b-MAR: bidirectional artifact representations learning framework for metal artifact reduction in dental CBCT.

OBJECTIVE: Metal artifacts in computed tomography (CT) images hinder diagnosis and treatment significantly. Specifically, dental cone-beam computed tomography (Dental CBCT) images are seriously contaminated by metal artifacts due to the widespread use of low tube voltages and the presence of various high-attenuation materials in dental structures. Existing supervised metal artifact reduction (MAR) methods mainly learn the mapping of artifact-affected images to clean images, while ignoring the modeling of the metal artifact generation process. Therefore, we propose the bidirectional artifact representations learning framework to adaptively encode metal artifacts caused by various dental implants and model the generation and elimination of metal artifacts, thereby improving MAR performance. Approach. we introduce an efficient artifact encoder to extract multi-scale representations of metal artifacts from artifact-affected images. These extracted metal artifact representations are then bidirectionally embedded into both the metal artifact generator and the metal artifact eliminator, which can simultaneously improve the performance of artifact removal and artifact generation. The artifact eliminator learns artifact removal in a supervised manner, while the artifact generator learns artifact generation in an adversarial manner. To further improve the performance of the bidirectional task networks, we propose artifact consistency loss to align the consistency of images generated by the eliminator and the generator with or without embedding artifact representations. Main results. To validate the effectiveness of our algorithm, experiments are conducted on simulated and clinical datasets containing various dental metal morphologies. Quantitative metrics are calculated to evaluate the results of the simulation tests,which demonstrate b-MAR improvements of > 1.4131 dB in PSNR, > 0.3473 HU decrements in RMSE, and > 0.0025 promotion in SSIM over the current state-of-the-art MAR methods. All results indicate that the proposed b-MAR method can remove artifacts caused by various metal morphologies and restore the structural integrity of dental tissues effectively. Significance. The proposed b-MAR method strengthens the joint learning of the artifact removal process and the artifact generation process by bidirectionally embedding artifact representations, thereby improving the model's artifact removal performance. Compared with other comparison methods, b-MAR can robustly and effectively correct metal artifacts in dental CBCT images caused by different dental metals.

Physics-informed sinogram completion for metal artifact reduction in CT imaging.

Objective.Metal artifacts in the computed tomography (CT) imaging are unavoidably adverse to the clinical diagnosis and treatment outcomes. Most metal artifact reduction (MAR) methods easily result in the over-smoothing problem and loss of structure details near the metal implants, especially for these metal implants with irregular elongated shapes. To address this problem, we present the physics-informed sinogram completion (PISC) method for MAR in CT imaging, to reduce metal artifacts and recover more structural textures.Approach.Specifically, the original uncorrected sinogram is firstly completed by the normalized linear interpolation algorithm to reduce metal artifacts. Simultaneously, the uncorrected sinogram is also corrected based on the beam-hardening correction physical model, to recover the latent structure information in metal trajectory region by leveraging the attenuation characteristics of different materials. Both corrected sinograms are fused with the pixel-wise adaptive weights, which are manually designed according to the shape and material information of metal implants. To furtherly reduce artifacts and improve the CT image quality, a post-processing frequency split algorithm is adopted to yield the final corrected CT image after reconstructing the fused sinogram.Main results.We qualitatively and quantitatively evaluated the presented PISC method on two simulated datasets and three real datasets. All results demonstrate that the presented PISC method can effectively correct the metal implants with various shapes and materials, in terms of artifact suppression and structure preservation.Significance.We proposed a sinogram-domain MAR method to compensate for the over-smoothing problem existing in most MAR methods by taking advantage of the physical prior knowledge, which has the potential to improve the performance of the deep learning based MAR approaches.

Duyun compound green tea extracts regulate bile acid metabolism on mice induced by high-fat diet.

Duyun compound green tea (DCGT) is a healthy beverage with lipid-lowering effect commonly consumed by local people, but its mechanism is not very clear. We evaluated the effect of DCGT treatment on bile acids (BA) metabolism of mice with high-fat diet (HFD) - induced hyperlipidaemia by biochemical indexes and metabolomics and preliminarily determined the potential biomarkers and metabolic pathways of hyperlipidaemia mice treated with DCGT as well as investigated its lipid-lowering mechanism. The results showed that DCGT treatment could reduce HFD - induced gain in weight and improve dyslipidaemia. In addition, a total of ten types of BA were detected, of which seven changed BA metabolites were observed in HFD group mice. After DCGT treatment, glycocholic acid, tauroursodeoxycholic acid and taurochenodeoxycholic acid were significantly down-regulated, while hyodeoxycholic acid, deoxycholic acid and chenodeoxycholic acid were markedly up-regulated. These results demonstrated that DCGT treatment was able to make the BA metabolites in the liver of hyperlipidaemia mice normal and alleviate hyperlipidaemia by regulating the metabolites such as glycocholic acid, tauroursodeoxycholic acid and taurochenodeoxycholic, as well as the BA metabolic pathway and cholesterol metabolic pathway involved.

Heterologous Expression and Characterization of Tea (Camellia sinensis) Polyamine Oxidase Homologs and Their Involvement in Stresses.

Polyamine oxidase (PAO) is a key enzyme maintaining polyamine homeostasis, which affects plant physiological activities. Until now, the gene members and function of PAOs in tea (Camellia sinenesis) have not been fully identified. Here, through the expression in Escherichia coli and Nicotiana benthamiana, we identified six genes annotated as CsPAO in tea genome and transcriptome and determined their enzyme reaction modes and gene expression profiles in tea cultivar 'Yinghong 9'. We found that CsPAO1,2,3 could catalyze spermine, thermospermine, and norspermidine, and CsPAO2,3 could catalyze spermidine in the back-conversion mode, which indicated that the precursor of γ-aminobutyric acid might originate from the oxidation of putrescin but not spermidine. We further investigated the changes of CsPAO activity with temperature and pH and their stability. Kinetic parameters suggested that CsPAO2 was the major PAO modifying polyamine composition in tea, and it could be inactivated by ß-hydroxyethylhydrazine and aminoguanidine. Putrescine content and CsPAO2 expression were high in tea flowers. CsPAO2 responded to wound, drought, and salt stress; CsPAO1 might be the main member responding to cold stress; anoxia induced CsPAO3. We conclude that in terms of phylogenetic tree, enzyme characteristics, and expression profile, CsPAO2 might be the dominant CsPAO in the polyamine degradation pathway.

Analysis of crosstalk in spectral beam combining of diode laser bar.

Spectral beam combining (SBC) of laser diodes has been proven to be an effective method to improve beam brightness. The crosstalk between different emitters in the SBC system will significantly affect the beam-combining efficiency and output beam properties without effective control. The interfering factors of the crosstalk beam intensity in semiconductor laser SBC have been theoretically analyzed, and experiments have been built to carry out the SBC of a semiconductor laser bar with a high filling factor of 80%. It is found that by adding an inverted Kepler telescope, reducing the focal length of the transmission lens or increasing the spacing of the grating and the output coupling mirror, the crosstalk can be suppressed. In an experiment of beam combining with five emitters, the ratio of the first-order crosstalk peak energy to that of the central beam spot is about 0.34 when the spacing of the grating and the output coupling mirror is 50 mm and the focal length of the transmission lens is 200 mm. The ratio decreases to 0.035 when the spacing of the grating and the output coupling mirror is 200 mm. With the addition of an inverted Kepler telescope with a magnification of 2, the ratio decreases to 0.085. In addition, the ratio decreases to 0.07 when the focal length of the transmission lens is 80 mm.

Optimization of brightness in a Nd:YAG laser by maximizing the single-mode power factor with an intra-cavity spatial light modulator.

We report a simple and effective approach for designing resonators with high brightness and high mode discrimination based on optimizing the single-mode power factor of the fundamental mode, which represents the total power extracted by the fundamental mode from the gain medium. By optimizing the single-mode power factor of the fundamental mode, the cavity can be designed to operate in mono-mode, increasing mode purity and improving brightness significantly. Our method is verified on a digital laser with a spatial light modulator as the rear mirror, and the loaded phase profile is acquired by a simulated annealing algorithm. As a result, the optimized resonator with a Fresnel number of 7.2 operates in a single fundamental mode, and the brightness of the output beam yields 240% and 276% improvement, compared with conventional plane-plane and plane-concave resonators, respectively. This approach is ready to be applied to more sophisticated mode selection and may serve as a general method for designing cavities with high efficiency and high brightness.

Natural dissolved organic matter (DOM) affects W(VI) adsorption onto Al (hydr)oxide: Mechanisms and influencing factors.

Tungsten (W) is a contaminant with health implications whose environmental behaviors are not understood well. Sorption to mineral surfaces is one of the primary processes controlling the mobility and fate of W in soils, sediments, and aquifers. However, few papers published hitherto have not yet figured out the influences of dissolved organic matter (DOM) on this process. Here, we examine W(VI) adsorption behaviors onto Al (hydr)oxide (AAH) in the presence or absence of DOM derived from plant rhizosphere, using batch experiments coupled with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The morphology and functional group analyses results show that DOM can facilitate the aggregation of AAH and block surface Al-OH groups. Coexisting DOM inhibits W(VI) adsorption onto AAH at acidic to neutral pH (4-7), and the presence of either Na + or PO43- can exert a completely different impact on W(VI) adsorption. XPS and FTIR characterizations further demonstrate surface W complexes with the Al-OH groups of AAH and carboxyl groups of DOM. There is no reduction of W(VI) during the adsorption processes, and poly-tungstate species are formed on the surface of both AAH and AAH-DOM coprecipitates. This study provides the first evidence of the roles of natural DOM on W sequestration at the mineral-water surface, which has an important implication for the prediction of the migration and bioavailability of W in natural environments.

Theoretical and experimental research on crosstalk in spectral beam combining of a laser diode bar with a high fill factor.

Spectral beam combining is an important way to improve the brightness of semiconductor laser beams. For a spectral beam combining system, crosstalk between different emitters would cause the deterioration of beam quality and the reduction of beam combining efficiency, especially for the laser diode bar with a high fill factor. In this paper, an analysis model of the spectral beam combining system with crosstalk is established. The most important advantage of this model is that it can analyze the spectral distribution of the combined beam and also give a relatively good estimation for the beam quality parameters, such as beam size and far-field divergence angle. This model is verified by the experimental results. Furthermore, based on the theoretical model, a method for eliminating crosstalk is developed. By introducing a spatial filter inside the grating external cavity, the crosstalk between different emitters is blocked in the far field, and the beam quality is improved. In the experiment of beam combining of five emitters, after crosstalk is eliminated, the divergence angle of the combined laser beam is reduced from 10.09 to 4.73 mrad, the beam parameter product is reduced from 2.95 to 0.91 mm⋅mrad, and the power of the main lobe is improved from 1.77 to 2 W.

Early Improvement of Acute Respiratory Distress Syndrome in Patients With COVID-19 in the Intensive Care Unit: Retrospective Analysis.

BACKGROUND: Since the start of the COVID-19 pandemic, there have been over 2 million deaths globally. Acute respiratory distress syndrome (ARDS) may be the main cause of death. OBJECTIVE: This study aimed to describe the clinical features, outcomes, and ARDS characteristics of patients with COVID-19 admitted to the intensive care unit (ICU) in Chongqing, China. METHODS: The epidemiology of COVID-19 from January 21, 2020, to March 15, 2020, in Chongqing, China, was analyzed retrospectively, and 75 ICU patients from two hospitals were included in this study. On day 1, 56 patients with ARDS were selected for subgroup analysis, and a modified Poisson regression was performed to identify predictors for the early improvement of ARDS (eiARDS). RESULTS: Chongqing reported a 5.3% case fatality rate for the 75 ICU patients. The median age of these patients was 57 (IQR 25-75) years, and no bias was present in the sex ratio. A total of 93% (n=70) of patients developed ARDS during ICU stay, and more than half had moderate ARDS. However, most patients (n=41, 55%) underwent high-flow nasal cannula oxygen therapy, but not mechanical ventilation. Nearly one-third of patients with ARDS improved (arterial blood oxygen partial pressure/oxygen concentration >300 mm Hg) in 1 week, which was defined as eiARDS. Patients with eiARDS had a higher survival rate and a shorter length of ICU stay than those without eiARDS. Age (<55 years) was the only variable independently associated with eiARDS, with a risk ratio of 2.67 (95% CI 1.17-6.08). CONCLUSIONS: A new subphenotype of ARDS-eiARDS-in patients with COVID-19 was identified. As clinical outcomes differ, the stratified management of patients based on eiARDS or age is highly recommended.

Effect of Duyun Compound Green Tea on Gut Microbiota Diversity in High-Fat-Diet-Induced Mice Revealed by Illumina High-Throughput Sequencing.

Intake of a high-fat diet (HFD) is closely related to disorders of the intestinal microbiota, which plays a key role in the pathogenesis of obesity. Duyun compound green tea, an ancient Chinese drink, is widely consumed to reduce weight, although the mechanism is not clear. In this study, 50 mice were randomly divided into 5 groups: normal control group (CK), HFD model control group (NK), positive control group with medicine (YK), low-dose compound tea group (DL), and high-dose compound tea group (DH). After 4 weeks of intervention, the feces of mice were taken under sterile conditions and evaluated using Illumina high-throughput sequencing technology. The results showed that the diversity of intestinal microbiota was the highest in the CK group, the lowest in the NK group, and relatively increased in the compound tea treatment group. Second, there were differences in intestinal microbiota in each group, among which the beneficial bacteria in the intestinal tract of the CK group were higher than those in the other groups, while the beneficial bacteria in each compound tea treatment group were more abundant than those in the NK group, in which harmful bacteria in the intestinal tract were found to be the highest. These results suggest that compounds in tea may be able to attenuate imbalances of intestinal microbiota induced by poor diet, acting as a therapeutic agent in obesity or other diseases associated with gut dysbiosis.

Chloroplast genome structure and phylogenetic position of Lophatherum gracile.

Lophatherum gracile is distributed in south China, Japan and South Asia, and it is wild in the valley, stream, woodland, forest edge and gully edge. In this study, the complete chloroplast genome sequence of Lophatherum gracile was successfully obtained using Illumina sequencing. The full length of the chloroplast genome length was 137,749 bp with a typical quadripartite structure: one large single copy (LSC) region (80,610 bp), one small single copy (SSC) region (12,429 bp), and a pair of inverted repeats (IRs) (22,355 bp each). The GC content of this genome was 38.64%. The whole genome contained 130 genes, including 85 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. Phylogenetic analysis indicated that Lophatherum gracile was closely related to Cenchrus americanus and Cenchrus longispinus.

Case Report: Recurrence of Positive SARS-CoV-2 Results in Patients Recovered From COVID-19.

Background: Coronavirus disease 2019 (COVID-19) is spreading throughout the world. Limited data are available for recurrence of positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) results in patients with long duration of COVID-19. Methods: We reported four cases recovered from COVID-19 with recurrence of positive SARS-CoV-2 results during the long-term follow-up. Results: The four patients recovered from COVID-19 showed recurrence of positive SARS-CoV-2 results for more than 120 days with no symptoms and normal chest CT scan. Conclusions: The dynamic surveillance of SARS-CoV-2 by nucleic acid detection and serological assays is important for asymptomatic patients who might be potentially infectious.

CoP and Ni2P implanted in a hollow porous N-doped carbon polyhedron for pH universal hydrogen evolution reaction and alkaline overall water splitting.

Developing low-cost and highly active bifunctional electrocatalysts for water splitting is very important but still remains a challenge. Herein, a novel bifunctional electrocatalyst composed of CoP and Ni2P nanoparticles implanted in a hollow porous N-doped carbon polyhedron (CoP/Ni2P@HPNCP) is synthesized by carbonization of Co/Ni-layered double hydroxide@zeolitic imidazolate framework-67 (Co/Ni-LDH@ZIF-67) followed by an oxidation and phosphorization strategy. The introduction of LDH can not only promote the formation of a hollow porous structure to supply more active sites, but also generate the CoP/Ni2P nanoheterostructure to afford extra active sites and modulate the electronic structure of the catalyst. As a result, CoP/Ni2P@HPNCP exhibits excellent pH universal hydrogen evolution reaction activity and alkaline oxygen evolution reaction activity. Furthermore, the electrolytic cell assembled from bifunctional CoP/Ni2P@HPNCP requires a cell voltage of 1.59 V in 1.0 M KOH at 10 mA cm-2, revealing its potential as a high performance bifunctional electrocatalyst.

Modeling of a picosecond CO2 amplifier with electrical and optical pumping.

As a long-wavelength laser with strong energy storage capacity and large scale of amplification, the CO2 laser is considered an effective amplifier in the next-generation picosecond terawatt infrared laser system, but the pulse splitting effect caused by its discrete gain spectrum limits its behavior. In this paper, we have developed a specific model of a CO2 amplifier, which is optically and electrically pumped at the same time. The model is based on gas discharge that is combined with photon absorption, temperature, and wave equation. The proposed hybrid pumped CO2 amplifier scheme can increase the gain proportion of the sequence band transition (0002-1001, 0003-1002, etc.) from 12% to nearly 50% of the regular band and broaden the bandwidth of each line by over 15.8% by the overlap of the sequence band and regular band. The relative energy concentration of the first subpulse can be increased by up to 190% when the amplification factor reaches 103. The study on the model of a picosecond CO2 amplifier with electrical and optical pumping may contribute to the amplification of an ultrafast mid-infrared pulse to the terawatt or higher region.

A retrospective study on the epidemiological characteristics and establishment of an early warning system of severe COVID-19 patients.

This paper estimates the magnitude of an informational friction limiting credit reallocation to firms during the 2007-2009 financial crisis. Because lenders rely on private information when deciding which relationship to end, borrowers looking for a new lender are adversely selected. I show how to identify private information separately from information common to all lenders but unobservable to the econometrician by using bank shocks within a discrete choice model of relationships. Quantitatively, these informational frictions seem too small to explain the credit crunch in the U.S. syndicated corporate loan market.

Multi-channel V-doped CoP hollow nanofibers as high-performance hydrogen evolution reaction electrocatalysts.

Rational design and construction of high-efficiency and low-cost non-noble metal-based electrocatalysts for the hydrogen evolution reaction (HER) is critical for future renewable energy systems. Herein, a multi-channel V-doped CoP (MC-V-CoP) hollow nanofiber is fabricated via electrospinning and a subsequent oxidation/phosphorization process. The formation of a multi-channel hollow structure and V doping can enlarge the exposure of active sites, facilitate the electron transfer and tune the electronic structure of the active sites, resulting in the enhancement of the HER performance. As a result, the MC-V-CoP hollow nanofiber exhibits excellent HER activity with a low overpotential of 65 and 189 mV at 10 and 300 mA cm-2 in alkaline medium, respectively. This is superior to the commercial 20 wt% Pt/C catalyst at a high current density (212 mV at 300 mA cm-2), manifesting its outstanding performance toward the HER at a high current density. In addition, the MC-V-CoP hollow nanofiber also exhibits outstanding HER activity in neutral medium. The proposed strategy for fabricating multi-channel hollow nanofibers can also be used to prepare other transition metal phosphides for advanced electrochemical applications.

An atmospheric visual analysis and exploration system.

Meteorological research involves the analysis of multi-field, multi-scale, and multi-source data sets. In order to better understand these data sets, models and measurements at different resolutions must be analyzed. Unfortunately, traditional atmospheric visualization systems only provide tools to view a limited number of variables and small segments of the data. These tools are often restricted to two-dimensional contour or vector plots or three-dimensional isosurfaces. The meteorologist must mentally synthesize the data from multiple plots to glean the information needed to produce a coherent picture of the weather phenomenon of interest. In order to provide better tools to meteorologists and reduce system limitations, we have designed an integrated atmospheric visual analysis and exploration system for interactive analysis of weather data sets. Our system allows for the integrated visualization of 1D, 2D, and 3D atmospheric data sets in common meteorological grid structures and utilizes a variety of rendering techniques. These tools provide meteorologists with new abilities to analyze their data and answer questions on regions of interest, ranging from physics-based atmospheric rendering to illustrative rendering containing particles and glyphs. In this paper, we will discuss the use and performance of our visual analysis for two important meteorological applications. The first application is warm rain formation in small cumulus clouds. Here, our three-dimensional, interactive visualization of modeled drop trajectories within spatially correlated fields from a cloud simulation has provided researchers with new insight. Our second application is improving and validating severe storm models, specifically the Weather Research and Forecasting (WRF) model. This is done through correlative visualization of WRF model and experimental Doppler storm data.