Enumeration, Nomenclature, and Stability Rules of Carbon Nanobelts

With recent breakthroughs and advances in synthetic chemistry, carbon nanobelts (CNBs) have become an emerging hot topic in chemistry and materials science. Owing to their unique molecular structures, CNBs have intriguing properties with applications in synthetic materials, host–guest chemistry, optoelectronics, and so on. Although a considerable number of CNBs with diverse forms have been synthesized, no systematic nomenclature is available yet for this important family of macrocycles. Moreover, little is known about the detailed isomerism of CNBs, which, in fact, exhibits greater complexity than that of carbon nanotubes. The copious variety of CNB isomers, along with the underlying structure–property relationships, bears fundamental relevance to the ongoing design and synthesis of novel nanobelts. In this paper, we propose an elegant approach to systematically enumerate, classify, and name all possible isomers of CNBs. Besides the simplest, standard CNBs defined by chiral indices (n, m), the nonstandard CNBs (n, m, l) involve an additional winding index l. Based on extensive quantum chemical calculations, we present a comprehensive study of the relative isomer stability of CNBs containing up to 30 rings. A simple Hückel-based model with a high predictive power reveals that the relative stability of standard CNBs is governed by the π stabilization and the strain destabilization induced by the cylindrical carbon framework, and the former effect prevails over the latter. For nonstandard CNBs, a third stability factor, the H···H repulsion in the benzo[c]phenanthrene-like motifs, is also shown to be important and can be incorporated into the simple quantitative model. In general, lower-energy CNB isomers have a larger HOMO–LUMO gap, suggesting that their thermodynamic stability coincides with kinetic stability. The most stable CNB isomers determined can be considered the optimal targets for future synthesis. These results lay an initial foundation and provide a useful theoretical tool for further research on CNBs and related analogues

Enumeration, Nomenclature, and Stability Rules of Carbon Nanobelts

With recent breakthroughs and advances in synthetic chemistry, carbon nanobelts (CNBs) have become an emerging hot topic in chemistry and materials science. Owing to their unique molecular structures, CNBs have intriguing properties with applications in synthetic materials, host–guest chemistry, optoelectronics, and so on. Although a considerable number of CNBs with diverse forms have been synthesized, no systematic nomenclature is available yet for this important family of macrocycles. Moreover, little is known about the detailed isomerism of CNBs, which, in fact, exhibits greater complexity than that of carbon nanotubes. The copious variety of CNB isomers, along with the underlying structure–property relationships, bears fundamental relevance to the ongoing design and synthesis of novel nanobelts. In this paper, we propose an elegant approach to systematically enumerate, classify, and name all possible isomers of CNBs. Besides the simplest, standard CNBs defined by chiral indices (n, m), the nonstandard CNBs (n, m, l) involve an additional winding index l. Based on extensive quantum chemical calculations, we present a comprehensive study of the relative isomer stability of CNBs containing up to 30 rings. A simple Hückel-based model with a high predictive power reveals that the relative stability of standard CNBs is governed by the π stabilization and the strain destabilization induced by the cylindrical carbon framework, and the former effect prevails over the latter. For nonstandard CNBs, a third stability factor, the H···H repulsion in the benzo[c]phenanthrene-like motifs, is also shown to be important and can be incorporated into the simple quantitative model. In general, lower-energy CNB isomers have a larger HOMO–LUMO gap, suggesting that their thermodynamic stability coincides with kinetic stability. The most stable CNB isomers determined can be considered the optimal targets for future synthesis. These results lay an initial foundation and provide a useful theoretical tool for further research on CNBs and related analogues

Optimized Model Surfaces for Advanced Atomic Force Microscopy Studies of Surface Nanobubbles

The formation of self-assembled monolayers (SAMs) of binary mixtures of 16-mercaptohexadecanoic acid (MHDA) and 1-octadecanethiol (ODT) on ultraflat template-stripped gold (TSG) surfaces was systematically investigated to clarify the assembly behavior, composition, and degree of possible phase segregation in light of atomic force microscopy (AFM) studies of surface nanobubbles on these substrates. The data for SAMs on TSG were compared to those obtained by adsorption on rough evaporated gold, as reported in a previous study. Quartz crystal microbalance and surface plasmon resonance data acquired <i>in situ</i> on TSG indicate that similar to SAM formation on conventional evaporated gold substrates ODT and MHDA form monolayers and bilayers, respectively. The second layer on MHDA, whose formation is attributed to hydrogen bonding, can be easily removed by adequate rinsing with water. The favorable agreement of the grazing incidence reflection Fourier transform infrared (GIR FTIR) spectroscopy and contact angle data analyzed with the Israelachvili–Gee model suggests that the binary SAMs do <i>not</i> segregate laterally. This conclusion is fully validated by high-resolution friction force AFM observations down to a length scale of 8–10 nm, which is much smaller than the typical observed surface nanobubble radii. Finally, correspondingly functionalized TSG substrates are shown to be valuable supports for studying surface nanobubbles by AFM in water and for addressing the relation between surface functionality and nanobubble formation and properties

'Monandria Monogynia Linnaei Genera'

The first well-defined 1,3-butadienylzinc trimers have been synthesized by transmetalation of 1,4-dilithio-1,3-butadienes with 1 equiv of ZnBr₂. Their structures have been determined by single-crystal X-ray structural analysis. Their reaction chemistry has been demonstrated by Pd-catalyzed Negishi cross-coupling with iodobenzenes

1,3-Butadienylzinc Trimer Formed via Transmetalation from 1,4-Dilithio-1,3-butadienes: Synthesis, Structural Characterization, and Application in Negishi Cross-Coupling

The first well-defined 1,3-butadienylzinc trimers have been synthesized by transmetalation of 1,4-dilithio-1,3-butadienes with 1 equiv of ZnBr₂. Their structures have been determined by single-crystal X-ray structural analysis. Their reaction chemistry has been demonstrated by Pd-catalyzed Negishi cross-coupling with iodobenzenes

Data_Sheet_1_Discovering optimal features for neuron-type identification from extracellular recordings.pdf

Advancements in multichannel recordings of single-unit activity (SUA) in vivo present an opportunity to discover novel features of spatially-varying extracellularly-recorded action potentials (EAPs) that are useful for identifying neuron-types. Traditional approaches to classifying neuron-types often rely on computing EAP waveform features based on conventions of single-channel recordings and thus inherit their limitations. However, spatiotemporal EAP waveforms are the product of signals from underlying current sources being mixed within the extracellular space. We introduce a machine learning approach to demix the underlying sources of spatiotemporal EAP waveforms. Using biophysically realistic computational models, we simulate EAP waveforms and characterize them by the relative prevalence of these sources, which we use as features for identifying the neuron-types corresponding to recorded single units. These EAP sources have distinct spatial and multi-resolution temporal patterns that are robust to various sampling biases. EAP sources also are shared across many neuron-types, are predictive of gross morphological features, and expose underlying morphological domains. We then organize known neuron-types into a hierarchy of latent morpho-electrophysiological types based on differences in the source prevalences, which provides a multi-level classification scheme. We validate the robustness, accuracy, and interpretations of our demixing approach by analyzing simulated EAPs from morphologically detailed models with classification and clustering methods. This simulation-based approach provides a machine learning strategy for neuron-type identification.</p

1,3-Butadienylzinc Trimer Formed via Transmetalation from 1,4-Dilithio-1,3-butadienes: Synthesis, Structural Characterization, and Application in Negishi Cross-Coupling

The first well-defined 1,3-butadienylzinc trimers have been synthesized by transmetalation of 1,4-dilithio-1,3-butadienes with 1 equiv of ZnBr₂. Their structures have been determined by single-crystal X-ray structural analysis. Their reaction chemistry has been demonstrated by Pd-catalyzed Negishi cross-coupling with iodobenzenes

Alternating Current Potentiometric Scanning Ion Conductance Microscopy (AC-PSICM)

Studies of ion transport at small length scales inform the fundamental understanding of various biophysical processes. Here, we describe a new method, alternating current potentiometric scanning ion conductance microscopy (AC-PSICM), which measures ion transport through nanopores as a function of AC perturbations over a range of frequencies (5 Hz to 50 kHz). Phase and amplitude of local potential in the vicinity of nanopores in polymer membranes were captured with a nanopipet. Phase was found to be sensitive to local conductive pathways (nanopores in this case) and can be used to quantify single nanopore resistance. Investigation of phase approach curves and lateral phase distributions with single nanopore samples predicted four distinct frequency ranges for resolving heterogeneous conductive pathways within a sample, which were confirmed with line profile measurements of the phase response in samples with different sized nanopores. AC-PSICM is suitable for ion transport studies at the nanometer scale and can be used to access wide ranges of time scales. Phase mapping shows promise for visualization of heterogeneous transport pathways and could be used in future studies to examine conductance at cell and tissue interfaces

Additional file 1 of A novel prognostic signature and therapy guidance for hepatocellular carcinoma based on STEAP family

Additional file 1: Fig. S1. The histogram of the distribution of risk scores in the TCGA and GSE14520. Fig. S2. The validation of the prognostic risk model and the nomogram and calibration curve of the model in the GSE14520 cohorts. Fig. S3. The correlation between the expression of STEAP1, STEAP4 and risk score with particular etiology and liver fibrosis in the TCGA and GSE14520

Initial and final wet weight (g·ind.⁻¹) of <i>A. japonicus</i> for five diet treatments.

<p>Note: values with different letters in the same row were significantly different from each other (n = 4, <i>p</i><0.05).</p