Spatial and environmental processes are two ecological processes that have attracted considerable attention in plant community assembly,depending on sampling scale and life history.However,the processes that determine...Spatial and environmental processes are two ecological processes that have attracted considerable attention in plant community assembly,depending on sampling scale and life history.However,the processes that determine community assembly have not been studied in the karst region of southwest China.In this study,a 25-ha(500 m×500 m)monitoring plot within the subtropical climax forest in the karst region was established and canonical correspondence analysis was used to reveal the effects of topography and soil on the spatial patterns of tree community assembly.Our study suggests that spatial processes dominate species composition and the combined effects of spatial and environmental processes play an important role.Overall interpretation rate increases with enlarging the sampling scale.However,the pattern of variation partitioning was similar in different life stages.Environmental variables significantly affected species composition at different sampling sizes and life histories and had a higher interpretation rate of species composition on larger s ampling sizes.Topographic wetness index was the most important variable to explain species composition of the environmental variables.These results suggest that it is necessary to consider the relative importance of environmental and spatial factors on community assembly to better understand,conserve,and manage subtropical karst forests.展开更多
To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea （ECS） shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom s...To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea （ECS） shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom simulating reflector （BSR） occurrence, but it is very rare. Besides several BSRs, a gas seepage was also found. As shown by the data, both the BSR and gas seepage are all related with local geological structures, such as mud diapir, anticline, and fault-controlled graben-like structure. However, similar structural ＂anomalies＂ are quite common in the tectonically very active Okinawa Trough region, but very few of them have developed BSR or gas seepage. The article points out that the main reason is probably the low concentration of organic carbon of the sediment in this area. It was speculated that the rare occurrence of gas hydrates in this region is governed by structure-controlled fluid flow. Numerous faults and fractures form a network of high-permeability channels in the sediment and highly fractured igneous basement to allow fluid circulation and ventilation. Fluid flow in this tectonic environment is driven primarily by thermal buoyancy and takes place on a wide range of spatial scales. The fluid flow may play two roles to facilitate hydrate formation： to help gather enough methane into a small area and to modulate the thermal regime.展开更多
As there is no need of permanent magnet(PM)material and only silicon steel sheet required on the rotor,synchronous reluctance machine(SynRM)can be used for many applications and draws a great research interest.For the...As there is no need of permanent magnet(PM)material and only silicon steel sheet required on the rotor,synchronous reluctance machine(SynRM)can be used for many applications and draws a great research interest.For the SynRM,the torque ripple is a big issue and a great of work could been done on reducing it.In this paper,asymmetrical magnetic flux barriers in the SynRM rotor were studied comprehensively,including angle and width of each layer and each side of the magnetic barrier.The SynRMb with asymmetrical and parallel magnetic flux barrier was found as the best way to design SynRM based on the multi-objective design optimization method.Moreover,each parameter was studied to show the design rule of the asymmetrical magnetic flux barrier.As the average torque will be reduced with the asymmetrical barrier is used,the grain-oriented silicon steel is used on stator teeth of the SynRMb(SynRMbG)was proposed and studied.The analysis results show that the proposed new method can make the SynRM have better performance.展开更多
Purpose: We investigated the margin recipes with different alignment techniques in the image-guided intensity-modulated radiotherapy (IMRT) of whole pelvis prostate cancer patients. Materials and Methods: Forty-eight ...Purpose: We investigated the margin recipes with different alignment techniques in the image-guided intensity-modulated radiotherapy (IMRT) of whole pelvis prostate cancer patients. Materials and Methods: Forty-eight computed tomography (CT) scans of eight prostate cancer patients were investigated. Each patient had an initial planning CT scan and 5 consecutive serial CT scans during the course of treatment, all of which were acquired using 3 mm slice separation and 0.94 mm resolution in the axial plane at 120 kVp, on a PQ 5000 CT scanner. Three different whole pelvis planning margin recipes, ranging from 3 to 13 mm, were investigated. A unique IMRT plan was created with each PTV on the initial CT scan, and was then registered to the 5 serial CT scans, by bony alignment or by prostate gland-based alignment. The dose computed on each serial CT scans was accumulated back to the initial CT scan using deformable image registration for final dosimetric evaluation of the interplay of the margin selection and alignment methods. Results: Bony alignment and prostate gland-based alignment gave very similar result to the pelvic lymphatic nodes (PLNs), regardless of its margin around. The prostate gland-based alignment greatly enhanced the coverage to the prostate and SV, especially with small margins. Meanwhile, the soft-tissue alignment also raised the incidental dose to the rectum and reduces the dose to the bladder. With small to intermediate margins, only soft-tissue alignment gave acceptable mean coverage to SV. Margin of 13mm or more was needed for PLNs to maintain good target coverage. Conclusion: We commend prostate-based alignment along with margins less than or equal to 5mm around prostate and SV, and margins greater than or equal to 13 mm around the vascular spaces.展开更多
Contemporary PET scanners for clinical use have spatial-resolution of 4 - 5 mm, caused by fundamental factors in medical imaging: detector sizes, free path of positrons, and non-colinearity uncertainty of annihilation...Contemporary PET scanners for clinical use have spatial-resolution of 4 - 5 mm, caused by fundamental factors in medical imaging: detector sizes, free path of positrons, and non-colinearity uncertainty of annihilation photon-pairs. The drawback in resolution significantly restrained the sensitivity of PET in imaging small lesions, which could be either early-stage cancers or small metastasis. In this study, the principle for a novel scanning mode to acquire high spatial-resolution images is proposed for clinical PET scanners. The concept of equivalent position was first proposed as different angular orientations of the scanner ring, at which comparable images could be achieved. Due to this concept, a typical static PET scan can be separated into m (m ≥ 2) equivalent sub-scans at different equivalent positions, when the scanner ring is systematically adjusted to m equivalent-positions of equal distance within one detector size. In this case each detector is virtually divided into m equal sub-detectors, without physical minimizing the detector size, and imaging contributions from every 1/m part of the detector can be determined by an analytically matrix, since there are m variables and m sub-scans. This novel concept is quite feasible to contemporary design because the high spatial resolution working modes (m ≥ 2) only demand the scanner to be slightly adjustable to other angular orientations. Adding high spatial resolutions modes to the scanner only has trifling influence on contrast resolutions as all imaging events at each sub-scan are independent. The time for performing a high-resolution scan could be comparable to a typical PET scan, as long as the Poisson noises are insignificant to low-uptake voxels. As a result, for a typical scanner design e.g. 80 cm in diameter with 18F as tracers, the spatial resolution of double sub-scans (m = 2) is 2.56 mm, and 2.19 mm for triple sub-scans (m = 3), which are significant improvements. The novelty of high spatial resolution design is compatible to digital PET or any other technological evolutions.展开更多
Purpose: To generate parametric images of tumor hypoxia in a tumor-bearing rat model using voxel-based compartmental analysis of dynamic fluorine-18 labeled misonidazole (18F-FMISO) microPET? images, and to compare th...Purpose: To generate parametric images of tumor hypoxia in a tumor-bearing rat model using voxel-based compartmental analysis of dynamic fluorine-18 labeled misonidazole (18F-FMISO) microPET? images, and to compare the parametric images thus derived with static “late” 18F-FMISO microPET? images for the detection of tumor hypoxia. Materials and Methods: Nude rats bearing HT-29 colorectal carcinoma xenografts (≈1.5 - 2 cm in diameter) in the right hind limb were positioned in a custom-fabricated, animal-specific foam mold. Animals were injected via the tail vein with ≈55.5 MBq 18F-FMISO and continuously imaged for either 60 or 120 minutes, with additional late static images up to 3 hour post-injection. The raw list-mode data was reconstructed into 37 - 64 frames with earlier frames of shorter time durations (12 - 15 seconds) and later frames of longer durations (up to 300 seconds). Time activity curves (TACs) were generated over regions encompassing the tumor as well as an artery, the latter for use as an input function. A beta version of a compartmental modeling package (BioGuide?, Philips Healthcare) was used to generate parametric images of k3 and Ki, rate constants of entrapment and flux of 18F-FMISO, respectively. Results: Data for 7 HT-29 tumor xenografts were presented, 6 of which yielded clear areas of tumor hypoxia as defined by Ki/k3 maps. Importantly, intratumoral foci with high 18F-FMISO uptakes on the late images did not always exhibit high Ki/k3 values and may there- fore represent false-positives for radiobiologically significant hypoxia. Conclusions: This study attempts to quantify tumor hypoxia using compartmental analysis of dynamic 18F-FMISO PET images in rodent xenograft tumor models. The results demonstrate feasibility of the approach in small-animal imaging studies, and provide evidence for the possible unreliability of late-time static imaging of 18F-FMISO PET in identifying tumor hypoxia.展开更多
Multi-channel cylindrical applicators for high dose-rate (HDR) brachytherapy are utilized mainly for special gynecology cases often involving image-guidance high dose-rate (IG-HDR or IGBT) brachytherapy. In these case...Multi-channel cylindrical applicators for high dose-rate (HDR) brachytherapy are utilized mainly for special gynecology cases often involving image-guidance high dose-rate (IG-HDR or IGBT) brachytherapy. In these cases, doses are prescribed to partial vaginal wall/depth where the disease is indicated by an MRI study scanned on the same day. These novel IG-HDR procedures are logistical challenges comparing to typical HDR out-patient treatments due to the complexity of planning for asymmetrical prescriptions as well as the extension of the whole procedure. Indeed the main advantages of HDR over LDR brachytherapy would be significantly weaken unless the IG-HDR procedures become more efficient in time, thus timely treatment planning becomes crucial. Based on our clinical experience, we propose the pseudo central-catheter method to reduce errors, to minimize uncertainty and to ensure efficiency. In this method, the central hollow path of the multi-channel cylindrical applicator is digitized into a pseudo catheter similar to other active catheters, and the asymmetrical prescription points could be generated corresponding to the pseudo dwelling points in the pseudo central-catheter. The pseudo dwelling points are later deleted after generating the prescription point arrays. This method is robust with minimal chance of errors or uncertainties, and demonstrates high efficiency with much less chance of uncertainty, which is significant for IG-HDR brachytherapy procedures utilizing multi-channel applicators.展开更多
Aiming at the problem that the existing risk assessment methods in China cannot simply and accurately assess the safety risk of gas wells, a rapid semi-quantitative risk assessment method for gas wells under high temp...Aiming at the problem that the existing risk assessment methods in China cannot simply and accurately assess the safety risk of gas wells, a rapid semi-quantitative risk assessment method for gas wells under high temperature and pressure is studied. Based on the rapid risk assessment method of annulus well with pressure in Chevron Company and the existing risk assessment methods, the well barrier and annulus pressure of high temperature and high pressure gas wells are fully considered. A rapid semi-quantitative risk assessment method for high temperature and high pressure gas wells is established, which takes the annulus pressure value, well service life, annulus pressure recovery after pressure relief, reservoir conditions (formation pressure, production) and well CO<sub style="font-family:" white-space:normal;"=""><span style="font-size:12px;font-family:Verdana;">2 </span></sub><span style="font-family:Verdana;">and H</span><sub style="font-family:" white-space:normal;"=""><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">S content as the key risk indexes. The method is applied in a gas field, and the risk value and risk grade of a practical well are semi-quantitatively evaluated. The overall risk situation of the well is obtained. The research results provide important technical guidance for the safe production of gas well.</span>展开更多
Under the background of large-scale ecological restoration, China's southwestern karst region has become a hotspot of global vegetation cover “greening” in the past 20 years. However, because of geological const...Under the background of large-scale ecological restoration, China's southwestern karst region has become a hotspot of global vegetation cover “greening” in the past 20 years. However, because of geological constraints, it is difficult to restore the forest landscapes in some areas. It is urgent to understand the impacts of human disturbances during the historical period on the difficult-to-forestation rocky-desertification areas of the karst region in order to guide future afforestation. In this study, we quantified the changes of specific sediment yield in typical karst depressions over the past 500 years by using ^(137)Cs,^(210)Pb, and ^(14)C dating methods in karst depressions, and identified the main human disturbances related to historical erosion and sedimentation by combining with historical data. The results showed that the erosion and sedimentation of the three depressions in 1921–1963 were significantly higher than that in 1963–2021, and the sedimentation rate(0.64–1.33 cm a^(-1)) and the specific sediment yield(2.51–13.11 t ha^(-1)a^(-1)) during Ming and Qing dynasties(1504–1812) were higher than the sedimentation rate(0.26–0.95 cm a^(-1)) and specific sediment yield(0.95–6.99 t ha^(-1)a^(-1)) in the recent century(1921–2021). Reconstruction data and literature from the Ming and Qing dynasties show an empirical link between changes in population, arable land, food, forest area,and deforestation events during the same period. It was found that the population and arable land in Guangxi increased more than three-fold and the forest area decreased significantly in the 17th century after the migration of the Yao ethnic group and the introduction of maize to the region, which may be the main reason for intensifying the erosion of depressions. This study is of great significance to understanding the evolution history of rocky desertification in this region and to answer the potential of afforestation.展开更多
Heterogeneous karst surfaces exerted scaling effects whereby specific runoff decrease with increasing area.The existing RUSLE-L equations are limited by the default implicit assumption that the surface-runoff intensit...Heterogeneous karst surfaces exerted scaling effects whereby specific runoff decrease with increasing area.The existing RUSLE-L equations are limited by the default implicit assumption that the surface-runoff intensity is constant at any slope length.The objective of this study was to modify the L-equation by establishing the functional relationship between surface-runoff intensity and karst slope length,and to evaluate its predictive capability at different resolution DEMs.Transfer grid layers were generated based on the area rate of surface karstification and considered the runoff transmission percentage at the exposed karst fractures or conduits to be zero.Using the multiple flow direction algorithm united with the transfer grid(MFDTG),the flow accumulation of each grid cell was simulated to estimate the average surface-runoff intensity over different slope lengths.The effectiveness of MFDTG algorithm was validated by runoff plot data in Southwestern China.The simulated results in a typical peak-cluster depression basin with an area rate of surface karstification of 6.5%showed that the relationship between surface-runoff intensity and slope length was a negative power function.Estimated by the proposed modified L-equation((al_(x)^((b+1))/22.13)^(m)),the L-factor averages of the study basin ranged from 0.35 to 0.41 at 1,5,25 and 90 m resolutions respectively.This study indicated that the modified L-equation enables an improved prediction of the much smaller L-factor and the use of any resolution DEMs on karst landscapes.Particular attention should be given to the variation of surface-runoff intensity with slope length when predicting L-factor on hillslopes with runoff scale effect.展开更多
Karst regions of Southwest China become a hotspot for global greening through large-scale vegetation restoration in recent two decades.However,the unique,fragile geological setting of carbonate rocks affects the susta...Karst regions of Southwest China become a hotspot for global greening through large-scale vegetation restoration in recent two decades.However,the unique,fragile geological setting of carbonate rocks affects the sustainability of vegetation greening.Here,we summarize and evaluate the impacts of the rock and soil compositions of karst landscapes on the types and quality of vegetation restoration.We introduce the concept of“soil mass”and establish its relationship with aboveground vegetation biomass across varying degrees of rocky desertification.The mineral nutrients and soil mass constrain the potential of vegetation carbon sequestration in karst regions.To enhance the sustainability of vegetation restoration and carbon sequestration under karst geological constraints,we suggest to push ecological intensification of tree plantations and optimize the zoning and classification of rocky desertification treatment,and these restoration initiatives will foster vegetation restoration to serve as a pivotal pathway towards carbon neutrality.展开更多
Genomic prediction is an effective way to accelerate the rate of agronomic trait improvement in plants.Traditional methods typically use linear regression models with clear assumptions;such methods are unable to captu...Genomic prediction is an effective way to accelerate the rate of agronomic trait improvement in plants.Traditional methods typically use linear regression models with clear assumptions;such methods are unable to capture the complex relationships between genotypes and phenotypes.Non-linear models(e.g.,deep neural networks)have been proposed as a superior alternative to linear models because they can capture complex non-additive effects.Here we introduce a deep learning(DL)method,deep neural network genomic prediction(DNNGP),for integration of multi-omics data in plants.We trained DNNGP on four datasets and compared its performance with methods built with five classic models:genomic best linear unbiased prediction(GBLUP);two methods based on a machine learning(ML)framework,light gradient boosting machine(LightGBM)and support vector regression(SVR);and two methods based on a DL framework,deep learning genomic selection(DeepGS)and deep learning genome-wide association study(DLGWAS).DNNGP is novel in five ways.First,it can be applied to a variety of omics data to predict phenotypes.Second,the multilayered hierarchical structure of DNNGP dynamically learns features from raw data,avoiding overfitting and improving the convergence rate using a batch normalization layer and early stopping and rectified linear activation(rectified linear unit)functions.Third,when small datasets were used,DNNGP produced results that are competitive with results from the other five methods,showing greater prediction accuracy than the other methods when large-scale breeding data were used.Fourth,the computation time required by DNNGP was comparable with that of commonly used methods,up to 10 times faster than DeepGS.Fifth,hyperparameters can easily be batch tuned on a local machine.Compared with GBLUP,LightGBM,SVR,DeepGS and DLGWAS,DNNGP is superior to these existing widely used genomic selection(GS)methods.Moreover,DNNGP can generate robust assessments from diverse datasets,including omics data,and quickly incorporate complex and large datasets into usable models,making it a promising and practical approach for straightforward integration into existing GS platforms.展开更多
Mixed cultivation of fast-growing grasses and nitrogen(N)-fixing legumes for forage production is widely considered effective for obtaining sustained high forage yields without depleting soil N levels.However,the effe...Mixed cultivation of fast-growing grasses and nitrogen(N)-fixing legumes for forage production is widely considered effective for obtaining sustained high forage yields without depleting soil N levels.However,the effects of monoculture and mixed culture of these species on soil food webs are poorly understood.In this study,soil nematode communities were examined as indicators of the soil food web structure of monoculture and mixed culture of grass and legume at three N levels,i.e.,338(low),450(moderate),and 675(high)kg N ha-1 year-1,across 2 years in wet and dry seasons,using the grass Paspalum wetsfeteini and the legume Medicago sativa(alfalfa),both commonly cultivated worldwide.Repeated-measures analysis of covariance showed that compared with grass monoculture,legume monoculture and grass-legume mixture increased abundances of herbivorous,bacterivorous,and fungivorous nematodes in the soil food web under the low and moderate N fertilization levels.Principal response curve results showed that the abundance of Helicotylenchus,a plant parasite,was significantly higher under legume monoculture than other planting systems at the low N fertilization level.Structural equation model analysis indicated that the legume increased bacterivore abundance,while increasing N fertilization decreased omnivore abundance.The legume might increase the quantity and quality of food resources for soil biota,resulting in the bottom-up control of soil nematode communities.Our results indicate that targeted control of a soilborne pathogen,Helicotylenchus,is required in alfalfa-based planting systems.In addition,high inorganic N application,which is detrimental to legume-rhizobia symbiosis,nullified the otherwise positive effects of legumes on soil nematodes.展开更多
The mercury flux in soils was investigated, which were amended by gypsums from flue gas desulphurization （FGD） units of coal- fired power plants. Studies have been carried out in confined greenhouses using FGD gypsu...The mercury flux in soils was investigated, which were amended by gypsums from flue gas desulphurization （FGD） units of coal- fired power plants. Studies have been carried out in confined greenhouses using FGD gypsum treated soils. Major research focus is uptakes of mercury by plants, and emission of mercury into the atmosphere under varying application rates of FGD gypsum, simulating rainfall irrigations, soils, and plants types. Higher FGD gypsum application rates generally led to higher mercury concentrations in the soils, the increased mercury emissions into the atmosphere, and the increased mercury contents in plants （especially in roots and leaves）. Soil properties and plant species can play important roles in mercury transports. Some plants, such as tall fescue, were able to prevent mercury from atmospheric emission and infiltration in the soil. Mercury concentration in the stem of plants was found to be increased and then leveled off upon increasing FGD gypsum application. However, mercury in roots and leaves was generally increased upon increasing FGD gypsum application rates. Some mercury was likely absorbed by leaves of plants from emitted mercury in the atmosphere.展开更多
Due to the complex hydrogeological conditions in karst regions,it is difficult to measure sediment source contributions at a catchment scale directly.The objective of this study was to quantify the relative contributi...Due to the complex hydrogeological conditions in karst regions,it is difficult to measure sediment source contributions at a catchment scale directly.The objective of this study was to quantify the relative contributions of sediment sources and their temporal variability in a karst catchment in southwest China.Karst depressions can trap eroded sediment similar to a dam or reservoir and,thus,are representative and typical test beds for identifying sediment sources in karst regions.Three sediment cores were taken from a karst depression,58 soil samples from three potential sediment sources were collected,and 18 soil properties were analyzed.The relative contributions of cropland,forestland,and fissure or crack soils were calculated using a multivariate mixing model.The fingerprinting results demonstrated that the cropland was the main sediment source in karst catchment.Specifically,according to the mean sediment contributions of the three deposited sediment cores,the sediment contribution from cropland topsoil was 69.3%,varying from 46.9%to 92.3%,and forestland soil and crack soil accounted for 8.6%and 22.1%of the sediment yield,and varying from 2.8%to 16.5%and 4.8%-36.6%,respectively.This result indicated that great attention should be paid when using only a single core to quantify sediment provenance.Due to the deposited sediment was generally disturbed as cropland in the karst depression,the area that has not been disturbed in recent decades in depression was more appropriate to trace sediment sources in karst catchment.To the best of our knowledge,this study was the first to quantify the contributions of sediment sources in the karst catchment of southwest China.This study provides valuable information and a preliminary reference for applying a composite fingerprinting technique to quantify sediment sources in karst catchments.展开更多
Soil nematodes are useful ecological indicators and can be extracted from soil by a variety of techniques.Because the extracted nematode samples(suspensions)can be quite turbid(i.e.,they contain soil particles and org...Soil nematodes are useful ecological indicators and can be extracted from soil by a variety of techniques.Because the extracted nematode samples(suspensions)can be quite turbid(i.e.,they contain soil particles and organic particles in addition to nematodes),quantitative and taxonomic analyses of the nematodes by microscopy can be difficult.In this study,the following three methods for cleaning turbid suspensions obtained from Baermann funnels were assessed:repeated centrifugation at 692.5´g for 1 min,repeated settling at low-temperature(4°C)for 24 h,and a combination of low-temperature settling and centrifugation.Nematodes were extracted with Baermann funnels from soil samples collected from four land-use types(since land-use type can affect the turbidity of nematode suspensions),and the resulting suspensions were cleaned by the three methods before nematode abundance was assessed.As a control,samples(i.e.,suspensions)were simply diluted with water,and nematodes were counted in the entire volume.The results showed that,within each land-use type,nematode abundance did not significantly differ between the control and the three cleaning methods.Averaged across all land-use types,however,the nematode recovery rate was slightly higher with repeated centrifugation than with the other two cleaning methods.Therefore,the proposed methods are sound for cleaning turbid nematode suspensions,and repeated centrifugation is the most efficient method.展开更多
基金supported by the National Natural Science Foundation of China (42071073,31971487)Youth Innovation Promotion Association of the Chinese Academy of Sciences (2021366)+2 种基金Guangxi Key Research and Development Program (AB17129009)the Hechi Distinguished Expert Program to Fuping Zengthe Guangxi Bagui Scholarship Program to Dejun Li。
文摘Spatial and environmental processes are two ecological processes that have attracted considerable attention in plant community assembly,depending on sampling scale and life history.However,the processes that determine community assembly have not been studied in the karst region of southwest China.In this study,a 25-ha(500 m×500 m)monitoring plot within the subtropical climax forest in the karst region was established and canonical correspondence analysis was used to reveal the effects of topography and soil on the spatial patterns of tree community assembly.Our study suggests that spatial processes dominate species composition and the combined effects of spatial and environmental processes play an important role.Overall interpretation rate increases with enlarging the sampling scale.However,the pattern of variation partitioning was similar in different life stages.Environmental variables significantly affected species composition at different sampling sizes and life histories and had a higher interpretation rate of species composition on larger s ampling sizes.Topographic wetness index was the most important variable to explain species composition of the environmental variables.These results suggest that it is necessary to consider the relative importance of environmental and spatial factors on community assembly to better understand,conserve,and manage subtropical karst forests.
基金the National Natural Science Foundation of China (No.40776032)Key Discipline Program of Chinese Academy of Sciences (No.KZCX2-211-01)National Basic Research Program of China (973 Program,No.207CB411702)
文摘To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea （ECS） shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom simulating reflector （BSR） occurrence, but it is very rare. Besides several BSRs, a gas seepage was also found. As shown by the data, both the BSR and gas seepage are all related with local geological structures, such as mud diapir, anticline, and fault-controlled graben-like structure. However, similar structural ＂anomalies＂ are quite common in the tectonically very active Okinawa Trough region, but very few of them have developed BSR or gas seepage. The article points out that the main reason is probably the low concentration of organic carbon of the sediment in this area. It was speculated that the rare occurrence of gas hydrates in this region is governed by structure-controlled fluid flow. Numerous faults and fractures form a network of high-permeability channels in the sediment and highly fractured igneous basement to allow fluid circulation and ventilation. Fluid flow in this tectonic environment is driven primarily by thermal buoyancy and takes place on a wide range of spatial scales. The fluid flow may play two roles to facilitate hydrate formation： to help gather enough methane into a small area and to modulate the thermal regime.
基金the National Natural Science Foundation of China under Project 52007047,in part by the National Natural Science Foundation of China under Project 51877065,and in part by Natural Science Foundation of Hebei Province under Project E2019202220.
文摘As there is no need of permanent magnet(PM)material and only silicon steel sheet required on the rotor,synchronous reluctance machine(SynRM)can be used for many applications and draws a great research interest.For the SynRM,the torque ripple is a big issue and a great of work could been done on reducing it.In this paper,asymmetrical magnetic flux barriers in the SynRM rotor were studied comprehensively,including angle and width of each layer and each side of the magnetic barrier.The SynRMb with asymmetrical and parallel magnetic flux barrier was found as the best way to design SynRM based on the multi-objective design optimization method.Moreover,each parameter was studied to show the design rule of the asymmetrical magnetic flux barrier.As the average torque will be reduced with the asymmetrical barrier is used,the grain-oriented silicon steel is used on stator teeth of the SynRMb(SynRMbG)was proposed and studied.The analysis results show that the proposed new method can make the SynRM have better performance.
文摘Purpose: We investigated the margin recipes with different alignment techniques in the image-guided intensity-modulated radiotherapy (IMRT) of whole pelvis prostate cancer patients. Materials and Methods: Forty-eight computed tomography (CT) scans of eight prostate cancer patients were investigated. Each patient had an initial planning CT scan and 5 consecutive serial CT scans during the course of treatment, all of which were acquired using 3 mm slice separation and 0.94 mm resolution in the axial plane at 120 kVp, on a PQ 5000 CT scanner. Three different whole pelvis planning margin recipes, ranging from 3 to 13 mm, were investigated. A unique IMRT plan was created with each PTV on the initial CT scan, and was then registered to the 5 serial CT scans, by bony alignment or by prostate gland-based alignment. The dose computed on each serial CT scans was accumulated back to the initial CT scan using deformable image registration for final dosimetric evaluation of the interplay of the margin selection and alignment methods. Results: Bony alignment and prostate gland-based alignment gave very similar result to the pelvic lymphatic nodes (PLNs), regardless of its margin around. The prostate gland-based alignment greatly enhanced the coverage to the prostate and SV, especially with small margins. Meanwhile, the soft-tissue alignment also raised the incidental dose to the rectum and reduces the dose to the bladder. With small to intermediate margins, only soft-tissue alignment gave acceptable mean coverage to SV. Margin of 13mm or more was needed for PLNs to maintain good target coverage. Conclusion: We commend prostate-based alignment along with margins less than or equal to 5mm around prostate and SV, and margins greater than or equal to 13 mm around the vascular spaces.
文摘Contemporary PET scanners for clinical use have spatial-resolution of 4 - 5 mm, caused by fundamental factors in medical imaging: detector sizes, free path of positrons, and non-colinearity uncertainty of annihilation photon-pairs. The drawback in resolution significantly restrained the sensitivity of PET in imaging small lesions, which could be either early-stage cancers or small metastasis. In this study, the principle for a novel scanning mode to acquire high spatial-resolution images is proposed for clinical PET scanners. The concept of equivalent position was first proposed as different angular orientations of the scanner ring, at which comparable images could be achieved. Due to this concept, a typical static PET scan can be separated into m (m ≥ 2) equivalent sub-scans at different equivalent positions, when the scanner ring is systematically adjusted to m equivalent-positions of equal distance within one detector size. In this case each detector is virtually divided into m equal sub-detectors, without physical minimizing the detector size, and imaging contributions from every 1/m part of the detector can be determined by an analytically matrix, since there are m variables and m sub-scans. This novel concept is quite feasible to contemporary design because the high spatial resolution working modes (m ≥ 2) only demand the scanner to be slightly adjustable to other angular orientations. Adding high spatial resolutions modes to the scanner only has trifling influence on contrast resolutions as all imaging events at each sub-scan are independent. The time for performing a high-resolution scan could be comparable to a typical PET scan, as long as the Poisson noises are insignificant to low-uptake voxels. As a result, for a typical scanner design e.g. 80 cm in diameter with 18F as tracers, the spatial resolution of double sub-scans (m = 2) is 2.56 mm, and 2.19 mm for triple sub-scans (m = 3), which are significant improvements. The novelty of high spatial resolution design is compatible to digital PET or any other technological evolutions.
文摘Purpose: To generate parametric images of tumor hypoxia in a tumor-bearing rat model using voxel-based compartmental analysis of dynamic fluorine-18 labeled misonidazole (18F-FMISO) microPET? images, and to compare the parametric images thus derived with static “late” 18F-FMISO microPET? images for the detection of tumor hypoxia. Materials and Methods: Nude rats bearing HT-29 colorectal carcinoma xenografts (≈1.5 - 2 cm in diameter) in the right hind limb were positioned in a custom-fabricated, animal-specific foam mold. Animals were injected via the tail vein with ≈55.5 MBq 18F-FMISO and continuously imaged for either 60 or 120 minutes, with additional late static images up to 3 hour post-injection. The raw list-mode data was reconstructed into 37 - 64 frames with earlier frames of shorter time durations (12 - 15 seconds) and later frames of longer durations (up to 300 seconds). Time activity curves (TACs) were generated over regions encompassing the tumor as well as an artery, the latter for use as an input function. A beta version of a compartmental modeling package (BioGuide?, Philips Healthcare) was used to generate parametric images of k3 and Ki, rate constants of entrapment and flux of 18F-FMISO, respectively. Results: Data for 7 HT-29 tumor xenografts were presented, 6 of which yielded clear areas of tumor hypoxia as defined by Ki/k3 maps. Importantly, intratumoral foci with high 18F-FMISO uptakes on the late images did not always exhibit high Ki/k3 values and may there- fore represent false-positives for radiobiologically significant hypoxia. Conclusions: This study attempts to quantify tumor hypoxia using compartmental analysis of dynamic 18F-FMISO PET images in rodent xenograft tumor models. The results demonstrate feasibility of the approach in small-animal imaging studies, and provide evidence for the possible unreliability of late-time static imaging of 18F-FMISO PET in identifying tumor hypoxia.
文摘Multi-channel cylindrical applicators for high dose-rate (HDR) brachytherapy are utilized mainly for special gynecology cases often involving image-guidance high dose-rate (IG-HDR or IGBT) brachytherapy. In these cases, doses are prescribed to partial vaginal wall/depth where the disease is indicated by an MRI study scanned on the same day. These novel IG-HDR procedures are logistical challenges comparing to typical HDR out-patient treatments due to the complexity of planning for asymmetrical prescriptions as well as the extension of the whole procedure. Indeed the main advantages of HDR over LDR brachytherapy would be significantly weaken unless the IG-HDR procedures become more efficient in time, thus timely treatment planning becomes crucial. Based on our clinical experience, we propose the pseudo central-catheter method to reduce errors, to minimize uncertainty and to ensure efficiency. In this method, the central hollow path of the multi-channel cylindrical applicator is digitized into a pseudo catheter similar to other active catheters, and the asymmetrical prescription points could be generated corresponding to the pseudo dwelling points in the pseudo central-catheter. The pseudo dwelling points are later deleted after generating the prescription point arrays. This method is robust with minimal chance of errors or uncertainties, and demonstrates high efficiency with much less chance of uncertainty, which is significant for IG-HDR brachytherapy procedures utilizing multi-channel applicators.
文摘Aiming at the problem that the existing risk assessment methods in China cannot simply and accurately assess the safety risk of gas wells, a rapid semi-quantitative risk assessment method for gas wells under high temperature and pressure is studied. Based on the rapid risk assessment method of annulus well with pressure in Chevron Company and the existing risk assessment methods, the well barrier and annulus pressure of high temperature and high pressure gas wells are fully considered. A rapid semi-quantitative risk assessment method for high temperature and high pressure gas wells is established, which takes the annulus pressure value, well service life, annulus pressure recovery after pressure relief, reservoir conditions (formation pressure, production) and well CO<sub style="font-family:" white-space:normal;"=""><span style="font-size:12px;font-family:Verdana;">2 </span></sub><span style="font-family:Verdana;">and H</span><sub style="font-family:" white-space:normal;"=""><span style="font-size:12px;font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">S content as the key risk indexes. The method is applied in a gas field, and the risk value and risk grade of a practical well are semi-quantitatively evaluated. The overall risk situation of the well is obtained. The research results provide important technical guidance for the safe production of gas well.</span>
基金supported by the National Natural Science Foundation of China (Grant Nos. U20A2048 & 41930652)the National Key Research and Development Program of China (Grant No. 2022YFF1300700)。
文摘Under the background of large-scale ecological restoration, China's southwestern karst region has become a hotspot of global vegetation cover “greening” in the past 20 years. However, because of geological constraints, it is difficult to restore the forest landscapes in some areas. It is urgent to understand the impacts of human disturbances during the historical period on the difficult-to-forestation rocky-desertification areas of the karst region in order to guide future afforestation. In this study, we quantified the changes of specific sediment yield in typical karst depressions over the past 500 years by using ^(137)Cs,^(210)Pb, and ^(14)C dating methods in karst depressions, and identified the main human disturbances related to historical erosion and sedimentation by combining with historical data. The results showed that the erosion and sedimentation of the three depressions in 1921–1963 were significantly higher than that in 1963–2021, and the sedimentation rate(0.64–1.33 cm a^(-1)) and the specific sediment yield(2.51–13.11 t ha^(-1)a^(-1)) during Ming and Qing dynasties(1504–1812) were higher than the sedimentation rate(0.26–0.95 cm a^(-1)) and specific sediment yield(0.95–6.99 t ha^(-1)a^(-1)) in the recent century(1921–2021). Reconstruction data and literature from the Ming and Qing dynasties show an empirical link between changes in population, arable land, food, forest area,and deforestation events during the same period. It was found that the population and arable land in Guangxi increased more than three-fold and the forest area decreased significantly in the 17th century after the migration of the Yao ethnic group and the introduction of maize to the region, which may be the main reason for intensifying the erosion of depressions. This study is of great significance to understanding the evolution history of rocky desertification in this region and to answer the potential of afforestation.
基金funded by the National Key Research and Development Program of China(2022YFF1300701)National Natural Science Foundation of China(41807074,41930652,U20A2048,42171134,U21A20189).
文摘Heterogeneous karst surfaces exerted scaling effects whereby specific runoff decrease with increasing area.The existing RUSLE-L equations are limited by the default implicit assumption that the surface-runoff intensity is constant at any slope length.The objective of this study was to modify the L-equation by establishing the functional relationship between surface-runoff intensity and karst slope length,and to evaluate its predictive capability at different resolution DEMs.Transfer grid layers were generated based on the area rate of surface karstification and considered the runoff transmission percentage at the exposed karst fractures or conduits to be zero.Using the multiple flow direction algorithm united with the transfer grid(MFDTG),the flow accumulation of each grid cell was simulated to estimate the average surface-runoff intensity over different slope lengths.The effectiveness of MFDTG algorithm was validated by runoff plot data in Southwestern China.The simulated results in a typical peak-cluster depression basin with an area rate of surface karstification of 6.5%showed that the relationship between surface-runoff intensity and slope length was a negative power function.Estimated by the proposed modified L-equation((al_(x)^((b+1))/22.13)^(m)),the L-factor averages of the study basin ranged from 0.35 to 0.41 at 1,5,25 and 90 m resolutions respectively.This study indicated that the modified L-equation enables an improved prediction of the much smaller L-factor and the use of any resolution DEMs on karst landscapes.Particular attention should be given to the variation of surface-runoff intensity with slope length when predicting L-factor on hillslopes with runoff scale effect.
基金funded by the National Key Research and Development Program of China(No.2022YFF1300700)the National Natural Science Foundation of China(Nos.41930652,U20A2048)+1 种基金the International Partnership Program of Chinese Academy of Sciences(No.092GJHZ2022029GC)the Double Thousand Talent Program of Jiangxi Province(No.jsxq2023102152).
文摘Karst regions of Southwest China become a hotspot for global greening through large-scale vegetation restoration in recent two decades.However,the unique,fragile geological setting of carbonate rocks affects the sustainability of vegetation greening.Here,we summarize and evaluate the impacts of the rock and soil compositions of karst landscapes on the types and quality of vegetation restoration.We introduce the concept of“soil mass”and establish its relationship with aboveground vegetation biomass across varying degrees of rocky desertification.The mineral nutrients and soil mass constrain the potential of vegetation carbon sequestration in karst regions.To enhance the sustainability of vegetation restoration and carbon sequestration under karst geological constraints,we suggest to push ecological intensification of tree plantations and optimize the zoning and classification of rocky desertification treatment,and these restoration initiatives will foster vegetation restoration to serve as a pivotal pathway towards carbon neutrality.
基金National Key R&D Program of China(2021YFD1201200)National Science Foundation of China(32022064)+1 种基金Project of Hainan Yazhou Bay Seed Lab(B21HJ0223)Innovation Program of the Chinese Academy of Agricultural Sciences.
文摘Genomic prediction is an effective way to accelerate the rate of agronomic trait improvement in plants.Traditional methods typically use linear regression models with clear assumptions;such methods are unable to capture the complex relationships between genotypes and phenotypes.Non-linear models(e.g.,deep neural networks)have been proposed as a superior alternative to linear models because they can capture complex non-additive effects.Here we introduce a deep learning(DL)method,deep neural network genomic prediction(DNNGP),for integration of multi-omics data in plants.We trained DNNGP on four datasets and compared its performance with methods built with five classic models:genomic best linear unbiased prediction(GBLUP);two methods based on a machine learning(ML)framework,light gradient boosting machine(LightGBM)and support vector regression(SVR);and two methods based on a DL framework,deep learning genomic selection(DeepGS)and deep learning genome-wide association study(DLGWAS).DNNGP is novel in five ways.First,it can be applied to a variety of omics data to predict phenotypes.Second,the multilayered hierarchical structure of DNNGP dynamically learns features from raw data,avoiding overfitting and improving the convergence rate using a batch normalization layer and early stopping and rectified linear activation(rectified linear unit)functions.Third,when small datasets were used,DNNGP produced results that are competitive with results from the other five methods,showing greater prediction accuracy than the other methods when large-scale breeding data were used.Fourth,the computation time required by DNNGP was comparable with that of commonly used methods,up to 10 times faster than DeepGS.Fifth,hyperparameters can easily be batch tuned on a local machine.Compared with GBLUP,LightGBM,SVR,DeepGS and DLGWAS,DNNGP is superior to these existing widely used genomic selection(GS)methods.Moreover,DNNGP can generate robust assessments from diverse datasets,including omics data,and quickly incorporate complex and large datasets into usable models,making it a promising and practical approach for straightforward integration into existing GS platforms.
基金supported by the National Natural Science Foundation of China(Nos.41877055,31870454,and 41930652)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA23060103)+3 种基金the Guangxi Natural Science Foundation,China(No.2018GXNSFAA281008)the Program of the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.Y201969)the Foundation for Young Scholars in Western China of Chinese Academy of Sciences given to Dr.Jie Zhaothe Youth Innovation Team Project of Institute of Subtropical Agriculture,Chinese Academy of Sciences(No.2017QNCXTD_ZJ)
文摘Mixed cultivation of fast-growing grasses and nitrogen(N)-fixing legumes for forage production is widely considered effective for obtaining sustained high forage yields without depleting soil N levels.However,the effects of monoculture and mixed culture of these species on soil food webs are poorly understood.In this study,soil nematode communities were examined as indicators of the soil food web structure of monoculture and mixed culture of grass and legume at three N levels,i.e.,338(low),450(moderate),and 675(high)kg N ha-1 year-1,across 2 years in wet and dry seasons,using the grass Paspalum wetsfeteini and the legume Medicago sativa(alfalfa),both commonly cultivated worldwide.Repeated-measures analysis of covariance showed that compared with grass monoculture,legume monoculture and grass-legume mixture increased abundances of herbivorous,bacterivorous,and fungivorous nematodes in the soil food web under the low and moderate N fertilization levels.Principal response curve results showed that the abundance of Helicotylenchus,a plant parasite,was significantly higher under legume monoculture than other planting systems at the low N fertilization level.Structural equation model analysis indicated that the legume increased bacterivore abundance,while increasing N fertilization decreased omnivore abundance.The legume might increase the quantity and quality of food resources for soil biota,resulting in the bottom-up control of soil nematode communities.Our results indicate that targeted control of a soilborne pathogen,Helicotylenchus,is required in alfalfa-based planting systems.In addition,high inorganic N application,which is detrimental to legume-rhizobia symbiosis,nullified the otherwise positive effects of legumes on soil nematodes.
基金Financial support for this project was provided by the U.S.Department of Agriculture (No. 6445-12630-003-00D)
文摘The mercury flux in soils was investigated, which were amended by gypsums from flue gas desulphurization （FGD） units of coal- fired power plants. Studies have been carried out in confined greenhouses using FGD gypsum treated soils. Major research focus is uptakes of mercury by plants, and emission of mercury into the atmosphere under varying application rates of FGD gypsum, simulating rainfall irrigations, soils, and plants types. Higher FGD gypsum application rates generally led to higher mercury concentrations in the soils, the increased mercury emissions into the atmosphere, and the increased mercury contents in plants （especially in roots and leaves）. Soil properties and plant species can play important roles in mercury transports. Some plants, such as tall fescue, were able to prevent mercury from atmospheric emission and infiltration in the soil. Mercury concentration in the stem of plants was found to be increased and then leveled off upon increasing FGD gypsum application. However, mercury in roots and leaves was generally increased upon increasing FGD gypsum application rates. Some mercury was likely absorbed by leaves of plants from emitted mercury in the atmosphere.
基金This study was supported by the State Key Program of National Natural Science Foundation of China(41730748)National Natural Science Foundation of China(41601299,41977073,41671287)+1 种基金Youth Innovation Promotion Association of CAS(2020359)CAS Interdisciplinary Innovation Team,and the Youth Innovation Team Project of ISA,CAS(2017QNCXTD_XXL).
文摘Due to the complex hydrogeological conditions in karst regions,it is difficult to measure sediment source contributions at a catchment scale directly.The objective of this study was to quantify the relative contributions of sediment sources and their temporal variability in a karst catchment in southwest China.Karst depressions can trap eroded sediment similar to a dam or reservoir and,thus,are representative and typical test beds for identifying sediment sources in karst regions.Three sediment cores were taken from a karst depression,58 soil samples from three potential sediment sources were collected,and 18 soil properties were analyzed.The relative contributions of cropland,forestland,and fissure or crack soils were calculated using a multivariate mixing model.The fingerprinting results demonstrated that the cropland was the main sediment source in karst catchment.Specifically,according to the mean sediment contributions of the three deposited sediment cores,the sediment contribution from cropland topsoil was 69.3%,varying from 46.9%to 92.3%,and forestland soil and crack soil accounted for 8.6%and 22.1%of the sediment yield,and varying from 2.8%to 16.5%and 4.8%-36.6%,respectively.This result indicated that great attention should be paid when using only a single core to quantify sediment provenance.Due to the deposited sediment was generally disturbed as cropland in the karst depression,the area that has not been disturbed in recent decades in depression was more appropriate to trace sediment sources in karst catchment.To the best of our knowledge,this study was the first to quantify the contributions of sediment sources in the karst catchment of southwest China.This study provides valuable information and a preliminary reference for applying a composite fingerprinting technique to quantify sediment sources in karst catchments.
基金This study was supported by the Natural Science Fund of China(41877055)Natural Science Foundation for Distinguished Young Scholars of Hunan Province given to Jie Zhao+2 种基金the Guangxi Natural Science Foundation Program(2018GXNSFAA281008)the Foundation for Young Scholars in Western China of CAS given to Jie Zhao(A class)the program of the Youth Innovation Promotion Association of Chinese Academy of Sciences(Y201969)。
文摘Soil nematodes are useful ecological indicators and can be extracted from soil by a variety of techniques.Because the extracted nematode samples(suspensions)can be quite turbid(i.e.,they contain soil particles and organic particles in addition to nematodes),quantitative and taxonomic analyses of the nematodes by microscopy can be difficult.In this study,the following three methods for cleaning turbid suspensions obtained from Baermann funnels were assessed:repeated centrifugation at 692.5´g for 1 min,repeated settling at low-temperature(4°C)for 24 h,and a combination of low-temperature settling and centrifugation.Nematodes were extracted with Baermann funnels from soil samples collected from four land-use types(since land-use type can affect the turbidity of nematode suspensions),and the resulting suspensions were cleaned by the three methods before nematode abundance was assessed.As a control,samples(i.e.,suspensions)were simply diluted with water,and nematodes were counted in the entire volume.The results showed that,within each land-use type,nematode abundance did not significantly differ between the control and the three cleaning methods.Averaged across all land-use types,however,the nematode recovery rate was slightly higher with repeated centrifugation than with the other two cleaning methods.Therefore,the proposed methods are sound for cleaning turbid nematode suspensions,and repeated centrifugation is the most efficient method.
