Moderate resolution imaging spectroradiometer (MODIS) data are very suitable for vast extent, long term and dynamic drought monitoring for its high temporal resolution, high spectral resolution and moderate spatial ...Moderate resolution imaging spectroradiometer (MODIS) data are very suitable for vast extent, long term and dynamic drought monitoring for its high temporal resolution, high spectral resolution and moderate spatial resolution. The composite Enhanced Vegetation Index (EVI) and composite land surface temperature (Ts) obtained from MODIS data MOD11A2 and MOD13A2 were used to construct the EVI-Ts space. And Temperature Vegetation Dryness Index (TVDI) was calculated to evaluate the agriculture drought in Guangxi province, China in October of 2006. The results showed that the drought area in Guangxi was evidently increasing and continuously deteriorating from the middle of September to the middle of November. The TVDI, coming from the EVI-Ts space, could effectively indicate the spatial distribution and temporal evolution of drought, so that it could provide a strong technical support for the forecasting agricultural drought in south China.展开更多
We discovered a new species of the genus Gracixalus, Gracixalus tianlinensis sp. nov. which is morphologically almost similar to G. jinggangensis, G. jinxiuensis and G. sapaensis, but is distinguished from these speci...We discovered a new species of the genus Gracixalus, Gracixalus tianlinensis sp. nov. which is morphologically almost similar to G. jinggangensis, G. jinxiuensis and G. sapaensis, but is distinguished from these species and all other rhacophorids in China and adjoining countries by a combination of the following characters: (1) SVL 30.3-35.9 mm in male, 35.6-38.7 mm in female, (2) head length less than head width, (3) vomerine teeth absent, (4) supratympanic fold distinct, (5) axilla and posterior surface of flanks pale yellow, (6) nuptial pads distinct on Finger I and slightly visible on Finger II, (7) dorsum brown to beige, with an inverse Y-shaped dark brown marking, (8) single subgular vocal sac. Our preliminary phylogenetic analyses implied G. tianlinensis sp. nov. is sister to G. sapaensis with well-supported values. Currently, this new species is known to be distributed in montane evergreen forests in association with montane bamboo in Cenwanglaoshan National Nature Reserve, Tianlin County, Guangxi, China.展开更多
Du’an Yao Autonomous County is a typical area for the distribution of karst rocky desertification in Guangxi. The indices for the grades of rocky desertification are selected according to the scientific meaning of ka...Du’an Yao Autonomous County is a typical area for the distribution of karst rocky desertification in Guangxi. The indices for the grades of rocky desertification are selected according to the scientific meaning of karst rocky desertification and after the interpretative symbol system of rocky desertification. RS images are established by the landscape characteristics of Du’an karst and its TM image. Relying on RS & GIS means and taking land use map as base map, this paper conducts synthetic analysis on the 1999a TM image (126-043) and the correlation data involving landform, soil, geological map and GPS—database and photo on the spot, and brings forth a map showing the Du’an rocky desertification grades and a digital lithology map. As can be viewed from spatial correlation, the inherent connection is also illuminated between the various levels of rocky desertification and the carbonate lithology.展开更多
[Objective] The study aimed at assessing the ecological security of Red River basin in Guangxi. [Method] Firstly, the ecological security assessment index system of Red River basin was established based on the framewo...[Objective] The study aimed at assessing the ecological security of Red River basin in Guangxi. [Method] Firstly, the ecological security assessment index system of Red River basin was established based on the framework of 'pressure-state-response' model, and index information of ecological security assessment was extracted by using RS and GIS technology; afterwards, the ecological security of Red River basin was divided into five grades according to ecological security index, and the distribution and characteristics of ecological security at various levels were analyzed; finally, the measures to maintain the ecological security of Red River basin were put forward on the basis of problems in ecological security. [Result] Most areas of Red River basin in Guangxi were in generally safe state, especially Lingyun County, Fengshan County, Du'an County, Dahua County, Shanglin County, Binyang County, Guiping City, etc., and the area accounted for 74.25% of total area; next came safer state (12.74%), the regions in the two states above were the most important environmental areas of Red River basin. The ecological security problems of Red River basin were mainly related to fragile ecological environment, lagging economic development, rapid population growth, excessive development and utilization of natural resources and so forth. [Conclusion] The research could provide scientific references for the rational development and utilization of land resources, protection and construction of ecological environment in Red River basin.展开更多
By using three different satellite remote sensing images, Guangxi coastline was extracted on the platforms of RS and GIS, and its change characteristics from 1990 to 2010 were studied. The results showed that the leng...By using three different satellite remote sensing images, Guangxi coastline was extracted on the platforms of RS and GIS, and its change characteristics from 1990 to 2010 were studied. The results showed that the length of Guangxi coastline generally decreased in the last 20 years; the total reduction length was 118.50 km, and the reduction range of coastline from 2000 to 2010 was significantly more than that from 1990 to 2000. With the development of coastal madculture and the construction of port terminals, the changes of coastline length in Fangchenggang and Qinzhou were larger. The total newly added land area was 136.81 km2, and the newly added land area in the last 10 years was greater than that in the first 10 years. The total fractal dimension of coastline presented decreasing trend; the curvature of coastline gradually decreased; the coastline will be straighter.展开更多
In order to study the rules of variations in the net primary productivity( NPP) of vegetation in Guangxi,this paper used MOD17 A3 H data to compare the spatial and temporal pattern of net primary productivity of veget...In order to study the rules of variations in the net primary productivity( NPP) of vegetation in Guangxi,this paper used MOD17 A3 H data to compare the spatial and temporal pattern of net primary productivity of vegetation in different cities by unary linear regression method and standard deviation analysis method. It obtained following results.( i) The annual average NPP of cities in Guangxi is in the range of 498. 77-803. 97 g C/m^2·a,and the Beihai has the lowest NPP and Wuzhou has the highest NPP.( ii) The region with small vegetation NPP fluctuation in Guangxi is 6 044. 22 km^2,the region with the larger fluctuation is 37 735. 38 km^2,the region with large fluctuation is43 690. 84 km^2,the region with general fluctuation is 73 938. 14 km^2,and the region with small fluctuation is 74 622. 43 km^2,most regions have small fluctuation in vegetation NPP.( iii) Regions with basically stable NPP are largest,followed by regions with slight decline.( iv)There are great differences in the spatial distribution of NPP variations in Guangxi. Regions with slight decline of NPP are mainly distributed in the northeastern Guangxi; regions with slight increase of NPP are mainly distributed in the southern Guangxi,and regions with basically stable NPP are mainly distributed in southeastern Guangxi.展开更多
Original ecotourism resources mainly refer to natural and human original ecotourism resources, and it's of fragility, rarity and irreversibility. As a valuable historic heritage and important tourism resources, it...Original ecotourism resources mainly refer to natural and human original ecotourism resources, and it's of fragility, rarity and irreversibility. As a valuable historic heritage and important tourism resources, it plays a significant role in developing tourism and economy in such areas as the underdeveloped areas, the mountain areas and mi-nority areas. The tourism resources in the western mountain areas of Guangxi owe superiorities and characteristics to their original ecology. Yet, western Guangxi is an ethnic region with fragile karst eco-environment, so it is special to exploit the tourism resources. The paper defines original ecotourism and analyses the specialties and advantages of the original ecotourism resources as well as the frailty of the ecotourism resources of the region. The ways of thinking are put forward for safe preservation and sustainable development of the original ecotourism resources, i.e. carrying out measures for the multi-grade protection of heritage resources, setting up a ethnic ecomuseum/ ethnic culture eco-park and a gene pool of ethnic cultures, etc.展开更多
Relationships between topography,soil properties and the distribution of plant communities on two different rocky hillsides are examined in two subtropical karst forests in the Maolan National Natural Reserve,southwes...Relationships between topography,soil properties and the distribution of plant communities on two different rocky hillsides are examined in two subtropical karst forests in the Maolan National Natural Reserve,southwestern China.Surveys of two 1-ha permanent plots at each forest,and measurements of four topographic and thirteen edaphic factors on the slopes were performed.Twoway Indicator Species Analysis(TWINSPAN) and Detrended Canonical Correspondence Analysis(DCCA) were used for the classification of plant communities and for vegetation ordination with environmental variables.One hundred 10m×10m quadrats in each plot were classified into four plant community types.A clear altitudinal gradient suggested that elevation was important in community differentiation.The topography and soil explained 51.06% and 54.69% of the variability of the distribution of plant species in the two forest plots,respectively,indicating both topographic factors(eg.elevation,slope and rock-bareness rate) and edaphic factors(e.g.total P,K and exchangeable Ca) were the important drivers of the distribution of woody plant species in subtropical karst forest.However,our results suggested that topographical factors were more important than edaphic ones in affecting local plant distribution on steep slopes with extensive rock outcrops,while edaphic factors were more influential on gentle slope and relatively thick soil over rock in subtropical karst forest.Understanding relationships between vegetation and environmental factors in karst forest ecosystems would enable us to apply these findings in vegetation management strategies and restoration of forest communities.展开更多
In this work, 25 3-O-β-chacotriosyl ursolic acid derivatives were employed to achieve the highly reliable and predictive 3 D-QSAR models by Co MFA and Co MSIA methods, respectively. The predictive capabilities of two...In this work, 25 3-O-β-chacotriosyl ursolic acid derivatives were employed to achieve the highly reliable and predictive 3 D-QSAR models by Co MFA and Co MSIA methods, respectively. The predictive capabilities of two constructed CoMFA and CoMSIA models were verified by the leave-one-out cross-validation method. The results showed that the cross-validated coefficient(q2) and non-cross-validated coefficient(R2) were 0.559, 0.981 in the CoMFA model and 0.696, 0.978 in the CoM SIA model, respectively, which suggests that these two models are robust and have good exterior predictive capabilities. Furthermore, based on the contour maps information of two models, ten novel inhibitors with higher inhibitory potency were designed, and the quantum chemical calculation of density functional theory(DFT) was performed to investigate the mechanism why the designed molecules have stronger inhibitory activity than the lead compound. The calculations show that the C-50 position of lead compound is a key active site for the enhancement of inhibitory activity, and it should be introduced into the large electron withdrawing group, which would result in generating potent and selective H5 N1 entry inhibitors. We expect that the results in this paper could provide important information to develop new potent H5 N1 entry inhibitors.展开更多
The properties of woody debris(WD) vary across different forests under various soil conditions.Owing to the relatively shallow and low amounts of soils on karst terrains, it is necessary to determine the WD carbon inv...The properties of woody debris(WD) vary across different forests under various soil conditions.Owing to the relatively shallow and low amounts of soils on karst terrains, it is necessary to determine the WD carbon inventory of karst forests. In this study, we recorded WD with a basal diameter for standing snags and the largeend diameter for fallen logs of ≥ 1 cm. The carbon density of WD in a secondary karst mixed evergreen and deciduous broad-leaved forest that had been clear-cut 55 years ago in southwestern China were inventoried in a 2 ha plot. Woody debris carbon density calculated using specific gravity and carbon concentration was 4.07 Mg C ha^-1. Woody debris with diameters ≥ 10 cm(coarse WD) constituted 53.8% of total carbon storage whereas WD < 10 cm in diameters(fine WD) accounted for more pieces of WD(89.9%).Lithocarpus confinis contributed the most WD carbon(26.5%). Intermediate decayed WD was relatively more abundant, but WD with final decay contributed the least to the total pieces of WD(6.7%). The contribution of WD to carbon storage of karst forest was low compared to other forests worldwide. Significant positive correlations were found between WD carbon and biodiversity(R^2= 0.035,p < 0.01) and elevation(R^2= 0.047, p < 0.01) and negative correlations was found in outcrop coverage(R^2= 0.034, p <0.01). Further studies are needed to elucidate the ecological functions of WD to better understand their roles in maintaining biodiversity, enhancing productivity, and controlling vegetation degradation in karst forest ecosystems.展开更多
Oleanolic acid derivatives act as newer protein tyrosine phosphatase 1B (PTP-1B) inhibitors for type 2 diabetes mellitus (T2DM). In order to understand the structural requirement of PTP-1B inhibitors, 52 oleanolic...Oleanolic acid derivatives act as newer protein tyrosine phosphatase 1B (PTP-1B) inhibitors for type 2 diabetes mellitus (T2DM). In order to understand the structural requirement of PTP-1B inhibitors, 52 oleanolic acid derivatives were divided into a training set (34 compounds) and a test set (18 compounds). The highly reliable and predictive 3D-QSAR models were constructed by CoMFA, CoMSIA and topomer CoMFA methods, respectively. The results showed that the cross validated coefficient (q2) and non-cross-validated coefficient (R2) were 0.554 and 0.999 in the CoMFA model, 0.675 and 0.971 in the CoMSIA model, and 0.628 and 0.939 in the topomer CoMFA model, which suggests that three models are robust and have good exterior predictive capabilities. Furthermore, ten novel inhibitors with much higher inhibitory potency were designed. Our design strategy was that (i) the electronegative substituents (Cl, -CH2OH, OH and -CH2Cl) were introduced into the double bond of ring C, (ii) the hydrogen bond acceptor groups (C≡N and N atom), electronegative groups (C≡N, N atom, -COOH and -COOCH3) and bulky substituents (C6H5N) were connected to the C-3 position, which would result in generating potent and selective PTP-1B inhibitors. We expect that the results in this paper have the potential to facilitate the process of design and to develop new potent PTP-1B inhibitors.展开更多
The double-side Tl2Ba2 CaCu2O8 (Tl-2212) superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphi...The double-side Tl2Ba2 CaCu2O8 (Tl-2212) superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO2 target. The Ti-2212 thin films on CeO2 buffered sapphire substrates were fabricated by adc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the e-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO2 buffered sapphire. The critical transition temperature Tc is around 106K, the critical current density Jc is around 3.5 MA/cm^2 at 77K, and the microwave surface resistance R8 at 77K and 10 CHz of the film is as low as 390μ Ω.展开更多
Payment for ecosystem services(PES) has become an increasingly popular means of ecosystem conservation. Opportunity cost is an important factor to increase the investment efficiency of PES projects.However, the distri...Payment for ecosystem services(PES) has become an increasingly popular means of ecosystem conservation. Opportunity cost is an important factor to increase the investment efficiency of PES projects.However, the distribution of opportunity cost is usually unclear in mountainous regions due to the obvious environment changes. In this study, we developed a framework to assess the distribution of agricultural opportunity costs in mountainous regions and applied this method to Baoxing County, a typical mountainous county in Sichuan Province of southwest China. Planting suitability of 17 crops was assessed based on agricultural statistics and natural conditions data within a GIS environment.Agricultural opportunity cost was quantified with a weighted summation of farmers' willingness to cultivate and each crop's opportunity cost. Finally,specific agricultural opportunity cost was obtained according to the spatial areas of the protection programs and land use status. The results showed that agricultural opportunity costs of PES in Baoxing County were estimated to be more than $30 million,with a mean of 400.85 $/ha. Agricultural opportunity costs in mountainous regions displayed some obvious spatial variation and areas with lower agricultural opportunity costs could be selected as priority areas for PES. Our findings revealed that the planting suitability evaluation can make agricultural opportunity costs mapping more reasonable. It will be helpful for the PES programs implementation in mountainous regions.展开更多
In order to improve image quality,a novel Retinex algorithm for image enhancement was presented.Different from conventional algorithms,it was based on certain defined points containing the illumination information in ...In order to improve image quality,a novel Retinex algorithm for image enhancement was presented.Different from conventional algorithms,it was based on certain defined points containing the illumination information in the intensity image to estimate the illumination.After locating the points,the whole illumination image was computed by an interpolation technique.When attempting to recover the reflectance image,an adaptive method which can be considered as an optimization problem was employed to suppress noise in dark environments and keep details in other areas.For color images,it was taken in the band of each channel separately.Experimental results demonstrate that the proposed algorithm is superior to the traditional Retinex algorithms in image展开更多
An minimum description length(MDL) criterion is proposed to choose a good partition for a bipartite network. A heuristic algorithm based on combination theory is presented to approach the optimal partition. As the heu...An minimum description length(MDL) criterion is proposed to choose a good partition for a bipartite network. A heuristic algorithm based on combination theory is presented to approach the optimal partition. As the heuristic algorithm automatically searches for the number of partitions, no user intervention is required. Finally, experiments are conducted on various datasets, and the results show that our method generates higher quality results than the state-of-art methods, cross-association and bipartite, recursively induced modules. Experiment results also show the good scalability of the proposed algorithm. The method is applied to traditional Chinese medicine(TCM) formula and Chinese herbal network whose community structure is not well known, and found that it detects significant and it is informative community division.展开更多
In this study,the quasi-static ebulliometric method was used to measure both of the vapor pressures of methyl N-phenyl carbamate(MPC),and the isobaric vapor–liquid equilibrium(VLE) data of the aniline and MPC binary ...In this study,the quasi-static ebulliometric method was used to measure both of the vapor pressures of methyl N-phenyl carbamate(MPC),and the isobaric vapor–liquid equilibrium(VLE) data of the aniline and MPC binary system.The measured vapor pressure data of MPC,at different temperature ranging from 369.60 to 389.54 K,fitted well with the Antoine equation.The VLE data for the aniline and MPC system at(2.00,4.00,6.00,7.00 and 8.00) k Pa were correlated by both of nonrandom two-liquid(NRTL) and Wilson models.The parameters of the two models were obtained by regressing the experimental data,with the absolute temperature deviations of 0.54 K and 0.53 K,respectively.The relative volatility of the binary system calculated was all far more than 1,which gives the conclusion that the high purity MPC can be separated from aniline and MPC binary system by rectification or distillation technology.展开更多
To provide hints for the design of new acetylcholinesterase(ACh E) inhibitors with higher potency and specificity, the binding modes of novel heterodimers comprised of donepezil and huperzine A fragments with ACh E ...To provide hints for the design of new acetylcholinesterase(ACh E) inhibitors with higher potency and specificity, the binding modes of novel heterodimers comprised of donepezil and huperzine A fragments with ACh E were explored by employing the docking simulations. The results show that the binding mode of S-17b(the most potent inhibitor in Ref. 2, i.e., Bioorg. Med. Chem. 2013, 21, 676-683) is clearly different from that of donepezil, while the binding modes of other heterodimers in Ref. 2 are the same as that of donepezil. In addition, based on the binding mode and structure modification of S-17 b, two novel inhibitors(S-17b1 and S-17bb1) with much higher inhibitory potency than S-17 b were obtained. Our design strategy was to replace the hupyridone moiety of S-17 b with the bulky group, and to replace the dimethoxyindanone moiety of S-17 b with more hydrophobic and bulky group with a highly positive charge, which would result in generating potent and selective AChE inhibitors.展开更多
A new ternary compound La8Al13Sn3 was synthesized and studied by means of X-ray powder diffraction technique. The compound La8Al13Sn3 crystallizes in a hexagonal AlB2-type structure with space group P6/mmm (No. 191)...A new ternary compound La8Al13Sn3 was synthesized and studied by means of X-ray powder diffraction technique. The compound La8Al13Sn3 crystallizes in a hexagonal AlB2-type structure with space group P6/mmm (No. 191) and the lattice parameters a = 0.44919(1) nm and c = 0.43835(1) nm. The Smith and Snyder figure of merit for index, FN, is F30 = 197.3(30). The Rietveld refinement for the crystal structure of the compound was carried out successfully. The liability R-factors of Rietveld refinement are Rp = 0.114 and Rwp = 0.148. The compound La8Al13Sn3 decomposes into LaAl2 with cubic structure and space group Fd 3m (227), LaAl3 with hexagonal structure and space group P63/mmc (194), and Sn at 720°C.展开更多
基金the National Natural Science Foundation of China (40461001)
文摘Moderate resolution imaging spectroradiometer (MODIS) data are very suitable for vast extent, long term and dynamic drought monitoring for its high temporal resolution, high spectral resolution and moderate spatial resolution. The composite Enhanced Vegetation Index (EVI) and composite land surface temperature (Ts) obtained from MODIS data MOD11A2 and MOD13A2 were used to construct the EVI-Ts space. And Temperature Vegetation Dryness Index (TVDI) was calculated to evaluate the agriculture drought in Guangxi province, China in October of 2006. The results showed that the drought area in Guangxi was evidently increasing and continuously deteriorating from the middle of September to the middle of November. The TVDI, coming from the EVI-Ts space, could effectively indicate the spatial distribution and temporal evolution of drought, so that it could provide a strong technical support for the forecasting agricultural drought in south China.
基金funded by Guangxi Natural Science Foundation under Grant No. 2016GXNSFAA380007
文摘We discovered a new species of the genus Gracixalus, Gracixalus tianlinensis sp. nov. which is morphologically almost similar to G. jinggangensis, G. jinxiuensis and G. sapaensis, but is distinguished from these species and all other rhacophorids in China and adjoining countries by a combination of the following characters: (1) SVL 30.3-35.9 mm in male, 35.6-38.7 mm in female, (2) head length less than head width, (3) vomerine teeth absent, (4) supratympanic fold distinct, (5) axilla and posterior surface of flanks pale yellow, (6) nuptial pads distinct on Finger I and slightly visible on Finger II, (7) dorsum brown to beige, with an inverse Y-shaped dark brown marking, (8) single subgular vocal sac. Our preliminary phylogenetic analyses implied G. tianlinensis sp. nov. is sister to G. sapaensis with well-supported values. Currently, this new species is known to be distributed in montane evergreen forests in association with montane bamboo in Cenwanglaoshan National Nature Reserve, Tianlin County, Guangxi, China.
基金supported jointly by National Natural Science Foundation of China(Grant Nos.40161004 and 40361002)Guangxi Natural Science Foundation(Guikeji Grant No.0236046 and Guikezi Grant No.0342001-2)the Resource and Environmental Information System Laboratory project of Guangxi Teachers Education University-Guangxi Science and Technological Innovation Unit.
文摘Du’an Yao Autonomous County is a typical area for the distribution of karst rocky desertification in Guangxi. The indices for the grades of rocky desertification are selected according to the scientific meaning of karst rocky desertification and after the interpretative symbol system of rocky desertification. RS images are established by the landscape characteristics of Du’an karst and its TM image. Relying on RS & GIS means and taking land use map as base map, this paper conducts synthetic analysis on the 1999a TM image (126-043) and the correlation data involving landform, soil, geological map and GPS—database and photo on the spot, and brings forth a map showing the Du’an rocky desertification grades and a digital lithology map. As can be viewed from spatial correlation, the inherent connection is also illuminated between the various levels of rocky desertification and the carbonate lithology.
基金Supported by Natural Science Foundation of Guangxi, China (0679026)
文摘[Objective] The study aimed at assessing the ecological security of Red River basin in Guangxi. [Method] Firstly, the ecological security assessment index system of Red River basin was established based on the framework of 'pressure-state-response' model, and index information of ecological security assessment was extracted by using RS and GIS technology; afterwards, the ecological security of Red River basin was divided into five grades according to ecological security index, and the distribution and characteristics of ecological security at various levels were analyzed; finally, the measures to maintain the ecological security of Red River basin were put forward on the basis of problems in ecological security. [Result] Most areas of Red River basin in Guangxi were in generally safe state, especially Lingyun County, Fengshan County, Du'an County, Dahua County, Shanglin County, Binyang County, Guiping City, etc., and the area accounted for 74.25% of total area; next came safer state (12.74%), the regions in the two states above were the most important environmental areas of Red River basin. The ecological security problems of Red River basin were mainly related to fragile ecological environment, lagging economic development, rapid population growth, excessive development and utilization of natural resources and so forth. [Conclusion] The research could provide scientific references for the rational development and utilization of land resources, protection and construction of ecological environment in Red River basin.
基金Supported by Guangxi Natural Science Foundation,ChinaKey Item of Science Technology Research,Ministry of Education,China(210167)
文摘By using three different satellite remote sensing images, Guangxi coastline was extracted on the platforms of RS and GIS, and its change characteristics from 1990 to 2010 were studied. The results showed that the length of Guangxi coastline generally decreased in the last 20 years; the total reduction length was 118.50 km, and the reduction range of coastline from 2000 to 2010 was significantly more than that from 1990 to 2000. With the development of coastal madculture and the construction of port terminals, the changes of coastline length in Fangchenggang and Qinzhou were larger. The total newly added land area was 136.81 km2, and the newly added land area in the last 10 years was greater than that in the first 10 years. The total fractal dimension of coastline presented decreasing trend; the curvature of coastline gradually decreased; the coastline will be straighter.
基金Supported by State Key Research and Development Program(2016YFC0502401)Project of National Natural Science Foundation(41661021)+1 种基金Innovation Team Project for Natural Science Foundation of Guangxi(2016JJF15001)District-level Project of Student Entrepreneurship and Enterprise Competition of Guangxi Teachers Education University(201810603277)
文摘In order to study the rules of variations in the net primary productivity( NPP) of vegetation in Guangxi,this paper used MOD17 A3 H data to compare the spatial and temporal pattern of net primary productivity of vegetation in different cities by unary linear regression method and standard deviation analysis method. It obtained following results.( i) The annual average NPP of cities in Guangxi is in the range of 498. 77-803. 97 g C/m^2·a,and the Beihai has the lowest NPP and Wuzhou has the highest NPP.( ii) The region with small vegetation NPP fluctuation in Guangxi is 6 044. 22 km^2,the region with the larger fluctuation is 37 735. 38 km^2,the region with large fluctuation is43 690. 84 km^2,the region with general fluctuation is 73 938. 14 km^2,and the region with small fluctuation is 74 622. 43 km^2,most regions have small fluctuation in vegetation NPP.( iii) Regions with basically stable NPP are largest,followed by regions with slight decline.( iv)There are great differences in the spatial distribution of NPP variations in Guangxi. Regions with slight decline of NPP are mainly distributed in the northeastern Guangxi; regions with slight increase of NPP are mainly distributed in the southern Guangxi,and regions with basically stable NPP are mainly distributed in southeastern Guangxi.
文摘Original ecotourism resources mainly refer to natural and human original ecotourism resources, and it's of fragility, rarity and irreversibility. As a valuable historic heritage and important tourism resources, it plays a significant role in developing tourism and economy in such areas as the underdeveloped areas, the mountain areas and mi-nority areas. The tourism resources in the western mountain areas of Guangxi owe superiorities and characteristics to their original ecology. Yet, western Guangxi is an ethnic region with fragile karst eco-environment, so it is special to exploit the tourism resources. The paper defines original ecotourism and analyses the specialties and advantages of the original ecotourism resources as well as the frailty of the ecotourism resources of the region. The ways of thinking are put forward for safe preservation and sustainable development of the original ecotourism resources, i.e. carrying out measures for the multi-grade protection of heritage resources, setting up a ethnic ecomuseum/ ethnic culture eco-park and a gene pool of ethnic cultures, etc.
基金supported by the "Hundred Talents Program" of the Chinese Academy of Sciences (to Jian Ni)the National Basic Research Program (No. 973) of the Ministry of Science and Technology of China(Grant No. 2013CB956704)the Scientific Research Foundation of the Education Department of Guangxi Zhuang Autonomous Region (Grant No.201106LX296)
文摘Relationships between topography,soil properties and the distribution of plant communities on two different rocky hillsides are examined in two subtropical karst forests in the Maolan National Natural Reserve,southwestern China.Surveys of two 1-ha permanent plots at each forest,and measurements of four topographic and thirteen edaphic factors on the slopes were performed.Twoway Indicator Species Analysis(TWINSPAN) and Detrended Canonical Correspondence Analysis(DCCA) were used for the classification of plant communities and for vegetation ordination with environmental variables.One hundred 10m×10m quadrats in each plot were classified into four plant community types.A clear altitudinal gradient suggested that elevation was important in community differentiation.The topography and soil explained 51.06% and 54.69% of the variability of the distribution of plant species in the two forest plots,respectively,indicating both topographic factors(eg.elevation,slope and rock-bareness rate) and edaphic factors(e.g.total P,K and exchangeable Ca) were the important drivers of the distribution of woody plant species in subtropical karst forest.However,our results suggested that topographical factors were more important than edaphic ones in affecting local plant distribution on steep slopes with extensive rock outcrops,while edaphic factors were more influential on gentle slope and relatively thick soil over rock in subtropical karst forest.Understanding relationships between vegetation and environmental factors in karst forest ecosystems would enable us to apply these findings in vegetation management strategies and restoration of forest communities.
基金Supported by the Natural Science Foundation of Guangxi Province(Nos.2013GXNSFAA019019 and 2013GXNSFAA019041)
文摘In this work, 25 3-O-β-chacotriosyl ursolic acid derivatives were employed to achieve the highly reliable and predictive 3 D-QSAR models by Co MFA and Co MSIA methods, respectively. The predictive capabilities of two constructed CoMFA and CoMSIA models were verified by the leave-one-out cross-validation method. The results showed that the cross-validated coefficient(q2) and non-cross-validated coefficient(R2) were 0.559, 0.981 in the CoMFA model and 0.696, 0.978 in the CoM SIA model, respectively, which suggests that these two models are robust and have good exterior predictive capabilities. Furthermore, based on the contour maps information of two models, ten novel inhibitors with higher inhibitory potency were designed, and the quantum chemical calculation of density functional theory(DFT) was performed to investigate the mechanism why the designed molecules have stronger inhibitory activity than the lead compound. The calculations show that the C-50 position of lead compound is a key active site for the enhancement of inhibitory activity, and it should be introduced into the large electron withdrawing group, which would result in generating potent and selective H5 N1 entry inhibitors. We expect that the results in this paper could provide important information to develop new potent H5 N1 entry inhibitors.
基金financially supported by National Natural Science Foundation of China (31870462)National Key Research & Development Program of China (2016YFC0502304 and 2016YFC0502101)
文摘The properties of woody debris(WD) vary across different forests under various soil conditions.Owing to the relatively shallow and low amounts of soils on karst terrains, it is necessary to determine the WD carbon inventory of karst forests. In this study, we recorded WD with a basal diameter for standing snags and the largeend diameter for fallen logs of ≥ 1 cm. The carbon density of WD in a secondary karst mixed evergreen and deciduous broad-leaved forest that had been clear-cut 55 years ago in southwestern China were inventoried in a 2 ha plot. Woody debris carbon density calculated using specific gravity and carbon concentration was 4.07 Mg C ha^-1. Woody debris with diameters ≥ 10 cm(coarse WD) constituted 53.8% of total carbon storage whereas WD < 10 cm in diameters(fine WD) accounted for more pieces of WD(89.9%).Lithocarpus confinis contributed the most WD carbon(26.5%). Intermediate decayed WD was relatively more abundant, but WD with final decay contributed the least to the total pieces of WD(6.7%). The contribution of WD to carbon storage of karst forest was low compared to other forests worldwide. Significant positive correlations were found between WD carbon and biodiversity(R^2= 0.035,p < 0.01) and elevation(R^2= 0.047, p < 0.01) and negative correlations was found in outcrop coverage(R^2= 0.034, p <0.01). Further studies are needed to elucidate the ecological functions of WD to better understand their roles in maintaining biodiversity, enhancing productivity, and controlling vegetation degradation in karst forest ecosystems.
基金Supported by the Natural Science Foundation of Guangxi Province(Nos.2013GXNSFAA019019 and 2013GXNSFAA019041)
文摘Oleanolic acid derivatives act as newer protein tyrosine phosphatase 1B (PTP-1B) inhibitors for type 2 diabetes mellitus (T2DM). In order to understand the structural requirement of PTP-1B inhibitors, 52 oleanolic acid derivatives were divided into a training set (34 compounds) and a test set (18 compounds). The highly reliable and predictive 3D-QSAR models were constructed by CoMFA, CoMSIA and topomer CoMFA methods, respectively. The results showed that the cross validated coefficient (q2) and non-cross-validated coefficient (R2) were 0.554 and 0.999 in the CoMFA model, 0.675 and 0.971 in the CoMSIA model, and 0.628 and 0.939 in the topomer CoMFA model, which suggests that three models are robust and have good exterior predictive capabilities. Furthermore, ten novel inhibitors with much higher inhibitory potency were designed. Our design strategy was that (i) the electronegative substituents (Cl, -CH2OH, OH and -CH2Cl) were introduced into the double bond of ring C, (ii) the hydrogen bond acceptor groups (C≡N and N atom), electronegative groups (C≡N, N atom, -COOH and -COOCH3) and bulky substituents (C6H5N) were connected to the C-3 position, which would result in generating potent and selective PTP-1B inhibitors. We expect that the results in this paper have the potential to facilitate the process of design and to develop new potent PTP-1B inhibitors.
文摘The double-side Tl2Ba2 CaCu2O8 (Tl-2212) superconducting thin films were fabricated on CeO2 buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO2 buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO2 target. The Ti-2212 thin films on CeO2 buffered sapphire substrates were fabricated by adc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the e-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO2 buffered sapphire. The critical transition temperature Tc is around 106K, the critical current density Jc is around 3.5 MA/cm^2 at 77K, and the microwave surface resistance R8 at 77K and 10 CHz of the film is as low as 390μ Ω.
基金funded by National Natural Science Foundation of China(Grant Nos.41371539)Western Light Talent Culture Project:Standard of Payment for Ecosystem Service based on GISGEF(Global Environment Fund)Project:Payment for Watershed Services in the Chishui River Basin for the Conservation of Globally Significant Biodiversity(Grant Nos.00089388)
文摘Payment for ecosystem services(PES) has become an increasingly popular means of ecosystem conservation. Opportunity cost is an important factor to increase the investment efficiency of PES projects.However, the distribution of opportunity cost is usually unclear in mountainous regions due to the obvious environment changes. In this study, we developed a framework to assess the distribution of agricultural opportunity costs in mountainous regions and applied this method to Baoxing County, a typical mountainous county in Sichuan Province of southwest China. Planting suitability of 17 crops was assessed based on agricultural statistics and natural conditions data within a GIS environment.Agricultural opportunity cost was quantified with a weighted summation of farmers' willingness to cultivate and each crop's opportunity cost. Finally,specific agricultural opportunity cost was obtained according to the spatial areas of the protection programs and land use status. The results showed that agricultural opportunity costs of PES in Baoxing County were estimated to be more than $30 million,with a mean of 400.85 $/ha. Agricultural opportunity costs in mountainous regions displayed some obvious spatial variation and areas with lower agricultural opportunity costs could be selected as priority areas for PES. Our findings revealed that the planting suitability evaluation can make agricultural opportunity costs mapping more reasonable. It will be helpful for the PES programs implementation in mountainous regions.
基金Project(61071162) supported by the National Natural Science Foundation of China
文摘In order to improve image quality,a novel Retinex algorithm for image enhancement was presented.Different from conventional algorithms,it was based on certain defined points containing the illumination information in the intensity image to estimate the illumination.After locating the points,the whole illumination image was computed by an interpolation technique.When attempting to recover the reflectance image,an adaptive method which can be considered as an optimization problem was employed to suppress noise in dark environments and keep details in other areas.For color images,it was taken in the band of each channel separately.Experimental results demonstrate that the proposed algorithm is superior to the traditional Retinex algorithms in image
基金Projects(61363037,31071700)supported by the National Natural Science Foundation of ChinaProject(2011GXNSFD018025)supported by the Natural Science Key Foundation of Guangxi Province,ChinaProject(KYTZ201108)supported by the Development Foundation of Chengdu University of Information Technology,China
文摘An minimum description length(MDL) criterion is proposed to choose a good partition for a bipartite network. A heuristic algorithm based on combination theory is presented to approach the optimal partition. As the heuristic algorithm automatically searches for the number of partitions, no user intervention is required. Finally, experiments are conducted on various datasets, and the results show that our method generates higher quality results than the state-of-art methods, cross-association and bipartite, recursively induced modules. Experiment results also show the good scalability of the proposed algorithm. The method is applied to traditional Chinese medicine(TCM) formula and Chinese herbal network whose community structure is not well known, and found that it detects significant and it is informative community division.
基金Supported by the National Key Technology R&D Program(2013BAC11B03)the National Natural Science Foundation of China(21206180,21406245,21476244)
文摘In this study,the quasi-static ebulliometric method was used to measure both of the vapor pressures of methyl N-phenyl carbamate(MPC),and the isobaric vapor–liquid equilibrium(VLE) data of the aniline and MPC binary system.The measured vapor pressure data of MPC,at different temperature ranging from 369.60 to 389.54 K,fitted well with the Antoine equation.The VLE data for the aniline and MPC system at(2.00,4.00,6.00,7.00 and 8.00) k Pa were correlated by both of nonrandom two-liquid(NRTL) and Wilson models.The parameters of the two models were obtained by regressing the experimental data,with the absolute temperature deviations of 0.54 K and 0.53 K,respectively.The relative volatility of the binary system calculated was all far more than 1,which gives the conclusion that the high purity MPC can be separated from aniline and MPC binary system by rectification or distillation technology.
基金Supported by the Natural Science Foundation of Guangxi Province(Nos.2013GXNSFAA019019 and 2013GXNSFAA019041)
文摘To provide hints for the design of new acetylcholinesterase(ACh E) inhibitors with higher potency and specificity, the binding modes of novel heterodimers comprised of donepezil and huperzine A fragments with ACh E were explored by employing the docking simulations. The results show that the binding mode of S-17b(the most potent inhibitor in Ref. 2, i.e., Bioorg. Med. Chem. 2013, 21, 676-683) is clearly different from that of donepezil, while the binding modes of other heterodimers in Ref. 2 are the same as that of donepezil. In addition, based on the binding mode and structure modification of S-17 b, two novel inhibitors(S-17b1 and S-17bb1) with much higher inhibitory potency than S-17 b were obtained. Our design strategy was to replace the hupyridone moiety of S-17 b with the bulky group, and to replace the dimethoxyindanone moiety of S-17 b with more hydrophobic and bulky group with a highly positive charge, which would result in generating potent and selective AChE inhibitors.
基金supported by the Natural Sci-ence Foundation of Guangxi Province, China (Nos. 0832027 and 0640072)
文摘A new ternary compound La8Al13Sn3 was synthesized and studied by means of X-ray powder diffraction technique. The compound La8Al13Sn3 crystallizes in a hexagonal AlB2-type structure with space group P6/mmm (No. 191) and the lattice parameters a = 0.44919(1) nm and c = 0.43835(1) nm. The Smith and Snyder figure of merit for index, FN, is F30 = 197.3(30). The Rietveld refinement for the crystal structure of the compound was carried out successfully. The liability R-factors of Rietveld refinement are Rp = 0.114 and Rwp = 0.148. The compound La8Al13Sn3 decomposes into LaAl2 with cubic structure and space group Fd 3m (227), LaAl3 with hexagonal structure and space group P63/mmc (194), and Sn at 720°C.