SUnSeT: spectral unmixing of hyperspectral images for phenotyping soybean seed traits.

KEY MESSAGE: Hyperspectral features enable accurate classification of soybean seeds using linear discriminant analysis and GWAS for novel seed trait genes. Evaluating crop seed traits such as size, shape, and color is crucial for assessing seed quality and improving agricultural productivity. The introduction of the SUnSet toolbox, which employs hyperspectral sensor-derived image analysis, addresses this necessity. In a validation test involving 420 seed accessions from the Korean Soybean Core Collections, the pixel purity index algorithm identified seed- specific hyperspectral endmembers to facilitate segmentation. Various metrics extracted from ventral and lateral side images facilitated the categorization of seeds into three size groups and four shape groups. Additionally, quantitative RGB triplets representing seven seed coat colors, averaged reflectance spectra, and pigment indices were acquired. Machine learning models, trained on a dataset comprising 420 accession seeds and 199 predictors encompassing seed size, shape, and reflectance spectra, achieved accuracy rates of 95.8% for linear discriminant analysis model. Furthermore, a genome-wide association study utilizing hyperspectral features uncovered associations between seed traits and genes governing seed pigmentation and shapes. This comprehensive approach underscores the effectiveness of SUnSet in advancing precision agriculture through meticulous seed trait analysis.

Nomogram for predicting in-hospital mortality in trauma patients undergoing resuscitative endovascular balloon occlusion of the aorta: a retrospective multicenter study.

Recently, resuscitative endovascular balloon occlusion of the aorta (REBOA) had been introduced as an innovative procedure for severe hemorrhage in the abdomen or pelvis. We aimed to investigate risk factors associated with mortality after REBOA and construct a model for predicting mortality. This multicenter retrospective study collected data from 251 patients admitted at five regional trauma centers across South Korea from 2015 to 2022. The indications for REBOA included patients experiencing hypovolemic shock due to hemorrhage in the abdomen, pelvis, or lower extremities, and those who were non-responders (systolic blood pressure (SBP) < 90 mmHg) to initial fluid treatment. The primary and secondary outcomes were mortality due to exsanguination and overall mortality, respectively. After feature selection using the least absolute shrinkage and selection operator (LASSO) logistic regression model to minimize overfitting, a multivariate logistic regression (MLR) model and nomogram were constructed. In the MLR model using risk factors selected in the LASSO, five risk factors, including initial heart rate (adjusted odds ratio [aOR], 0.99; 95% confidence interval [CI], 0.98-1.00; p = 0.030), initial Glasgow coma scale (aOR, 0.86; 95% CI 0.80-0.93; p < 0.001), RBC transfusion within 4 h (unit, aOR, 1.12; 95% CI 1.07-1.17; p < 0.001), balloon occlusion type (reference: partial occlusion; total occlusion, aOR, 2.53; 95% CI 1.27-5.02; p = 0.008; partial + total occlusion, aOR, 2.04; 95% CI 0.71-5.86; p = 0.187), and post-REBOA systolic blood pressure (SBP) (aOR, 0.98; 95% CI 0.97-0.99; p < 0.001) were significantly associated with mortality due to exsanguination. The prediction model showed an area under curve, sensitivity, and specificity of 0.855, 73.2%, and 83.6%, respectively. Decision curve analysis showed that the predictive model had increased net benefits across a wide range of threshold probabilities. This study developed a novel intuitive nomogram for predicting mortality in patients undergoing REBOA. Our proposed model exhibited excellent performance and revealed that total occlusion was associated with poor outcomes, with post-REBOA SBP potentially being an effective surrogate measure.

Clinical features of COVID-19 among patients with end-stage renal disease on hemodialysis in the context of high vaccination coverage during the omicron surge period: a retrospective cohort study.

BACKGROUND: We determined the clinical presentation and outcomes of the Omicron variant of severe acute respiratory syndrome coronavirus 2 infection in hemodialysis patients and identified the risk factors for severe coronavirus disease (COVID-19) and mortality in the context of high vaccination coverage. METHODS: This was a retrospective cohort study involving hemodialysis patients who were vaccinated against COVID-19 during March-September 2022, when the Omicron variant was predominant, and the COVID-19 vaccination rate was high. The proportion of people with severe COVID-19 or mortality was evaluated using univariate logistic regression. RESULTS: Eighty-three (78.3%) patients had asymptomatic/mild symptoms, 10 (9.4%) had moderate symptoms, and 13 (12.3%) had severe symptoms. Six (5.7%) patients required intensive care admission, two (1.9%) required mechanical ventilation, and one (0.9%) was kept on high-flow nasal cannula. Of the five (4.7%) mortality cases, one was directly attributed to COVID-19 and four to pre-existing comorbidities. Risk factors for both severe COVID-19 and mortality were advanced age; number of comorbidities; cardiovascular diseases; increased levels of aspartate transaminase, lactate dehydrogenase, blood urea nitrogen/creatinine ratio, brain natriuretic peptide, and red cell distribution; and decreased levels of hematocrit and albumin. Moreover, the number of COVID-19 vaccinations wasa protective factor against both severe disease and mortality. CONCLUSIONS: Clinical features of hemodialysis patients during the Omicron surge with high COVID-19 vaccination coverage were significant for low mortality. The risk features for severe COVID-19 or mortality were similar to those in the pre-Omicron period in the context of low vaccination coverage.

Crack-Assisted Charge Injection into Solvent-Free Liquid Organic Semiconductors via Local Electric Field Enhancement.

Non-volatile liquid organic semiconducting materials have received much attention as emerging functional materials for organic electronic and optoelectronic devices due to their remarkable advantages. However, charge injection and transport processes are significantly impeded at interfaces between electrodes and liquid organic semiconductors, resulting in overall lower performance compared to conventional solid-state electronic devices. Here we successfully demonstrate efficient charge injection into solvent-free liquid organic semiconductors via cracked metal structures with a large number of edges leading to local electric field enhancement. For this work, thin metal films on deformable polymer substrates were mechanically stretched to generate cracks on the metal surfaces in a controlled manner, and charge injection properties into a typical non-volatile liquid organic semiconducting material, (9-2-ethylhexyl)carbazole (EHCz), were investigated in low bias region (i.e., ohmic current region). It was found that the cracked structures significantly increased the current density at a fixed external bias voltage via the local electric field enhancement, which was strongly supported by field intensity calculation using COMSOL Multiphysics software. We anticipate that these results will significantly contribute to the development and further refinement of various organic electronic and optoelectronic devices based on non-volatile liquid organic semiconducting materials.

Measurement of carrier lifetime in micron-scaled materials using resonant microwave circuits.

The measurement of minority carrier lifetimes is vital to determining the material quality and operational bandwidth of a broad range of optoelectronic devices. Typically, these measurements are made by recording the temporal decay of a carrier-concentration-dependent material property following pulsed optical excitation. Such approaches require some combination of efficient emission from the material under test, specialized collection optics, large sample areas, spatially uniform excitation, and/or the fabrication of ohmic contacts, depending on the technique used. In contrast, here we introduce a technique that provides electrical readout of minority carrier lifetimes using a passive microwave resonator circuit. We demonstrate >105 improvement in sensitivity, compared with traditional photoemission decay experiments and the ability to measure carrier dynamics in micron-scale volumes, much smaller than is possible with other techniques. The approach presented is applicable to a wide range of 2D, micro-, or nano-scaled materials, as well as weak emitters or non-radiative materials.

Evidence for moiré excitons in van der Waals heterostructures.

Recent advances in the isolation and stacking of monolayers of van der Waals materials have provided approaches for the preparation of quantum materials in the ultimate two-dimensional limit1,2. In van der Waals heterostructures formed by stacking two monolayer semiconductors, lattice mismatch or rotational misalignment introduces an in-plane moiré superlattice3. It is widely recognized that the moiré superlattice can modulate the electronic band structure of the material and lead to transport properties such as unconventional superconductivity4 and insulating behaviour driven by correlations5-7; however, the influence of the moiré superlattice on optical properties has not been investigated experimentally. Here we report the observation of multiple interlayer exciton resonances with either positive or negative circularly polarized emission in a molybdenum diselenide/tungsten diselenide (MoSe2/WSe2) heterobilayer with a small twist angle. We attribute these resonances to excitonic ground and excited states confined within the moiré potential. This interpretation is supported by recombination dynamics and by the dependence of these interlayer exciton resonances on twist angle and temperature. These results suggest the feasibility of engineering artificial excitonic crystals using van der Waals heterostructures for nanophotonics and quantum information applications.

Non-power-driven organic photodiode via junction engineering.

Here we introduce a junction engineering approach to realize a high performance non-power-driven organic photodiode. To overcome the external power source dependency of conventional photodiodes, in this work, we try not only to implement an inherently large built-in-potential of the junction but also to utilize an inherently low charge carrier concentration of the semiconductor. The strategically designed ITO/plasma-treated ZnO/poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV)/MoO3/Ag geometry showed near-ideal Schottky junction properties with a high zero-bias built-in potential of 0.54 eV, leading to a zero-bias depletion width of 470 nm. As a result, a green-selective polymeric photodiode with high zero-bias detectivity up to 5 × 1011 Jones and a low noise equivalent power of 2.98 × 10-12 W Hz-1/2 are demonstrated, revealing the possibility of a thin film, color-selective and non-power-driven polymeric photodiode for battery-free application.

Spin-Conserving Resonant Tunneling in Twist-Controlled WSe2-hBN-WSe2 Heterostructures.

We investigate interlayer tunneling in heterostructures consisting of two tungsten diselenide (WSe2) monolayers with controlled rotational alignment, and separated by hexagonal boron nitride. In samples where the two WSe2 monolayers are rotationally aligned we observe resonant tunneling, manifested by a large conductance and negative differential resistance in the vicinity of zero interlayer bias, which stem from energy- and momentum-conserving tunneling. Because the spin-orbit coupling leads to coupled spin-valley degrees of freedom, the twist between the two WSe2 monolayers allows us to probe the conservation of spin-valley degree of freedom in tunneling. In heterostructures where the two WSe2 monolayers have a 180° relative twist, such that the Brillouin zone of one layer is aligned with the time-reversed Brillouin zone of the opposite layer, the resonant tunneling between the layers is suppressed. These findings provide evidence that, in addition to momentum, the spin-valley degree of freedom is also conserved in vertical transport.

Topologically Protected Helical States in Minimally Twisted Bilayer Graphene.

In minimally twisted bilayer graphene, a moiré pattern consisting of AB and BA stacking regions separated by domain walls forms. These domain walls are predicted to support counterpropogating topologically protected helical (TPH) edge states when the AB and BA regions are gapped. We fabricate designer moiré crystals with wavelengths longer than 50 nm and demonstrate the emergence of TPH states on the domain wall network by scanning tunneling spectroscopy measurements. We observe a double-line profile of the TPH states on the domain walls, only occurring when the AB and BA regions are gapped. Our results demonstrate a practical and flexible method for TPH state network construction.

Strongly Enhanced Tunneling at Total Charge Neutrality in Double-Bilayer Graphene-WSe_{2} Heterostructures.

We report the experimental observation of strongly enhanced tunneling between graphene bilayers through a WSe_{2} barrier when the graphene bilayers are populated with carriers of opposite polarity and equal density. The enhanced tunneling increases sharply in strength with decreasing temperature, and the tunneling current exhibits a vertical onset as a function of interlayer voltage at a temperature of 1.5 K. The strongly enhanced tunneling at overall neutrality departs markedly from single-particle model calculations that otherwise match the measured tunneling current-voltage characteristics well, and suggests the emergence of a many-body state with condensed interbilayer excitons when electrons and holes of equal densities populate the two layers.

Tunable Γ-K Valley Populations in Hole-Doped Trilayer WSe_{2}.

We present a combined experimental and theoretical study of valley populations in the valence bands of trilayer WSe_{2}. Shubnikov-de Haas oscillations show that trilayer holes populate two distinct subbands associated with the K and Γ valleys, with effective masses 0.5m_{e} and 1.2m_{e}, respectively; m_{e} is the bare electron mass. At a fixed total hole density, an applied transverse electric field transfers holes from Γ orbitals to K orbitals. We are able to explain this behavior in terms of the larger layer polarizability of the K orbital subband.

Density-Dependent Quantum Hall States and Zeeman Splitting in Monolayer and Bilayer WSe_{2}.

We report a study of the quantum Hall states (QHS) of holes in mono- and bilayer WSe_{2}. The QHS sequence transitions between predominantly even and predominantly odd filling factors as the hole density is tuned in the range 1.6-12×10^{12} cm^{-2}. Measurements in tilted magnetic fields reveal an insensitivity of the QHS to the in-plane magnetic field, evincing that the hole spin is locked perpendicular to the WSe_{2} plane. Furthermore, the QHS sequence is insensitive to an applied electric field. These observations imply that the QHS sequence is controlled by the Zeeman-to-cyclotron energy ratio, which remains constant as a function of perpendicular magnetic field at a fixed carrier density, but changes as a function of density due to strong electron-electron interaction.

Coherent Interlayer Tunneling and Negative Differential Resistance with High Current Density in Double Bilayer Graphene-WSe2 Heterostructures.

We demonstrate gate-tunable resonant tunneling and negative differential resistance between two rotationally aligned bilayer graphene sheets separated by bilayer WSe2. We observe large interlayer current densities of 2 and 2.5 µA/µm2 and peak-to-valley ratios approaching 4 and 6 at room temperature and 1.5 K, respectively, values that are comparable to epitaxially grown resonant tunneling heterostructures. An excellent agreement between theoretical calculations using a Lorentzian spectral function for the two-dimensional (2D) quasiparticle states, and the experimental data indicates that the interlayer current stems primarily from energy and in-plane momentum conserving 2D-2D tunneling, with minimal contributions from inelastic or non-momentum-conserving tunneling. We demonstrate narrow tunneling resonances with intrinsic half-widths of 4 and 6 meV at 1.5 and 300 K, respectively.

Reconfigurable Complementary Monolayer MoTe2 Field-Effect Transistors for Integrated Circuits.

Transition metal dichalcogenides are of interest for next generation switches, but the lack of low resistance electron and hole contacts in the same material has hindered the development of complementary field-effect transistors and circuits. We demonstrate an air-stable, reconfigurable, complementary monolayer MoTe2 field-effect transistor encapsulated in hexagonal boron nitride, using electrostatically doped contacts. The introduction of a multigate design with prepatterned bottom contacts allows us to independently achieve low contact resistance and threshold voltage tuning, while also decoupling the Schottky contacts and channel gating. We illustrate a complementary inverter and a p-i-n diode as potential applications.

Tunable moiré bands and strong correlations in small-twist-angle bilayer graphene.

According to electronic structure theory, bilayer graphene is expected to have anomalous electronic properties when it has long-period moiré patterns produced by small misalignments between its individual layer honeycomb lattices. We have realized bilayer graphene moiré crystals with accurately controlled twist angles smaller than 1° and studied their properties using scanning probe microscopy and electron transport. We observe conductivity minima at charge neutrality, satellite gaps that appear at anomalous carrier densities for twist angles smaller than 1°, and tunneling densities-of-states that are strongly dependent on carrier density. These features are robust up to large transverse electric fields. In perpendicular magnetic fields, we observe the emergence of a Hofstadter butterfly in the energy spectrum, with fourfold degenerate Landau levels, and broken symmetry quantum Hall states at filling factors ±1, 2, 3. These observations demonstrate that at small twist angles, the electronic properties of bilayer graphene moiré crystals are strongly altered by electron-electron interactions.

Effects of mushroom extract on textural properties and muscle protein degradation of bovine longissimus dorsi muscle.

We investigated the effects of Sarcodon aspratus, Agaricus bisporus, and Lentinula edodes aqueous extracts on the tenderization of bovine longissimus dorsi muscle. Meat quality and muscle protein degradation were examined as well. Beef chunks were marinated in distilled water (control), 5% S. aspratus (SA), 5% A. bisporus (AB), or 5% L. edodes (LE) extracts. SA was shown to have a higher enzymatic activity (p < 0.001) and water-holding capacity than LE (p < 0.01). SA and AB extracts exhibited lower shear force values compared with the control (p < 0.05). SA, AB, and LE showed superior muscle proteolytic effects compared with the control. SA demonstrated the ability to degrade myosin heavy chains and actin, which was not observed after AB and LE extract treatments. This suggests that SA extract may affect tenderization. Taken together, our results show that aqueous extract of S. aspratus affects the tenderness of the bovine longissimus dorsi muscle.

Effects of Electrode Layer Band Structure on the Performance of Multilayer Graphene-hBN-Graphene Interlayer Tunnel Field Effect Transistors.

Interlayer tunnel field-effect transistors based on graphene and hexagonal boron nitride (hBN) have recently attracted much interest for their potential as beyond-CMOS devices. Using a recently developed method for fabricating rotationally aligned two-dimensional heterostructures, we show experimental results for devices with varying thicknesses and stacking order of the graphene electrode layers and also model the current-voltage behavior. We show that an increase in the graphene layer thickness results in narrower resonance. However, due to a simultaneous increase in the number of sub-bands and decrease of sub-band separation with an increase in thickness, the negative differential resistance peaks becomes less prominent and do not appear for certain conditions at room temperature. Also, we show that due to the unique band structure of odd number of layer Bernal-stacked graphene, the number of closely spaced resonance conditions increase, causing interference between neighboring resonance peaks. Although this can be avoided with even number of layer graphene, we find that in this case the bandgap opening present at high biases tend to broaden the resonance peaks.

Shubnikov-de Haas Oscillations of High-Mobility Holes in Monolayer and Bilayer WSe_{2}: Landau Level Degeneracy, Effective Mass, and Negative Compressibility.

We study the magnetotransport properties of high-mobility holes in monolayer and bilayer WSe_{2}, which display well defined Shubnikov-de Haas (SdH) oscillations, and quantum Hall states in high magnetic fields. In both mono- and bilayer WSe_{2}, the SdH oscillations and the quantum Hall states occur predominantly at even filling factors, evincing a twofold Landau level degeneracy. The Fourier transform analysis of the SdH oscillations in bilayer WSe_{2} reveals the presence of two subbands localized in the top or the bottom layer, as well as negative compressibility. From the temperature dependence of the SdH oscillations we determine a hole effective mass of 0.45m_{0} for both mono- and bilayer WSe_{2}.

Structural and Electrical Properties of MoTe2 and MoSe2 Grown by Molecular Beam Epitaxy.

We demonstrate the growth of thin films of molybdenum ditelluride and molybdenum diselenide on sapphire substrates by molecular beam epitaxy. In situ structural and chemical analyses reveal stoichiometric layered film growth with atomically smooth surface morphologies. Film growth along the (001) direction is confirmed by X-ray diffraction, and the crystalline nature of growth in the 2H phase is evident from Raman spectroscopy. Transmission electron microscopy is used to confirm the layered film structure and hexagonal arrangement of surface atoms. Temperature-dependent electrical measurements show an insulating behavior that agrees well with a two-dimensional variable-range hopping model, suggesting that transport in these films is dominated by localized charge-carrier states.