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Objectives: To visualize and quantitatively assess regional lung function of survivors of COVID-19 who were hospitalized using pulmonary free-breathing 1H MRI. Methods: A total of 12 healthy volunteers and 27 COVID-19 survivors (62.4 ± 8.1 days between infection and image acquisition) were recruited in this prospective study and performed chest 1H MRI acquisitions with free tidal breathing. Then, conventional Fourier decomposition ventilation (FD-V) and global fractional ventilation (FVGlobal) were analyzed. Besides, a modified PREFUL (mPREFUL) method was developed to adapt to COVID-19 survivors and generate dynamic ventilation maps and parameters. All the ventilation maps and parameters were analyzed using Student's t-test. Pearson's correlation and a Bland-Altman plot between FVGlobal and mPREFUL were analyzed. Results: There was no significant difference between COVID-19 and healthy groups regarding a static FD-V map (0.47 ± 0.12 vs 0.42 ± 0.08; p =.233). However, mPREFUL demonstrated lots of regional high ventilation areas (high ventilation percentage (HVP): 23.7% ± 10.6%) existed in survivors. This regional heterogeneity (i.e., HVP) in survivors was significantly higher than in healthy volunteers (p =.003). The survivors breathed deeper (flow-volume loop: 5375 ± 3978 vs 1688 ± 789; p =.005), and breathed more air in respiratory cycle (total amount: 62.6 ± 19.3 vs 37.3 ± 9.9; p <.001). Besides, mPREFUL showed both good Pearson's correlation (r = 0.74; p <.001) and Bland-Altman consistency (mean bias = −0.01) with FVGlobal. Conclusions: Dynamic ventilation imaging using pulmonary free-breathing 1H MRI found regional abnormity of dynamic ventilation function in COVID-19 survivors. Key Points: • Pulmonary free-breathing1H MRI was used to visualize and quantitatively assess regional lung ventilation function of COVID-19 survivors. • Dynamic ventilation maps generated from1H MRI were more sensitive to distinguish the COVID-19 and healthy groups (total air amount: 62.6 ± 19.3 vs 37.3 ± 9.9; p <.001), compared with static ventilation maps (FD-V value: 0.47 ± 0.12 vs 0.42 ± 0.08; p =.233). • COVID-19 survivors had larger regional heterogeneity (high ventilation percentage: 23.7% ± 10.6% vs 13.1% ± 7.9%; p =.003), and breathed deeper (flow-volume loop: 5375 ± 3978 vs 1688 ± 789; p =.005) than healthy volunteers. [ABSTRACT FROM AUTHOR]

Purpose: In the prediction of COVID-19 disease progression, a clear illustration and early determination of an area that will be affected by pneumonia remain great challenges. In this study, we aimed to predict and visualize the progression of lung lesions in COVID-19 patients in the early stage of illness by using chest CT. Methods: COVID-19 patients who underwent three chest CT scans in the progressive phase were retrospectively enrolled. An extended CT ventilation imaging (CTVI) method was proposed in this work that was adapted to use two chest CT scans acquired on different days, and then lung ventilation maps were generated. The prediction maps were obtained according to the fractional ventilation values, which were related to pulmonary regional function and tissue property changes. The third CT scan was used to validate whether the prediction maps could be used to distinguish healthy regions and potential lesions. Results: A total of 30 patients (mean age ± SD, 43 ± 10 years, 19 females, and 2–12 days between the second and third CT scans) were included in this study. The predicted lesion locations and sizes were almost the same as the true ones visualized in third CT scan. Quantitatively, the predicted lesion volumes and true lesion volumes showed both a good Pearson correlation (R2 = 0.80; P < 0.001) and good consistency in the Bland–Altman plot (mean bias = 0.04 cm3). Regarding the enlargements of the existing lesions, prediction results also exhibited a good Pearson correlation (R2 = 0.76; P < 0.001) with true lesion enlargements. Conclusion: The present findings demonstrated that the extended CTVI method could accurately predict and visualize the progression of lung lesions in COVID-19 patients in the early stage of illness, which is helpful for physicians to predetermine the severity of COVID-19 pneumonia and make effective treatment plans in advance. [ABSTRACT FROM AUTHOR]

A recently developed energy flux diagnosis scheme, which incorporates a smooth connection between the tropical and subtropical zones, is used in the present study to investigate vertically propagating waves in the tropical Indian Ocean (IO) based on the result of a linear, continuously stratified ocean model driven by climatological wind forcing. This extended diagnosis reveals deep-reaching eastward energy fluxes at the equator which develop four times per year and are associated with equatorial Kelvin waves (KWs) generated by semiannual winds. The authors find that the downward transfer of wave energy is particularly deep in the southern Bay of Bengal (SBoB). This downward flux is attributed to off-equatorial Rossby waves and appears four times per year, maximizing its amplitude during November–December. Southwesterly winds in the Arabian Sea intensify eastward energy flux of KWs at mid-depth, which maximizes in amplitude in August. This is contrastive to KW energy flux at the surface which peaks in May. These mid-depth equatorial KW packets subsequently arrive at the eastern boundary of the IO and are diffracted poleward to produce downward energy flux in November and December detected in the SBoB. [ABSTRACT FROM AUTHOR]

The trade-offs between sexual reproduction and clonal propagation are of great significance in terms of ecology and evolution for clonal plants, and they vary with environmental change. Nitrogen (N) deposition can increase litter accumulation in grassland and promote litter decomposition and consequently increase nutrient availability. However, the response of plant reproduction to N and litter addition in grasslands remains unclear. We examined the combined effects of N addition and litter manipulation (i.e. initial litter, removal, addition) on sexual reproduction and clonal propagation of a perennial clonal grass, Leymus chinensis, at the population (total number) and individual (number per ramet) levels in an 11-year field experiment. Nitrogen addition and litter additionally decreased spike and seed number at the population level, and N addition reduced those at the individual level. Nitrogen addition and litter interactively affected bud number at the two levels, and N addition decreased bud number in the litter removal treatments and increased that in the litter addition treatments. The increased soil available N, rather than light and soil water content, explained the change in sexual reproduction and clonal propagation. The positive effects of litter addition on bud number in the treatments with N addition, suggested that the N deposition increased litter accumulation could intensify clonal propagation of perennial grasses and increase their dominance in grasslands. Grassland management that reduces litter accumulation, such as grazing and mowing, can therefore, help alleviate the negative effects of N deposition on plant diversity through decreasing clonal propagation of the dominant species. [ABSTRACT FROM AUTHOR]

Silica hollow microspheres with moonscape-like rough surface (RS) and macroporous surface (MS) have been controllably synthesized by a water–oil–water three-phase emulsion method, which are used as supports of the heterogeneous catalysts for the catalytic hydrogenation of nitrile-butadiene rubber (NBR). It is found that Pd can be uniformly dispersed on both amino-functionalized RS and MS supports and both the catalysts show high hydrogenation activity with 100% selectivity to C=C bonds. However, the reusability of Pd/N-RS is much better than that of Pd/N-MS, maintaining 92% of activity without any regeneration treatment after five times of recycling experiment. The high activity retention is because the moonscape-like surface of the RS support is favorable for the contact of NBR macromolecules with the active sites, and more importantly, the NBR macromolecules do not need to diffuse into the interior of the catalyst, leading to fast desorption of the hydrogenated NBR from the surface of catalyst and re-exposure of the active sites. [ABSTRACT FROM AUTHOR]

We develop an electrodynamic method for analysis of the near- and far-zone fields of dielectric lenses, which is based on solving a high-frequency integral equation. It is shown that the accuracy of this method is high for the lens size exceeding four wavelengths. Its advantages are fast internal convergence of the solution, short computation times, and small computer resources needed. The near-zone fields of lenses having various profiles and sizes of about ten wavelengths are analyzed. [ABSTRACT FROM AUTHOR]

An electrochemical sensor for nitrite was fabricated by modifying a glassy carbon electrode (GCE) with the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) that is doped with carbon quantum dots (CQDs). The negatively charged CQDs were doped into PEDOT via electrodeposition to form a conducting polymer nanocomposite on the GCE. The electrode surface has a flake-like nanostructure and a large specific surface area. The elemental mapping analysis revealed that the CQDs are uniformly distributed across the whole nanocomposite. As a result of the superior catalytic activity of CQDs and the good conductivity of PEDOT, the modified GCE displays excellent electrocatalytic activity towards the oxidation of nitrite, and the oxidation peak current is ten times higher than that of a PEDOT modified GCE without CQDs. Under optimum conditions and at a working voltage of 0.80 V (vs. Ag/AgCl), the sensor has a linear response in the 0.5-1110 μM nitrite concentration range, and an 88 nM limit of detection (at S/N = 3). Three different electrodes prepared under the same experimental conditions were applied for the detection of nitrite, and the RSD was 3.1%. The same sensor was employed to quantify nitrite in three replicate measurements, and the RSD was 2.2%.Poly(3,4-ethylenedioxythiophene) (PEDOT) was doped with carbon quantum dots and deposited on a glassy carbon electrode to obtain an amperometric sensor for nitrite. [ABSTRACT FROM AUTHOR]

Background and aims: Litter input plays an important role in maintaining soil phosphorus (P) availability in terrestrial ecosystems. Moreover, nitrogen (N) deposition can alter litter accumulation and decomposition and, consequently, soil P availability. However, the combined effects of N and litter addition on soil P availability remain unclear.We examined how N addition (0 and 10 g N m−2 yr−1) and litter manipulation (initial litter, litter removal and litter addition) affected the seasonal dynamics of soil P availability in an 11-year grassland experiment.During the mid-growing season, N addition significantly increased soil available P but decreased soil total P, while litter addition increased soil total P. At the end of the growing season, litter addition increased soil available P, while N addition increased soil total P. Structural equation modelling (SEM) revealed that N addition increased soil available P by increasing aboveground biomass and decreasing soil pH during the mid-growing season. At the end of the growing season, litter addition increased soil available P by enhancing microbial biomass P.Our findings suggested that N and litter addition increased soil P availability from the middle to the end of the growing season. Moreover, the positive effects of litter on soil available and total P under N addition at the end of the growing season indicated that grassland management that reduce litter accumulation, such as grazing and mowing, may decrease the soil P supply under increased N deposition.Methods: Litter input plays an important role in maintaining soil phosphorus (P) availability in terrestrial ecosystems. Moreover, nitrogen (N) deposition can alter litter accumulation and decomposition and, consequently, soil P availability. However, the combined effects of N and litter addition on soil P availability remain unclear.We examined how N addition (0 and 10 g N m−2 yr−1) and litter manipulation (initial litter, litter removal and litter addition) affected the seasonal dynamics of soil P availability in an 11-year grassland experiment.During the mid-growing season, N addition significantly increased soil available P but decreased soil total P, while litter addition increased soil total P. At the end of the growing season, litter addition increased soil available P, while N addition increased soil total P. Structural equation modelling (SEM) revealed that N addition increased soil available P by increasing aboveground biomass and decreasing soil pH during the mid-growing season. At the end of the growing season, litter addition increased soil available P by enhancing microbial biomass P.Our findings suggested that N and litter addition increased soil P availability from the middle to the end of the growing season. Moreover, the positive effects of litter on soil available and total P under N addition at the end of the growing season indicated that grassland management that reduce litter accumulation, such as grazing and mowing, may decrease the soil P supply under increased N deposition.Results: Litter input plays an important role in maintaining soil phosphorus (P) availability in terrestrial ecosystems. Moreover, nitrogen (N) deposition can alter litter accumulation and decomposition and, consequently, soil P availability. However, the combined effects of N and litter addition on soil P availability remain unclear.We examined how N addition (0 and 10 g N m−2 yr−1) and litter manipulation (initial litter, litter removal and litter addition) affected the seasonal dynamics of soil P availability in an 11-year grassland experiment.During the mid-growing season, N addition significantly increased soil available P but decreased soil total P, while litter addition increased soil total P. At the end of the growing season, litter addition increased soil available P, while N addition increased soil total P. Structural equation modelling (SEM) revealed that N addition increased soil available P by increasing aboveground biomass and decreasing soil pH during the mid-growing season. At the end of the growing season, litter addition increased soil available P by enhancing microbial biomass P.Our findings suggested that N and litter addition increased soil P availability from the middle to the end of the growing season. Moreover, the positive effects of litter on soil available and total P under N addition at the end of the growing season indicated that grassland management that reduce litter accumulation, such as grazing and mowing, may decrease the soil P supply under increased N deposition.Conclusion: Litter input plays an important role in maintaining soil phosphorus (P) availability in terrestrial ecosystems. Moreover, nitrogen (N) deposition can alter litter accumulation and decomposition and, consequently, soil P availability. However, the combined effects of N and litter addition on soil P availability remain unclear.We examined how N addition (0 and 10 g N m−2 yr−1) and litter manipulation (initial litter, litter removal and litter addition) affected the seasonal dynamics of soil P availability in an 11-year grassland experiment.During the mid-growing season, N addition significantly increased soil available P but decreased soil total P, while litter addition increased soil total P. At the end of the growing season, litter addition increased soil available P, while N addition increased soil total P. Structural equation modelling (SEM) revealed that N addition increased soil available P by increasing aboveground biomass and decreasing soil pH during the mid-growing season. At the end of the growing season, litter addition increased soil available P by enhancing microbial biomass P.Our findings suggested that N and litter addition increased soil P availability from the middle to the end of the growing season. Moreover, the positive effects of litter on soil available and total P under N addition at the end of the growing season indicated that grassland management that reduce litter accumulation, such as grazing and mowing, may decrease the soil P supply under increased N deposition. [ABSTRACT FROM AUTHOR]