Influence of hydrological features on CO2 and CH4 concentrations in the surface water of lakes, Southwest China: A seasonal and mixing regime analysis.

Due to the large spatiotemporal variability in the processes controlling carbon emissions from lakes, estimates of global lake carbon emission remain uncertain. Identifying the most reliable predictors of CO2 and CH4 concentrations across different hydrological features can enhance the accuracy of carbon emission estimates locally and globally. Here, we used data from 71 lakes in Southwest China varying in surface area (0.01‒702.4 km2), mean depth (< 1‒89.6 m), and climate to analyze differences in CO2 and CH4 concentrations and their driving mechanisms between the dry and rainy seasons and between different mixing regimes. The results showed that the average concentrations of CO2 and CH4 in the rainy season were 23.9 ± 18.8 µmol L-1 and 2.5 ± 4.9 µmol L-1, respectively, which were significantly higher than in the dry season (10.5 ± 10.3 µmol L-1 and 1.8 ± 4.2 µmol L-1, respectively). The average concentrations of CO2 and CH4 at the vertically mixed sites were 24.1 ± 21.8 µmol L-1 and 2.6 ± 5.4 µmol L-1, being higher than those at the stratified sites (14.8 ± 13.4 µmol L-1 and 1.7 ± 3.5 µmol L-1, respectively). Moreover, the environmental factors were divided into four categories, i.e., system productivity (represented by the contents of total nitrogen, total phosphorus, chlorophyll a and dissolved organic matter), physicochemical factors (water temperature, Secchi disk depth, dissolved oxygen and pH value), lake morphology (lake area, water depth and drainage ratio), and geoclimatic factors (altitude, wind speed, precipitation and land-use intensity). In addition to the regression and variance partitioning analyses between the concentrations of CO2 and CH4 and environmental factors, the cascading effects of environmental factors on CO2 and CH4 concentrations were further elucidated under four distinct hydrological scenarios, indicating the different driving mechanisms between the scenarios. Lake morphology and geoclimatic factors were the main direct drivers of the carbon concentrations during the rainy season, while they indirectly affected the carbon concentrations via influencing physicochemical factors and further system productivity during the dry season; although lake morphology and geoclimatic factors directly contributed to the carbon concentrations at the vertically mixed and stratified sites, the direct effect of system productivity was only observed at the stratified sites. Our results emphasize that, when estimating carbon emissions from lakes at broad spatial scales, it is essential to consider the influence of precipitation-related seasons and lake mixing regimes.

Integration of dye-sensitized solar cells, thermoelectric modules and electrical storage loop system to constitute a novel photothermoelectric generator.

This study self-develops a novel type of photothermoelectric power generation modules. Dye-sensitized solar cells (DSSCs) serve as the photoelectric conversion system and a copper (Cu) heat-transfer nanofilm coating on both sides of the thermoelectric generator (TEG) acts as a thermoelectric conversion system. Thus module assembly absorbs light and generates electricity by DSSCs, and also recycles waste heat and generates power by the TEG. In addition, a set of pulsating heat pipes (PHP) filled with Cu nanofluid is placed on the cooling side to increase cooling effects and enhance the power generation efficiency. Results show that when the heat source of thermoelectric modules reaches 90 degrees C, TEG power output is increased by 85.7%. Besides, after thermoelectric modules are heated by additional heat source at 80 degrees C, the electrical energy generated by them can let a NiMH cell (1.25 V) be sufficiently charged in about 30 minutes. When photothermoelectric modules is illumined by simulated light, the temperature difference of two sides of TEG can reach 7 degrees C and the thermoelectric conversion efficiency is 2.17%. Furthermore, the power output of the thermoelectric modules is 11.48 mW/cm2, enhancing 1.4 % compared to merely using DSSCs module.

Patterns of thermocline structure and the deep chlorophyll maximum feature in multiple stratified lakes related to environmental drivers.

Thermal stratification and the deep chlorophyll maximum (DCM), two commonly related phenomena in stratified lakes, play fundamental roles in eco-environmental processes. However, the progressive linkages among multi-dimensional environmental factors, thermal stratification and DCM were poorly explored, which greatly constrains our understanding of cross-level governance in deep lakes. In this study, the thermocline structure (i.e., thermocline depth, thickness and strength) and DCM feature (depth and thickness) and their driving factors were investigated at regional scale using data from 18 stratified lakes differing in limnological characteristics, Southwest China. Our study showed that (1) DCM occurred close to the thermocline in most lakes (represented by their depth and thickness), (2) the depths of the thermocline and DCM were both shallower than the euphotic depth, and (3) spatial heterogeneity occurred the thermocline structure and the DCM feature, reflecting different environmental factors. Specifically, water depth and light penetration depths were both positively correlated with thermocline depth and thickness and the DCM feature, and ultraviolet radiation (UVR) was more important than photosynthetically active radiation (PAR) for thermocline depth, but PAR was more important for thermocline thickness; moreover, PAR played a more prominent role than UVR for the DCM feature. As there were interactions between some environmental factors, we built a cascading path using a partial least squares path modelling for the DCM feature: lake morphometry directly impacted the thermocline structure and surface water quality; the water quality further affected light penetration depths as well as the thermocline structure; light penetration depth and thermocline structure combined directly determined the DCM feature, where the importance of light was larger. Our findings provide information on the cascading drivers of the thermocline structure and DCM feature in deep lakes and also constitute a valuable reference for deep lake management under the dual pressure of climate change and eutrophication.

Recruitment of voluntary non-remunerated apheresis donors: the second five years' experience in Shenzhen.

The voluntary non-remunerated blood donation campaign in Shenzhen, China, was launched in 1993 and the smooth change from paid donors to unpaid took only a decade. In the first half the volunteer donation system and a sufficient blood supply was promoted and this paved the way for further development in the second half during which the non-remunerated donation system became substantial and integral due to recruitment for plateletapheresis and peripheral stem cells donation as well as whole blood donations. Ninety percent of the donors registered for plateletapheresis do donate and none of the twenty-three non-related donors with matched HLA genotypes broke their promise to donate their peripheral stem cells.

Comparison of segmental pedicle screw instrumentation versus anterior instrumentation in adolescent idiopathic thoracolumbar and lumbar scoliosis.

STUDY DESIGN: A retrospective study. OBJECTIVE: To compare the results of anterior instrumentation versus segmental pedicle screw instrumentation in adolescent idiopathic thoracolumbar and lumbar scoliosis. SUMMARY OF BACKGROUND DATA: Anterior instrumentation is an established method of correcting adolescent idiopathic thoracolumbar and lumbar scoliosis. Posterior segmental pedicle screw instrumentation, with its more powerful corrective force over hooks, could offer significant advantages. METHODS: A retrospective analysis was conducted on 36 consecutive female patients with adolescent idiopathic thoracolumbar and lumbar scoliosis who had surgery from December 1997. All had a minimum of 2-year follow-up. Eleven patients had posterior surgery. RESULTS: Mean age at surgery was similar between both groups. Length of surgery was significantly shorter in the posterior group (189 minutes vs. 272 minutes). Length of hospital stay was shorter in the posterior group (6.2 days vs. 8 days). Estimated blood loss, duration of analgesia, and ICU stay did not differ significantly between the 2 groups. No complications were encountered in both groups at the latest follow-up. The magnitudes and flexibility of the thoracolumbar/lumbar curves did not differ significantly between the 2 groups. The number of levels in the major curve was also similar between the groups. Fusion levels were shorter in the anterior group (mean, 4.1 vs. 5.0). The percentage correction of scoliosis was similar between the 2 groups at all stages of follow-up, being 74% at 1 week postsurgery, 70% at 6 months postsurgery, 68% at 1 year postsurgery and latest follow-up for the anterior group, and 71% at 1 week postsurgery, 67% at 6 months postsurgery, 68% at 1 year postsurgery, and 67% at the latest follow-up for the posterior group. Thoracolumbar sagittal alignment at T11-L2 was maintained for both groups throughout the follow-up period. The incidence of proximal junctional kyphosis was higher in the posterior group (P < 0.01). CONCLUSION: Surgical correction of both the frontal and sagittal plane deformity are comparable to anterior instrumentation. Shorter lengths of surgery and hospital stay are the potential benefits of posterior surgery. Posterior segmental pedicle screw instrumentation offer significant advantages and is a viable alternative to standard anterior instrumentation in idiopathic thoracolumbar and lumbar scoliosis.

Results of thoracoscopic instrumented fusion versus conventional posterior instrumented fusion in adolescent idiopathic scoliosis undergoing selective thoracic fusion.

STUDY DESIGN: Retrospective review of 31 consecutive female patients with adolescent idiopathic scoliosis undergoing selective thoracic fusion. OBJECTIVE: To compare safety and efficacy of two techniques in treating adolescent idiopathic scoliosis undergoing selective thoracic fusion. SUMMARY OF BACKGROUND DATA: There is paucity in the literature comparing posterior versus thoracoscopic instrumented fusion in scoliosis. METHODS: Nineteen patients (group 1) underwent posterior instrumented fusion. Twelve patients (group 2) had thoracoscopic anterior instrumented fusion. All patients had a minimum of 25 months of follow-up observation. RESULTS: Both groups were similar in terms of age at menarche and surgery. Preoperative Cobb angles in the coronal (erect and bending) and sagittal planes did not differ between the two groups. Group 1 patients had higher estimated blood loss (P = 0.006). Operative time (P < 0.001) and intensive care unit stay (P = 0.01) were longer in group 2 patients. There was no difference in parenteral analgesia requirement. There were no complications in group 1. Complications in group 2 included lobar collapse (1) and scapula winging (1). Improvement in scoliosis among group 1 patients averaged 77 (1 week), 72 (6 months), and 67% (most recent follow-up review). In group 2 patients, mean improvement in scoliosis was 66 (1 week), 62 (6 months), and 62% (most recent follow-up review). The differences between the two groups in terms of scoliosis improvement were not significant. Thoracic kyphosis (T2-T12) did not increase significantly with thoracoscopic versus posterior instrumentation. No significant change in lumbar lordosis (T12-S1) was noted with either procedure. CONCLUSIONS: The efficacy of thoracoscopic surgery was similar to standard posterior procedures. Advantages included lower intraoperative blood loss. The longer operative time and intensive care unit stay were attributed to the steep learning curve of this technique.