[Tracing the sources of sedimentary organic matter in Nanyue small watershed based on 13C, 15N and C/N]. / 基于13C、15N和C/N识别南岳小流域沉积有机质的来源.

Losses of organic matter in agricultural watersheds result in eutrophication and land degra-dation, which not only threaten water quality and food security, but also lead to environmental problems such as the greenhouse gases emission. We used 13C, 15N and C/N as fingerprint markers to trace the sources of sedimentary organic matter at the outlet in the Nanyue small watershed. We analyzed the spatial distribution in watershed sedimentary organic matter and soils of typical land use types, including forest, paddy field, and vegetable fields. The Bayesian stable isotope mixing model was used to quantitatively estimate the contribution of different sources. The results showed that there was significant spatial variation of δ13C. The δ13C of sediment organic matter (-22.6‰±0.53‰) and forest soil (-23.13‰±1.71‰) was significantly higher than that of paddy soil (-25.24‰±1.4‰). The differences of δ15N among the sources were not significant, with sediment having the maximum (4.37±0.83)‰ and forest soil having the minimum (2.38±1.97)‰. Forest soil had the highest C/N of 16.66±7.18, while paddy soil had the lowest C/N of 11.95±0.92. The results of the Bayesian stable isotope mixture model showed that the contribution rates of forest land, paddy fields and vegetable fields to the organic matter deposited at the outlet in the watershed were 19.6%, 15.7%, and 64.7%, respectively. Paddy filed and vegetable field had a combined contribution rate of 80.4%. It was concluded that, soils of agricultural land were the main sources of organic matter deposited in the Nanyue small watershed, and that nutrient loss in the watershed would be effectively controlled by optimizing farmland management.

Longitudinal Dynamics of the Neutralizing Antibody Response to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is a global pandemic with no licensed vaccine or specific antiviral agents for therapy. Little is known about the longitudinal dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific neutralizing antibodies (NAbs) in patients with COVID-19. METHODS: Blood samples (n = 173) were collected from 30 patients with COVID-19 over a 3-month period after symptom onset and analyzed for SARS-CoV-2-specific NAbs using the lentiviral pseudotype assay, coincident with the levels of IgG and proinflammatory cytokines. RESULTS: SARS-CoV-2-specific NAb titers were low for the first 7-10 days after symptom onset and increased after 2-3 weeks. The median peak time for NAbs was 33 days (interquartile range [IQR], 24-59 days) after symptom onset. NAb titers in 93.3% (28/30) of the patients declined gradually over the 3-month study period, with a median decrease of 34.8% (IQR, 19.6-42.4%). NAb titers increased over time in parallel with the rise in immunoglobulin G (IgG) antibody levels, correlating well at week 3 (r = 0.41, P < .05). The NAb titers also demonstrated a significant positive correlation with levels of plasma proinflammatory cytokines, including stem cell factor (SCF), TNF-related apoptosis-inducing ligand (TRAIL), and macrophage colony-stimulating factor (M-CSF). CONCLUSIONS: These data provide useful information regarding dynamic changes in NAbs in patients with COVID-19 during the acute and convalescent phases.

[Responses of net assimilation rate to elevated atmospheric CO2and temperature at different growth stages in a double rice cropping system]. / 双季稻不同生育期净同化速率对大气CO2浓度和温度升高的响应.

Effects of elevated atmospheric CO2 concentration and temperature on rice dry matter accumulation vary in planting regions and cropping systems. It remains unclear how dry matter productivity responds to factorial combination of elevated CO2 and temperature in the double rice cropping system of China. Field experiments were conducted using open-top chambers (OTC) to simulate different scenarios of elevated CO2 and/or temperature for three rotations of double rice in Jingzhou, Hubei Province. Liangyou 287 and Xiangfengyou 9 were used as rice cultivar for early rice and late rice, respectively. There were five treatments: UC, paddy field without OTC covering; CK, OTC with the similar temperature and CO2 concentration to field environment; ET, OTC with 2 ℃ temperature elevation; EC, OTC with 60 µmol·mol-1 CO2 elevation; ETEC, OTC with simu-ltaneous 2 ℃ temperature elevation and 60 µmol·mol-1 CO2 elevation. We measured aboveground biomass, leaf area index (LAI) and net assimilation rate (NAR) of dry matter under different treatments. Our results showed that elevated CO2 and/or temperature had no significant effects on NAR from transplanting to jointing, increased NAR from jointing to heading, but decreased NAR from heading to maturity (except for EC treatment in early rice). Elevated CO2 and/or temperature promoted leaf area development at all growth stages, with ETEC showing the highest increase in LAI except at maturity. Warming and CO2 enrichment jointly promoted dry matter accumulation at heading, with ETEC increasing aboveground biomass by 10.3%-39.8% and 23.6%-34.4% compared with CK in early rice and late rice, respectively. At maturity of early rice, elevated temperature partly offset the positive effects of elevated CO2 on aboveground biomass, as shown by a reduction of 3.2%-14.1% under ETEC compared with EC. Contrarily at maturity of late rice, co-elevation of CO2 and temperature further increased aboveground biomass, showing a synergistic interaction. Results from regression analysis showed that warming and CO2 enrichment had positive effects on NAR at vegetative stages of double rice, while warming showed negative effects on NAR at reproductive stages. Considering the dissimilarities in growth characteristics, growing periods and ambient temperature, elevated CO2 and temperature might increase dry matter production in the Chinese double rice cropping system.

A Peptide-Based Magnetic Chemiluminescence Enzyme Immunoassay for Serological Diagnosis of Coronavirus Disease 2019.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel ß-coronavirus, causes severe pneumonia and has spread throughout the globe rapidly. The disease associated with SARS-CoV-2 infection is named coronavirus disease 2019 (COVID-19). To date, real-time reverse-transcription polymerase chain reaction (RT-PCR) is the only test able to confirm this infection. However, the accuracy of RT-PCR depends on several factors; variations in these factors might significantly lower the sensitivity of detection. METHODS: In this study, we developed a peptide-based luminescent immunoassay that detected immunoglobulin (Ig)G and IgM. The assay cutoff value was determined by evaluating the sera from healthy and infected patients for pathogens other than SARS-CoV-2. RESULTS: To evaluate assay performance, we detected IgG and IgM in the sera from confirmed patients. The positive rate of IgG and IgM was 71.4% and 57.2%, respectively. CONCLUSIONS: Therefore, combining our immunoassay with real-time RT-PCR might enhance the diagnostic accuracy of COVID-19.

[Temporal and spatial variations of hydrogen and oxygen isotopes in Tuojia River and its influencing factors.] / è„±ç”²æ²³æ°¢æ°§åŒä½ç´ ç»„åˆ†æ—¶ç©ºåˆ†å¸ƒç‰¹å¾åŠå ¶å½±å“å› ç´ .

The characteristics of hydrogen and oxygen stable isotopes in river is important for regional hydrologic cycle research. To uncover water supply sources in subtropical agricultural basin from a perspective of stable isotopes, field measurements were conducted in four reaches (S1, S2, S3 and S4) of Tuojia River from April to August 2017. We analyzed the spatial and temporal variations in hydrogen and oxygen isotopes and deuterium excess parameters and their relationship with precipitation, altitude and water quality. Results showed that hydrogen and oxygen isotopes and deuterium excess values ranged from -43.17‰ to -26.43‰ (-35.50‰±5.44‰), -7.94‰ to -5.70‰ (-6.86‰±0.74‰), and 16.77‰ to 23.49‰ (19.39‰±1.95‰), respectively. Under the influence of monsoon circulation, hydrogen and oxygen isotopes showed substantial seasonal variation, with spring (δD: -29.88‰±3.31‰; δ18O: -6.18‰±0.57‰) > summer (δD: -39.25‰±2.65‰; δ18O: -7.32‰±0.42‰). The spatial distribution of hydrogen and oxygen isotopes values increased fluctuantly with the position from the sampling site to the river's source, with δD: S1＜S4＜S3＜S2, and δ18O: S1＜S3＜S4＜S2. The deuterium excess values had no significant temporal variation, while it spatially increased gradually with the river levels. The slope and intercept of water line in this river were smaller than that of the local meteoric water line, suggesting that precipitation was the primary water source for this river. At the seasonal scale, both δD and δ18O were significantly negatively correlated with water temperature (δD: r=-0.92; δ18O: r=-0.88) and δ18O was negatively correlated with altitude (r=-0.96). At spatial scale, δ18O had a significantly positive correlation with water temperature. The δD and δ18O had negative correlation with precipitation, but being not statistically significant.

[Impacts of climate warming on nine element contents in Mongolian drug Agi using ICP-AES].

Global warming has become a fact of life, and the night temperature increase higher than during the day. In the present research, to explore the effects of climate warming on element contents of plants, ICP-AES was used for the direct determination of nine kinds of element contents of reproductive branches and vegetative branches of the Mongolian drug Agi, which grew in the day, night and diurnal warming field. The results of the study show that the responses of reproductive branches and vegetative branches to day, night and diurnal warming were not significant different, but the negative response was greater than the positive response. The effects of day warming on the element contents were not significant, but night warming lower the contents of Al, Fe and Mn significantly. There was interaction between day warming and night warming.

[Observation for CH4 and N2O emissions under different rates of nitrogen and phosphate fertilization in double rice fields].

Two non-CO2 greenhouse gas emissions (methane and nitrous oxide) and related environmental factors were measured within rice growing season under five treatments including non-fertilization (CK), balanced fertilization (BF), decreased nitrogen and phosphate 1 (DNP1), decreased nitrogen and phosphate 2 (DNP2) and increased nitrogen and phosphate 1 (INP) in double rice fields of red clay soil in 2009, using the method of static chamber-gas chromatograph techniques. The results showed that the average CH4 emission fluxes for treatments of BF, DNP1, DNP2 and INP were 4.57, 5.42, 4.70 and 4.65 mg x (m2 x h)(-1) during early rice growing period, which increased by 39%, 49%, 41% and 40% compared with non-fertilizer treatment, respectively. The average CH4 emission fluxes in late rice growing season was higher than preseason's. Compared to CK, CH4 emission increased by 11%, 1%, 26% and - 4% in treatments of BF, DNP1, DNP2 and INP within late rice growing season. Applying nitrogen and phosphate enhanced CH4 emission in turning green period for early and late rice. No significant difference was observed between the CH4 emissions of five treatments during early and late rice growing season (p > 0.05). N2O emission was very little during mid-seasonal drainage period. In contrast, N2O emission peaks were observed in period of alternation of wetting and drying after mid-seasonal drainage in this experiment. N2O emission was, on average, equivalent to 0.18% of the nitrogen applied in double rice growing season. Statistically, air temperature, soil Eh and soil moisture (water-filled pore space, WFPS) at 0-10cm depth significantly affected the fluctuations of the seasonal CH4 flux, but no significant correlationship has been found between N2O flux and related environmental factors. CH4 was the dominated greenhouse gas in double rice fields which contributed approximately 90% for the integrated global warming potential of CH4 and N2O released during the rice growing season. Therefore, the mitigation options should focus on how to reduce CH4 emission in local area. The result indicates that BF is a recommended fertilization method for early rice production, and a optimum fertilization for late season can increase rates of nitrogen and phosphate fertilizers on the basis of BF treatment slightly by considering total global warming potential and grain yield. The rates of BF treatment were 150-90-90 kg x hm(-2) N-P2O5-K2O for early rice, and 180-90-135 kg x hm(-2) N-P2O5-K2O for late rice, respectively.

[Grassland net primary productivity and its spatiotemporal distribution in northern Tibet: a study with CASA model].

Based on the remote sensing data, meteorological data and other related data from 1981 to 2004, the grassland net primary productivity (NPP) and its spatiotemporal distribution in Northern Tibet were analyzed by CASA (Carnegie-Ames-Stanford Approach) model. The results indicated that in the study area, the spatial distribution of grassland NPP was affected by the local water and heat conditions, and represented a horizontal zonality. From southeast to northwest, the grassland NPP reduced from 230 g C x m(-2) x a(-1) to near 0 g C x m(-2) x a(-1). The overall level of grassland NPP in Northern Tibet was rather low, with the multi-years average value of total NPP being 21.3 x 10(12) g C x a(-1) and the mean value of NPP being 48.1 g C x m(-2) x a(-1), which were obviously lower than those in Qinghai-Tibetan Plateau and other grassland areas of China. The mean values of NPP on flat land (slope gradient <1 degree) and south slope were relatively lower. On the main alpine grasslands in Northern Tibet, the NPP from July to September occupied 64.0%-70.0% of the whole year. From 1981 to 2004, the grassland NPP within the whole Northern Tibet had a greater annual fluctuation, and tended to further reduce.