Pentadactyl limbs represent a conserved morphological feature among tetrapods,with anterior digits considered more important than posterior digits for refined movement.While posterior digit formation is governed by gr...Pentadactyl limbs represent a conserved morphological feature among tetrapods,with anterior digits considered more important than posterior digits for refined movement.While posterior digit formation is governed by graded expression of the Shh and 5’Hox genes,the regulatory mechanisms underlying anterior digit development,especially digit I(DI),remain poorly defined.This study identified an anterior expression pattern of Zic3 in the limb buds of representative tetrapods,including humans,which exerted an inhibitory effect on skeletal development.Zic3 was highly expressed in the anterior region of limb buds at early developmental stages,with species-specific divergence emerging during later development.Overexpression of Zic3 significantly delayed chondrogenesis and ossification,leading to bone shortening but not loss.Furthermore,RNA sequencing demonstrated that Zic3 down-regulated key genes associated with skeletal development,including Cytl1,Sox9,Ihh,Ptch1,Runx2,and Wnt16.These findings demonstrate that Zic3 acts as a conserved inhibitor of anterior skeletal maturation and contributes to the molecular asymmetry of tetrapod limb development.展开更多
Tetrapod-shaped ZnO microcrystals in forms of whiskers and microrods have been grown in the same crucible by thermal evaporation of Zn/C mixtures at a temperature of 930℃ in air without using any catalyst. The tetrap...Tetrapod-shaped ZnO microcrystals in forms of whiskers and microrods have been grown in the same crucible by thermal evaporation of Zn/C mixtures at a temperature of 930℃ in air without using any catalyst. The tetrapod-shaped ZnO microrods were capped by hexagonal pyramids. It is for the first time observed that the tetrapod-shaped ZnO whiskers and microrods have quite different morphologies, and this is believed to be a result of different growth behaviors associated with these two forms of ZnO microcrystals. The octa-twin model has been used to discuss their growth behaviors. Photoluminescence properties of these two forms of tetrapod-shaped ZnO microcrystals have been investigated using different excitation wavelengths. Both of the two forms of ZnO microcrystals showed strong green emission and weak ultraviolet emission behaviors. The excitation spectrum of the tetrapod-shaped ZnO whiskers showed a strong excitation peak at 395 nm, which was not observed for the tetrapod-shaped ZnO microrods.展开更多
Two kinds of Tb（ Ⅲ ） complexes with tetrapodal ligand, [TbL（NO3）]^3＋ and [TbL]^3＋ （L： 1,1, 1＇, 1＇-tera （ 2-pyridinecarboxylester ）-di （ trimethylpropane）） were intercalated into the interlayer space of...Two kinds of Tb（ Ⅲ ） complexes with tetrapodal ligand, [TbL（NO3）]^3＋ and [TbL]^3＋ （L： 1,1, 1＇, 1＇-tera （ 2-pyridinecarboxylester ）-di （ trimethylpropane）） were intercalated into the interlayer space of montmorillonite （MT） by ion exchange and coordination reaction of L with the Tb^3＋ ion existing in the interlayer space of Tb-MT respectively. The obtained luminescent supramolecular composite materials, [ TbL （NO3） ]^2＋-MT and [TbL]^3＋-MT were characterized by elemental analysis, XRD, FT-IR, UV-vis and thermal analysis. At the same time, the luminescent properties of the materials were also studied. The results show that the intercalated materials with regular layered structure, good thermal stability and the interlayer spacing （d001） approximates to the size of the complex ions which are located in the interlayer space of MT in the form of a monolayer.展开更多
A new aryl amide type tetrapodal ligand L (1, 1, 1, 1 tetrakis-{[(2 benzylaminoformyl) phenoxyl]methyl}methane) and its europium and terbium nitrate complexes were synthesized. The luminescence properties of these c...A new aryl amide type tetrapodal ligand L (1, 1, 1, 1 tetrakis-{[(2 benzylaminoformyl) phenoxyl]methyl}methane) and its europium and terbium nitrate complexes were synthesized. The luminescence properties of these complexes were also studied.展开更多
As the Armor shape has a significant effect on the reduction of wave overtopping, this study compares the performance of various shapes of concrete armored blocks of X block and Tetrapod as the most suitable armors. I...As the Armor shape has a significant effect on the reduction of wave overtopping, this study compares the performance of various shapes of concrete armored blocks of X block and Tetrapod as the most suitable armors. In this study, a three-dimensional numerical model was used for simulation of the effects of waves on the armors of Tetrapod and X Block breakwaters. In this regard, in order to calibrate the numerical model, a sample of conventional stone armor has been selected and using available experimental data on the design of armor such as wave overtopping, wave height, period of waves and energy density of the required spectral range of wave verification was conducted on a numerical model. In this regard, it is necessary to calibrate all the conditions of the model including boundary conditions, numerical modeling, initial conditions, numerical solvers and other parameters in the numerical model and simulation error rate is determined. The maximum error of the numerical model for the relative height values of the impact waves on the structure of breakwater is 7.87% for different conditions. Accordingly, the maximum error of the numerical model in determining overtopping values is 7.81%. The average fluctuation value of overtopping in the X block armor has dropped by about 31% compared to the tetrapod armor.展开更多
Air floating transport is one of the key construction technologies of bucket foundation.The influences of draft,water depth and bucket spacing on the motion response characteristics of tetrapod bucket foundation(TBF)d...Air floating transport is one of the key construction technologies of bucket foundation.The influences of draft,water depth and bucket spacing on the motion response characteristics of tetrapod bucket foundation(TBF)during air-floating transportation were studied by models tests.The results showed that with the increase of draft,the natural periods of heave motion increased,while the maximum amplitudes of oscillating motion decreased.The maximum amplitudes of heave motion decreased while pitch motion increased with the increasing of water depth;further,the period range of oscillating amplitude close to the maximum amplitude was expanded due to shallow water effect.With increasing bucket spacing,the maximum amplitudes of heave motion first increase and then decreased,whereas the maximum amplitudes of pitch motion decreased.Therefore,the favorable air-floating transportation performance can be achieved by choosing a larger bucket spacing under the condition of meeting the design requirements and reducing the draft under shallower water.展开更多
The infrared absorption spectrum of zinc oxide whiskers with tetrapod shape was recorded and compared with ZnO powder. The absorptions of microwave and sound were investigated with a result showing that the ZnO whisk...The infrared absorption spectrum of zinc oxide whiskers with tetrapod shape was recorded and compared with ZnO powder. The absorptions of microwave and sound were investigated with a result showing that the ZnO whiskers are of excellence as absorbents of microwave and soundproofing. The results of vibration damping tests of polyvinyl chloride indicate that the material containing the tetrapod shaped ZnO whiskers appears superior damping characteristics.展开更多
ZnO tetrapods were synthesized by a typical thermal vapor-solid deposition method in a horizontal tube furnace.Structural characterization was carried out by transmission electron microscopy （TEM） and select-area el...ZnO tetrapods were synthesized by a typical thermal vapor-solid deposition method in a horizontal tube furnace.Structural characterization was carried out by transmission electron microscopy （TEM） and select-area electron diffraction （SAED）,which shows the presence of zinc blende nucleus in the center of tetrapods while the four branches taking hexagonal wurtzite structure.The electrical transport property of ZnO tetrapods was investigated through an in-situ nanoprobe system.The three branches of a tetrapod serve as source,drain,and ＂gate＂,respectively;while the fourth branch pointing upward works as the force trigger by vertically applying external force downward.The conductivity of each branch of ZnO-tetrapods increases 3-4 times under pressure.In such situation,the electrical current through the branches of ZnO tetrapods can be tuned by external force,and therefore a simple force sensor based on ZnO tetrapods has been demonstrated for the first time.展开更多
Tetrapod, one of the well-known artificial concrete units, is frequently used as an armor unit on breakwaters. Two layers of tetrapod units are normmaly placed on the breakwaters with different placement methods. In t...Tetrapod, one of the well-known artificial concrete units, is frequently used as an armor unit on breakwaters. Two layers of tetrapod units are normmaly placed on the breakwaters with different placement methods. In this study, the stability of tetrapod units with two different regularly placement methods are investigated experimentally in irregular waves. Stability coefficients of tetrapod units for both placement methods are obtained. The important characteristic wave parameters of irregular waves causing the same damage ratio as those of the regular waves are also determined. It reveals that the average of one-tenth highest wave heights within the wave train （H1/lo） causes the similar damage as regular waves.展开更多
Chemosensation is the most ubiquitous sense in animals,enacted by the products of complex gene families that detect environmental chemical cues and larger-scale sensory structures that process these cues.While there i...Chemosensation is the most ubiquitous sense in animals,enacted by the products of complex gene families that detect environmental chemical cues and larger-scale sensory structures that process these cues.While there is a general conception that olfactory receptor(OR)genes evolve rapidly,the universality of this phenomenon across vertebrates,and its magnitude,are unclear.The supposed correlation between molecular rates of chemosensory evolution and phenotypic diversity of chemosensory systems is largely untested.We combine comparative genomics and sensory morphology to test whether OR genes and olfactory phenotypic traits evolve at faster rates than other genes or traits.Using published genomes,we identified ORs in 21 tetrapods,including amphibia ns,reptiles,birds,and mammals and compared their rates of evolution to those of orthologous non-OR protein-coding genes.We found that,for all clades investigated,most OR genes evolve nearly an order of magnitude faster than other protein-coding genes,with many OR genes showing signatures of diversifying selection across nearly all taxa in this study.This rapid rate of evolution suggests that chemoreceptor genes are in "evolutionary overdrive,"perhaps evolving in response to the ever-changing chemical space of the environment.To obtain complementary morphological data,we stained whole fixed specimens with iodine,μCT-scanned the specimens,and digitally segmented chemosensory and nonchemosensory brain regions.We then estimated phenotypic variation within traits and among tetrapods.While we found considerable variation in chemosensory structures,they were no more diverse than nonchemosensory regions.We suggest chemoreceptor genes evolve quickly in reflection of an ever-changing chemical space,whereas chemosensory phe no types and processing regions are more conserved because they use a standardized or constrained architecture to receive and process a range of chemical cues.展开更多
Three kinds of tetrapod-like ZnO nanostructures have been synthesized simultaneously via pure Zn chemical vapor deposition on silicon wafers with （111） orientation （Si （111）） at 920 ℃. X-ray diffraction indicat...Three kinds of tetrapod-like ZnO nanostructures have been synthesized simultaneously via pure Zn chemical vapor deposition on silicon wafers with （111） orientation （Si （111）） at 920 ℃. X-ray diffraction indicates that the nanotetrapods are of wurtzite structure. The morphology and the microstructure of the nanotetrapods are investigated by the scanning electron microscopy. Selected area electron diffraction shows the growth direction, and energy dispersive X-ray spectroscopy reveals the atomic composition ratio of Zn/O. The growth process is briefly discussed. The optical property of the products was also recorded by means of photoluminescence spectroscopy.展开更多
Planar tetrapods ZnO (PTP-ZnO) or cross shaped tetrapod nanostructures were synthesized by a cethyltrimethylamonium hydroxide (CTAOH)-assisted hydrothermal method at low temperature (120°C). The XRD diffractogram...Planar tetrapods ZnO (PTP-ZnO) or cross shaped tetrapod nanostructures were synthesized by a cethyltrimethylamonium hydroxide (CTAOH)-assisted hydrothermal method at low temperature (120°C). The XRD diffractogram showed that the PTP-ZnO nanostructures showed a hexagonal wurtzite phase. The studies with high resolution transmission electron microscopy (HRTEM) and select area specific diffraction (SAED) revealed that the ZnO pods were single crystals and preferentially grew up along [002] direction. The growth mechanism of the CTAOH assisted-hydrothermal synthesized PTP-ZnO nanostructures is explained using the final shape guiding of materials nanostructured and surfactant-action theories.展开更多
As reported in a recent issue of Nature (Aug. 15, 2002),two Chinese scientists pinpoint their newly discovered fossil fish as the most direct piece of evi dence on the common ancestry shared by tetrapods (all land... As reported in a recent issue of Nature (Aug. 15, 2002),two Chinese scientists pinpoint their newly discovered fossil fish as the most direct piece of evi dence on the common ancestry shared by tetrapods (all land verte brates including human beings) and lungfish. This latest advance in studying the origin and evolution of early fishes was jointly made by Professor Zhu Min from the CAS Institute of Vertebrate Paleontology & Paleoanthropology and his colleague Yu Xiaobo, now a Professor at the Biology Department of Kean University (New Jersey, USA).……展开更多
Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst.The digital camera,optical microscopy,scanning electron microsc...Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst.The digital camera,optical microscopy,scanning electron microscopy,energy dispersive X-ray spectroscopy,and X-ray diffraction techniques were used to study the morphologies and crystal structures of these tetrapod-shaped ZnO microcrystals.The results show that these two types of ZnO tetrapods are grown at different heights within the same crucible.The legs of these tetrapod-shaped ZnO crystals are hexagonally faceted.Some tetrapod-shaped ZnO whiskers show hierarchical structures.A short button-like hexagonal ZnO microcrystal is observed at the triple junctions of some tetrapod-shaped ZnO whiskers.The tetrapod-shaped ZnO microrods are capped by two sets of hexagonal pyramids with two different groups of crystal planes for the surfaces.These two types of tetrapod-shaped ZnO microcrystals have different side faces and aspect ratio,which are believed to be the result of their different growth behaviors.The octa-twin model was used to discuss the different growth behaviors of these two types of ZnO tetrapods.The crystal planes of the legs and the pyramids were determined.展开更多
The tetrapod ZnO nanostructures are synthesized on the Si （100） substrates using the chemical va- por deposition （CVD） method at 1000 ℃. Each nanostructure has four arms which are about 3-10 μm in length and 0.2...The tetrapod ZnO nanostructures are synthesized on the Si （100） substrates using the chemical va- por deposition （CVD） method at 1000 ℃. Each nanostructure has four arms which are about 3-10 μm in length and 0.2-1.5 μm in diameter. Further analyses on structure demonstrate that the tetrapod ZnO nanostructures have single crystalline wurtzite hexagonal structure preferentially oriented in c-axis. The photoluminescence （PL） mea- surements of the tetrapod ZnO nanostructures revealed a UV peak at 382 nm corresponding to the free exciton emission, and a green peak at 523 nm arising from deep level emission. For comparative analysis, cathodolumines- cence （CL） spectra obtained from different regions of an individual tetrapod are investigated. Moreover, a possible growth mechanism of the tetrapod ZnO nanostructures is also discussed based on the experimental results.展开更多
基金supported by the Department of Science&Technology of Liaoning Province(2024-MS-099,2024-BS-093)。
文摘Pentadactyl limbs represent a conserved morphological feature among tetrapods,with anterior digits considered more important than posterior digits for refined movement.While posterior digit formation is governed by graded expression of the Shh and 5’Hox genes,the regulatory mechanisms underlying anterior digit development,especially digit I(DI),remain poorly defined.This study identified an anterior expression pattern of Zic3 in the limb buds of representative tetrapods,including humans,which exerted an inhibitory effect on skeletal development.Zic3 was highly expressed in the anterior region of limb buds at early developmental stages,with species-specific divergence emerging during later development.Overexpression of Zic3 significantly delayed chondrogenesis and ossification,leading to bone shortening but not loss.Furthermore,RNA sequencing demonstrated that Zic3 down-regulated key genes associated with skeletal development,including Cytl1,Sox9,Ihh,Ptch1,Runx2,and Wnt16.These findings demonstrate that Zic3 acts as a conserved inhibitor of anterior skeletal maturation and contributes to the molecular asymmetry of tetrapod limb development.
基金supported by the Doctorate Research Plan of Nanchang University (Grant No. 0061)
文摘Tetrapod-shaped ZnO microcrystals in forms of whiskers and microrods have been grown in the same crucible by thermal evaporation of Zn/C mixtures at a temperature of 930℃ in air without using any catalyst. The tetrapod-shaped ZnO microrods were capped by hexagonal pyramids. It is for the first time observed that the tetrapod-shaped ZnO whiskers and microrods have quite different morphologies, and this is believed to be a result of different growth behaviors associated with these two forms of ZnO microcrystals. The octa-twin model has been used to discuss their growth behaviors. Photoluminescence properties of these two forms of tetrapod-shaped ZnO microcrystals have been investigated using different excitation wavelengths. Both of the two forms of ZnO microcrystals showed strong green emission and weak ultraviolet emission behaviors. The excitation spectrum of the tetrapod-shaped ZnO whiskers showed a strong excitation peak at 395 nm, which was not observed for the tetrapod-shaped ZnO microrods.
文摘Two kinds of Tb（ Ⅲ ） complexes with tetrapodal ligand, [TbL（NO3）]^3＋ and [TbL]^3＋ （L： 1,1, 1＇, 1＇-tera （ 2-pyridinecarboxylester ）-di （ trimethylpropane）） were intercalated into the interlayer space of montmorillonite （MT） by ion exchange and coordination reaction of L with the Tb^3＋ ion existing in the interlayer space of Tb-MT respectively. The obtained luminescent supramolecular composite materials, [ TbL （NO3） ]^2＋-MT and [TbL]^3＋-MT were characterized by elemental analysis, XRD, FT-IR, UV-vis and thermal analysis. At the same time, the luminescent properties of the materials were also studied. The results show that the intercalated materials with regular layered structure, good thermal stability and the interlayer spacing （d001） approximates to the size of the complex ions which are located in the interlayer space of MT in the form of a monolayer.
文摘A new aryl amide type tetrapodal ligand L (1, 1, 1, 1 tetrakis-{[(2 benzylaminoformyl) phenoxyl]methyl}methane) and its europium and terbium nitrate complexes were synthesized. The luminescence properties of these complexes were also studied.
文摘As the Armor shape has a significant effect on the reduction of wave overtopping, this study compares the performance of various shapes of concrete armored blocks of X block and Tetrapod as the most suitable armors. In this study, a three-dimensional numerical model was used for simulation of the effects of waves on the armors of Tetrapod and X Block breakwaters. In this regard, in order to calibrate the numerical model, a sample of conventional stone armor has been selected and using available experimental data on the design of armor such as wave overtopping, wave height, period of waves and energy density of the required spectral range of wave verification was conducted on a numerical model. In this regard, it is necessary to calibrate all the conditions of the model including boundary conditions, numerical modeling, initial conditions, numerical solvers and other parameters in the numerical model and simulation error rate is determined. The maximum error of the numerical model for the relative height values of the impact waves on the structure of breakwater is 7.87% for different conditions. Accordingly, the maximum error of the numerical model in determining overtopping values is 7.81%. The average fluctuation value of overtopping in the X block armor has dropped by about 31% compared to the tetrapod armor.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.52171274)the National Key Research and Development Project(Grant No.2018YFC0810402)+2 种基金Chongqing Elite Innovation and Entrepreneurship Demonstration Team(Grant No.CQYC201903204)Chongqing Special Post-Doctoral Science Foundation(Grant No.XM2019)the State Key Laboratory of Hydraulic Engineering Simulation and Safety(Tianjin University)(Grant No.HESS-12).
文摘Air floating transport is one of the key construction technologies of bucket foundation.The influences of draft,water depth and bucket spacing on the motion response characteristics of tetrapod bucket foundation(TBF)during air-floating transportation were studied by models tests.The results showed that with the increase of draft,the natural periods of heave motion increased,while the maximum amplitudes of oscillating motion decreased.The maximum amplitudes of heave motion decreased while pitch motion increased with the increasing of water depth;further,the period range of oscillating amplitude close to the maximum amplitude was expanded due to shallow water effect.With increasing bucket spacing,the maximum amplitudes of heave motion first increase and then decreased,whereas the maximum amplitudes of pitch motion decreased.Therefore,the favorable air-floating transportation performance can be achieved by choosing a larger bucket spacing under the condition of meeting the design requirements and reducing the draft under shallower water.
文摘The infrared absorption spectrum of zinc oxide whiskers with tetrapod shape was recorded and compared with ZnO powder. The absorptions of microwave and sound were investigated with a result showing that the ZnO whiskers are of excellence as absorbents of microwave and soundproofing. The results of vibration damping tests of polyvinyl chloride indicate that the material containing the tetrapod shaped ZnO whiskers appears superior damping characteristics.
基金supported by the China Scholarship Council (CSC) (No.20083019)Fundamental Research Funds for the Central Universities (Nos.21611603,21611424,and 216113143)+1 种基金Jinan University Start-up Funds (No.50624019)the Knowledge Innovation Program of the Chinese Academy of Sciences (No.KJCX2-YW-M13)
文摘ZnO tetrapods were synthesized by a typical thermal vapor-solid deposition method in a horizontal tube furnace.Structural characterization was carried out by transmission electron microscopy （TEM） and select-area electron diffraction （SAED）,which shows the presence of zinc blende nucleus in the center of tetrapods while the four branches taking hexagonal wurtzite structure.The electrical transport property of ZnO tetrapods was investigated through an in-situ nanoprobe system.The three branches of a tetrapod serve as source,drain,and ＂gate＂,respectively;while the fourth branch pointing upward works as the force trigger by vertically applying external force downward.The conductivity of each branch of ZnO-tetrapods increases 3-4 times under pressure.In such situation,the electrical current through the branches of ZnO tetrapods can be tuned by external force,and therefore a simple force sensor based on ZnO tetrapods has been demonstrated for the first time.
基金the Research Foundation of Yildiz Technical University for their financial support
文摘Tetrapod, one of the well-known artificial concrete units, is frequently used as an armor unit on breakwaters. Two layers of tetrapod units are normmaly placed on the breakwaters with different placement methods. In this study, the stability of tetrapod units with two different regularly placement methods are investigated experimentally in irregular waves. Stability coefficients of tetrapod units for both placement methods are obtained. The important characteristic wave parameters of irregular waves causing the same damage ratio as those of the regular waves are also determined. It reveals that the average of one-tenth highest wave heights within the wave train （H1/lo） causes the similar damage as regular waves.
基金L.R.Y.was supported by the National Science Foundation Postdoctoral Research Fellowship in Biology(NSF-DBI 1812035)and the Linnean Society of London and the Systematics Association Systematics Research Fund.M.H.was supported by the Yale Institute for Biospheric Studies Small Grants Program Doctoral Pilot Award.B.A.S.B.was supported by Yale University and the Yale Institute for Biospheric Studies.
文摘Chemosensation is the most ubiquitous sense in animals,enacted by the products of complex gene families that detect environmental chemical cues and larger-scale sensory structures that process these cues.While there is a general conception that olfactory receptor(OR)genes evolve rapidly,the universality of this phenomenon across vertebrates,and its magnitude,are unclear.The supposed correlation between molecular rates of chemosensory evolution and phenotypic diversity of chemosensory systems is largely untested.We combine comparative genomics and sensory morphology to test whether OR genes and olfactory phenotypic traits evolve at faster rates than other genes or traits.Using published genomes,we identified ORs in 21 tetrapods,including amphibia ns,reptiles,birds,and mammals and compared their rates of evolution to those of orthologous non-OR protein-coding genes.We found that,for all clades investigated,most OR genes evolve nearly an order of magnitude faster than other protein-coding genes,with many OR genes showing signatures of diversifying selection across nearly all taxa in this study.This rapid rate of evolution suggests that chemoreceptor genes are in "evolutionary overdrive,"perhaps evolving in response to the ever-changing chemical space of the environment.To obtain complementary morphological data,we stained whole fixed specimens with iodine,μCT-scanned the specimens,and digitally segmented chemosensory and nonchemosensory brain regions.We then estimated phenotypic variation within traits and among tetrapods.While we found considerable variation in chemosensory structures,they were no more diverse than nonchemosensory regions.We suggest chemoreceptor genes evolve quickly in reflection of an ever-changing chemical space,whereas chemosensory phe no types and processing regions are more conserved because they use a standardized or constrained architecture to receive and process a range of chemical cues.
文摘Three kinds of tetrapod-like ZnO nanostructures have been synthesized simultaneously via pure Zn chemical vapor deposition on silicon wafers with （111） orientation （Si （111）） at 920 ℃. X-ray diffraction indicates that the nanotetrapods are of wurtzite structure. The morphology and the microstructure of the nanotetrapods are investigated by the scanning electron microscopy. Selected area electron diffraction shows the growth direction, and energy dispersive X-ray spectroscopy reveals the atomic composition ratio of Zn/O. The growth process is briefly discussed. The optical property of the products was also recorded by means of photoluminescence spectroscopy.
文摘Planar tetrapods ZnO (PTP-ZnO) or cross shaped tetrapod nanostructures were synthesized by a cethyltrimethylamonium hydroxide (CTAOH)-assisted hydrothermal method at low temperature (120°C). The XRD diffractogram showed that the PTP-ZnO nanostructures showed a hexagonal wurtzite phase. The studies with high resolution transmission electron microscopy (HRTEM) and select area specific diffraction (SAED) revealed that the ZnO pods were single crystals and preferentially grew up along [002] direction. The growth mechanism of the CTAOH assisted-hydrothermal synthesized PTP-ZnO nanostructures is explained using the final shape guiding of materials nanostructured and surfactant-action theories.
文摘 As reported in a recent issue of Nature (Aug. 15, 2002),two Chinese scientists pinpoint their newly discovered fossil fish as the most direct piece of evi dence on the common ancestry shared by tetrapods (all land verte brates including human beings) and lungfish. This latest advance in studying the origin and evolution of early fishes was jointly made by Professor Zhu Min from the CAS Institute of Vertebrate Paleontology & Paleoanthropology and his colleague Yu Xiaobo, now a Professor at the Biology Department of Kean University (New Jersey, USA).……
基金Project(0061)supported by the Doctorate Foundation of Nanchang University,ChinaProject(2006015)supported by the Center for Analysis and Testing,Nanchang University,China
文摘Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst.The digital camera,optical microscopy,scanning electron microscopy,energy dispersive X-ray spectroscopy,and X-ray diffraction techniques were used to study the morphologies and crystal structures of these tetrapod-shaped ZnO microcrystals.The results show that these two types of ZnO tetrapods are grown at different heights within the same crucible.The legs of these tetrapod-shaped ZnO crystals are hexagonally faceted.Some tetrapod-shaped ZnO whiskers show hierarchical structures.A short button-like hexagonal ZnO microcrystal is observed at the triple junctions of some tetrapod-shaped ZnO whiskers.The tetrapod-shaped ZnO microrods are capped by two sets of hexagonal pyramids with two different groups of crystal planes for the surfaces.These two types of tetrapod-shaped ZnO microcrystals have different side faces and aspect ratio,which are believed to be the result of their different growth behaviors.The octa-twin model was used to discuss the different growth behaviors of these two types of ZnO tetrapods.The crystal planes of the legs and the pyramids were determined.
基金Project supported by the Fundamental Research Funds for the Central Universities(Nos.JUSRP11230,JUSRP51323B)the Natural Science Foundation of Jiangsu Province(No.BK2012110)+1 种基金the PAPD of Jiangsu Higher Education Institutionsthe Summit of the Six TopTalents Program of Jiangsu Province(No.DZXX-053)
文摘The tetrapod ZnO nanostructures are synthesized on the Si （100） substrates using the chemical va- por deposition （CVD） method at 1000 ℃. Each nanostructure has four arms which are about 3-10 μm in length and 0.2-1.5 μm in diameter. Further analyses on structure demonstrate that the tetrapod ZnO nanostructures have single crystalline wurtzite hexagonal structure preferentially oriented in c-axis. The photoluminescence （PL） mea- surements of the tetrapod ZnO nanostructures revealed a UV peak at 382 nm corresponding to the free exciton emission, and a green peak at 523 nm arising from deep level emission. For comparative analysis, cathodolumines- cence （CL） spectra obtained from different regions of an individual tetrapod are investigated. Moreover, a possible growth mechanism of the tetrapod ZnO nanostructures is also discussed based on the experimental results.
