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An ultrasensitive electrochemical platform for p53 gene via MB-mediated CSD and TdT-mediated signal amplification strategy with detection limit of 0.018 fM.

A label-free and ultrasensitive electrochemical biosensor for ORAOV1 gene via exonuclease III-assisted target recycling and dual enzyme-assisted signal amplification strategies. The detection limit of ORAOV1 gene was as low as 0.019 fM.

Daxing’anling Mountain, in the northeastern part of China, contains a large amount of soil organic carbon (SOC). Using data including topography, climate, and vegetation, the spatial distribution of SOC content was modeled using classical and geography-based statistics, as well as a geographically weighted kriging model. The study findings include: (1) SOC content generally ranges 40–70 g/kg, with high SOC content in the southwest and low SOC content in the southeast; (2) Results of principal component analysis suggested the normalized difference vegetation index is the best predictor of patterns in SOC; and (3) The geo-weighted regression Kriging model well reflects factors influencing spatial distribution of SOC content. This study provides important baseline information for environmental protection in the Daxing’anling Mountain area, as well as general information as to important factors that mediate this important reservoir of soil carbon.

OBJECTIVE. The purpose of this study was to investigate early clinical and CT manifestations of coronavirus disease (COVID-19) pneumonia. MATERIALS AND METHODS. Patients with COVID-19 pneumonia confirmed by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid test (reverse transcription-polymerase chain reaction) were enrolled in this retrospective study. The clinical manifestations, laboratory results, and CT findings were evaluated. RESULTS. One hundred eight patients (38 men, 70 women; age range, 21-90 years) were included in the study. The clinical manifestations were fever in 94 of 108 (87%) patients, dry cough in 65 (60%), and fatigue in 42 (39%). The laboratory results were normal WBC count in 97 (90%) patients and normal or reduced lymphocyte count in 65 (60%). High-sensitivity C-reactive protein level was elevated in 107 (99%) patients. The distribution of involved lobes was one lobe in 38 (35%) patients, two or three lobes in 24 (22%), and four or five lobes in 46 (43%). The major involvement was peripheral (97 patients [90%]), and the common lesion shape was patchy (93 patients [86%]). Sixty-five (60%) patients had ground-glass opacity (GGO), and 44 (41%) had GGO with consolidation. The size of lesions varied from smaller than 1 cm (10 patients [9%]) to larger than 3 cm (56 patients [52%]). Vascular thickening (86 patients [80%]), crazy paving pattern (43 patients [40%]), air bronchogram sign (52 patients [48%]), and halo sign (69 [64%]) were also observed in this study. CONCLUSION. The early clinical and laboratory findings of COVID-19 pneumonia are low to midgrade fever, dry cough, and fatigue with normal WBC count, reduced lymphocyte count, and elevated high-sensitivity C-reactive protein level. The early CT findings are patchy GGO with or without consolidation involving multiple lobes, mainly in the peripheral zone, accompanied by halo sign, vascular thickening, crazy paving pattern, or air bronchogram sign.

The coronavirus disease 2019 (COVID-19) that occurred in Wuhan, Hubei Province, China, has been declared a public health emergency of international concern and a pandemic by the World Health Organization. The Chinese government has temporarily taken strong response measures and effective procedures to stop the further expansion and development of the epidemic. It is important for clinicians to screen, diagnose, and monitor COVID-19.

Tumor suppressor p53 gene is one vital anticancer gene that plays critical role in the prevention, diagnosis, and prognosis evaluation of cancers. Specific recognition and sensitive detection of p53 gene is important for early cancer screening and diagnosis. A ratiometric electrochemical biosensor is developed for ultrasensitive detection of tumor suppressor p53 gene in this work. Hairpin capture probe (Fc-HP-SH) is labeled with ferrocene (Fc) at the 3′ termini and thiol group at the 5′ termini. Fc-HP-SH was self-assembled on the surface of gold electrode through Au-S binding, while 6-mercaptohexanol was used to block the unoccupied sites on electrode surface. At the presents of p53 gene and nicking endonuclease, p53 gene specifically hybridizes with the loop sequences of Fc-HP-SH to unwind the hairpin structure. Nicking endonuclease subsequently cleaves DNA duplex to release p53 gene for target recycling. Residual single-stranded oligonucleotide is prolonged with the help of phi29 DNA polymerase via rolling circle amplification, leading to the increased gathering of electroactive probe methylene blue (MB) on long polynucleotide. Such variations cause the alterations of the differential pulse voltammetry peak currents of Fc at + 0.32 V (vs. Ag/AgCl) and MB at − 0.25 V (vs. Ag/AgCl), resulting in an obvious enhancement of the ratiometric signal of two peak currents. Under optimum experimental conditions, this biosensor has a response that covers the 1 fM to 10 pM p53 gene concentration range, and the detection limit is 0.23 fM (for S/N = 3). This biosensor highly recognized p53 gene over its mutants and was successfully applied in human serum samples. This approach shows excellent reproducibility, acceptable stability, good selectivity, and ultrahigh sensitivity toward p53 gene detection.

Soil properties, especially physical properties and macropore characteristics, are controlling factors for vertical water flow in paddy fields. However, the effects of paddy rice cultivation history on vertical water flows and related soil properties have been rarely studied. The objectives were to identify the differences in soil physical properties and macropore parameters and to reveal the effects of these soil properties on vertical water flow patterns in paddy fields under different cultivation times. In this study, soil physical properties in a very young paddy field (2 y, VYPF), a young paddy field (18 y, YPF), and an old paddy field (>100 y, OPF) were analyzed. Meanwhile, macropore parameters (resolution of 0.6 mm) and vertical water flow patterns in these fields were identified by computed tomography and dye tracing experiment, respectively. As cultivation history lengthened in paddy rice, the average content of soil clay and organic carbon in the 80 cm depth soil profile increased, as did the thickness and bulk density of the plow pan. Also, macroporosity, macropore area density, macropore number density, node density, macropore angle, and hydraulic radius significantly decreased as length of cultivation age increased. As a result, differences in these soil propeties affected vertical water flow in three studied paddy fields. Steady-state infiltration rates decreased significantly in accordance with the reduced saturated hydraulic conductivity of soil cores from the plow pan; median values were 9.76 cm d−1, 2.93 cm d−1, and 0.13 cm d−1 for VYPF, YPF, and OPF, respectively. A greater abundance and distribution of a dye tracer and a higher stained area ratio under the plow pan in younger paddy fields indicated that more obvious preferential water flows occurred in VYPF and YPF than in OPF. This implied that the conversion of farmland from upland field to paddy field resulted in greater use of irrigation water and also posed a risk of groundwater pollution through increased percolation. Therefore, a longer puddling time before planting paddy rice should be conducted in paddy fields (i.e. YPF and VYPF) with a short cultivation history, which can reduce water percolation by enhancing bulk density, reducing macropores, and lowering the saturated water conductivity of the plow pan.

Fires are the major disturbances in the Greater Hinggan Mountains, the only boreal forest in Northeast China. A comprehensive understanding of the fire regimes and influencing environmental parameters driving them from small to large fires is critical for effective forest fire prevention and management. Assisted with satellite imagery, topographic data, and climatic records in this region, this study examines its fire regimes in terms of ignition causes, frequencies, seasonality, and burned sizes in the period of 1980–2005. We found an upward trend for fire occurrences and burned areas and an elongated fire season over the three decades. The dates of the first fire in a year did not vary largely but those of the last fire were significantly delayed. Topographically, spring fires were prevalent throughout the entire region, while summer fires mainly occurred at higher elevations under severe drought conditions. Fall fires were mostly human-caused in areas at lower elevations with gentle terrains. An ordinal logistic regression revealed temperature and elevation were both significant factors to the fire size severity in spring and summer. Other than that, environmental impacts were different. Precipitation in the preceding year greatly influenced spring fires, while summer fires were significantly affected by wind speed, fuel moisture, and human accessibility. An important message from this study is that distinct seasonal variability and a significantly increasing number of summer and fall fires since the mid-1990s suggest a changing fire regime of the boreal forests in the study area. The observed and modeled results could provide insights on establishing a sustainable, localized forest fire prevention strategy in a seasonal manner.

Preferential flow can develop in soil macropores, and macropores are sensitive to human disturbances. This study investigated soil macropore features and the main factors controlling preferential flow at four sites with different levels of human disturbance in a mountainous area in Central China. The level of human disturbance decreased with increasing elevation, with the lowest elevation areas covered with coniferous trees (LF) > middle mountain areas covered with tea gardens (TG) > middle mountain areas covered with deciduous trees and mixed shrubs (MF) > subalpine areas covered with evergreen coniferous trees (HF). At each site, the soil macropore structure at 0–20 cm soil depth was analysed using computed tomography scans (0.6 mm resolution) and Image J software. Preferential flow was determined by analysing the breakthrough curve (BTC) of nitrate. The macroporosity, surface area density, mean macropore size, macropore number density, length density and node density were all ranked in the order of HF ≥ MF ≥ TG = LF. Less disturbed sites had stronger evidence of preferential flow as shown by faster breakthrough, longer tails and greater asymmetry of the BTCs. There were significant (P < 0.05) positive influences of soil macropore properties on pore water velocity and the solute dispersion coefficient. The dispersivity parameter was mainly affected by the macropore equivalent hydraulic radius. This study showed that human disturbance in the mountain forest areas significantly decreased soil macropores by changing soil physical properties (e.g. bulk density, texture and soil organic matter content) and root distribution, thus increasing the risk of surface runoff and nutrient losses.

Objectives: This study was designed to investigate the feasibility of apparent diffusion coefficient (ADC) values in evaluating normal fetal brain development from gestational week 24 up to term age. Methods: Diffusion-weighted imaging (DWI) was performed on 40 normal fetuses (with normal results on sonography and normal fetal MRI results), with two b-values of 0 and 600 s/mm2 in the three (x, y, z) orthogonal axes. Ten regions of interest (ROIs) were manually placed symmetrically in the bilateral frontal white matter (FWM), occipital white matter (OWM), thalamus (THAL), basal ganglia (BG), and cerebellar hemispheres (CH). ADC values of the ten ROIs in all subjects were measured by two radiologists independently. One-way ANOVA was used to calculate the differences among the five regions in the fetal brain and linear regression analysis was used to evaluate the correlation between ADC values and gestational age (GA). p < 0.05 was considered significantly different. Results: Mean GA was 31.3 ± 3.9 (range 24-41) weeks. The overall mean ADC values (×10-6 mm2/s) of the fetuses were 1,800 ± 214 (FWM), 1,400 ± 100 (BG), 1,300 ± 126 (THAL), 1,700 ± 133 (OWM) and 1,400 ± 155 (CH), respectively. The ADC value of BG was not significantly different from those of THAL and CH, while the other four ROIs had significant differences with each other. The ADC values of BG, THAL, OWM and CH had strong negative correlations with increasing GA (R were -0.568, -0.716, -0.830 and -0.700, respectively, all p < 0.01), OWM declined fastest with GA, followed by CH and THAL, the slowest being BG. The ADC value of FWM had no significant change with GA (p = 0.366). Conclusions: The measurement of ADC values is feasible to evaluate fetal brain development with high reliability and reproducibility.

Ectomycorrhizal (ECM) fungal communities of Pinus densiflora were studied along a chronosequence. Four age classes were sampled: 5, 30, 55 and 80 year-old. Morphotyping (anatomical and morphological identification) and molecular analysis (internal transcribed spacer region amplification and sequencing) were used to identify ECM root tips. A total of 43 ECM morphotypes were distinguished, 38 of which were successfully sequenced. Cenococcum geophilum, Cortinarius sp.1, Rhizopogon sp.1, and Russula densifolia dominated the ectomycorrhiza community of P. densiflora. C. geophilum had its peak of abundance in the 5-year-old stand, R. densifolia in the 30 year-old stand and Cortinarius sp.1 in the 80 year-old stand. However abundance ofRhizopogon sp.1 differed little with stand age. ECM fungus species diversity indices increased with stand age along the chronosequence. ECM fungal species diversity was significantly higher in the 5 year-old than in the 30 year-old stand and 55 and 80 year-old stands had similar diversities. Key words: Diversity, ectomycorrhizal, ITS, Pinus densiflora.

The content and distribution of heavy metal elements, including cadmium (Cd), lead (Pb), chromium (Cr), copper (Cu), zinc (Zn), in urban soil of Harbin was studied to assess the heavy metal integrated pollution and potentially ecological hazards. The results showed that the content of heavy metal had high accumulation in Harbin urban soil by comparison to the background concentration of soil elements in SongLiao Plain. Analysis the possible sources of heavy metal elements in the different areas. The heavy metals integrated pollution from high to low is industrial area>traffic area>suburbs farmland>botanical garden. The potentially ecological risk is moderate in industrial area and traffic area, but it is light in suburbs farmland and botanical garden.