ChAdOx1 COVID vaccines express RBD open prefusion SARS-CoV-2 spikes on the cell surface

Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been proven to be an effective means of decreasing COVID-19 mortality, hospitalization rates, and transmission. One of the vaccines deployed worldwide is ChAdOx1 nCoV-19, which uses an adenovirus vector to drive the expression of the original SARS-CoV-2 spike on the surface of transduced cells. Using cryo-electron tomography and subtomogram averaging, we determined the native structures of the vaccine product expressed on cell surfaces in situ. We show that ChAdOx1-vectored vaccines expressing the Beta SARS-CoV-2 variant produce abundant native prefusion spikes predominantly in one-RBD-up conformation. Furthermore, the ChAdOx1-vectored HexaPro-stabilized spike yields higher cell surface expression, enhanced RBD exposure, and reduced shedding of S1 compared to the wild type. We demonstrate in situ structure determination as a powerful means for studying antigen design options in future vaccine development against emerging novel SARS-CoV-2 variants and broadly against other infectious viruses.

Automatic Treatment Planning for Multi-focal Dynamic Conformal Arc GRID Therapy for Late-Stage Lung Cancer: A Feasibility Study

PURPOSE/OBJECTIVE(S)

Palliative management of large, symptomatic pulmonary lesions, either as primary lung cancers or metastases, can be challenging due to need to balance effective radiation doses for cytoreduction with safety. Spatially Fractionated Radiation Therapy (SFRT), or GRID Therapy, is an emerging technique, which delivers ablative doses of radiotherapy to small, selected areas of tumor, while sparing organs-at-risk (OARs), and has been shown to debulk large lesions in preliminary studies. Conventionally, an alloy GRID block is manufactured to deliver GRID therapy. However, this delivery technique poses a challenge due to need for block, and dosimetrically when the tumor is deep-seated as excess dose may be delivered to OARs, such as skin and chest wall. This study aims to develop a fast, automatic planning solution using multi-focal dynamic conformal arcs (DCA) on modern Linear Accelerator.

MATERIALS/METHODS

One late-stage lung cancer patient with simulated sphere target grid was included in this study. The sphere targets are 1.5cm in diameter and 4.3cm spacing. Four co-planar full arcs were used for optimization. The problem is formalized as finding optimal multi-leaf collimator (MLC) sequencing to cover N targets with K control points (CPs) for each arc. The state of each target's MLC opening at each CP is binary. In order to solve this NP-hard problem, the optimal solution was approximated by eliminating projection collision at each CP. MLC motion continuity and maximum speed were included in the cost function to ensure deliverability. The optimization started with randomized initial CP apertures, followed by solving state-transition equations for following CPs. Two grid arrays (9 and 10 targets respectively) were tested for plan quality. For each grid of target, the arc collimator angle was planned with 0 and 30 degrees for comparison. Prescription was 20 Gy per fraction. Monte Carlo simulation dose engine from matRad toolkit was used for dose calculation. Key dosimetric endpoints including target mean dose, D5%(Gy) and D95%(Gy), were reported.

RESULTS

Average calculation time on the AMD Ryzen 5 5600 × 6-Core 3.7GHz CPU and 32GB RAM platform varied from 31 to 44 minutes. One zero-degree collimator and one thirty-degree collimator were generated for each target array. For nine-target array, mean target dose from both plans ranged from 23.41 to 26.55 Gy, while D5%(Gy) and D95%(Gy) ranged from 25.45 to 30.16 Gy, and 20.00 to 22.21 Gy, respectively. For ten-target array, the range of target mean, D5%(Gy) and D95%(Gy) were 23.82 to 28.74 Gy, 26.50 to 33.11 Gy, and 20.00 to 22.49 Gy.

CONCLUSION

A fast, automatic planning solution for multi-focal DCA GRID therapy was developed. It provides clinically feasible plans with high efficiency for small target arrays for the late-stage cancer patient. The implementation provides excellent coverage for deep-seated tumors where alloy grid solution could fail to meet coverage objectives. Additional patients are needed in the future to further refine the technique.

Genome-wide identification and expression analysis of SlRR genes in response to abiotic stress in tomato

The cytokinin two-component signal transduction system (TCS) is involved in many biological processes, including hormone signal transduction and plant growth regulation. Although cytokinin TCS has been well characterized in Arabidopsis thaliana, its role in tomato remains elusive. In this study, we characterized the diversity and function of response regulator (RR) genes, a critical component of TCS, in tomato. In total, we identified 31 RR genes in the tomato genome. These SlRR genes were classified into three subgroups (type-A, type-B and type-C). Various stress-responsive cis-elements were present in the tomato RR gene promoters. Their expression responses under pesticide treatment were evaluated by transcriptome analysis. Their expression under heat, cold, ABA, salinity and NaHCO₃ treatments was further investigated by qRT-PCR and complemented with the available transcription data under these treatments. Specifically, SlRR13 expression was significantly upregulated under salinity, drought, cold and pesticide stress and was downregulated under ABA treatment. SlRR23 expression was induced under salt treatment, while the transcription level of SlRR1 was increased under cold and decreased under salt stress. We also found that GATA transcription factors played a significant role in the regulation of SlRR genes. Based on our results, tomato SlRR genes are involved in responses to abiotic stress in tomato and could be implemented in molecular breeding approaches to increase resistance of tomato to environmental stresses.

Seeking Repeating Anthropogenic Seismic Sources: Implications for Seismic Velocity Monitoring at Fault Zones

Seismic velocities in rocks are highly sensitive to changes in permanent deformation and fluid content. The temporal variation of seismic velocity during the preparation phase of earthquakes has been well documented in laboratories but rarely observed in nature. It has been recently found that some anthropogenic, high-frequency (>1 Hz) seismic sources are powerful enough to generate body waves that travel down to a few kilometers and can be used to monitor fault zones at seismogenic depth. Anthropogenic seismic sources typically have fixed spatial distribution and provide new perspectives for velocity monitoring. In this work, we propose a systematic workflow to seek such powerful seismic sources in a rapid and straightforward manner. We tackle the problem from a statistical point of view, considering that persistent, powerful seismic sources yield highly coherent correlation functions (CFs) between pairs of seismic sensors. The algorithm is tested in California and Japan. Multiple sites close to fault zones show high-frequency CFs stable for an extended period of time. These findings have great potential for monitoring fault zones, including the San Jacinto Fault and the Ridgecrest area in Southern California, Napa in Northern California, and faults in central Japan. However, extra steps, such as beamforming or polarization analysis, are required to determine the dominant seismic sources and study the source characteristics, which are crucial to interpreting the velocity monitoring results. Train tremors identified by the present approach have been successfully used for seismic velocity monitoring of the San Jacinto Fault in previous studies.

Application of super-resolution and correlative double sampling in cryo-electron microscopy

Developments in cryo-EM have allowed atomic or near-atomic resolution structure determination to become routine in single particle analysis (SPA). However, near-atomic resolution structures determined using cryo-electron tomography and sub-tomogram averaging (cryo-ET STA) are much less routine. In this paper, we show that collecting cryo-ET STA data using the same conditions as SPA, with both correlated double sampling (CDS) and the super-resolution mode, allowed apoferritin to be reconstructed out to the physical Nyquist frequency of the images. Even with just two tilt series, STA yields an apoferritin map at 2.9 Å resolution. These results highlight the exciting potential of cryo-ET STA in the future of protein structure determination. While processing SPA data recorded in super-resolution mode may yield structures surpassing the physical Nyquist limit, processing cryo-ET STA data in the super-resolution mode gave no additional resolution benefit. We further show that collecting SPA data in the super-resolution mode, with CDS activated, reduces the estimated B-factor, leading to a reduction in the number of particles required to reach a target resolution without compromising the data size on disk and the area imaged in SerialEM. However, collecting SPA data in CDS does reduce throughput, given that a similar resolution structure, with a slightly larger B-factor, is achievable with optimised parameters for speed in EPU (without CDS).

Monitoring Seismic Velocity Changes Across the San Jacinto Fault Using Train-Generated Seismic Tremors

Microseismic noise has been used for seismic velocity monitoring. However, such signals are dominated by low-frequency surface waves that are not ideal for detecting changes associated with small tectonic processes. Here we show that it is possible to extract stable, high-frequency body waves using seismic tremors generated by freight trains. Such body waves allow us to focus on small velocity perturbations in the crust with high spatial resolution. We report on 10 years of seismic velocity temporal changes at the San Jacinto Fault. We observe and map a two-month-long episode of velocity changes with complex spatial distribution and interpret the velocity perturbation as produced by a previously undocumented slow-slip event. We verify the hypothesis through numerical simulations and locate this event along a fault segment believed to be locked. Such a slow-slip event stresses its surroundings and may trigger a major earthquake on a fault section approaching failure.

Structure and activity of particulate methane monooxygenase arrays in methanotrophs

Methane-oxidizing bacteria play a central role in greenhouse gas mitigation and have potential applications in biomanufacturing. Their primary metabolic enzyme, particulate methane monooxygenase (pMMO), is housed in copper-induced intracytoplasmic membranes (ICMs), of which the function and biogenesis are not known. We show by serial cryo-focused ion beam (cryoFIB) milling/scanning electron microscope (SEM) volume imaging and lamellae-based cellular cryo-electron tomography (cryoET) that these ICMs are derived from the inner cell membrane. The pMMO trimer, resolved by cryoET and subtomogram averaging to 4.8 Å in the ICM, forms higher-order hexagonal arrays in intact cells. Array formation correlates with increased enzymatic activity, highlighting the importance of studying the enzyme in its native environment. These findings also demonstrate the power of cryoET to structurally characterize native membrane enzymes in the cellular context.

Cryo-electron Tomography Remote Data Collection and Subtomogram Averaging

Cryo-electron tomography (cryo-ET) has been gaining momentum in recent years, especially since the introduction of direct electron detectors, improved automated acquisition strategies, preparative techniques that expand the possibilities of what the electron microscope can image at high-resolution using cryo-ET and new subtomogram averaging software. Additionally, data acquisition has become increasingly streamlined, making it more accessible to many users. The SARS-CoV-2 pandemic has further accelerated remote cryo-electron microscopy (cryo-EM) data collection, especially for single-particle cryo-EM, in many facilities globally, providing uninterrupted user access to state-of-the-art instruments during the pandemic. With the recent advances in Tomo5 (software for 3D electron tomography), remote cryo-ET data collection has become robust and easy to handle from anywhere in the world. This article aims to provide a detailed walk-through, starting from the data collection setup in the tomography software for the process of a (remote) cryo-ET data collection session with detailed troubleshooting. The (remote) data collection protocol is further complemented with the workflow for structure determination at near-atomic resolution by subtomogram averaging with emClarity, using apoferritin as an example.

High-resolution in situ structure determination by cryo-electron tomography and subtomogram averaging using emClarity

Cryo-electron tomography and subtomogram averaging (STA) has developed rapidly in recent years. It provides structures of macromolecular complexes in situ and in cellular context at or below subnanometer resolution and has led to unprecedented insights into the inner working of molecular machines in their native environment, as well as their functional relevant conformations and spatial distribution within biological cells or tissues. Given the tremendous potential of cryo-electron tomography STA in in situ structural cell biology, we previously developed emClarity, a graphics processing unit-accelerated image-processing software that offers STA and classification of macromolecular complexes at high resolution. However, the workflow remains challenging, especially for newcomers to the field. In this protocol, we describe a detailed workflow, processing and parameters associated with each step, from initial tomography tilt-series data to the final 3D density map, with several features unique to emClarity. We use four different samples, including human immunodeficiency virus type 1 Gag assemblies, ribosome and apoferritin, to illustrate the procedure and results of STA and classification. Following the processing steps described in this protocol, along with a comprehensive tutorial and guidelines for troubleshooting and parameter optimization, one can obtain density maps up to 2.8 Å resolution from six tilt series by cryo-electron tomography STA.

GaS:WS2 Heterojunctions for Ultrathin Two-Dimensional Photodetectors with Large Linear Dynamic Range across Broad Wavelengths

Two-dimensional (2D) photodetectors based on photovoltaic effect or photogating effect can hardly achieve both high photoresponsivity and large linear dynamic range at the same time, which greatly limits many practical applications such as imaging sensors. Here, the conductive-sensitizer strategy, a general design for improving photoresponsivity and linear dynamic range in 2D photodetectors is provided and experimentally demonstrated on vertically stacked bilayer WS₂/GaS_0.87 under a parallel circuit mode. Owing to successful band alignment engineering, the isotype type-II heterojunction enables efficient charge carrier transfer from WS₂, the high-mobility sensitizer, to GaS_0.87, the low-mobility channel, under illumination from a broad visible spectrum. The transferred electron charges introduce a reverse electric field which efficiently lowers the band offset between the two materials, facilitating a transition from low-mobility photocarrier transport to high-mobility photocarrier transport with increasing illumination power. We achieved a large linear dynamic range of 73 dB as well as a high and constant photoresponsivity of 13 A/W under green light. X-ray photoelectron spectroscopy, cathodoluminescence, and Kelvin probe force microscopy further identify the key role of defects in monolayer GaS_0.87 in engineering the band alignment with monolayer WS₂. This work proposes a design route based on band and interface modulation for improving performance of 2D photodetectors and provides deep insights into the important role of strong interlayer coupling in offering heterostructures with desired properties and functions.

[Application of diffusion-weighted magnetic resonance imaging in evaluating the efficacy of radiotherapy and chemotherapy for esophageal cancer]

This study was a prospective single arm trial conducted in Zhejiang Jinhua Guangfu hospital from February 2018 to June 2020. A total of 39 patients (32 males and 7 females) with esophageal cancer, aged from 44 to 82 (69±9) years were enrolled. Diffusion weighted magnetic resonance imaging(MR-DWI) was implemented to evaluate the changes of apparent diffusion coefficient(ADC) value before and after chemoradiotherapy. The results showed that the ADC value after chemoradiotherapy was higher than that before treatment[(2.03±0.42)×10⁻³ mm ²/s vs (1.60±0.28)×10⁻³ mm²/s], and there was a positive correlation between the increase of ADC value and the prognosis of patients.

Folate hydrolase-1 (FOLH1) is a novel target for antibody-based brachytherapy in Merkel cell carcinoma

Backgrounds

Folate Hydrolase‐1 (FOLH1; PSMA) is a type II transmembrane protein, luminally expressed by solid tumour neo‐vasculature. Monoclonal antibody (mAb), J591, is a vehicle for mAb‐based brachytherapy in FOLH1+ cancers. Brachytherapy is a form of radiotherapy that involves placing a radioactive material a short distance from the target tissue (e.g., on the skin or internally); brachytherapy is commonly accomplished with the use of catheters, needles, metal seeds and antibody or small peptide conjugates. Herein, FOLH1 expression in primary (p) and metastatic (m) Merkel cell carcinoma (MCC) is characterized to determine its targeting potential for J591‐brachytherapy.

Materials & Methods

Paraffin sections from pMCC and mMCC were evaluated by immunohistochemistry for FOLH1. Monte Carlo simulation was performed using the physical properties of conjugated radioisotope lutetium‐177. Kaplan–Meier survival curves were calculated based on patient outcome data and FOLH1 expression.

Results

Eighty‐one MCC tumours were evaluated. 67% (54/81) of all cases, 77% (24/31) pMCC and 60% (30/50) mMCC tumours were FOLH1+. Monte Carlo simulation showed highly localized ionizing tracks of electrons emitted from the targeted neo‐vessel. 42% (34/81) of patients with FOLH1+/− MCC had available survival data for analysis. No significant differences in our limited data set were detected based on FOLH1 status (p = 0.4718; p = 0.6470), staining intensity score (p = 0.6966; p = 0.9841) or by grouping staining intensity scores (− and + vs. ++, +++, +++) (p = 0.8022; p = 0.8496) for MCC‐specific survival or recurrence free survival, respectively.

Conclusions

We report the first evidence of prevalent FOLH1 expression within MCC‐associated neo‐vessels, in 60‐77% of patients in a large MCC cohort. Given this data, and the need for alternatives to immune therapies it is appropriate to explore the safety and efficacy of FOLH1‐targeted brachytherapy for MCC.

What's already known about this topic?

We report the first evidence of prevalent folate hydrolase‐1 (FOLH1; also known as prostate‐specific membrane antigen) expression within MCC‐associated neovessels.

What does this study add?

Herein, FOLH1 expression in Merkel cell carcinoma neovasculature is validated, and the therapeutic mechanism of specific, systemic targeting of disseminated disease with antibody‐based brachytherapy, is defined.

Effect of menopausal symptom treatment options on palpitations: a systematic review

This systematic review provides an overview of the effects of menopausal symptom treatment options on palpitations, defined as feelings of missed or exaggerated heart beats, reported by perimenopausal and postmenopausal women. Guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, searches were conducted in PubMed, CINAHL and PsycINFO to identify articles meeting pre-specified inclusion criteria. Of 670 unique articles identified, 37 were included in the review. Treatments included drug therapies and non-drug therapies. Palpitations were studied as an outcome in 89% of articles and as an adverse effect in 11%. Articles provided mostly level II/III evidence due to their design and/or small sample sizes. Based on available evidence, no therapies can be fully recommended for clinical practice. Only some hormonal agents (e.g. estradiol) can be recommended with caution based on some positive evidence for reducing palpitation prevalence or severity. However, other drug therapies (e.g. moxonidine, atenolol), dietary supplementary treatments (e.g. isoflavones, Rheum rhaponticum, sage), cognitive-behavioral intervention and auricular acupressure cannot be recommended given the existing evidence. Additional well-designed randomized controlled treatment trials focusing on palpitations during the menopause transition as an inclusion criteria and outcome are needed to advance the field.

Correlative multi-scale cryo-imaging unveils SARS-CoV-2 assembly and egress

Since the outbreak of the SARS-CoV-2 pandemic, there have been intense structural studies on purified viral components and inactivated viruses. However, structural and ultrastructural evidence on how the SARS-CoV-2 infection progresses in the native cellular context is scarce, and there is a lack of comprehensive knowledge on the SARS-CoV-2 replicative cycle. To correlate cytopathic events induced by SARS-CoV-2 with virus replication processes in frozen-hydrated cells, we established a unique multi-modal, multi-scale cryo-correlative platform to image SARS-CoV-2 infection in Vero cells. This platform combines serial cryoFIB/SEM volume imaging and soft X-ray cryo-tomography with cell lamellae-based cryo-electron tomography (cryoET) and subtomogram averaging. Here we report critical SARS-CoV-2 structural events - e.g. viral RNA transport portals, virus assembly intermediates, virus egress pathway, and native virus spike structures, in the context of whole-cell volumes revealing drastic cytppathic changes. This integrated approach allows a holistic view of SARS-CoV-2 infection, from the whole cell to individual molecules.

Correlative Multi-scale Cryo-imaging Unveils SARS-CoV-2 Assembly and Egress

Since the outbreak of the SARS-CoV-2 pandemic, there have been intense structural studies on purified recombinant viral components and inactivated viruses. However, structural and ultrastructural evidence on how the SARS-CoV-2 infection progresses in the frozen-hydrated native cellular context is scarce, and there is a lack of comprehensive knowledge on the SARS-CoV-2 replicative cycle. To correlate the cytopathic events induced by SARS-CoV-2 with virus replication process under the frozen-hydrated condition, here we established a unique multi-modal, multi-scale cryo-correlative platform to image SARS-CoV-2 infection in Vero cells. This platform combines serial cryoFIB/SEM volume imaging and soft X-ray cryo-tomography with cell lamellae-based cryo-electron tomography (cryoET) and subtomogram averaging. The results place critical SARS-CoV-2 structural events – e.g. viral RNA transport portals on double membrane vesicles, virus assembly and budding intermediates, virus egress pathways, and native virus spike structures from intracellular assembled and extracellular released virus - in the context of whole-cell images. The latter revealed numerous heterogeneous cytoplasmic vesicles, the formation of membrane tunnels through which viruses exit, and the drastic cytoplasm invasion into the nucleus. This integrated approach allows a holistic view of SARS-CoV-2 infection, from the whole cell to individual molecules.

SARS-CoV-2 Assembly and Egress Pathway Revealed by Correlative Multi-modal Multi-scale Cryo-imaging

Since the outbreak of the SARS-CoV-2 pandemic, there have been intense structural studies on purified recombinant viral components and inactivated viruses. However, investigation of the SARS-CoV-2 infection in the native cellular context is scarce, and there is a lack of comprehensive knowledge on SARS-CoV-2 replicative cycle. Understanding the genome replication, assembly and egress of SARS-CoV-2, a multistage process that involves different cellular compartments and the activity of many viral and cellular proteins, is critically important as it bears the means of medical intervention to stop infection. Here, we investigated SARS-CoV-2 replication in Vero cells under the near-native frozen-hydrated condition using a unique correlative multi-modal, multi-scale cryo-imaging approach combining soft X-ray cryo-tomography and serial cryoFIB/SEM volume imaging of the entire SARS-CoV-2 infected cell with cryo-electron tomography (cryoET) of cellular lamellae and cell periphery, as well as structure determination of viral components by subtomogram averaging. Our results reveal at the whole cell level profound cytopathic effects of SARS-CoV-2 infection, exemplified by a large amount of heterogeneous vesicles in the cytoplasm for RNA synthesis and virus assembly, formation of membrane tunnels through which viruses exit, and drastic cytoplasm invasion into nucleus. Furthermore, cryoET of cell lamellae reveals how viral RNAs are transported from double-membrane vesicles where they are synthesized to viral assembly sites; how viral spikes and RNPs assist in virus assembly and budding; and how fully assembled virus particles exit the cell, thus stablishing a model of SARS-CoV-2 genome replication, virus assembly and egress pathways.

Superior rectal artery embolization for bleeding internal hemorrhoids

BACKGROUND

The aim of the present study was to evaluate clinical efficacy and safety of superselective embolization of the superior rectal artery (SRA) for the treatment of internal hemorrhoidal bleeding.

METHODS

Patients with stage II and stage III internal hemorrhoids, treated by interventional embolization of the SRA in our department between January 2017 and June 2019 were retrospectively evaluated. All patients suffering from disabling chronic hematochezia and some with relative contraindications for operation (n = 17) or rejection of conventional hemorrhoidectomy (n = 15). Superselective SRA branch embolization was performed using gelatin sponge particles (350-560 μm) and metallic coils (2-3 mm). This treatment process was planned by a multidisciplinary team consisting of proctologist, gastroenterologist and radiologist. The surgical efficacy, postoperative complications and follow-up outcomes were observed.

RESULTS

There were 32 patients (18 males, mean age 52 ± 12 years, range: 22-78 years), 12 (37%) with stage II hemorrhoids and 20 (63%) with stage III hemorrhoids. Embolization was successful in all patients, and bleeding symptoms resolved in 27 (84.4%) patients. The remaining 5 (15.6%) patients underwent either stapled hemorrhoidopexy (n = 4) or sclerotherapy (n = 1). Some patients experienced different degrees of pain (n = 4;12.5%), low fever (n = 11;34.4%), and tenesmus (n = 17;53.1%), which all spontaneously regressed without further treatment. All patients were followed up for at least 1 year. There were no serious complications, such as infection, intestinal ischemia or massive hemorrhage. Four patients (14.8%) had rebleeding during the first months of follow-up. All patients with re-bleeding were successfully treated with internal iliac arteriography and branch embolization and did not experience further bleeds after a minimum follow up 3 months follow-up.

CONCLUSIONS

The short-term efficacy of superselective SRA embolization for grade II-III internal hemorrhoids is good, and this method is safe and feasible.

Cyclophosphamide induces a significant increase in iron content in the liver and spleen of mice

Objective:

Oxidative stress is one of the major mechanisms of cyclophosphamide (CPX)-induced toxicities. However, it is unknown how CPX induces oxidative stress. Based on the available information, we speculated that CPX could increase iron content in the tissues and then induce oxidative stress.

Method:

We tested this hypothesis by investigating the effects of CPX on iron and ferritin contents, expression of transferrin receptor 1 (TfR1), ferroportin 1 (Fpn1), iron regulatory proteins (IRPs), hepcidin, and nuclear factor erythroid 2-related factor-2 (Nrf2) in the liver and spleen, and also on reticulocyte count, immature reticulocyte fraction, and hemoglobin (Hb) in the blood in c57/B6 mouse.

Results:

We demonstrated that CPX could induce a significant increase in iron contents and ferritin expression in the liver and spleen, notably inhibit erythropoiesis and Hb synthesis and lead to a reduction in iron usage. The reduced expression in TfR1 and Fpn1 is a secondary effect of CPX-induced iron accumulation in the liver and spleen and also partly associated with the suppressed IRP/iron-responsive element system, upregulation of hepcidin, and downregulation of Nrf2.

Conclusions:

The reduced iron usage is one of the causes for iron overload in the liver and spleen and the increased tissue iron might be one of the mechanisms for CPX to induce oxidative stress and toxicities.

Atomic structure and defect dynamics of monolayer lead iodide nanodisks with epitaxial alignment on graphene

Lead Iodide (PbI2) is a large bandgap 2D layered material that has potential for semiconductor applications. However, atomic level study of PbI2 monolayer has been limited due to challenges in obtaining thin crystals. Here, we use liquid exfoliation to produce monolayer PbI2 nanodisks (30-40 nm in diameter and > 99% monolayer purity) and deposit them onto suspended graphene supports to enable atomic structure study of PbI2. Strong epitaxial alignment of PbI2 monolayers with the underlying graphene lattice occurs, leading to a phase shift from the 1 T to 1 H structure to increase the level of commensuration in the two lattice spacings. The fundamental point vacancy and nanopore structures in PbI2 monolayers are directly imaged, showing rapid vacancy migration and self-healing. These results provide a detailed insight into the atomic structure of monolayer PbI2, and the impact of the strong van der Waals interaction with graphene, which has importance for future applications in optoelectronics.

Controlling Defects in Continuous 2D GaS Films for High-Performance Wavelength-Tunable UV-Discriminating Photodetectors

A chemical vapor deposition method is developed for thickness-controlled (one to four layers), uniform, and continuous films of both defective gallium(II) sulfide (GaS): GaS_0.87 and stoichiometric GaS. The unique degradation mechanism of GaS_0.87 with X-ray photoelectron spectroscopy and annular dark-field scanning transmission electron microscopy is studied, and it is found that the poor stability and weak optical signal from GaS are strongly related to photo-induced oxidation at defects. An enhanced stability of the stoichiometric GaS is demonstrated under laser and strong UV light, and by controlling defects in GaS, the photoresponse range can be changed from vis-to-UV to UV-discriminating. The stoichiometric GaS is suitable for large-scale, UV-sensitive, high-performance photodetector arrays for information encoding under large vis-light noise, with short response time (<66 ms), excellent UV photoresponsivity (4.7 A W^-1 for trilayer GaS), and 26-times increase of signal-to-noise ratio compared with small-bandgap 2D semiconductors. By comprehensive characterizations from atomic-scale structures to large-scale device performances in 2D semiconductors, the study provides insights into the role of defects, the importance of neglected material-quality control, and how to enhance device performance, and both layer-controlled defective GaS_0.87 and stoichiometric GaS prove to be promising platforms for study of novel phenomena and new applications.

Controlling Photoluminescence Enhancement and Energy Transfer in WS2 :hBN:WS2 Vertical Stacks by Precise Interlayer Distances

2D semiconducting transition metal dichalcogenides (TMDs) are endowed with fascinating optical properties especially in their monolayer limit. Insulating hBN films possessing customizable thickness can act as a separation barrier to dictate the interactions between TMDs. In this work, vertical layered heterostructures (VLHs) of WS₂ :hBN:WS₂ are fabricated utilizing chemical vapor deposition (CVD)-grown materials, and the optical performance is evaluated through photoluminescence (PL) spectroscopy. Apart from the prohibited indirect optical transition due to the insertion of hBN spacers, the variation in the doping level of WS₂ drives energy transfer to arise from the layer with lower quantum efficiency to the other layer with higher quantum efficiency, whereby the total PL yield of the heterosystem is increased and the stack exhibits a higher PL intensity compared to the sum of those in the two WS₂ constituents. Such doping effects originate from the interfaces that WS₂ monolayers reside on and interact with. The electron density in the WS₂ is also controlled and subsequent modulation of PL in the heterostructure is demonstrated by applying back-gated voltages. Other influential factors include the strain in WS₂ and temperature. Being able to tune the energy transfer in the VLHs may expand the development of photonic applications in 2D systems.

Ultrathin All-2D Lateral Graphene/GaS/Graphene UV Photodetectors by Direct CVD Growth

UV-sensitive lateral all-two-dimensional (2D) photodetecting devices are produced by growing the large band gap layered GaS between graphene electrode pairs directly using chemical vapor deposition methods. The use of prepatterned graphene electrode pairs on the Si wafer enables more than 200 devices to be fabricated simultaneously. We show that the surface chemistry of the substrate during GaS leads to selective growth in graphene gaps, forming the lateral heterostructures, rather than on the surface of graphene. The graphene/GaS/graphene lateral photodetecting devices are demonstrated to be sensitive to UV light only, with no measurable response to visible light. Furthermore, we demonstrate UV-band discrimination in photosensing, with measured photocurrents only produced for middle-UV and not for near-UV wavelength regions. The detection limit could reach down to 2.61 μW/cm² with a photoresponsivity as high as 11.7 A/W and a photo gain of 53.7 under 270 nm excitation. Gate-dependent modulation of the photocurrent is also demonstrated. The photodetectors exhibit long-term stability and reproducible ON-OFF switching behavior, with a response time lower than 60 ms. These results provide insights into how ultrathin UV sensing devices can be created using only 2D materials by exploiting large band gap 2D semiconductors such as GaS.

Direct Laser Patterning and Phase Transformation of 2D PdSe2 Films for On-Demand Device Fabrication

Heterophase homojunction formation in atomically thin 2D layers is of great importance for next-generation nanoelectronics and optoelectronics applications. Technologically challenging, controllable transformation between the semiconducting and metallic phases of transition metal chalcogenides is of particular importance. Here, we demonstrate that controlled laser irradiation can be used to directly ablate PdSe₂ thin films using high power or trigger the local transformation of PdSe₂ into a metallic phase PdSe_2-x using lower laser power. Such transformations are possible due to the low decomposition temperature of PdSe₂ and a variety of stable phases compared to other 2D transition metal dichalcogenides. Scanning transmission electron microscopy is used to reveal the laser-induced Se-deficient phases of PdSe₂ material. The process sensitivity to the laser power allows patterning flexibility for resist-free device fabrication. The laser-patterned devices demonstrate that a laser-induced metallic phase PdSe_2-x is stable with increased conductivity by a factor of about 20 compared to PdSe₂. These findings contribute to the development of nanoscale devices with homojunctions and scalable methods to achieve structural transformations in 2D materials.

Photocurrent Direction Control and Increased Photovoltaic Effects in All-2D Ultrathin Vertical Heterostructures Using Asymmetric h-BN Tunneling Barriers

Two-dimensional (2D) materials are atomically thick and without out-of-plane dangling bonds. As a result, they could break the confinement of lattice matching, and thus can be freely mixed and matched together to construct vertical van der Waals heterostructures. Here, we demonstrated an asymmetrical vertical structure of graphene/hexagonal boron nitride (h-BN)/tungsten disulfide (WS₂)/graphene using all chemical vapor deposition grown 2D materials. Three building blocks are utilized in this construction: conductive graphene as a good alternative for the metal electrode due to its tunable Fermi level and ultrathin nature, semiconducting transition-metal dichalcogenides (TMDs) as an ultrathin photoactive material, and insulating h-BNas a tunneling barrier. Such an asymmetrical vertical structure exhibits a much stronger photovoltaic effect than the symmetrical vertical one without h-BN. By changing the sequence of h-BN in the vertical stack, we could even control the electron flow direction. Also, improvement has been further made by increasing the thickness of h-BN. The photovoltaic effect is attributed to different possibilities of excited electrons on TMDs to migrate to top and bottom graphene electrodes, which is caused by potential differences introduced by an insulating h-BN layer. This study shows that h-BN could be effectively used as a tunneling barrier in the asymmetrical vertical heterostructure to improve photovoltaic effect and control the electron flow direction, which is crucial for the design of other 2D vertical heterostructures to meet various needs of electronic and optoelectronic devices.

Postgrowth Substitutional Tin Doping of 2D WS2 Crystals Using Chemical Vapor Deposition

Doping of two-dimensional materials provides them tunable physical properties and widens their applications. Here, we demonstrate the postgrowth doping strategy in monolayer and bilayer tungsten disulfide (WS₂) crystals, which utilizes a metal exchange mechanism, whereby Sn atoms become substitutional dopants in the W sites by energetically favorable replacement. We achieve this using chemical vapor deposition techniques, where high-quality grown WS₂ single crystals are first grown and then subsequently reacted with a SnS precursor. Thermal control of the exchange doping mechanism is revealed, indicating that a sufficiently high enough temperature is required to create the S vacancies that are the initial binding sites for the SnS precursor and metal exchange occurrence. This results in a better control of dopant distribution compared to the tradition all-in-one approach, where dopants are added during the growth phase. The Sn dopants exhibit an n-type doping behavior in the WS₂ layers based on the decreased threshold voltage obtained from transistor device measurements. Annular dark-field scanning transmission electron microscopy shows that in bilayer WS₂ the Sn doping occurs only in the top layer, creating vertical heterostructures with atomic layer doping precision. This postgrowth modification opens up ways to selectively dope one layer at a time and construct mixed stoichiometry vertical heterojunctions in bilayer crystals.

Metal Atom Markers for Imaging Epitaxial Molecular Self-Assembly on Graphene by Scanning Transmission Electron Microscopy

Direct imaging of single molecules has to date been primarily achieved using scanning probe microscopy, with limited success using transmission electron microscopy due to electron beam damage and low contrast from the light elements that make up the majority of molecules. Here, we show single complex molecule interactions can be imaged using annular dark field scanning TEM (ADF-STEM) by inserting heavy metal markers of Pt atoms and detecting their positions. Using the high angle ADF-STEM Z^1.7 contrast, combined with graphene as an electron transparent support, we track the 2D monolayer self-assembly of solution-deposited individual linear porphyrin hexamer (Pt-L6) molecules and reveal preferential alignment along the graphene zigzag direction. The epitaxial interactions between graphene and Pt-L6 drive a reduction in the interporphyrin distance to allow perfect commensuration with the graphene. These results demonstrate how single metal atom markers in complex molecules can be used to study large scale packing and chain bending at the single molecule level.

High-Performance WS2 Monolayer Light-Emitting Tunneling Devices Using 2D Materials Grown by Chemical Vapor Deposition

The solid progress in the study of a single two-dimensional (2D) material underpins the development for creating 2D material assemblies with various electronic and optoelectronic properties. We introduce an asymmetric structure by stacking monolayer semiconducting tungsten disulfide, metallic graphene, and insulating boron nitride to fabricate numerous red channel light-emitting devices (LEDs). All the 2D crystals were grown by chemical vapor deposition (CVD), which has great potential for future industrial scale-up. Our LEDs exhibit visibly observable electroluminescence (EL) at both 5.5 V forward and 7.0 V backward biasing, which correlates well with our asymmetric design. The red emission can last for at least several minutes, and the success rate of the working device that can emit detectable EL is up to 80%. In addition, we show that sample degradation is prone to happen when a continuing bias, much higher than the threshold voltage, is applied. Our success of using high-quality CVD-grown 2D materials for red light emitters is expected to provide the basis for flexible and transparent displays.

MoS2 Liquid Cell Electron Microscopy Through Clean and Fast Polymer-Free MoS2 Transfer

Two dimensional (2D) materials have found various applications because of their unique physical properties. For example, graphene has been used as the electron transparent membrane for liquid cell transmission electron microscopy (TEM) due to its high mechanical strength and flexibility, single-atom thickness, chemical inertness, etc. Here, we report using 2D MoS₂ as a functional substrate as well as the membrane window for liquid cell TEM, which is enabled by our facile and polymer-free MoS₂ transfer process. This provides the opportunity to investigate the growth of Pt nanocrystals on MoS₂ substrates, which elucidates the formation mechanisms of such heterostructured 2D materials. We find that Pt nanocrystals formed in MoS₂ liquid cells have a strong tendency to align their crystal lattice with that of MoS₂, suggesting a van der Waals epitaxial relationship. Importantly, we can study its impact on the kinetics of the nanocrystal formation. The development of MoS₂ liquid cells will allow further study of various liquid phenomena on MoS₂, and the polymer-free MoS₂ transfer process will be implemented in a wide range of applications.

Abstract P1-02-10: Early stage breast cancer screening using an emerging novel liquid biopsy screening technology

Background: An emerging novel liquid biopsy technology called Cancer Differentiation Analysis (CDA) has been evaluated as a viable early stage breast cancer screening tool. CDA technology is a blood-sample based, multi-level, multi-parameter diagnostic method which detects signals from both protein, cellular, and to some extent, molecular levels, in which multiple aspects of information can be collected to improve diagnostic accuracy, even for early stage of cancer. Improving capability to screen breast cancer is an important on-going research effort, as breast cancer represents a leading cancer with high incidence rate.

Methods: In this single-blind study, 22 breast cancer patients and 25 healthy individuals were recruited at Changhai Hospital of Shanghai. Histopathological examination results of breast cancer patients were collected, 22 cases were diagnosed as infiltrating ductal carcinoma of breast, of which 10 patients were stage I breast cancer. 25 individuals were confirmed healthy after physical examinations. Peripheral blood was drawn in EDTA tubes For CDA tests. CDA data of 22 breast cancer patients and 25 healthy individuals were conducted using SPSS, and the results were shown in the table below.

Results: The average CDA of breast cancer, stageIbreast cancer, and controls were 43.20, 44.17 and 36.17 (rel. units) respectively as shown in Table 1. Both breast cancer and stage I breast cancer could be significantly distinguished from the control (p = 0.000, p = 0.001, respectively). For stage I breast cancer vs. control group, Area under ROC curve was 0.876, sensitivity and specificity were both 80.0% (Table 2). In contrast to traditional breast cancer screening methodologies which have relatively low sensitivity and high false positives for stage I detection, often with radiation side effects and high costs, advantages of CDA technology include ability to detect early stage cancer with relatively high sensitivity and specificity, and it is also highly cost effective without side effects.

Conclusions: Initial results showed that CDA technology could effectively distinguish stageIbreast cancer from healthy individuals, CDA could be a potential candidate for breast cancer screening.

Table 1Summary of CDA test resultsGroupSample SizeAge RangeAge MeanAge MedianCDA Mean (rel. units)CDA Median (rel. units)CDA STDEVControl2523 - 67413735.6336.176.98Breast Cancer2239 - 78545343.2042.304.18Stage I Breast Cancer1043 - 78595944.1743.254.29Stage II Breast Cancer839 - 55474941.2840.303.06Stage III Breast Cancer255555542.2042.202.12Stage IV Breast Cancer251 - 64585847.0047.007.78

Table 2AUC, Sensitivity and Specificity of Control vs. Stage I breast cancerStage I Breast Cancer vs. ControlArea Under the CurveSensitivitySpecificity 0.87680.0%80.0%

Citation Format: Liu C, Dou J, Sheng Y, Wu J, Hu W, Li Y, Lin Y, Tao H, Tang X, Du X, Yu C. Early stage breast cancer screening using an emerging novel liquid biopsy screening technology [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-02-10.

Abstract P1-02-09: CDA screening technology for multi-ethnic group, early stage breast cancer screening

Background: Breast cancer is the second leading cause of death from cancer in American women. Current breast cancer screening technologies have issues with poor sensitivity for early stage breast cancer, high false positives, radiation side effects, etc. Cancer Differentiation Analysis (CDA) technology is a blood-sample based, multi-level, multi-parameter diagnostic method which detects signals from both proteins, cells, and to some extent, molecular level, in which multiple aspects of information are collected to improve diagnostic accuracy. CDA technology has been investigated as a viable clinical utility in breast cancer screening, particularly for early stage breast screening with clear advantages (both whole blood and serum can be used, ability to detect early, easy, simple, no side effects, and high degree of sensitivity and specificity).

Methods: In this study, the human subjects involved are Caucasians, with serum samples of 44 pathologically confirmed breast cancer patients and 34 healthy individuals from 3 blood bank centers in the USA, of which 40 cases were stageIbreast cancer, 2 cases were stageII, and the other 2 cases were stage III breast cancer. CDA data of 44 breast cancer patients and 34 healthy individuals were collected in US lab and analyzed using SPSS, and the results were shown in the table below. Results from the above study was compared with a clinical study on Asian group with data collected in lab in China using CDA technology.

Results: The average CDA value of all breast cancer and stageIbreast cancer samples, and controls were 45.99, 45.76 and 42.36 (rel. units) respectively (see Table 1). Both breast cancer and stageIbreast cancer could be significantly distinguished from the control group (p &lt; 0.001) (Table 2). For stageIbreast cancer vs. control group, Area under ROC curve was 0.727, sensitivity and specificity were 62.5% and 82.4% respectively, which is higher than a typical mammogram. To compare with different ethnic groups, data collected on an Asian group is also shown in Table 2, which showed that overall, AUC, sensitivity and specificity are comparable (some difference may be attributed to sample type difference (whole blood vs. serum)) for early stage breast cancer patients for those two ethnic groups, demonstrating that CDA technology can be extended to multiple ethnic groups.

Conclusions: CDA screening can be extended to different ethnic group including Caucasian and Asian with good sensitivity and specificity for stageIbreast cancer.

We thank Ugur Basmaci, Sunsil Pandit and Sharon Vorse-Yu for their support.

Table 1Summary of CDA Test ResultsGroupSample SizeAge RangeAge MeanAge MedianCDA Mean (rel. units)CDA Median (rel. units)CDA STDEVControl3436 -79575742.3642.652.75Breast Cancer4436 – 77606145.9946.504.22Stage I Breast Cancer4036 – 77606145.7645.554.26Stage II Breast Cancer251 – 64585847.0547.054.88Stage III Breast Cancer262 – 75696949.5049.502.55

Table 2AUC, Sensitivity and Specificity of Control vs. Stage I Breast CancerStage I Breast Cancer vs. ControlArea Under the CurveSensitivitySpecificityCaucasian (Stage I)0.72762.5%82.4%Asian# (Stage I)0.87680.0%80.0%# Whole blood samples. 10 stage I breast cancer samples and 25 control samples

Citation Format: Tao H, Lin Y, Liu C, Dou J, Sheng Y, Wu J, Hu W, Li Y, Tang X, Yu C, Du X. CDA screening technology for multi-ethnic group, early stage breast cancer screening [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-02-09.

High Photoresponsivity in Ultrathin 2D Lateral Graphene:WS2:Graphene Photodetectors Using Direct CVD Growth

We show that reducing the degree of van der Waals overlapping in all 2D ultrathin lateral devices composed of graphene:WS₂:graphene leads to significant increase in photodetector responsivity. This is achieved by directly growing WS₂ using chemical vapor deposition (CVD) in prepatterned graphene gaps to create epitaxial interfaces. Direct-CVD-grown graphene:WS₂:graphene lateral photodetecting transistors exhibit high photoresponsivities reaching 121 A/W under 2.7 × 10⁵ mW/cm² 532 nm illumination, which is around 2 orders of magnitude higher than similar devices made by the layer-by-layer transfer method. The photoresponsivity of our direct-CVD-grown device shows negative correlation with illumination power under different gate voltages, which is different from similar devices made by the transfer method. We show that the high photoresponsivity is due to the lowering of effective Schottky barrier height by improving the contact between graphene and WS₂. Furthermore, the direct CVD growth reduces overlapping sections of WS₂:Gr and leads to more uniform lateral systems. This approach provides insights into scalable manufacturing of high-quality 2D lateral electronic and optoelectronic devices.

Symmetry-Controlled Reversible Photovoltaic Current Flow in Ultrathin All 2D Vertically Stacked Graphene/MoS2/WS2/Graphene Devices

Atomically thin vertical heterostructures are promising candidates for optoelectronic applications, especially for flexible and transparent technologies. Here, we show how ultrathin all two-dimensional vertical-stacked type-II heterostructure devices can be assembled using only materials grown by chemical vapor deposition, with graphene (Gr) as top and bottom electrodes and MoS₂/WS₂ as the active semiconductor layers in the middle. Furthermore, we show that the stack symmetry, which dictates the type-II directionality, is the dominant factor in controlling the photocurrent direction upon light irradiation, whereas in homobilayers, photocurrent direction cannot be easily controlled because the tunnel barrier is determined by the doping levels of the graphene, which appears fixed for top and bottom graphene layers due to their dielectric environments. Therefore, the ability to direct photovoltaic current flow is demonstrated to be only possible using heterobilayers (HBs) and not homobilayers. We study the photovoltaic effects in more than 40 devices, which allows for statistical verification of performance and comparative behavior. The photovoltage in the graphene/transition-metal dichalcogenide-heterobilayer/graphene (Gr/TMD-HB (MoS₂/WS₂)/Gr) increases up to 10 times that generated in the monolayer TMD devices under the same optical illumination power, due to efficient charge transfer between WS₂ and MoS₂ and extraction to graphene electrodes. By applying external gate voltages ( V_g), the band alignment can be tuned, which in turn controls the photovoltaic effect in the vertical heterostructures. The tunneling-assisted interlayer charge recombination also plays a significant role in modulating the photovoltaic effect in the Gr/TMD-HB/Gr. These results provide important insights into how layer symmetry in vertical-stacked graphene/TMD/graphene ultrathin optoelectronics can be used to control electron flow directions during photoexcitation and open up opportunities for tandem cell assembly.

Geometrically Enhanced Thermoelectric Effects in Graphene Nanoconstrictions

The influence of nanostructuring and quantum confinement on the thermoelectric properties of materials has been extensively studied. While this has made possible multiple breakthroughs in the achievable figure of merit, classical confinement, and its effect on the local Seebeck coefficient has mostly been neglected, as has the Peltier effect in general due to the complexity of measuring small temperature gradients locally. Here we report that reducing the width of a graphene channel to 100 nm changes the Seebeck coefficient by orders of magnitude. Using a scanning thermal microscope allows us to probe the local temperature of electrically contacted graphene two-terminal devices or to locally heat the sample. We show that constrictions in mono- and bilayer graphene facilitate a spatially correlated gradient in the Seebeck and Peltier coefficient, as evidenced by the pronounced thermovoltage V_th and heating/cooling response Δ T_Peltier, respectively. This geometry dependent effect, which has not been reported previously in 2D materials, has important implications for measurements of patterned nanostructures in graphene and points to novel solutions for effective thermal management in electronic graphene devices or concepts for single material thermocouples.

[Rosai-Dorfman disease with nasal septum involvement:two cases report]

Clinical data of 2 cases with Rosai-Dorfman disease(RDD) originating from nasal septal mucosa were reported retrospectively,and the pertinent literature was reviewed. Without specific clinical features,RDD in nasal cavity could be misdiagnosed easily. Pathology revealed different morphologies of cell proliferation with engulfed lymphocytes,plasma cells and neutrophils. Immunohistochemical staining showed S-100(+),CD68(+)，CD1(-).RDD disease generally has a benign course and is self-limited. Its diagnosis depends mainly on biopsy．As for the treatment of this disease,the strategies are not systemic and standard. Surgical treatment is used to excise the mass in nasal cavity,glucocorticoids treatment after surgery is inconclusive. The long-term effect need to be further observed．.

Inhomogeneous Strain Release during Bending of WS2 on Flexible Substrates

Two-dimensional (2D) materials hold great promise in flexible electronics, but the weak van der Waals interlayer bonding may pose a problem during bending, where easy interlayer sliding can occur. Furthermore, thin films of rigid materials are often observed to delaminate from soft substrates during straining. Here, we study the influence of substrate strain on some of the heterostructure configurations we expect to find in devices, composed of three common 2D materials: graphene, tungsten disulfide, and boron nitride. We used photoluminescence (PL) spectroscopy to measure changes in the heterostructures with strain applied in situ. All heterostructures were fabricated directly on polymer substrates, using materials synthesized by chemical vapor deposition. We observed an inhomogeneous release of strain in all structures, leading to a nonrecoverable broadening of the PL peak and shift of the bandgap. This suggests the need for preconditioning devices before service to ensure stable behavior. A gradual time-dependent relaxation of strain between strain cycles was characterized using time-dependent measurements-an effect which could lead to drift of device behavior during operation. Furthermore, possible degradation was assessed by performing the strain and relax the cycle up to 200 times, where we found little further change after the initial shifts had stabilized. These results have important ramifications for devices fabricated from these and other 2D materials, as they suggest extra processing steps and considerations that must be taken to achieve consistent and stable properties.