This paper explores growth induced morphological instabilities in biological soft materials. In view of that the growth of a living tissue not only changes its geometry but also can alter its mechanical properties, we...This paper explores growth induced morphological instabilities in biological soft materials. In view of that the growth of a living tissue not only changes its geometry but also can alter its mechanical properties, we suggest a refined volumetric growth model incorporating the effects of growth on the mechanical properties of materials. Analogy between this volumetric growth model and the conventional thermal stress model is addressed for both small and finite de- formation problems, which brings great ease for the finite element analysis based on the suggested model. Examples of growth induced surface wrinkling behavior in soft composites, including core- shell soft cylinders and three-layered soft tissues, are explored. The results and discussions foresee possible applications of the model in understanding the correlation between the morphogenesis and growth of soft biological tissues （e.g. skins and tumors）, as well as in evaluating the defor- mation and surface instability behavior of soft artificial materials induced by swelling/shrinkage.展开更多
To investigate the behavior of all-trans-β-carotene during digestion,in-vitro digestion coupled with HPLC-DAD,Raman spectroscopy and Fourier transform-infrared spectroscopy were used to monitor it.All-trans-β-carote...To investigate the behavior of all-trans-β-carotene during digestion,in-vitro digestion coupled with HPLC-DAD,Raman spectroscopy and Fourier transform-infrared spectroscopy were used to monitor it.All-trans-β-carotene reduced by 75%during the in-vitro digestion and had a highest degradation during intestinal digestion compared with oral and gastro digestion.All-trans-β-carotene occurred isomerization and degradation during oral digestion and occurred degradation during gastro and intestinal digestion.Isomers were identifi ed as 15-cis-β-carotene and 9-cis-β-carotene,degradation products were compounds with function group of C—O,C—O—C or C=C—C=C.The biological fate ofβ-carotene during digestion was clarifi ed,and one of the reasons for low bioavailability ofβ-carotene was explained by high degradation rate during digestion.展开更多
There are only limited surface water resources available in the Heihe River Basin （HRB）, a typical inland river basin in the arid region of northwestern China, where groundwater overexploitation is a serious problem...There are only limited surface water resources available in the Heihe River Basin （HRB）, a typical inland river basin in the arid region of northwestern China, where groundwater overexploitation is a serious problem. Groundwater has become one of main resources of fresh water in the HRB. In this paper, temporal and spatial variations of groundwater in the HRB are estimated by the Gravity Recovery and Climate Experiment （GRACE） satellites. Our analysis shows that groundwater storage in the HRB reaches its highest in the summer of 2005, and then begins to decline in the following years and reaches steady status in 2008. Spatially, groundwater shows a decline in the upper HRB in the first two years and a slight increase in the following years, while this phenomenon is reversed in the middle HRB where groundwater slightly increases in 2005 and then declines in the following three years. In the lower HRB, GRACE detects a continual increase in the full six-year period. This approach is proven successful when employed in the HRB and thus offers a new insight into monitoring groundwater variations in a river basin with limited or even without any observed data.展开更多
Diverse wrinkling patterns can occur on curved bilayer systems under differential growth or expansion.In such systems,stress anisotropy is frequently encountered,and the coupling effect of curvature and stress anisotr...Diverse wrinkling patterns can occur on curved bilayer systems under differential growth or expansion.In such systems,stress anisotropy is frequently encountered,and the coupling effect of curvature and stress anisotropy on the pattern evolution remains largely unexplored.In this study,we investigate the evolution of wrinkling patterns on a cylinder core-shell system with stress anisotropy leveraging both theoretical analysis and finite element simulations.Critical buckling analysis has identified three distinct critical buckling modes regulated by the stress anisotropy,i.e.,axial sinusoidal mode,checkerboard mode,and circumferential sinusoidal mode.Our finite element simulations,along with post-buckling analysis,reveal seven distinct evolutionary paths stemming from the three critical buckling modes.We present phase diagrams for both the critical buckling modes and their evolutionary paths,which are determined by dimensionless curvature and stress anisotropy.Our results not only expand the theoretical research on surface wrinkling of a core-shell soft cylinder but also introduce stress anisotropy as a significant parameter for regulating the wrinkling patterns and their evolutionary paths in curved bilayer systems.The revelation of a multitude of wrinkling patterns and their evolutionary pathways holds great potential for advancing applications that leverage tunable wrinkle surfaces.展开更多
Characterizing the mechanical properties of soft materials and biological tissues is of great significance for understanding their deformation behaviors. In this paper, a regional stretching method is proposed to meas...Characterizing the mechanical properties of soft materials and biological tissues is of great significance for understanding their deformation behaviors. In this paper, a regional stretching method is proposed to measure the elastic and hyperelastic properties of a soft material with an adhesive surface or with the aid of glue. Theoretical and dimensional analyses are performed to investigate the regional stretch problem for soft materials that obey the neo-Hookean model, the Mooney-Rivlin model, or the Arruda-Boyce model. Finite element simulations are made to determine the expressions of the dimensionless functions that correlate the stretch response with the constitutive parameters. Thereby, an inverse approach is established to determine the elastic and hyperelastic properties of the tested materials. The regional stretch method is also compared to the indentation technique. Finally, experiments are performed to demonstrate the effectiveness of the proposed method.展开更多
The Sandstorm Source Control Project in and around the Beijing-Tianjin region was one of the most important ecological projects in China.Terrestrial water storage(TWS)has important impacts on the ecological constructi...The Sandstorm Source Control Project in and around the Beijing-Tianjin region was one of the most important ecological projects in China.Terrestrial water storage(TWS)has important impacts on the ecological construction,agriculture,industry,and resident's lives.Based on the Gravity Recovery and Climate Experiment(GRACE)data,meteorological and Moderate Resolution Imaging Spectroradiometer(MODIS)data,etc.,this paper analyzed spatiotemporal characteristics of TWS,groundwater storage,and precipitation,and explored the influencing factors of regional TWS combined with land use and land cover(LULC),social and economic data.The most important results were as follows:(1)From 2003 to 2016,TWS in the Beijing-Tianjin Sandstorm Source Region showed a decreasing trend with a rate of 3.14 mm yr-1.(2)The TWS decline was caused mainly by groundwater overexploitation,but not pre-cipitation variation.(3)Spatiotemporal variations of TWS were related to LULC.The area with the most serious decrease of TWS was mainly located in the southwestern part of the region,where farmland percentage and population density were greater.(4)Reducing the percent of farmland and tree planting,and adding the shrub and grass planting,could be a viable choice for the Beijing-Tianjin Sandstorm Source Control Project.These results provide a scientific basis for regional water resource and ecological management.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 10972112 and 11172155)Tsinghua University973 Program (2010CB631005)
文摘This paper explores growth induced morphological instabilities in biological soft materials. In view of that the growth of a living tissue not only changes its geometry but also can alter its mechanical properties, we suggest a refined volumetric growth model incorporating the effects of growth on the mechanical properties of materials. Analogy between this volumetric growth model and the conventional thermal stress model is addressed for both small and finite de- formation problems, which brings great ease for the finite element analysis based on the suggested model. Examples of growth induced surface wrinkling behavior in soft composites, including core- shell soft cylinders and three-layered soft tissues, are explored. The results and discussions foresee possible applications of the model in understanding the correlation between the morphogenesis and growth of soft biological tissues （e.g. skins and tumors）, as well as in evaluating the defor- mation and surface instability behavior of soft artificial materials induced by swelling/shrinkage.
基金This project was supported by National Natural Science Foundation of China(31771982).
文摘To investigate the behavior of all-trans-β-carotene during digestion,in-vitro digestion coupled with HPLC-DAD,Raman spectroscopy and Fourier transform-infrared spectroscopy were used to monitor it.All-trans-β-carotene reduced by 75%during the in-vitro digestion and had a highest degradation during intestinal digestion compared with oral and gastro digestion.All-trans-β-carotene occurred isomerization and degradation during oral digestion and occurred degradation during gastro and intestinal digestion.Isomers were identifi ed as 15-cis-β-carotene and 9-cis-β-carotene,degradation products were compounds with function group of C—O,C—O—C or C=C—C=C.The biological fate ofβ-carotene during digestion was clarifi ed,and one of the reasons for low bioavailability ofβ-carotene was explained by high degradation rate during digestion.
基金supported by NSFC/China (No. 91125006)IAM grant (No. IAM201215)partially by State Key Laboratory funding (No. SKLFSE201009)
文摘There are only limited surface water resources available in the Heihe River Basin （HRB）, a typical inland river basin in the arid region of northwestern China, where groundwater overexploitation is a serious problem. Groundwater has become one of main resources of fresh water in the HRB. In this paper, temporal and spatial variations of groundwater in the HRB are estimated by the Gravity Recovery and Climate Experiment （GRACE） satellites. Our analysis shows that groundwater storage in the HRB reaches its highest in the summer of 2005, and then begins to decline in the following years and reaches steady status in 2008. Spatially, groundwater shows a decline in the upper HRB in the first two years and a slight increase in the following years, while this phenomenon is reversed in the middle HRB where groundwater slightly increases in 2005 and then declines in the following three years. In the lower HRB, GRACE detects a continual increase in the full six-year period. This approach is proven successful when employed in the HRB and thus offers a new insight into monitoring groundwater variations in a river basin with limited or even without any observed data.
基金the support from the National Natural Science Foundation of China(Grant Nos.12272130,and 11902114)the support from the National Natural Science Foundation of China(Grant No.52235005)+1 种基金the Natural Science Foundation for Excellent Young Scholars of Hunan Province(Grant No.2022JJ20003)the support from“The Fundamental Research Funds for the Central Universities,Peking University”。
文摘Diverse wrinkling patterns can occur on curved bilayer systems under differential growth or expansion.In such systems,stress anisotropy is frequently encountered,and the coupling effect of curvature and stress anisotropy on the pattern evolution remains largely unexplored.In this study,we investigate the evolution of wrinkling patterns on a cylinder core-shell system with stress anisotropy leveraging both theoretical analysis and finite element simulations.Critical buckling analysis has identified three distinct critical buckling modes regulated by the stress anisotropy,i.e.,axial sinusoidal mode,checkerboard mode,and circumferential sinusoidal mode.Our finite element simulations,along with post-buckling analysis,reveal seven distinct evolutionary paths stemming from the three critical buckling modes.We present phase diagrams for both the critical buckling modes and their evolutionary paths,which are determined by dimensionless curvature and stress anisotropy.Our results not only expand the theoretical research on surface wrinkling of a core-shell soft cylinder but also introduce stress anisotropy as a significant parameter for regulating the wrinkling patterns and their evolutionary paths in curved bilayer systems.The revelation of a multitude of wrinkling patterns and their evolutionary pathways holds great potential for advancing applications that leverage tunable wrinkle surfaces.
基金supported by the National Natural Science Foundation of China(Grant Nos.11432008,11572179,and 11172155)
文摘Characterizing the mechanical properties of soft materials and biological tissues is of great significance for understanding their deformation behaviors. In this paper, a regional stretching method is proposed to measure the elastic and hyperelastic properties of a soft material with an adhesive surface or with the aid of glue. Theoretical and dimensional analyses are performed to investigate the regional stretch problem for soft materials that obey the neo-Hookean model, the Mooney-Rivlin model, or the Arruda-Boyce model. Finite element simulations are made to determine the expressions of the dimensionless functions that correlate the stretch response with the constitutive parameters. Thereby, an inverse approach is established to determine the elastic and hyperelastic properties of the tested materials. The regional stretch method is also compared to the indentation technique. Finally, experiments are performed to demonstrate the effectiveness of the proposed method.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2016YFC0500801 and 2016YFC0500804)the National Natural Science Foundation of China(Grant Nos.41701010 and 410701503)the Fundamental Research Funds for the Central Non-profit Research Institution of Chinese Academy of Forestry(Grant No.CAFYBB2019MA009).
文摘The Sandstorm Source Control Project in and around the Beijing-Tianjin region was one of the most important ecological projects in China.Terrestrial water storage(TWS)has important impacts on the ecological construction,agriculture,industry,and resident's lives.Based on the Gravity Recovery and Climate Experiment(GRACE)data,meteorological and Moderate Resolution Imaging Spectroradiometer(MODIS)data,etc.,this paper analyzed spatiotemporal characteristics of TWS,groundwater storage,and precipitation,and explored the influencing factors of regional TWS combined with land use and land cover(LULC),social and economic data.The most important results were as follows:(1)From 2003 to 2016,TWS in the Beijing-Tianjin Sandstorm Source Region showed a decreasing trend with a rate of 3.14 mm yr-1.(2)The TWS decline was caused mainly by groundwater overexploitation,but not pre-cipitation variation.(3)Spatiotemporal variations of TWS were related to LULC.The area with the most serious decrease of TWS was mainly located in the southwestern part of the region,where farmland percentage and population density were greater.(4)Reducing the percent of farmland and tree planting,and adding the shrub and grass planting,could be a viable choice for the Beijing-Tianjin Sandstorm Source Control Project.These results provide a scientific basis for regional water resource and ecological management.
