Dynamic simulation of nutrient distribution in lakes during ice cover growth and ablation.

Nutrient transport in seasonally ice-covered lakes is an important factor affecting spring algal blooms in eutrophic waters; because phase changes during the ice growth process redistribute the nutrients. In this study, nutrient transport under static conditions was simulated by using two ice thickness models in combination with an indoor freezing experiment under different segregation coefficient conditions for nutrients. A real-time prediction model for nutrient and pollutant concentrations in ice-covered lakes was established to explore the impact of the ice-on period in eutrophic shallow lakes. The results demonstrated that the empirical degree-day model and the high-resolution thermodynamic snow and sea-ice model (HIGHTSI) could both be used to simulate lake ice thickness. The empirical degree-day model performed better at predicting the maximum ice thickness (measured thickness 0.22-0.55 m; simulated thickness 0.48 m), whereas the HIGHTSI model was more accurate when estimating the mean thickness (5-6% error). When simulating ice growth, the HIGHTSI model considered more meteorological factors impacting ice cover ablation; hence, it performed better during the ablation stage relative to the empirical degree-day model. Two non-dynamic nutrient transport models were developed by combining the segregation coefficient model and the ice thickness prediction model. The HIGHTSI nutrient transport model can be used to predict real-time changes in nutrient concentrations under ice cover, and the degree-day model can be used to predict changes in the lake water ecosystem.

Effect mechanism of biochar application on soil structure and organic matter in semi-arid areas.

There are global concerns regarding soil remediation and water conservation in arid and semi-arid areas. Studying the mechanism and factors influencing soil structure and organic matter content is very important for soil remediation and the rational utilization of water resources. We tracked the changes in soil aggregates and organic matter content during the growth period of maize using different application rates of straw biochar (10, 20, 30, and 50 t/ha) to investigate the effects of biochar on the structure of weakly alkaline soil. The results were as follows: 1) Biochar significantly increased the content of water-stable soil aggregates. The content of water-stable macroaggregates (≥0.25 mm) increased by 8.3-35.0%, and the increase was the highest (35%) when biochar was applied at a rate of 30 t/ha 2) After applying biochar, the content of air-dried aggregates on the surface layer increased by 112.6-168.5%. 3). Biochar increased the organic matter content to varying degrees from the spatiotemporal aspect. In terms of soil depth, organic matter content increased by 2.15-5.88 g/kg. The jointing stage, which the time demand for organic matter is the highest, organic matter content increased by 35.4% when biochar was applied at 50 t/ha 4) We established a three-dimensional surface correlation equation based on the synergistic relationships among biochar, water-stable aggregates, and organic matter content. The particle size of soil aggregates was the highest when the biochar application rate was 29.38 t/ha and the organic matter content increased by 25.7%. It provided evidence that applies to biochar has good potential for water-saving irrigation and soil remediation.

Effects of straw biochar application on soil temperature, available nitrogen and growth of corn.

Straw biochar could improve the water holding capacity effectivity of salinized soil, increase soil fertili, enhance crop yield, reduce greenhouse gas emission, and mitigate climate change. The mechanism of using straw biochar for soil improvement is different under various climate and soil texture conditions. To explore the mechanism of using straw biochar to improve soil and its influence on crop yield in the typical arid and semi-arid, a large temperature difference between day and night, soil temperature at different depths, and physiological changes and crop yield of maize at different growth stages were studied. It is assumed that straw biochar can improve the properties of salinized soil including physicochemical indexes, and crop physiological index, stimulates the positive circulation between soil, vegetation, and microorganisms, and plays a role in improving soil quality. The results showed that biochar application increased the average soil temperature (T) by 2 °C and reduced day-night T differences. Application of 30 t/ha biochar increased the average maize leaf T by 2.2 °C and photosynthetic rate by 16.5%. Furthermore, the average transpiration rate doubled compared to control, and the chlorophyll value increased by 21%. The application of biochar improved the utilization rate of nitrogen fertilizer by enhancing ammonification. Biochar application caused a maximum overall yield increase of 11.9% compared to control treatment (CK). Therefore, these results provide a practical basis for improving weakly alkaline farmland soils in arid and semi-arid areas, and provide an effective method to potentially mitigate the environmental crisis and promote sustainable development in agriculture.

Platelet-to-lymphocyte ratio as a potential prognostic factor in nasopharyngeal carcinoma: A meta-analysis.

BACKGROUND: The aim of this study was to investigate the use of pretreatment platelet-to-lymphocyte ratio (PLR) as a prognostic marker in patients with nasopharyngeal carcinoma (NPC). METHODS: A literature search was conducted using online databases such as MEDLINE, EMBASE, Cochrane Library, and WangFang. Overall survival (OS), progression-free survival (PFS), and clinicopathological features were generated and compared. RESULTS: Ten studies that included 3388 patients were analyzed in this meta-analysis. Among them, 8 studies with 3033 patients with NPC investigated the prognostic role of PLR for OS and showed that elevated PLR was associated with poor OS (HR: 1.77, 95% CI: 1.46-2.15, P < .001). Five studies that included 1156 patients investigated the role of PLR in predicting PFS, and showed that high PLR was associated with poor PFS (HR: 1.65, 95% CI: 1.26-2.17, P < .001). Moreover, high PLR correlated with the N stage (N2-3 vs N0-1; OR: 1.55, 95% CI: 1.02-2.34, P = .04). CONCLUSION: Our study suggested that high PLR is associated with worse prognosis in patients with NPC. Pretreatment PLR could serve as a simple, promising indicator for prognostic evaluation in patients with NPC.

[Investigation on long-term efficacy of CPAP treatment for the elderly with obstructive sleep apnea syndrome].

OBJECTIVE: To investigate the long-term efficacy of continuous positive airway pressure (CPAP) treatment for the elderly with obstructive sleep apnea syndrome (OSAS). METHODS: Case control study was performed among 106 elderly with obstructive sleep apnea syndrome (OSAS). They were divided into treatment group (n=34) and control group (n=72), based on whether they underwent long-term CPAP treatment or not. The long-term efficacy of CPAP treatment was evaluated by long-term clinical observation. RESULTS: The incidence of cardiovascular events was 12% (4/34) in treatment group and 47% (34/72) in control group (P<0.01). Kaplan-Meier survival analysis showed that after controlling the factors of age, sex, body mass index, apnea hypopnea index and previous diseases, failing to receive CPAP treatment was the independent risk factor for cardiovascular events (chi2=17.0, P<0.01). CONCLUSIONS: CPAP treatment for moderate-severe OSAS could reduce cardiovascular and neurovascular events risk for elderly patients with OSAS.

[Clinical analysis of coronary artery disease in elderly patients with sleep disordered breathing].

OBJECTIVE: To understand the prevalence of sleep disordered breathing (SDB) in elderly patients with coronary artery disease (CAD) and explore the relations between SDB and CAD. METHODS: Sixty-two elderly patients with and 18 without CAD identified by coronary angiography underwent examinations by polysomnography (PSG). Left ventricular ejection fraction (LVEF) was measured by 99Tc equilibrium radionuclide angiography. RESULTS: In the 62 elderly patients with CAD, 53.2% had SDB, a rate significantly higher that (22.2%) in the 18 non-CAD patients. The CAD patients with SDB had higher respiratory disturbance index (RDI) and body mass index (BMI) and lower arterial saturation of oxygen (SaO2) during sleep, with longer duration of low SPO2 (less that 90%). The incidence of hypertension was higher in CAD patients with SDB than in those without SDB. No significant correlation was found between the severity of coronary artery disease and RDI (r=-0.16, P>0.05). CONCLUSION: The elderly patients with CAD have higher incidence of SDB, and appropriate interventions should be administered in those with severe SDB.

[Effect of peripheral blood mononuclear cells from patients with obstructive sleep apnea-hypopnea syndrome on apoptosis of vascular endothelial cells].

OBJECTIVE: To investigate the mechanism of vascular endothelial cell injury in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). METHODS: Peripheral blood samples were collected early in the morning from 20 normal persons, 21 patients with mild OSAHS, 24 patients with moderate OSAHS, and 20 patients with severe OSAHS according to the results of polysomnography (PSG). Mononuclear cells (MNCs) were isolated and co-cultured with human umbilical vein endothelial cells of the strain ECV304 for 48 h. The levels of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 in the supernatant were measured by ELISA, and the apoptosis rate and the protein expression level of Fas of the endothelial cells were detected by flow cytometry. RESULTS: The TNF-alpha level of the severe OSAHS group was (2.10 +/- 0.60) microg/L, significantly higher than those of the moderate OSAHS, mild OSAHS, and normal control groups [(1.40 +/- 0.50) microg/L, (1.20 +/- 0.30) microg/L, and (0.80 +/- 0.10) microg/L, F = 69.65, P < 0.01]. The IL-6 level of the severe OSAHS group was (64.80 +/- 9.90) microg/L, significantly higher than those of the moderate OSAHS, mild OSAHS, and normal control groups [(46.90 +/- 10.80) microg/L, (49.60 +/- 2.80) microg/L, and (23.50 +/- 6.50) microg/L, F = 182.83, P < 0.01]. The TNF-alpha and IL-6 levels of the severe OSAHS group were both significantly higher than those of the moderate and mild OSAHS groups (both P < 0.01). However, there was no significant differences in the TNF-alpha and IL-6 levels between the mild and moderate OSAHS groups (both P > 0.05). The apoptosis rates of endothelial cells in the severe and moderate OSAHS groups were 19.6% +/- 3.8% and 19.3% +/- 6.3% respectively, both significantly higher than those of the mild OSAHS and control groups (9.2% +/- 3.0% and 8.3% +/- 3.2% (both P < 0.01) whereas there were no significant differences between the mild OSAHS group and control group and between the moderate OSAHS group and severe group (both P > 0.05). There was no significant difference in the protein level of Fas expressed in the endothelial cells between the OSAHS patients and the controls (all P > 0.05). There was a significant positive correlation between the apoptosis rate of endothelial cells and AHI (r = 0.589 13, P = 0.0106), and a significant negative correlation between the apoptosis rate and the minimum oxygen saturation (r = -0.507 37, P < 0.0001). CONCLUSION: MNCs may play an important role in vascular endothelial cell injury in the OSAHS patients, and may be associated closely with the severity of the OSAHS and night hypoxemia.

[Relationship between chronic congestive heart failure and sleep-disordered breathing in elderly patients].

OBJECTIVE: To determine the prevalence of sleep disordered breathing (SDB) in elderly patients with chronic congestive heart failure (CHF) and explore the relations between SDB and left ventricular function. METHODS: By means of polysomnography, 56 elderly patients with CHF were divided into non-SDB, mild SDB, moderate SDB, and severe SDB groups, and the left ventricular ejection fraction (LVEF) was measure by (99)Tc equilibrium radionuclide angiography. RESULTS: In the 56 elderly patients with CHF, 38 (67.9%) had SDB, including 12 (21.4%) mild SDB, 14 (25.0%) moderate SDB, and 12 (21.4%) severe SDB patients. Thirty (53.6%) of the 56 patients with CHF had obstructive sleep apnea (OSA), 4 (7.1%) had central sleep apnea and 22 (39.2%) had mixed sleep apnea. The moderate and severe SDB groups had lower minimum arterial oxyhemoglobin saturation during sleep than the non-SDB groups, and the apnea-hyponea index was closely related to LVEF (r=-0.74, P<0.01). CONCLUSION: The prevalence of SDB, predominantly OSA, is high in elderly patients with CHF. Moderate and severe SDB might affect the left ventricular function in these patients, who require polysomnography monitoring.