The survival strategy of plants is to adjust their functional traits to adapt to the environment.However,these traits and survival strategies of evergreen broad-leaved forest species are not well understood.This study...The survival strategy of plants is to adjust their functional traits to adapt to the environment.However,these traits and survival strategies of evergreen broad-leaved forest species are not well understood.This study examined 10 leaf functional traits(LFTs)of 70 common plant species in an evergreen broad-leaved forest in Huangshan Mountain to decipher their adaptive strategies.The phylogenetic signals of these LFTs were assessed and phylogenetically independent contrasts(PIC)and correlation analyses were carried out.LFTs were analyzed to determine their CSR(C:competitor,S:stress-tolerator,R:ruderal)strategies.The results show that plant species exhibit different leaf functional traits and ecological strategies(nine strategies were identified;the most abundant were S/CS and S/CSR strategies).Some traits showed significant phylogenetic signals,indicating the effect of phylogeny on LFTs to an extent.Trait variations among species suggest distinct adaptation strategies to environmental changes.The study species were mainly clustered on the C-S strategy axis,with a high S component.Species leaning toward the C-strategy end(e.g.,deciduous species),favored a resource acquisition strategy characterized by higher specific leaf area(SLA),greater nutrient contents(N and P),lower leaf dry matter content(LDMC),and reduced nutrient utilization efficiency(C:N and C:P).Conversely,species closer to the S-strategy end(e.g.,evergreen species)usually adopted a resource conservative strategy with trait combinations contrary to those of C-strategy species.Overall,this study corroborated the applicability of the CSR strategy at a local scale and provides insights into the varied trait combinations and ecological strategies employed by plant species to adapt to their environment.These findings contribute to a better understanding of the mechanisms involved in biodiversity maintenance.展开更多
Hydrogel scaffolds have numerous potential applications in the tissue engineering field.However,tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and hi...Hydrogel scaffolds have numerous potential applications in the tissue engineering field.However,tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and high mechanical properties.Inspired by Chinese ramen,we propose a universal fabricating method(printing-P,training-T,cross-linking-C,PTC&PCT)for tough hydrogel scaffolds to fill this gap.First,3D printing fabricates a hydrogel scaffold with desired structures(P).Then,the scaffold could have extraordinarily high mechanical properties and functional surface structure by cycle mechanical training with salting-out assistance(T).Finally,the training results are fixed by photo-cross-linking processing(C).The tough gelatin hydrogel scaffolds exhibit excellent tensile strength of 6.66 MPa(622-fold untreated)and have excellent biocompatibility.Furthermore,this scaffold possesses functional surface structures from nanometer to micron to millimeter,which can efficiently induce directional cell growth.Interestingly,this strategy can produce bionic human tissue with mechanical properties of 10 kPa-10 MPa by changing the type of salt,and many hydrogels,such as gelatin and silk,could be improved with PTC or PCT strategies.Animal experiments show that this scaffold can effectively promote the new generation of muscle fibers,blood vessels,and nerves within 4 weeks,prompting the rapid regeneration of large-volume muscle loss injuries.展开更多
Changbai pine (Pinus sylvestris var.Sylvestriformis) is an endemic and important tree species in Changbai Mountain. There were only 63 plant species in Changbai pine plantation, where hemicryptophyte was dominant(39.6...Changbai pine (Pinus sylvestris var.Sylvestriformis) is an endemic and important tree species in Changbai Mountain. There were only 63 plant species in Changbai pine plantation, where hemicryptophyte was dominant(39.68%). Simpson diversity index was 0.87, Shannon-Wiener diversity index was 2.96, and evenness index was 0.82. Community structure were divided into three layers: tree layer, shrub layer and herb layer. The total biomass and net production were 111.982 t/hm2 and 8942.80 kg/(hm2 a) respectively. The total biomass for tree, shrub and herb layers were 106.150, 2.230, 2.264 t/hm2, accounting for 94.79%, 1.99%, and 2.02%, respectively, and net production for those were 7465, 223, and 1182 kg/(hm2 a), accounting for 83.47%, 2.49%, and 13.22% of the total respectively. The nutrient content in various organs is in the order of needle> branch> root> bark> trunk, For the assimilated organ, the nutrient content is in the order of N> K> Ca> P> Mg, and that in absorption organ is in the order of Ca> N> K> P> Mg. For the whole plantation ecosystem, nutrient content is in the order of soil> litter> herb layer> shrub layer> tree layer. Nutrient storage and its accumulation rate in tree layer take up 88.79% and 76.43% of the total, respectively.展开更多
From the 1950s to 1960s, large area of Populus simonii shelterbelts system was established in northern area of Shanxi Province. For reconstructing the old shelterbelts, more attentions should be paid to selecting suit...From the 1950s to 1960s, large area of Populus simonii shelterbelts system was established in northern area of Shanxi Province. For reconstructing the old shelterbelts, more attentions should be paid to selecting suitable tree species and design of logical shelterbelts structure. In order to provide a profound basis for the efficient establishment of shelterbelts, the study on function and structure of the farmland shelterbelts was conducted in Shuozhou and Datong areas, both are semi-arid areas in Northern Shanxi Province during 1996-2001. The wind-control effects of shelterbelts with different structures (close-spaced, wider-spaced, and widest-spaced) were investigated by portable wind vane and anemometer, wet and dry bulb thermometer, ground thermometer, glass service instrument. The results showed that the wind-control capacity of the shelterbelts during the leafing period should be thought as the criteria index in shelterbelts established. The wider-spaced shelterbelt that was made of 4-6 rows of trees, with a spacing of 2.0 m×3.0 m, had the best wind-control result.展开更多
Primary forests are spatially diverse terrestrial ecosystems with unique characteristics,being naturally regenerative and heterogeneous,which supports the stability of their carbon storage through the accumulation of ...Primary forests are spatially diverse terrestrial ecosystems with unique characteristics,being naturally regenerative and heterogeneous,which supports the stability of their carbon storage through the accumulation of live and dead biomass.Yet,little is known about the interactions between biomass stocks,tree genus diversity and structure across a temperate montane primary forest.Here,we investigated the relationship between tree structure(variability in basal area and tree size),genus-level diversity(abundance,tree diversity)and biomass stocks in temperate primary mountain forests across Central and Eastern Europe.We used inventory data from726 permanent sample plots from mixed beech and spruce across the Carpathian Mountains.We used nonlinear regression to analyse the spatial variability in forest biomass,structure,and genus-level diversity and how they interact with plot-level tree age,disturbances,temperature and altitude.We found that the combined effects of genus and structural indices were important for addressing the variability in biomass across different spatial scales.Local processes in disturbance regimes and uneven tree age support forest hete rogeneity and the accumulation of live and dead biomass through the natural regeneration,growth and decay of the forest ecosystem.Structural complexities in basal area index,supporte d by genus-level abundance,positively influence total biomass stocks,which was modulated by tree age and disturbances.Spruce forests showed higher tree density and basal area than mixed beech forests,though mixed beech still contributes significantly to biomass across landscapes.Forest heterogeneity was strongly influenced by complexities in forest composition(tree genus diversity,structure).We addressed the importance of primary forests as stable carbon stores,achieved through structure and diversity.Safeguarding such ecosystems is critical for ensuring the stability of the primary forest,carbon store and biodiversity into the future.展开更多
Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure.Superalkalis have low ionization energy.Doping a superalkali in cyclo[18]carbon is an ef...Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure.Superalkalis have low ionization energy.Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs.In this paper,the geometry,bonding properties,electronic structure,absorption spectrum,and nonlinear optical(NLO)properties of superalkaline M_(3)O(M=Li,Na)-doped cyclo[18]carbon were studied by using density functional theory.M_(3)O and the C_(18) rings are not coplanar.The C_(18) ring still exhibits alternating long and short bonds.The charge transfer between M_(3)O and C_(18) forms stable[M_(3)O]+[C_(18)]-ionic complexes.C_(18)M_(3)O(M=Li,Na)shows striking optical nonlinearity,i.e.,their first-and second-order hyperpolarizability(βvec andγ||)increase considerably atλ=1907 nm and 1460 nm.展开更多
Bamboo forest is an important forest type in subtropical and tropical areas.Due to its biological characteristic and growth habits, bamboo is not only an ideal economicinvestment that can be utilized in many different...Bamboo forest is an important forest type in subtropical and tropical areas.Due to its biological characteristic and growth habits, bamboo is not only an ideal economicinvestment that can be utilized in many different manners but also has enormous potential foralleviating many environmental problems facing the world today. This review describes ecologicalfunctions of the bamboo forest on soil erosion control, water conservation, land rehabilitation, andcarbon sequestration.展开更多
The effect of In doping on the electronic structure and optical properties of SrTiO3 is investigated by the first-principles calculation of plane wave ultra-soft pseudo-potential based on the density function theory ...The effect of In doping on the electronic structure and optical properties of SrTiO3 is investigated by the first-principles calculation of plane wave ultra-soft pseudo-potential based on the density function theory （DFT）. The calculated results reveal that due to the hole doping, the Fermi level shifts into valence bands （VBs） for SrTi1-x InxO3 with x = 0.125 and the system exhibits p-type degenerate semiconductor features. It is suggested according to the density of states （DOS） of SrTi0.875In0.125O3 that the band structure of p-type SrTIO3 can be described by a rigid band model. At the same time, the DOS shifts towards high energies and the optical band gap is broadened. The wide band gap, small transition probability and weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the optical transparency of the film. The optical transmittance of In doped SrTiO3 is higher than 85% in a visible region, and the transmittance improves greatly. And the cut-off wavelength shifts into a blue-light region with the increase of In doping concentration.展开更多
It has been reported that fresh edible rice has more bioactive compounds and its protein is easier to digest and has lower hypoallergenic than mature rice. In this paper, the changes in structure and functional proper...It has been reported that fresh edible rice has more bioactive compounds and its protein is easier to digest and has lower hypoallergenic than mature rice. In this paper, the changes in structure and functional properties of proteins at five different stages, including early milky stage(EMS), middle milky stage(MMS), late milky stage(LMS), waxy ripe stage(WS)and ripening stage(RS), during the seed development were investigated. It was found that with the seed developing, the molecular weight of fresh rice protein gradually become larger while the secondary structure changed from the highest content of disordered structure at MMS to the highest content of ordered structure at RS, which affect the surface hydrophobicity and then the functional properties of proteins, including foaming properties, emulsifying properties and oil holding capacity. Fresh rice protein at MMS has the strongest surface hydrophobicity while fresh edible rice protein at RS has the strongest oil holding capability. The results of our study can provide a theoretical basis for the application of fresh rice protein in the food industry and help to develop new fresh edible rice food.展开更多
First-principles calculations have been performed to investigate the ground state electronic properties of BaFeO3 （BFO）. Local spin density approximation （LSDA） plus U （LSDA＋U） treatment modified the metallic b...First-principles calculations have been performed to investigate the ground state electronic properties of BaFeO3 （BFO）. Local spin density approximation （LSDA） plus U （LSDA＋U） treatment modified the metallic behaviour to insulated one with a band gap of 4.12eV. The spontaneous polarization was found to be 89.3μC/cm^2 with Berry phase scheme in terms of the modern theory of polarization. Fe-3d eg were split into two singlet states （dz2 and dx2-v2）, and Fe-3d t2g were split into one doublet states（dze and dyz） and one singlet states（dzy） after Fe and O displaced along the c axis. Meanwhile the occupation numbers of dx2, dxz, dyz and OT pz （on the top of Fe） were increased at the expense of those in xy plane. Our results showed that it was the sensitivity of hybridization to ferroelectric distortions, not just the total change of hybridization, that produced the possibility of ferroelectricity. Moreover, the increasing occupation numbers of OT pz and Fe dz2 favoured the 180° coupling between Fe-3d eg and Fe-3d t2g, leading to ferromagnetic ordering, which has been confirmed by the increase of magnetic moment by 0.13μB per formula unit in the polarized direction. Hence, the magnetization can be altered by the reversal of external electric field.展开更多
This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional t...This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional theory （DFT）.The calculated results reveal that due to the electron doping,the Fermi level shifts into conduction bands（CBs） for Sr2NbxTi1-xO4 with x=0.125 and the system shows n-type degenerate semiconductor features. Sr2TiO4 exhibits optical anisotropy in its main crystal axes,and the c-axis shows the most suitable crystal growth direction for obtaining a wide transparent region.The optical transmittance is higher than 90% in the visible range for Sr2Nb0.125Ti0.875O4.展开更多
The pointwise space-time behaviors of the Green’s function and the global solution to the Vlasov-Poisson-Fokker-Planck(VPFP)system in three dimensional space are studied in this paper.It is shown that the Green’s fu...The pointwise space-time behaviors of the Green’s function and the global solution to the Vlasov-Poisson-Fokker-Planck(VPFP)system in three dimensional space are studied in this paper.It is shown that the Green’s function consists of the diffusion waves decaying exponentially in time but algebraically in space,and the singular kinetic waves which become smooth for all(t,x,v)when t>0.Furthermore,we establish the pointwise space-time behaviors of the global solution to the nonlinear VPFP system when the initial data is not necessarily smooth in terms of the Green’s function.展开更多
Non-renewable fossil fuels have led to serious problems such as global warming,environmental pollution,etc.Oxygen electrocatalysis including oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)plays a cent...Non-renewable fossil fuels have led to serious problems such as global warming,environmental pollution,etc.Oxygen electrocatalysis including oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)plays a central role in clean energy conversion,enabling a number of sustainable processes for future air battery technologies.Fluorine,as the most electronegative element(4.0)not only can induce more efficient regulation for the electronic structure,but also can bring more abundant defects and other novel effects in materials selection and preparation for favorable catalysis with respect to the other nonmetal elements.However,an individual and comprehensive overview of fluorine-containing functional materials for oxygen electrocatalysis field is still blank.Therefore,it is very meaningful to review the recent progresses of fluorine-containing oxygen electrocatalysts.In this review,we first systematically summarize the controllable preparation methods and their possible development directions based on fluorine-containing materials from four preparation methods.Due to the strong electron-withdrawing properties of fluorine,its control of the electronic structure can effectively enhance the oxygen electrocatalytic activity of the materials.In addition,the catalytic enhancement effect of fluorine on carbonbased materials also includes the prevent oxidation and the layer peeling,and realizes the precise atomic control.And the catalytic improvement mechanism of fluorine containing metal-based compounds also includes the hydration of metal site,the crystal transformation,and the oxygen vacancy induction.Then,based on their various dimensions(0D–3D),we also have summarized the advantages of different morphologies on oxygen electrocatalytic performances.Finally,the prospects and possible future researching direction of F-containing oxygen electrocatalysts are presented(e.g.,novel pathways,advanced methods for measurement and simulation,field assistance and multi-functions).The review is considered valuable and helpful in exploring the novel designs and mechanism analyses of advanced fluorine-containing electrocatalysts.展开更多
Two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , are proposed and studied numerically. The band gaps structures of the photonic c...Two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , are proposed and studied numerically. The band gaps structures of the photonic crystals for TE and TM waves are different from the two-dimensional conventional photonic crystals. Some absolute band gaps and semiDirac points are found. When the medium column radius and the function form of the dielectric constant are modulated, the numbers, width, and position of band gaps are changed, and the semi-Dirac point can either occur or disappear. Therefore,the special band gaps structures and semi-Dirac points can be achieved through the modulation on the two-dimensional function photonic crystals. The results will provide a new design method of optical devices based on the two-dimensional function photonic crystals.展开更多
First-principles calculations for several aromatic molecules with anhydride and thio groups on Ag(111) and Au(111)reveal that the self-assembly structures and the interface properties are mainly determined by the func...First-principles calculations for several aromatic molecules with anhydride and thio groups on Ag(111) and Au(111)reveal that the self-assembly structures and the interface properties are mainly determined by the functional groups of aromatic molecules. Detailed investigations of the electronic structures show that the electrons in molecular backbone are redistributed and charge transfer occurs through the bond between the metal and the functional groups after these molecules have been deposited on a metal substrate. The interaction between Ag(111)(or Au(111)) and aromatic molecules with anhydride functional groups strengthens the π bonds in the molecular backbone, while that between Ag(111)(or Au(111))and aromatic molecules with sulfur weakens the π bonds. However, the intrinsic electronic structures of the molecules are mostly conserved. The large-sized aromatic backbone has less influence on the nature of electronic structures than the small-sized one, either at the interface or at the molecules. These results are useful to build the good metal-molecule contact in molecule-based devices.展开更多
The stability, electronic structures, and mechanical properties of the Fe-Mn-Al system were determined by firstprinciples calculations. The formation enthalpy and cohesive energy of these Fe-Mn-Al alloys are negative ...The stability, electronic structures, and mechanical properties of the Fe-Mn-Al system were determined by firstprinciples calculations. The formation enthalpy and cohesive energy of these Fe-Mn-Al alloys are negative and show that the alloys are thermodynamically stable. Fe3Al, with the lowest formation enthalpy, is the most stable compound in the Fe-Mn-Al system. The partial density of states, total density of states, and electron density distribution maps of the Fe-Mn-Al alloys were analyzed. The bonding characteristics of these Fe-Mn-Al alloys are mainly combinations of covalent bonding and metallic bonds. The stress-strain method and Voigt-Reuss-Hill approximation were used to calculate the elastic constants and moduli, respectively. Fe2.5Mn0.5Al has the highest bulk modulus, 234.5 GPa. Fel.sMn1.5Al has the highest shear modulus and Young＇s modulus, with values of 98.8 GPa and 259.2 GPa, respectively. These Fe-Mn-Al alloys display disparate anisotropies due to the calculated different shape of the three-dimensional curved surface of the Young＇s modulus and anisotropic index. Moreover, the anisotropic sound velocities and Debye temperatures of these Fe-Mn-Al alloys were explored.展开更多
The geometries, electronic structures and related properties of SimN8-m（0 〈 m 〈 8） clusters are studied using density functional theory （DFT） with hybrid functional B3LYP. The calculated results reveal several t...The geometries, electronic structures and related properties of SimN8-m（0 〈 m 〈 8） clusters are studied using density functional theory （DFT） with hybrid functional B3LYP. The calculated results reveal several trends. For any stoichiometric clusters, the lowest energy isomers with an alteration of N and Si atoms are favourable in energy if the numbers of Si and N atoms are large enough to form ... Si N-Si-N... alternative chains. The bond lengths of single Si-N bonds are very close to the corresponding values of the bulk and other SiN clusters. The geometries for N-rich and Si4N4 clusters are planar structures, but three-dimensional structures are favourable in energy for Si-rich clusters. With the increase of m, the isotropic polarizability and average polarizability increase, the total binding energies generally decrease, the HOMO-LUMO gap and vertical ionization potential oscillate with increasing number of valence electrons, and their values with even valence electrons are larger than those with odd valence electrons. The atomic charges, IR and Raman properties are also reported.展开更多
In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2^- and S3^- have been calculated at QCISD/6-311＋＋G（3d2f） and B3P86/6-311＋＋G（3d2f） level. The S2^- ground state is of 2II...In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2^- and S3^- have been calculated at QCISD/6-311＋＋G（3d2f） and B3P86/6-311＋＋G（3d2f） level. The S2^- ground state is of 2IIg, the S3^- ground state is of 2B1 and S3^- has a bent （C2v） structure with an angle of 115.65° The results are in good agreement with these reported in other literature. For S3^- ion, the vibration frequencies and the force constants have also been calculated. Base on the general principles of microscopic reversibility, the dissociation limits has been deduced. The Murrell-Sorbie potential energy function for S2^- has been derived according to the ab initio data through the least- squares fitting. The force constants and spectroscopic data for S2^- have been calculated, then compared with other theoretical data. The analytical potential energy function of S3^- have been obtained based on the many-body expansion theory. The structure and energy can correctly reappear on the potential surface.展开更多
The lowest-energy structures and the electronic properties of Mo2nNn （n=1-5） clusters have been studied by using the density functional theory （DFT） simulating package DMol3 in the generalized gradient approximati...The lowest-energy structures and the electronic properties of Mo2nNn （n=1-5） clusters have been studied by using the density functional theory （DFT） simulating package DMol3 in the generalized gradient approximation （GGA）. The resulting equilibrium geometries show that the lowest-energy structures are dominated by central cores which correspond to the ground states of Mon （n = 2, 4, 6, 8, 10） clusters and nitrogen atoms which surround these cores. The average binding energy, the adiabatic electron affinity （AEA）, the vertical electron affinity （VEA）, the adiabatic ionization potential （AIP） and the vertical ionization potential （VIP） of Mo2nNn （n=1-5） clusters have been estimated. The HOMO LUMO gaps reveal that the clusters have strong chemical activities. An analysis of Mulliken charge distribution shows that charge-transfer moves from Mo atoms to N atoms and increases with cluster size.展开更多
This paper reports that the equilibrium structure of NH2 has been optimized at the QCISD/6-311＋＋G （3df, 3pd） level. The ground-state NH2 has a bent （C2v, X^2B1） structure with an angle of 103.0582°. The geo...This paper reports that the equilibrium structure of NH2 has been optimized at the QCISD/6-311＋＋G （3df, 3pd） level. The ground-state NH2 has a bent （C2v, X^2B1） structure with an angle of 103.0582°. The geometrical structure is in good agreement with the other calculational and experimental results. The harmonic frequencies and the force constants have also been calculated. Based on the group theory and the principle of microscopic reversibility, the dissociation limits of NH2（C2v, X^2B1） have been derived. The potential energy surface of NH2（X^2B1） is reasonable. The contour lines are constructed, the structure and energy of NH2 reappear on the potential energy surface.展开更多
基金supported by the Special Foundation for National Science and Technology Basic Resources Investigation of China(2019FY202300)the Biodiversity Survey,Observation and Assessment Project of the Ministry of Ecology and Environment(2110404).
文摘The survival strategy of plants is to adjust their functional traits to adapt to the environment.However,these traits and survival strategies of evergreen broad-leaved forest species are not well understood.This study examined 10 leaf functional traits(LFTs)of 70 common plant species in an evergreen broad-leaved forest in Huangshan Mountain to decipher their adaptive strategies.The phylogenetic signals of these LFTs were assessed and phylogenetically independent contrasts(PIC)and correlation analyses were carried out.LFTs were analyzed to determine their CSR(C:competitor,S:stress-tolerator,R:ruderal)strategies.The results show that plant species exhibit different leaf functional traits and ecological strategies(nine strategies were identified;the most abundant were S/CS and S/CSR strategies).Some traits showed significant phylogenetic signals,indicating the effect of phylogeny on LFTs to an extent.Trait variations among species suggest distinct adaptation strategies to environmental changes.The study species were mainly clustered on the C-S strategy axis,with a high S component.Species leaning toward the C-strategy end(e.g.,deciduous species),favored a resource acquisition strategy characterized by higher specific leaf area(SLA),greater nutrient contents(N and P),lower leaf dry matter content(LDMC),and reduced nutrient utilization efficiency(C:N and C:P).Conversely,species closer to the S-strategy end(e.g.,evergreen species)usually adopted a resource conservative strategy with trait combinations contrary to those of C-strategy species.Overall,this study corroborated the applicability of the CSR strategy at a local scale and provides insights into the varied trait combinations and ecological strategies employed by plant species to adapt to their environment.These findings contribute to a better understanding of the mechanisms involved in biodiversity maintenance.
基金supported by the Innovative Research Group Project of the National Natural Science Foundation of China(T2121004)Key Programme(52235007)National Outstanding Youth Foundation of China(52325504).
文摘Hydrogel scaffolds have numerous potential applications in the tissue engineering field.However,tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and high mechanical properties.Inspired by Chinese ramen,we propose a universal fabricating method(printing-P,training-T,cross-linking-C,PTC&PCT)for tough hydrogel scaffolds to fill this gap.First,3D printing fabricates a hydrogel scaffold with desired structures(P).Then,the scaffold could have extraordinarily high mechanical properties and functional surface structure by cycle mechanical training with salting-out assistance(T).Finally,the training results are fixed by photo-cross-linking processing(C).The tough gelatin hydrogel scaffolds exhibit excellent tensile strength of 6.66 MPa(622-fold untreated)and have excellent biocompatibility.Furthermore,this scaffold possesses functional surface structures from nanometer to micron to millimeter,which can efficiently induce directional cell growth.Interestingly,this strategy can produce bionic human tissue with mechanical properties of 10 kPa-10 MPa by changing the type of salt,and many hydrogels,such as gelatin and silk,could be improved with PTC or PCT strategies.Animal experiments show that this scaffold can effectively promote the new generation of muscle fibers,blood vessels,and nerves within 4 weeks,prompting the rapid regeneration of large-volume muscle loss injuries.
文摘Changbai pine (Pinus sylvestris var.Sylvestriformis) is an endemic and important tree species in Changbai Mountain. There were only 63 plant species in Changbai pine plantation, where hemicryptophyte was dominant(39.68%). Simpson diversity index was 0.87, Shannon-Wiener diversity index was 2.96, and evenness index was 0.82. Community structure were divided into three layers: tree layer, shrub layer and herb layer. The total biomass and net production were 111.982 t/hm2 and 8942.80 kg/(hm2 a) respectively. The total biomass for tree, shrub and herb layers were 106.150, 2.230, 2.264 t/hm2, accounting for 94.79%, 1.99%, and 2.02%, respectively, and net production for those were 7465, 223, and 1182 kg/(hm2 a), accounting for 83.47%, 2.49%, and 13.22% of the total respectively. The nutrient content in various organs is in the order of needle> branch> root> bark> trunk, For the assimilated organ, the nutrient content is in the order of N> K> Ca> P> Mg, and that in absorption organ is in the order of Ca> N> K> P> Mg. For the whole plantation ecosystem, nutrient content is in the order of soil> litter> herb layer> shrub layer> tree layer. Nutrient storage and its accumulation rate in tree layer take up 88.79% and 76.43% of the total, respectively.
基金The study was supported by Shanxi Ninth Five-year Plan Project (No. 961016).
文摘From the 1950s to 1960s, large area of Populus simonii shelterbelts system was established in northern area of Shanxi Province. For reconstructing the old shelterbelts, more attentions should be paid to selecting suitable tree species and design of logical shelterbelts structure. In order to provide a profound basis for the efficient establishment of shelterbelts, the study on function and structure of the farmland shelterbelts was conducted in Shuozhou and Datong areas, both are semi-arid areas in Northern Shanxi Province during 1996-2001. The wind-control effects of shelterbelts with different structures (close-spaced, wider-spaced, and widest-spaced) were investigated by portable wind vane and anemometer, wet and dry bulb thermometer, ground thermometer, glass service instrument. The results showed that the wind-control capacity of the shelterbelts during the leafing period should be thought as the criteria index in shelterbelts established. The wider-spaced shelterbelt that was made of 4-6 rows of trees, with a spacing of 2.0 m×3.0 m, had the best wind-control result.
基金funded by the Czech University of Life Sciences Prague(Internal Grant Agency:A_03_22-43110/1312/3101)the Czech Science(GACR 21-27454S)。
文摘Primary forests are spatially diverse terrestrial ecosystems with unique characteristics,being naturally regenerative and heterogeneous,which supports the stability of their carbon storage through the accumulation of live and dead biomass.Yet,little is known about the interactions between biomass stocks,tree genus diversity and structure across a temperate montane primary forest.Here,we investigated the relationship between tree structure(variability in basal area and tree size),genus-level diversity(abundance,tree diversity)and biomass stocks in temperate primary mountain forests across Central and Eastern Europe.We used inventory data from726 permanent sample plots from mixed beech and spruce across the Carpathian Mountains.We used nonlinear regression to analyse the spatial variability in forest biomass,structure,and genus-level diversity and how they interact with plot-level tree age,disturbances,temperature and altitude.We found that the combined effects of genus and structural indices were important for addressing the variability in biomass across different spatial scales.Local processes in disturbance regimes and uneven tree age support forest hete rogeneity and the accumulation of live and dead biomass through the natural regeneration,growth and decay of the forest ecosystem.Structural complexities in basal area index,supporte d by genus-level abundance,positively influence total biomass stocks,which was modulated by tree age and disturbances.Spruce forests showed higher tree density and basal area than mixed beech forests,though mixed beech still contributes significantly to biomass across landscapes.Forest heterogeneity was strongly influenced by complexities in forest composition(tree genus diversity,structure).We addressed the importance of primary forests as stable carbon stores,achieved through structure and diversity.Safeguarding such ecosystems is critical for ensuring the stability of the primary forest,carbon store and biodiversity into the future.
基金Project supported by the Natural Science Foundation of Anhui Province(Grant No.1908085MA12)the National Natural Science Foundation of China(Grant No.21703222)。
文摘Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure.Superalkalis have low ionization energy.Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs.In this paper,the geometry,bonding properties,electronic structure,absorption spectrum,and nonlinear optical(NLO)properties of superalkaline M_(3)O(M=Li,Na)-doped cyclo[18]carbon were studied by using density functional theory.M_(3)O and the C_(18) rings are not coplanar.The C_(18) ring still exhibits alternating long and short bonds.The charge transfer between M_(3)O and C_(18) forms stable[M_(3)O]+[C_(18)]-ionic complexes.C_(18)M_(3)O(M=Li,Na)shows striking optical nonlinearity,i.e.,their first-and second-order hyperpolarizability(βvec andγ||)increase considerably atλ=1907 nm and 1460 nm.
基金This paper was supported by International Tropical Timber Organization (ITTO) (No. PD10/00REV.2(I,F)) and National Natural Science Foundation of China (No. 30300273).
文摘Bamboo forest is an important forest type in subtropical and tropical areas.Due to its biological characteristic and growth habits, bamboo is not only an ideal economicinvestment that can be utilized in many different manners but also has enormous potential foralleviating many environmental problems facing the world today. This review describes ecologicalfunctions of the bamboo forest on soil erosion control, water conservation, land rehabilitation, andcarbon sequestration.
基金Project supported by the Natural Science Foundation of Shaanxi Province, China （Grant No 2005F06）.
文摘The effect of In doping on the electronic structure and optical properties of SrTiO3 is investigated by the first-principles calculation of plane wave ultra-soft pseudo-potential based on the density function theory （DFT）. The calculated results reveal that due to the hole doping, the Fermi level shifts into valence bands （VBs） for SrTi1-x InxO3 with x = 0.125 and the system exhibits p-type degenerate semiconductor features. It is suggested according to the density of states （DOS） of SrTi0.875In0.125O3 that the band structure of p-type SrTIO3 can be described by a rigid band model. At the same time, the DOS shifts towards high energies and the optical band gap is broadened. The wide band gap, small transition probability and weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the optical transparency of the film. The optical transmittance of In doped SrTiO3 is higher than 85% in a visible region, and the transmittance improves greatly. And the cut-off wavelength shifts into a blue-light region with the increase of In doping concentration.
基金the financial support from the Postdoctoral Research Project of Heilongjiang Provincial Department of Human Resources and Social Security (LBH-Q21156)Heilongjiang BaYi Agricultural University Support Program for San Zong San Heng (ZDZX202104)+3 种基金Science Foundation Project of Heilongjiang Province (QC2015028)National Natural Science Foundation of China (32072258)Major Science and technology Program of Heilongjiang (2019ZX08B02,2020ZX08B02)Central financial support for the development of local colleges and universities,Graduate research and innovation project of Harbin University of Commerce (YJSCX2020636HSD)。
文摘It has been reported that fresh edible rice has more bioactive compounds and its protein is easier to digest and has lower hypoallergenic than mature rice. In this paper, the changes in structure and functional properties of proteins at five different stages, including early milky stage(EMS), middle milky stage(MMS), late milky stage(LMS), waxy ripe stage(WS)and ripening stage(RS), during the seed development were investigated. It was found that with the seed developing, the molecular weight of fresh rice protein gradually become larger while the secondary structure changed from the highest content of disordered structure at MMS to the highest content of ordered structure at RS, which affect the surface hydrophobicity and then the functional properties of proteins, including foaming properties, emulsifying properties and oil holding capacity. Fresh rice protein at MMS has the strongest surface hydrophobicity while fresh edible rice protein at RS has the strongest oil holding capability. The results of our study can provide a theoretical basis for the application of fresh rice protein in the food industry and help to develop new fresh edible rice food.
基金supported by the Aeronautical Science Foundation of China (Grant No 2003ZG51069)
文摘First-principles calculations have been performed to investigate the ground state electronic properties of BaFeO3 （BFO）. Local spin density approximation （LSDA） plus U （LSDA＋U） treatment modified the metallic behaviour to insulated one with a band gap of 4.12eV. The spontaneous polarization was found to be 89.3μC/cm^2 with Berry phase scheme in terms of the modern theory of polarization. Fe-3d eg were split into two singlet states （dz2 and dx2-v2）, and Fe-3d t2g were split into one doublet states（dze and dyz） and one singlet states（dzy） after Fe and O displaced along the c axis. Meanwhile the occupation numbers of dx2, dxz, dyz and OT pz （on the top of Fe） were increased at the expense of those in xy plane. Our results showed that it was the sensitivity of hybridization to ferroelectric distortions, not just the total change of hybridization, that produced the possibility of ferroelectricity. Moreover, the increasing occupation numbers of OT pz and Fe dz2 favoured the 180° coupling between Fe-3d eg and Fe-3d t2g, leading to ferromagnetic ordering, which has been confirmed by the increase of magnetic moment by 0.13μB per formula unit in the polarized direction. Hence, the magnetization can be altered by the reversal of external electric field.
基金Project supported by the Natural Science Foundation of ShaanXi Province of China (Grant No 2005F06)Northwest University(NWU) Graduate Innovation and Creativity Funds (Grant No 08YZZ47)
文摘This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional theory （DFT）.The calculated results reveal that due to the electron doping,the Fermi level shifts into conduction bands（CBs） for Sr2NbxTi1-xO4 with x=0.125 and the system shows n-type degenerate semiconductor features. Sr2TiO4 exhibits optical anisotropy in its main crystal axes,and the c-axis shows the most suitable crystal growth direction for obtaining a wide transparent region.The optical transmittance is higher than 90% in the visible range for Sr2Nb0.125Ti0.875O4.
基金supported by National Natural Science Foundation of China(11671100 and 12171104)the National Science Fund for Excellent Young Scholars(11922107)Guangxi Natural Science Foundation(2018GXNSFAA138210 and 2019JJG110010)。
文摘The pointwise space-time behaviors of the Green’s function and the global solution to the Vlasov-Poisson-Fokker-Planck(VPFP)system in three dimensional space are studied in this paper.It is shown that the Green’s function consists of the diffusion waves decaying exponentially in time but algebraically in space,and the singular kinetic waves which become smooth for all(t,x,v)when t>0.Furthermore,we establish the pointwise space-time behaviors of the global solution to the nonlinear VPFP system when the initial data is not necessarily smooth in terms of the Green’s function.
基金supported by the National Natural Science Foundation of China,China(52203066,51973157,51673148 and 51678411)the Science and Technology Plans of Tianjin,China(19PTSYJC00010)+3 种基金China Postdoctoral Science Foundation Grant,China(2019M651047)the Tianjin Research Innovation Project for Postgraduate Students,China(2020YJSB062)the Tianjin Municipal College Student’Innovation And Entrepreneurship Training Program,China(202110058052)the National Innovation and Entrepreneurship Training Program for College Students,China(202110058017)。
文摘Non-renewable fossil fuels have led to serious problems such as global warming,environmental pollution,etc.Oxygen electrocatalysis including oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)plays a central role in clean energy conversion,enabling a number of sustainable processes for future air battery technologies.Fluorine,as the most electronegative element(4.0)not only can induce more efficient regulation for the electronic structure,but also can bring more abundant defects and other novel effects in materials selection and preparation for favorable catalysis with respect to the other nonmetal elements.However,an individual and comprehensive overview of fluorine-containing functional materials for oxygen electrocatalysis field is still blank.Therefore,it is very meaningful to review the recent progresses of fluorine-containing oxygen electrocatalysts.In this review,we first systematically summarize the controllable preparation methods and their possible development directions based on fluorine-containing materials from four preparation methods.Due to the strong electron-withdrawing properties of fluorine,its control of the electronic structure can effectively enhance the oxygen electrocatalytic activity of the materials.In addition,the catalytic enhancement effect of fluorine on carbonbased materials also includes the prevent oxidation and the layer peeling,and realizes the precise atomic control.And the catalytic improvement mechanism of fluorine containing metal-based compounds also includes the hydration of metal site,the crystal transformation,and the oxygen vacancy induction.Then,based on their various dimensions(0D–3D),we also have summarized the advantages of different morphologies on oxygen electrocatalytic performances.Finally,the prospects and possible future researching direction of F-containing oxygen electrocatalysts are presented(e.g.,novel pathways,advanced methods for measurement and simulation,field assistance and multi-functions).The review is considered valuable and helpful in exploring the novel designs and mechanism analyses of advanced fluorine-containing electrocatalysts.
基金Project supported by the National Natural Science Foundations of China(Grant No.61275047)the Research Project of Chinese Ministry of Education(Grant No.213009A)the Scientific and Technological Development Foundation of Jilin Province,China(Grant No.20130101031JC)
文摘Two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , are proposed and studied numerically. The band gaps structures of the photonic crystals for TE and TM waves are different from the two-dimensional conventional photonic crystals. Some absolute band gaps and semiDirac points are found. When the medium column radius and the function form of the dielectric constant are modulated, the numbers, width, and position of band gaps are changed, and the semi-Dirac point can either occur or disappear. Therefore,the special band gaps structures and semi-Dirac points can be achieved through the modulation on the two-dimensional function photonic crystals. The results will provide a new design method of optical devices based on the two-dimensional function photonic crystals.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51471185 and 51325204)the National Key Research and Development Program of China(Grant No.2016YFJC020013)the National Supercomputing Center in Tianjin
文摘First-principles calculations for several aromatic molecules with anhydride and thio groups on Ag(111) and Au(111)reveal that the self-assembly structures and the interface properties are mainly determined by the functional groups of aromatic molecules. Detailed investigations of the electronic structures show that the electrons in molecular backbone are redistributed and charge transfer occurs through the bond between the metal and the functional groups after these molecules have been deposited on a metal substrate. The interaction between Ag(111)(or Au(111)) and aromatic molecules with anhydride functional groups strengthens the π bonds in the molecular backbone, while that between Ag(111)(or Au(111))and aromatic molecules with sulfur weakens the π bonds. However, the intrinsic electronic structures of the molecules are mostly conserved. The large-sized aromatic backbone has less influence on the nature of electronic structures than the small-sized one, either at the interface or at the molecules. These results are useful to build the good metal-molecule contact in molecule-based devices.
基金Project supported by the National Natural Science Foundation of China(Grant No.51261013)
文摘The stability, electronic structures, and mechanical properties of the Fe-Mn-Al system were determined by firstprinciples calculations. The formation enthalpy and cohesive energy of these Fe-Mn-Al alloys are negative and show that the alloys are thermodynamically stable. Fe3Al, with the lowest formation enthalpy, is the most stable compound in the Fe-Mn-Al system. The partial density of states, total density of states, and electron density distribution maps of the Fe-Mn-Al alloys were analyzed. The bonding characteristics of these Fe-Mn-Al alloys are mainly combinations of covalent bonding and metallic bonds. The stress-strain method and Voigt-Reuss-Hill approximation were used to calculate the elastic constants and moduli, respectively. Fe2.5Mn0.5Al has the highest bulk modulus, 234.5 GPa. Fel.sMn1.5Al has the highest shear modulus and Young＇s modulus, with values of 98.8 GPa and 259.2 GPa, respectively. These Fe-Mn-Al alloys display disparate anisotropies due to the calculated different shape of the three-dimensional curved surface of the Young＇s modulus and anisotropic index. Moreover, the anisotropic sound velocities and Debye temperatures of these Fe-Mn-Al alloys were explored.
基金supported by the National Natural Science Foundation of China (Grant Nos 10647006 and 10547007)the Natural Science Foundation of Gansu Province of China (Grant No 3ZS042-B25-023)the Prominent Youth Foundation (Grant No Q200704) of LUT and the Scientific Developmental Foundation of LUT
文摘The geometries, electronic structures and related properties of SimN8-m（0 〈 m 〈 8） clusters are studied using density functional theory （DFT） with hybrid functional B3LYP. The calculated results reveal several trends. For any stoichiometric clusters, the lowest energy isomers with an alteration of N and Si atoms are favourable in energy if the numbers of Si and N atoms are large enough to form ... Si N-Si-N... alternative chains. The bond lengths of single Si-N bonds are very close to the corresponding values of the bulk and other SiN clusters. The geometries for N-rich and Si4N4 clusters are planar structures, but three-dimensional structures are favourable in energy for Si-rich clusters. With the increase of m, the isotropic polarizability and average polarizability increase, the total binding energies generally decrease, the HOMO-LUMO gap and vertical ionization potential oscillate with increasing number of valence electrons, and their values with even valence electrons are larger than those with odd valence electrons. The atomic charges, IR and Raman properties are also reported.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574039）,the Key Program of Science and Technology Research of Education Ministry, China （Grant No 206084）, Innovation Talents of Institution of Higher Education of Henan Province, China （Grant No 2006KYCX002）, the Natural Science Foundation of Education Bureau of Henan Province, China （Grant No 200510476004）.
文摘In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2^- and S3^- have been calculated at QCISD/6-311＋＋G（3d2f） and B3P86/6-311＋＋G（3d2f） level. The S2^- ground state is of 2IIg, the S3^- ground state is of 2B1 and S3^- has a bent （C2v） structure with an angle of 115.65° The results are in good agreement with these reported in other literature. For S3^- ion, the vibration frequencies and the force constants have also been calculated. Base on the general principles of microscopic reversibility, the dissociation limits has been deduced. The Murrell-Sorbie potential energy function for S2^- has been derived according to the ab initio data through the least- squares fitting. The force constants and spectroscopic data for S2^- have been calculated, then compared with other theoretical data. The analytical potential energy function of S3^- have been obtained based on the many-body expansion theory. The structure and energy can correctly reappear on the potential surface.
基金Project supported by the Science and Technology Innovation Foundation for Graduate Students of Xinjiang Normal University,China (Grant No. 20091205)the Xinjiang Normal University Priority Developing Discipline Foundation,Chinathe National Natural Science Foundation of China (Grant No. 10964012)
文摘The lowest-energy structures and the electronic properties of Mo2nNn （n=1-5） clusters have been studied by using the density functional theory （DFT） simulating package DMol3 in the generalized gradient approximation （GGA）. The resulting equilibrium geometries show that the lowest-energy structures are dominated by central cores which correspond to the ground states of Mon （n = 2, 4, 6, 8, 10） clusters and nitrogen atoms which surround these cores. The average binding energy, the adiabatic electron affinity （AEA）, the vertical electron affinity （VEA）, the adiabatic ionization potential （AIP） and the vertical ionization potential （VIP） of Mo2nNn （n=1-5） clusters have been estimated. The HOMO LUMO gaps reveal that the clusters have strong chemical activities. An analysis of Mulliken charge distribution shows that charge-transfer moves from Mo atoms to N atoms and increases with cluster size.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10574039 and 10174019)Henan Innovation Project For University Prominent Research Talents (Grant No HAIPUTT2006KYCX002)the Natural Science Foundation of Education Commission of Henan Province (Grant Nos 2003140028 and 200510476004)
文摘This paper reports that the equilibrium structure of NH2 has been optimized at the QCISD/6-311＋＋G （3df, 3pd） level. The ground-state NH2 has a bent （C2v, X^2B1） structure with an angle of 103.0582°. The geometrical structure is in good agreement with the other calculational and experimental results. The harmonic frequencies and the force constants have also been calculated. Based on the group theory and the principle of microscopic reversibility, the dissociation limits of NH2（C2v, X^2B1） have been derived. The potential energy surface of NH2（X^2B1） is reasonable. The contour lines are constructed, the structure and energy of NH2 reappear on the potential energy surface.
