exchange interaction between the qubits. We found an optimal configuration to implement the CPHASE gate by a single pulse of the order 2.3 ns. Using this gate, in combination with single qubit operations, we searched for optimal conditions to perform the other gates: CNOT, QFT and SWAP. Our studies take into account environment effects and leakage processes as well. The results suggest that the system can be implemented for fault tolerant quantum computations.

Genome-wide association study identifies a novel locus for cannabis dependence.

Despite moderate heritability, only one study has identified genome-wide significant loci for cannabis-related phenotypes. We conducted meta-analyses of genome-wide association study data on 2080 cannabis-dependent cases and 6435 cannabis-exposed controls of European descent. A cluster of correlated single-nucleotide polymorphisms (SNPs) in a novel region on chromosome 10 was genome-wide significant (lowest P=1.3E-8). Among the SNPs, rs1409568 showed enrichment for H3K4me1 and H3K427ac marks, suggesting its role as an enhancer in addiction-relevant brain regions, such as the dorsolateral prefrontal cortex and the angular and cingulate gyri. This SNP is also predicted to modify binding scores for several transcription factors. We found modest evidence for replication for rs1409568 in an independent cohort of African American (896 cases and 1591 controls; P=0.03) but not European American (EA; 781 cases and 1905 controls) participants. The combined meta-analysis (3757 cases and 9931 controls) indicated trend-level significance for rs1409568 (P=2.85E-7). No genome-wide significant loci emerged for cannabis dependence criterion count (n=8050). There was also evidence that the minor allele of rs1409568 was associated with a 2.1% increase in right hippocampal volume in an independent sample of 430 EA college students (fwe-P=0.008). The identification and characterization of genome-wide significant loci for cannabis dependence is among the first steps toward understanding the biological contributions to the etiology of this psychiatric disorder, which appears to be rising in some developed nations.

Perceived stress is associated with increased rostral middle frontal gyrus cortical thickness: a family-based and discordant-sibling investigation.

Elevated stress perception and depression commonly co-occur, suggesting that they share a common neurobiology. Cortical thickness of the rostral middle frontal gyrus (RMFG), a region critical for executive function, has been associated with depression- and stress-related phenotypes. Here, we examined whether RMFG cortical thickness is associated with these phenotypes in a large family-based community sample. RMFG cortical thickness was estimated using FreeSurfer among participants (n = 879) who completed the ongoing Human Connectome Project. Depression-related phenotypes (i.e. sadness, positive affect) and perceived stress were assessed via self-report. After accounting for sex, age, ethnicity, average whole-brain cortical thickness, twin status and familial structure, RMFG thickness was positively associated with perceived stress and sadness and negatively associated with positive affect at small effect sizes (accounting for 0.2-2.4% of variance; p-fdr: 0.0051-0.1900). Perceived stress was uniquely associated with RMFG thickness after accounting for depression-related phenotypes. Further, among siblings discordant for perceived stress, those reporting higher perceived stress had increased RMFG thickness (P = 4 × 10-7 ). Lastly, RMFG thickness, perceived stress, depressive symptoms, and positive affect were all significantly heritable, with evidence of shared genetic and environmental contributions between self-report measures. Stress perception and depression share common genetic, environmental, and neural correlates. Variability in RMFG cortical thickness may play a role in stress-related depression, although effects may be small in magnitude. Prospective studies are required to examine whether variability in RMFG thickness may function as a risk factor for stress exposure and/or perception, and/or arises as a consequence of these phenotypes.