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The dissociation of O2 molecules chemisorbed on silver surfaces is an essential reaction in industry, and the dissociation mechanism has long attracted attention. The detailed dissociation mechanism was studied at the single-molecule level on Ag(110) by using a scanning tunneling microscope (STM). The dissociation reaction was found to be predominantly triggered by inelastically tunneled holes from the STM tip due to the significantly distributed density of states below the Fermi level of the substrate. A combination of action spectroscopy with the STM and density functional theory calculations revealed that the O2 dissociation reaction is caused by direct ladder-climbing excitation of the high-order overtones of the O-O stretching mode arising from anharmonicity enhanced by molecule-surface interactions.

A graphene nanowrinkle (GNW) formed on a Ni substrate, with a width below 5 nm, exhibits a unique feature (van Hove singularities (vHS)) in its electronic structure, owing to the one-dimensional (1D) electron confinement in GNWs. Considering that the 1D electron confinement effect normally appears when the electron motion is isolated in a 1D structure with the insulator-surrounding environment, the experimental observation of vHS in the electronic structure of GNW wedged between metallic graphene sheets has been regarded as extraordinary. Density functional theory calculations were systematically performed and revealed the origin of the 1D quantum confinement in GNW on the Ni substrate, which originated from the crucial role of chemisorption-like interaction between the graphene sheet and Ni surface in spatially separating the π-conjugated state of GNW from that of the graphene sheet. A series of standing waves corresponding to “the 1D particle-in-a-box model” was confirmed by computationally obtained charge densities of GNW. These results demonstrated that the graphene–GNW–graphene on the Ni substrate served a sufficient potential to lead to 1D-electron confinement. Our investigations provide a deeper understanding of the electronic structure in pseudo-1D materials and suggest a novel approach for modulating the electronic structure without chemical modification or complicated etching to break the C–C bond to produce graphene-based 1D nanomaterials, e.g., graphene nanoribbon.

We report a chemical route to synthesize centimeter-scale stoichiometric "graphenol (C6OH1)", a 2D crystalline alcohol, via vapor phase hydroxylation of epitaxial graphene on Cu(111). Atomic resolution scanning tunneling microscopy revealed this highly-ordered configuration of graphenol and low energy electron diffraction studies on a large-area single crystal graphene film demonstrated the feasibility of the same superstructure being achieved at the centimeter length scale. Periodic density functional theory (DFT) calculations about the formation of C6(OH)1 and its electronic structure are also reported.

The catalytic transfer hydrogenation (CTH) reaction is considered as a potential route for upgrading bio-based carbonyls to their corresponding alcohols. Herein, a series of Zr-based metal−organic ...

The dissociation of O

Oxo-bridged trimeric chromium acetate clusters [Cr3 O(OOCCH3 )6 (H2 O)3 ]NO3 have been encapsulated for the first time in the mesoporous cages of the chromium terephthalate MIL-101(Cr). The isolated clusters in MIL-101(Cr) have increased affinity towards propylene compared to propane, due to generation of a new kind of pocket-based propylene-binding site, as supported by DFT calculations.

We report a chemical route to synthesize centimeter-scale stoichiometric "graphenol (C

Chemical reactions induced by plasmons achieve effective solar-to-chemical energy conversion. However, the mechanism of these reactions, which generate a strong electric field, hot carriers, and heat through the excitation and decay processes, is still controversial. In addition, it is not fully understood which factor governs the mechanism. To obtain mechanistic knowledge, we investigated the plasmon-induced dissociation of a single-molecule strongly chemisorbed on a metal surface, two O2 species chemisorbed on Ag(110) with different orientations and electronic structures, using a scanning tunneling microscope (STM) combined with light irradiation at 5 K. A combination of quantitative analysis by the STM and density functional theory calculations revealed that the hot carriers are transferred to the antibonding (π*) orbitals of O2 strongly hybridized with the metal states and that the dominant pathway and reaction yield are determined by the electronic structures formed by the molecule-metal chemical interaction.

This study proposes a reliable evaluation method for three-phase saturation (water, gas hydrate (GH), and gas) evaluation during the GH dissociation core experiment using deep learning. A convolutional neural network (CNN) takes computed tomography (CT) images obtained during the GH core experiment as an input and provides three-phase saturation as an output. Although machine/deep learning methods have been applied to the saturation evaluation from CT images in previous research, they were not reliable due to the lack of adequate amount of training data where the model could not find appropriate parameters. Besides, non-zero gas hydrate saturation showed where it was supposed to be zero. This study improved the evaluation of three-phase saturation and solved the non-zero GH saturation problem by acquirement of extra data and application of data augmentation with CNN. The results of CNN and CNN with data augmentation presented 34% and 29% error compared to those of random forest. CNN with data augmentation brought 85% and 44% of error and its variance compared to those of CNN without data augmentation, respectively. Consequently, based on domain knowledge for GH, when it comes to the robustness of random data composition and consistency of performance, the evaluation of three-phase saturation can be boosted using CNN with data augmentation.

The purpose of this study was to determine the three-phase saturation (water; gas hydrate, GH; and gas) in real time to gain insights into the GH depressurization process. Although X-ray computed tomography (CT) can be used to investigate the density changes in the GH core during the depressurization experiment, it is hard to distinguish between water and GH due to their similar densities and the limited resolution of the CT image. To address this issue, random forest (RF) was applied to quantitatively predict the three-phase saturation: CT images were used as input data and the three-phase saturation was the output. In the previous research, a RF model was developed based on training data that only involved the five preliminary stages before the depressurization step. However, the previous RF model failed to estimate the saturation values of the CT images during the depressurization. It could not properly estimate general GH dissociation trend and the GH equilibrium pressure, neither. In this study, CT data obtained in the early and late depressurization stage were used for the training of the RF model. The proposed method can be used to reliably estimate the GH dissociation behavior. The trained RF in this study can identify the GH equilibrium at which the dissociation starts (~16 MPa), which is consistent with the theoretical dissociation at a temperature and salinity of 16 °C and 3 wt%, respectively. The reliability of the proposed method was tested by checking if the estimated results approached zero GH saturation at the end of the GH dissociation (6 and 0 MPa). Therefore, the originality of this study is to improve RF model to reliably predict the three-phase saturation in real time during the GH depressurization by properly utilizing CT images in the depressurization stage for training RF. Based on further improvement, the proposed method could be utilized in the future to help finding adequate depressurization velocity by reliable saturation modeling and analysis of GH experiment because GH productivity depends on depressurization gradient.

Numerical estimation of physical properties from digital pore microstructures has drawn great attention and is being used for quantifying interrelation between various physical properties. The pore microstructures are commonly obtained by the X-ray microtomographic technique, which can give fairly accurate pore geometry. However, there is minor distortion due to the limited resolution or smoothing. This distortion can cause errors in estimating physical properties by pore-scale simulation techniques. Among the properties, seismic velocity would have relatively large errors since a small amount of change in grain contacts can cause significant over-estimation. In this paper, we analyzed the errors in seismic velocity by resolution and smoothing of pore geometry using three samples: an unconsolidated sand pack and two medium-porosity sandstones with different degrees of consolidation. As the resolution becomes poor, the calculated velocity increases linearly, while smoothing gives nonlinear trends; higher errors in the early stage of smoothing. As we expected, soft rocks have higher sensitivity, since the grain contacts are small and are sensitive to minor distortion. Within similar ranges, the resolution causes larger errors than smoothing. In addition, smoothing does not cause velocity over-estimation once the resolution becomes poor, while the resolution can create considerable errors in velocity even after significant smoothing. We conclude that the resolution should be considered in the first place when obtaining digital pore microstructures to minimize errors in velocity estimation. We can also suggest that a good care should be taken when applying smoothing filters, if a sample is suspected to be poorly-consolidated or to have high porosity.

Summary Malformations of the cerebral cortex (MCCs) are devastating developmental disorders. We report here that mice with embryonic neural stem-cell-specific deletion of Llgl1 ( Nestin-Cre/Llgl1 fl/fl ), a mammalian ortholog of the Drosophila cell polarity gene lgl , exhibit MCCs resembling severe periventricular heterotopia (PH). Immunohistochemical analyses and live cortical imaging of PH formation revealed that disruption of apical junctional complexes (AJCs) was responsible for PH in Nestin-Cre/Llgl1 fl/fl brains. While it is well known that cell polarity proteins govern the formation of AJCs, the exact mechanisms remain unclear. We show that LLGL1 directly binds to and promotes internalization of N-cadherin, and N-cadherin/LLGL1 interaction is inhibited by atypical protein kinase C-mediated phosphorylation of LLGL1, restricting the accumulation of AJCs to the basolateral-apical boundary. Disruption of the N-cadherin-LLGL1 interaction during cortical development in vivo is sufficient for PH. These findings reveal a mechanism responsible for the physical and functional connection between cell polarity and cell-cell adhesion machineries in mammalian cells.

Ultrasonic method is widely used for the evaluation of weathering index and of degree of deterioration because it is easily applicable . The basic idea of the method is that the ultrasonic velocity decreases as a rock is being weathered. Thus, the difference of ultrasonic velocities between fresh rock and weathered rock indicates the degree of weathering. In this method, the ultrasonic velocity of fresh rock is assumed to be 5,000 m/s. However, this assumption can cause significant errors in estimating weathering index, especially in case that those rocks of the same type have a wide range of ultrasonic velocities such as in Korea. Therefore, we obtained twenty rock specimens and sixty core samples commonly used for stone cultural heritages in Korea, and measured ultrasonic velocities. From the results, we found that the ultrasonic velocities of the same rock type, granite samples range from 3,118 to 5,380 m/s, and that the estimated weathering index can be highly biased if we use the fixed value of 5,000 m/s. We created a database (DB) by combining the measurement data and reported it. We also measured ultrasonic velocities by direct and indirect methods to quantify the calibration coefficient for each sampling site. We found that the calibration coefficients vary widely from site to site (1.31-1.76). Other factors, such as operator bias and temperature did not show any significant effect on errors in ultrasonic velocity measurements. Lastly, we applied our ultrasonic velocity DB and calibration coefficients to a stone cultural heritage, Bonghwang-ri Buddha statue. Our estimation of the weathering index was 0.3, 0.1 smaller than that by conventional method. The degree of deterioration was also different, "moderately weathered", while conventional method gave "highly weathered". Since other independent studies reported that the degree of deterioration of the Buddha statue was "moderately weathered", our estimation seems to be more accurate. Thus our method can help accurately evaluate the weathering index and the conservation planning for a stone cultural heritage.

Despite potential advantages of covalent organic frameworks (COFs) in wide area applications, several limitations in conventional solvothermal synthesis, such as long reaction time and high reaction temperature, reduce reaction efficiency and prohibit technical processes for practical applications. Therefore, the development of a novel synthesis method that provides better reaction efficiency and spatial controllability has become a critical challenge. Herein, a photochemical synthesis of C9H4BO2 (COF-5) is demonstrated for the first time, by which “sea urchin-shaped” COF-5 (UV-COF-5) with uniform size is synthesized with a highly enhanced growth rate, ≈48 times faster than that of the solvothermal method for 75% yield. In addition, an enlarged surface area is measured from UV-COF-5, which originates from its hierarchical morphology. The selectively increased growth rate of UV-COF-5 in the [001] direction observed by microscopic analysis results in the local 1D morphology of the hierarchical structure. Density functional theory calculations determine that the enhanced growth rate along the [001] direction can be understood by the characteristic of the interlayer orbital coupling at the frontier energy region. In addition, this study successfully demonstrates the preparation of COF-5 patterns without any complicated postsynthesis lithography process, but simply by utilizing optical masks during the photochemical method.

Cell polarity plays a critical role in the development of all metazoans; however, the mechanisms of cell polarity and the specific role of cell polarity pathways in mammalian organisms are still poorly understood. Lethal giant larvae (Lgl) is an apical-basal polarity gene identified in Drosophila, where it functions as a tumor suppressor controlling self-renewal and differentiation of progenitor cells. There are two orthologs of Lgl in mammalian genomes: Llgl1 and Llgl2. While mammalian Lgls are assumed to be tumor suppressor genes, little is known about their function in vivo. Here we report the functional analysis of murine Llgl2. We generated Llgl2(-/-) mice and found that Llgl2 functions as a polarity protein required for proper branching morphogenesis during placental development. Llgl2(-/-) pups are born as runts but quickly catch up in size and grow into normal-size adults. Surprisingly, no prominent phenotypes or spontaneous tumors were observed in adult Llgl2(-/-) mice. Analyses of placental trophoblasts reveal a critical role for Llgl2 in cell polarization and polarized cell invasion. We conclude that mammalian Llgl2 is required for proper polarized invasion of trophoblasts and efficient branching morphogenesis during placental development, but, unlike its Drosophila ortholog, it does not function as a canonical tumor suppressor gene.

Correct establishment and maintenance of cell polarity is required for the development and homeostasis of all metazoans. Cell-polarity mechanisms are responsible not only for the diversification of cell shapes but also for regulation of the asymmetric cell divisions of stem cells that are crucial for their correct self-renewal and differentiation. Disruption of cell polarity is a hallmark of cancer. Furthermore, recent evidence indicates that loss of cell polarity is intimately involved in cancer: several crucial cell-polarity proteins are known proto-oncogenes or tumor suppressors, basic mechanisms of cell polarity are often targeted by oncogenic signaling pathways, and deregulation of asymmetric cell divisions of stem or progenitor cells may be responsible for abnormal self-renewal and differentiation of cancer stem cells. Data from in vivo and three-dimensional (3D) cell-culture models demonstrate that tissue organization attenuates the phenotypic outcome of oncogenic signaling. We suggest that polarized 3D tissue organization uses cell-cell and cell-substratum adhesion structures to reinforce and maintain the cell polarity of pre-cancerous cells. In this model, polarized 3D tissue organization functions as a non-canonical tumor suppressor that prevents the manifestation of neoplastic features in mutant cells and, ultimately, suppresses tumor development and progression.

To investigate the role of promoters in regulating variable gene rearrangement and allelic exclusion, we constructed mutant mice in which a 1.2-kb region of the V beta 13 promoter was either deleted (P13(-/-)) or replaced with the simian virus 40 minimal promoter plus five copies of Gal4 DNA sequences (P13(R/R)). In P13(-/-) mice, cleavage, rearrangement, and transcription of V beta 13, but not the flanking V beta gene segments, were significantly inhibited. In P13(R/R) mice, inhibition of V beta 13 rearrangement was less severe and was not associated with any apparent reduction in V beta 13 cleavage. Expression of a T-cell receptor (TCR) transgene blocked cleavages at the normal V beta 13-recombination signal sequence junction and V beta 13 coding joint formation of both wild-type and mutant V beta 13 alleles. However, a low level of aberrant V beta 13 cleavage was consistently detected, especially in TCR transgenic P13(R/R) mice. These findings suggest that the variable gene promoter is required for promoting local recombination accessibility of the associated V beta gene segment. Although the promoter is dispensable for allelic exclusion, it appears to suppress aberrant V beta cleavages during allelic exclusion.