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Graph neural networks (GNNs) have been proven effective in the fast and accurate prediction of nuclear magnetic resonance (NMR) chemical shifts of a molecule. Existing methods, despite their effectiveness, suffer from high space complexity and are therefore limited to relatively small molecules. In this work, we propose a scalable GNN for NMR chemical shift prediction. To reduce the space complexity, we sparsify the graph representation of a molecule by regarding only heavy atoms as nodes and their chemical bonds as edges. To better learn from the sparsified graph representation, we improve the message passing and readout functions in the GNN. For the message passing function, we adapt the attention mechanism and residual connection to better capture local information around each node. For the readout function, we use both node-level and graph-level embeddings as the local and global information to better predict node-level chemical shifts. Through the experimental investigation using

The seasonal characteristics of atmospheric water-soluble organic nitrogen (WSON) in particulate matter with a diameter of 2.5 μm or smaller (PM

We demonstrate the nonvolatile and volatile memory characteristics of a gate-all-around silicon nanowire feedback field-effect transistor (FBFET) with a nitride charge-storage layer analyzed by a commercial TCAD simulator. Our FBFET exhibits a threshold voltage window of 0.76 V with a programming/erasing time of ${1}~\mu \text{s}$ in the nonvolatile memory mode. We investigated the delay of read operations with accumulated charges in the intrinsic channel region in this memory mode. Moreover, the FBFET exhibits a sensing margin of 6.3 $\mu \text{A}$ and a read/write speed of 10 ns with an outstanding retention time, as well as nondestructive read characteristics in the volatile memory mode, allowing this device to operate without any refresh operation. In addition, we describe the operating principle of our device and demonstrate its potential as integrated memory for 3-D integrations.

Severe haze episodes occur frequently in the Seoul Metropolitan Area (SMA) and throughout East Asian countries, especially during the winter and early spring. We investigated the sources and chemistry of particulate matter (PM) during three winter haze episodes in Seoul that occurred between January 1st and February 10th in 2017 using a high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and positive matrix factorization (PMF) analysis. The average concentration of sub-micrometer aerosol (PM1 = NR-PM1 + black carbon (BC)) was 32.6 μg/m3, which was composed of 42% organics, 27% nitrate, 11% sulfate, 13% ammonium and 4% BC by mass. Six distinct sources of organic aerosol (OA) were identified: vehicle emitted hydrocarbon-like OA (HOA), cooking OA (COA), biomass burning OA (BBOA), and 3 different types of secondary OA (SOA) with varying degrees of oxidation and temporal trends. The nitrate mass fraction increased during the three haze episodes, with nitrate accounting for 27-33% of PM1 mass. Enhanced nitrate concentrations and higher nitrate oxidation ratios (NOR), despite lower enhancement in relative humidity (RH) than the low PM loading period, suggest that regional transport of nitrate contributed to the nitrate mass during the haze periods. Lower HOA and COA concentrations during the high PM loading periods further confirm that local emissions or stagnant meteorological conditions were not the main reason for the severe haze. Residence time analysis (RTA), concentration field analysis (CFA), and column-CFA results from FLEXPART also showed that the measurement period was accompanied by atmospheric transport of nitrate, sulfate, and ammonium from eastern China. Nevertheless, we found that NO2, a precursor of nitrate, was predominantly from local emissions. These findings suggest that nitrate in Seoul is not only locally formed, but also transported from upwind areas.

In this paper, we investigate the performance of ring oscillators composed of gate-all-around (GAA) silicon nanowire (NW) field-effect transistors (FETs) with four different numbers of NW channels, for sub-10-nm logic applications. Our simulations reveal that ring oscillators with double, triple, and quadruple NW channels exhibit improvements of up to 50%, 85%, and 97%, respectively, in the oscillation frequencies (fosc), compared to a ring oscillator with a single NW channel, due to the large drive current, in spite of the increased intrinsic capacitance of a given device. Moreover, our work shows that the fosc improvement ratio of the ring oscillators becomes saturated with triple NW channels with additional load capacitances of 0.1 fF and 0.01 fF, which are similar to, or less than the intrinsic device capacitance (∼0.1 fF). Thus, our study provides an insight for determining the capacitive load and optimal number of NW channels, for device development and circuit design of GAA NW FETs.

In this paper, we present the impact ionization and tunneling operations in a newly designed dopingless device. Our proposed device functions selectively—as either a p-channel impact-ionization MOSFET (p-IMOS) or an n-channel tunneling field-effect transistor (n-TFET)—according to the bias conditions. To realize the dopingless device, the charge-plasma effect is employed to induce n- or p-type regions without any doping process, by choosing an electrode metal with an appropriate work function. The band diagrams, I–V characteristics, subthreshold swings (SS), and carrier-concentration profiles of the device under the p-IMOS and n-TFET operation modes are analyzed in our study, using a commercial device simulator. The device yields an extremely low SS of 0.53 mV/dec under the p-IMOS operation mode. It also exhibits a low off-current of approximately 10−14 A/μm and a high ION/IOFF of approximately 108, under the n-TFET operation mode.

We present results from a high-resolution chemical ionization time-of-flight mass spectrometer (HRToF-CIMS), operated with two different thermal desorption inlets, designed to characterize the gas and aerosol composition. Data from two field campaigns at forested sites are shown. Particle volatility distributions are estimated using three different methods: thermograms, elemental formulas, and measured partitioning. Thermogram-based results are consistent with those from an aerosol mass spectrometer (AMS) with a thermal denuder, implying that thermal desorption is reproducible across very different experimental setups. Estimated volatilities from the detected elemental formulas are much higher than from thermograms since many of the detected species are thermal decomposition products rather than actual SOA molecules. We show that up to 65% of citric acid decomposes substantially in the FIGAERO–CIMS, with ∼20% of its mass detected as gas-phase CO2, CO, and H2O. Once thermal decomposition effects on the det...

One to one relationship of energy transfer rate and Yb3+ quenching ratio in an erbium- ytterbium-doped fiber (EYDF) is obtained in a semi-analytical model. This model can be applied to the determination of the Yb3+ quenching ratio for various erbium-ytterbium-doped fiber samples.

Aptamers are promising next-generation ligands used in molecular imaging and theragnosis. Aptamers are synthetic nucleic acids that can be held together with complementary sequences by base-pair hybridization. In this study, the complementary oligonucleotide (cODN) hybridization-based aptamer conjugation platform was developed to use aptamers as the molecular imaging agent. The cODN was pre-labeled with fluorescent dye or radioisotope and hybridized with a matched sequence containing aptamers in aqueous conditions. The cODN platform-hybridized aptamers exhibited good serum stability and specific binding affinity towards target cancer cells both in vitro and in vivo. These results suggest that the newly designed aptamer conjugation platform offers great potential for the versatile application of aptamers as molecular imaging agents.

Background/Purpose Aptamers are oligonucleotide or peptide molecules that bind to a target molecule with high affinity and specificity. The present study aimed to evaluate the target specificity and applicability for in vivo molecular imaging of an aptamer labeled with a radioisotope. Methods The human epidermal growth factor receptor 2 (HER2/ErbB2) aptamer was radiolabeled with 18F-fluoride. HER2-positive tumor cell uptake of the aptamer was evaluated in comparison to negative controls by flow cytometry and confocal microscopy. Using 18F-labeled HER2-specific aptamer positron emission tomography (PET), in vivo molecular images of BT474 tumor-bearing mice were taken at 60, 90 and 120 minutes after injection. Results In flow cytometric analysis, HER2 aptamer showed strong binding to HER2-positive BT474 cells, while binding to HER2-negative MDA-MB231 cells was quite low. Likewise, in confocal microscopic images, the aptamer was bound to HER2-positive breast cancer cells, with minimal binding to HER2-negative cells. In vivo PET molecular imaging of BT474 tumor-bearing mice revealed significant higher uptake of the 18F-labeled HER2 specific aptamer into the tumor compared to the that of HER2-negative cell tumor(p = 0.033). HER2 aptamer was able to preferentially bind to HER2-positive breast cancer cells both in vitro and in vivo, by recognizing HER2 structure on the surface of these cells. Conclusion The 18F-labeled aptamer enabled appropriate visualization of HER2 expression by human breast cancer cells. The results suggest that a radiolabeled HER2 aptamer could potentially be applied in the development of treatment strategies or in targeted therapy against HER2-positive breast cancer cells.

In this paper, we investigate the performance of inverters and ring oscillators composed of gate-all-around (GAA) silicon nanowire and nanosheet (NSH) field-effect transistors (FETs), compared with FinFETs, for sub-10nm logic technology applications. Our TCAD transient simulations reveal that ring oscillators with 3 stacked channels with NSH width, three times wider than the fin width, exhibit improvements of up to 22% in the oscillation frequencies. compared to a ring oscillator with FinFETs. Thus, our study provides an insight for device down-selection in the development of GAA FET technology.