Seasonal catchment memory of high mountain rivers in the Tibetan Plateau.

Rivers originating in the Tibetan Plateau are crucial to the population in Asia. However, research about quantifying seasonal catchment memory of these rivers is still limited. Here, we propose a model able to accurately estimate terrestrial water storage change (TWSC), and characterize catchment memory processes and durations using the memory curve and the influence/domination time, respectively. By investigating eight representative basins of the region, we find that the seasonal catchment memory in precipitation-dominated basins is mainly controlled by precipitation, and that in non-precipitation-dominated basins is strongly influenced by temperature. We further uncover that in precipitation-dominated basins, longer influence time corresponds to longer domination time, with the influence/domination time of approximately six/four months during monsoon season. In addition, the long-term catchment memory is observed in non-precipitation-dominated basins. Quantifying catchment memory can identify efficient lead times for seasonal streamflow forecasts and water resource management.

Scenario-based multi-objective optimization of reservoirs in silt-laden rivers: A case study in the Lower Yellow River.

Severe sedimentation often takes place in the river channel of silt-laden rivers, which is often mitigated through water-sediment regulation of the reservoirs. However, watersediment regulation is often competitive with other objectives of reservoirs, like water supply and hydropower generation; on the other hand, the reduction of channel sedimentation is often achieved at the expense of reservoir sedimentation, which reduces the service life of reservoirs. The Yellow River used to be the river with largest sediment transport over the world, but has experienced significant declination of runoff and sediment in recent years. This study presents a scenario-based multi-objective optimization operation model for the Xiaolangdi reservoir considering hydropower generation, reservoir sedimentation and channel sedimentation, with a generalized linear model coupled to calculate channel sedimentation based on runoff and sediment time series. A stochastic model that can reproduce both spatial correlations and low frequency attributes of the data series is adopted to generate two different scenarios based on different periods of observation and the performance of the multi-objective operation model under different scenarios is tested. The results indicate that: (1) the proposed optimization model can generate different schemes of reservoir operation and enhance operation performance; (2) the generalized linear model can well fit the relationship between daily channel sedimentation and runoff-sediment factors, but tends to overestimate the erosion efficiency after 2005; (3) the reservoir sedimentation and channel sedimentation show linear competitive relation, i.e., an average increase of 1 ton in reservoir sedimentation would result in declination of channel sedimentation from 0.455 to 0.488 tons, while the competitive relationship between hydropower generation and reservoir sedimentation is non-linear and weak; (4) the increase in the proportion of non-flood sediment load to the total sediment load makes it more difficult to prevent the reservoir from silting up.

Identifying how future climate and land use/cover changes impact streamflow in Xinanjiang Basin, East China.

Climate and land use/cover changes are the main factors altering hydrological regimes. To understand the impacts of climate and land use/cover changes on streamflow within a specific catchment, it is essential to accurately quantify their changes given many possibilities. We propose an integrated framework to assess how individual and combined climate and land use/cover changes impact the streamflow of Xinanjiang Basin, in East China, in the future. Five bias-corrected and downscaled General Circulation Model (GCM) projections are used to indicate the inter-model uncertainties under three Representative Concentration Pathways (RCPs). Additionally, three land use/cover change scenarios representing a range of tradeoffs between ecological protection (EP) and urban development (UD) are projected by Cellular Automata - Markov (CA-Markov). The streamflow in 2021-2050 is then assessed using the calibrated Soil and Water Assessment Tool (SWAT) with 15 scenarios and 75 possibilities. Finally, the uncertainty and attribution of streamflow changes to climate and land use/cover changes at monthly and annual scale are analyzed. Results show that while both land use/cover change alone and combined changes project an increase in streamflow, there is a disagreement on the direction of streamflow change under climate change alone. Future streamflow may undergo a more blurred boundary between the flood and non-flood seasons, potentially easing the operation stress of Xinanjiang Reservoir for water supply or hydropower generation. We find that the impacts of climate and land use/cover changes on monthly mean streamflow are sensitive to the impermeable area (IA). The impacts of climate change are stronger than those induced by land use/cover change under EP (i.e., lower IA); and land use/cover change has a greater impact in case of UD (i.e., higher IA). However, changes in annual mean streamflow are mainly driven by land use/cover change, and climate change may decrease the influence attributed to land use/cover change.

Rice Yield Estimation Using Parcel-Level Relative Spectral Variables From UAV-Based Hyperspectral Imagery.

Time-series Vegetation Indices (VIs) are usually used for estimating grain yield. However, multi-temporal VIs may be affected by different background, illumination, and atmospheric conditions, so the absolute differences among time-series VIs may include the effects induced from external conditions in addition to vegetation changes, which will pose a negative effect on the accuracy of crop yield estimation. Therefore, in this study, the parcel-based relative vegetation index (ΔVI) and the parcel-based relative yield are proposed and further used to estimate rice yield. Hyperspectral images at key growth stages, including tillering stage, jointing stage, booting stage, heading stage, filling stage, and ripening stage, as well as rice yield, were obtained with Rikola hyperspectral imager mounted on Unmanned Aerial Vehicle (UAV) in 2017 growing season. Three types of parcel-level relative vegetation indices, including Relative Normalized Difference Vegetation Index (RNDVI), Relative Ratio Vegetation Index (RRVI), and Relative Difference Vegetation Index (RDVI) are created by using all possible two-band combinations of discrete channels from 500 to 900 nm. The optimal VI type and its band combinations at different growth stages are identified for rice yield estimation. Furthermore, the optimal combinations of different growth stages for yield estimation are determined by F-test and validated using leave-one-out cross validation (LOOCV) method. The comparison results show that, for the single-growth-stage model, RNDVI[880,712] at booting stage has the best correlation with rice yield with a R 2-value of 0.75. For the multiple-growth-stage model, RNDVI[808,744] at jointing stage, RNDVI[880,712] at booting stage and RNDVI[808,744] at filling stage gain a higher R 2-value of 0.83 with the mean absolute percentage error of estimated rice yield of 3%. The study demonstrates that the proposed method with parcel-level relative vegetation indices and relative yield can achieve higher yield estimation accuracy because it can make full use of the advantage that remote sensing can monitor relative changes accurately. The new method will further enrich the technology system for crop yield estimation based on remotely sensed data.

Treatment of cervical disc herniation through percutaneous minimally invasive techniques.

PURPOSE: The goal of this study is to compare the therapeutic effectiveness of percutaneous cervical discectomy, percutaneous cervical disc nucleoplasty, and a combination of the two for the treatment of cervical disc herniation and the effective stabilization of the cervical vertebral column. METHODS: A retrospective study was performed from February 2003 to April 2011. One hundred and seventy-one cervical disc herniation patients with a mean age of 47.8 years (ranging from 21 to 74 years) participated in the study and were treated with the three types of percutaneous minimally invasive techniques: percutaneous cervical discectomy (PCD, 97 cases), percutaneous cervical disc nucleoplasty (PCN, 50 cases), and a combination of the two (PCDN, 24 cases). After treatment, the postoperative clinical results and the stability of the cervical vertebral columns of these three groups were evaluated and compared. RESULTS: Patients in the PCD group received follow-up care for approximately 4.1 years (ranging from 0.2 to 8.5 years), while those in the PCN group received only an average of 2.6 years (ranging from 0.3 to 7.8 years), and the PCDN group received an average of 3.3 years (ranging from 0.2 to 8 years of follow-up). According to the Japanese Orthopedic Association scoring system, the functional scores (JOA scores) differed significantly between the pre- and postoperative patients within the three groups (PCD t = 21.849, P = <0.05; PCN t = 14.503, P < 0.05; PCDN t = 8.555, P < 0.05). All patients had been successfully operated on by the same spinal surgeon team. According to the Odom criterion, the clinical outcomes were not significantly different for any of the three groups (the recovery rate using the JOA standard evaluation, F = 2.19, P = 0.116, P > 0.05). The percentages of each procedure that received either an excellent or a good rating were PCD at 81.35 %, PCN at 82.44 % and PCDN at 83.19 %. In addition, the clinical success rates among the three were not significantly different (P > 0.05). Notably, there was no postoperative instability of the cervical vertebral column in any of the patients (P > 0.05), and there was no difference in the pre- or postoperative stability of the cervical vertebral columns in each group. CONCLUSIONS: Each group achieved good clinical outcomes with this safe, minimally invasive spinal surgery for the treatment of cervical disc herniation. In addition, no postoperative risk of cervical instability was found.

Digital three-dimensional model of lumbar region 4-5 and its adjacent structures based on a virtual Chinese human.

OBJECTIVE: To study the methods for constructing a digitized three-dimensional (3D) model of a virtual lumbar region and its adjacent structures in order to assist anatomical study and virtual surgery. METHODS: Images of DSCF5375-p1 to DSCF5745-p1 were taken from the database of the digitized Virtual Chinese human of Southern Medical University in Guangzhou. This region encompasses the superior facet joint of L4 to the inferior edge of the intervertebral body of L5. The regions of interest were interactively segmented from the images utilizing Adobe Photoshop software. The images were further processed using format conversion and segmentation. Finally, a 3D model of the L4-5 region and its neighboring structures was reconstructed with the assistance of Mimics 10.01 software. RESULTS: A digitized 3D model of this part of the virtual lumbar spine and its adjacent structures was reconstructed. This model allows all constructed structures to be displayed individually or jointly, moved or rotated arbitrarily, setting of different transparencies and convenient measurement of the diameters and angles of the reconstructed structures. The 3D model precisely displays the anatomical relationships between all structures and provides a reliable 3D model for a spinal endoscopic surgery simulation system. CONCLUSION: Visualization of the digitized 3D reconstruction of the virtual lower lumbar region displays this region and its adjacent structures stereoscopically and in actuality, thus providing morphological data concerning anatomy, image diagnosis and virtual operations in this region.

Effects of cetyltrimethylammonium chloride on uptake of pyrene by fish gills.

Laboratory experiments were carried out to study the effects of cationic surfactant cetyltrimethylammonium chloride (CTAC) on the uptake of pyrene by fish gills. The uptake (including adsorption) of pyrene by gills of the color carp (C. carpio var. color) exposed to 20-100 microg/L pyrene in the presence or absence of 0.2-1.0 mg/L CTAC were determined. The sorption of pyrene by mucus was preliminary studied using a four-step sequential extraction procedure. Fish gills were extracted with H2O, 0.01 M CaCl2, CH3OH and a mixture of 1:1 n-C6H14/CH2Cl2 in sequence. Results showed that pyrene mostly accumulated in mucus and on the surface of gills tissue; the cationic surfactant CTAC significantly enhanced these accumulation or adsorption on the fish gills (not in gills). CTAC could affect the bioavailability ofpyrene in aquatic systems.

Effects of sodium dodecylbenzenesulfonate on uptake of pyrene by fish gills.

Laboratory experiments were carried out to study the effects of anionic surfactant sodium dodecylbenzenesulfonate (SDBS) on the uptake of pyrene by fish gills. The uptake (including adsorption) of pyrene by gills of the color carp (C. carpio var. color) exposed to 20-100 microg/L pyrene in the presence or absence of 0.2-6.0 mg/L SDBS were determined. The sorption of pyrene by mucus was preliminary studied using a four-step sequential extraction procedure. Fish gills were extracted with H(2)O, 0.01 M CaCl(2), CH(3)OH and a mixture of 1:1 n-C(6)H(14)/CH(2)Cl(2) in sequence. Results showed that SDBS significantly affected these accumulation or adsorption on the fish gills (not in gills). SDBS could affect the bioavailability of pyrene in aquatic systems.