Sea Urchin Spines as a Model-System for Permeable, Light-Weight Ceramics with Graceful Failure Behavior. Part I. Mechanical Behavior of Sea Urchin Spines under Compression

The spines of pencil and lance urchins Heterocentrotus mammillatus and Phyllacanthus imperialis were studied as a modelof light-weight material with high impact resistance.The complex and variable skeleton construction ("stereom") of body andspines of sea urchins consists of highly porous Mg-bearing calcium carbonate.This basically brittle material with pronouncedsingle-crystal cleavage does not fracture by spontaneous catastrophic device failure but by graceful failure over the range of tensof millimeter of bulk compression instead.This was observed in bulk compression tests and blunt indentation experiments onregular,infiltrated and latex coated sea urchin spine segments.Microstructural characterization was carried out using X-raycomputer tomography,optical and scanning electron microscopy.The behavior is interpreted to result from the hierarchicstructure of sea urchin spines from the rnacroscale down to the nanoscale.Guidelines derived from this study see ceramics withlayered porosity as a possible biomimetic construction for appropriate applications.     

Comparative Genomic Study Reveals a Transition from TA Richness in Invertebrates to GC Richness in Vertebrates at CpG Flanking Sites： An Indication for Context-Dependent Mutagenicity of Methylated CpG Sites

Vertebrate genomes are characterized with CpG deficiency, particularly for GCpoor regions. The GC content-related CpG deficiency is probably caused by context-dependent deamination of methylated CpG sites. This hypothesis was examined in this study by comparing nucleotide frequencies at CpG flanking positions among invertebrate and vertebrate genomes. The finding is a transition of nucleotide preference of 5＇ T to 5＇ A at the invertebrate-vertebrate boundary, indicating that a large number of CpG sites with 5＇ Ts were depleted because of global DNA methylation developed in vertebrates. At genome level, we investigated CpG observed/expected （obs/exp） values in 500 bp fragments, and found that higher CpG obs/exp value is shown in GC-poor regions of invertebrate genomes （except sea urchin） but in GC-rich sequences of vertebrate genomes. We next compared GC content at CpG flanking positions with genomic average, showing that the GC content is lower than the average in invertebrate genomes, but higher than that in vertebrate genomes. These results indicate that although 5＇ T and 5＇ A are different in inducing deamination of methylated CpG sites, GC content is even more important in affecting the deamination rate. In all the tests, the results of sea urchin are similar to vertebrates perhaps due to its fractional DNA methylation. CpG deficiency is therefore suggested to be mainly a result of high mutation rates of methylated CpG sites in GC-poor regions.     

辽东栎林净初级生产力对气候变化情景响应的模拟与分析

An ecosystem process model, BIOME-BGC, was used to explore the sensitivity of net primary productivity (NPP) of an oak (Quercus liaotungensis Koidz) forest ecosystem in Beijing area to global climate changes caused by increasing atmospheric CO₂ concentrations. Firstly we tested the model, and validated the modeled outputs using observational data; the outputs of BIOME-BGC model were consistent with observed soil water content and annual NPP. Secondly the potential impacts of climate change on the oak forest ecosystem were predicted with BIOME-BGC model. We found that the simulated NPP was much more sensitive to a 20% precipitation increase or a doubling of atmospheric CO₂ from 355 to 710 祄ol/mol than to a 2 ℃ temperature increase. Our results also indicated that the effects of elevated CO₂ and climate change on the response of NPP were not interactive.     

Cellulose structure and lignin distribution in normal and compression wood of the Maidenhair tree(Ginkgo biloba L.)

We studied in detail the mean micro fibril angle and the width of cellulose crystals from the pith to the bark of a 15-year-old Maidenhair tree(Ginkgo biloba L.). The orientation of cellulose micro fibrils with respect to the cell axis and the width and length of cellulose crystallites were determined using Xray diffraction. Raman microscopy was used to compare the lignin distribution in the cell wall of normal/opposite and compression wood, which was found near the pith. Ginkgo biloba showed a relatively large mean micro fibril angle,varying between 19° and 39° in the S2 layer, and the average width of cellulose crystallites was 3.1–3.2 nm. Mild compression wood without any intercellular spaces or helical cavities was observed near the pith. Slit-like bordered pit openings and a heavily lignified S2 L layer con firmed the presence of compression wood. Ginkgo biloba showed typical features present in the juvenile wood of conifers. The micro fibril angle remained large over the 14 annual rings. The entire stem disc,with a diameter of 18 cm, was considered to consist of juvenile wood. The properties of juvenile and compression wood as well as the cellulose orientation and crystalline width indicate that the wood formation of G. biloba is similar to that of modern conifers.     

The Interaction of Spinach Nitrite Reductase with Ferredoxin： A Site-Directed Mutation Study

A series of site-directed mutants of the ferredoxin-dependent spinach nitrite reductase has been characterized and several amino acids have been identified that appear to be involved in the interaction of the enzyme with ferredoxin. In a complementary study, binding constants to nitrite reductase and steady-state kinetic parameters of site-directed mutants of ferredoxin were determined in an attempt to identify ferredoxin amino acids involved in the interaction with nitrite reductase. The results have been interpreted in terms of an in-silico docking model for the 1：1 complex of ferredoxin with nitrite reductase.     

Conservation of the WD-repeat, microtubule-binding protein, EMAP, in sea urchins, humans, and the nematode C. elegans

The echinoderm microtubule-associated protein (EMAP) is the most abundant microtubule-binding protein in the first cleavage mitotic apparatus in sea urchin embryos. The first goal of this study was to determine whether there is sufficient EMAP in the egg and embryo to modify microtubule dynamics during the early cleavages divisions and whether EMAP functions at a specific time or place in the embryo. To accomplish this goal, we examined the relative abundance, tissue distribution, and temporal pattern of EMAP expression during embryonic development. The second goal of this study was to identify important functional domains within the EMAP coding sequence. A conserved sequence might reveal a potential microtubule-binding domain. We cloned, sequenced and compared overlapping EMAP cDNAs from two different sea urchin species that diverged approximately 80 million years ago, and compared these with cDNA sequences from a vertebrate and nematode species. From quantitative immunoblots, we determined the EMAP concentration in eggs to be 4 μM. The steady-state levels of EMAP mRNA and protein accumulated during development, and all three germ layers expressed EMAP. During the early stages of development, EMAP and tubulin were both abundant in the ectoderm, mesoderm and endoderm. However, during late gastrulation and the formation of the early pluteus larvae, EMAP was enriched in the mesoderm, while tubulin staining was most abundant in the archenteron. These results indicate that EMAP may have tissue-specific functions in the late stage embryo. To identify conserved functional domains, we compared the predicted amino acid sequence encoded by Strongylocentrotus purpuratus and Lytechinus variegatus EMAP cDNAs, and determined that these two sea urchin EMAPs were 95% conserved and shared an identical domain organization. A parsimonious analysis of these sea urchin protein sequences, as well as human and C. elegans EMAP sequences was used to construct a gene tree. Together these results suggest that EMAP is an important microtubule protein required at all developmental stages of sea urchins, and whose cellular function may be conserved amongst metazoans. Received: 2 March 1999 / Accepted: 28 June 1999     

Synchronized oscillation in a modular neural network composed of columns

The columnar organization is a ubiquitous feature in the cerebral cortex. In this study, a neural network model simulating the cortical columns has been constructed. When fed with random pulse input with constant rate, a column generates synchronized oscillations, with a frequency varying from 3 to 43 Hz depending on parameter values. The behavior of the model under periodic stimulation was studied and the input-output relationship was non-linear. When identical columns were sparsely interconnected, the column oscillator could be locked in synchrony. In a network composed of heterogeneous columns, the columns were organized by intrinsic properties and formed partially synchronized assemblies.     

Animal Modelling of Lumbar Corpectomy and Fusion and in vivo Growth of Spine Supporting Bone by Titanium Cage Implants: An Experimental Study

##正## In this study a lumbar spinal fusion animal model is established to assess the effect of spinal fusion cage,and explore theminimum area ratio of titanium cage section to vertebral section that ensures bone healing and biomechanical property.Lumbarcorpectomy was conducted by posterolateral approach with titanium cage implantation combined with plate fixation.Titaniumcages with the same length but different diameters were used.After implantation of titanium cages,the progress of bone healingwas observed and the bone biomechanical properties were measured,including deformation and displacement in axial compression,flexion,extension,and lateral bending motion.The factors affecting the in vivo growth of spine supporting body wereanalyzed.The results show that the area ratio of titanium cage section to vertebral section should reach 1/2 to ensure the bonehealing,sufficient bone intensity and biomechanical properties.Some bone healing indicators,such as BMP,suggest that there isa relationship between the peak time and the peak value of bone formation and metabolism markers and the bone healing strength.     

Particle-Image Velocimetry and Force Measurements of Leading-Edge Serrations on Owl-Based Wing Models

High-resolution Particle-Image Velocimetry （PIV） and time-resolved force measurements were performed to analyze the impact of the comb-like structure on the leading edge of barn owl wings on the flow field and overall aerodynamic performance. The Reynolds number was varied in the range of 40,000 to 120,000 and the range of angle of attack was 0° to 6° for the PIV and -15° to ＋20° for the force measurements to cover the full flight envelope of the owl. As a reference, a wind-tunnel model which possessed a geometry based on the shape of a typical barn owl wing without any owl-specific adaptations was built, and measurements were performed in the aforementioned Reynolds number and angle of attack： range. This clean wing model shows a separation bubble in the distal part of the wing at higher angles of attack. Two types of comb-like structures, i.e., artificial serrations, were manufactured to model the owl＇s leading edge with respect to its length, thickness, and material properties. The artificial structures were able to reduce the size of the separation region and additionally cause a more uniform size of the vortical structures shed by the separation bubble within the Reynolds number range investigated, resulting in stable gliding flight independent of the flight velocity. However, due to increased drag coefficients in conjunction with similar lift coefficients, the overall aerodynamic performance, i.e., lift-to-drag ratio is reduced for the serrated models. Nevertheless, especially at lower Reynolds numbers the stabilizing effect of the uniform vortex size outperforms the lower aerodynamic performance.     

Experiment about Drag Reduction of Bionic Non-smooth Surface in Low Speed Wind Tunnel

The body surface of some organisms has non-smooth structure, which is related to drag reduction in moving fluid. To imitate these structures, models with a non-smooth surface were made. In order to find a relationship between drag reduction and the non-smooth surface, an orthogonal design test was employed in a low speed wind tunnel. Six factors likely to influence drag reduction were considered, and each factor tested at three levels. The six factors were the configuration, diameter/bottom width, height/depth, distribution, the arrangement of the rough structures on the experimental model and the wind speed. It was shown that the non-smooth surface causes drag reduction and the distribution of non-smooth structures on the model, and wind speed, are the predominant factors affecting drag reduction. Using analysis of variance, the optimal combination and levels were obtained, which were a wind speed of 44 m/s, distribution of the non-smooth structure on the tail of the experimental model, the configuratio     

JINKENITES——A STRANGE FOSSIL FROM EARLIEST CAMBRIAN IN W. HUBEI

A strange fossil described and illustrated in the present paper was collected by the writer in 1978 from the Huangshandong Member of the Lower Cambrian Tongying Formation in western Hubei. The material was preserved in greyish brown phosphoritic dolomites in association with elements of the Yangtze Micromolluscan Fauna, such as Tchangsichiton notabilus Yu and Sinuconus clypeus, Yu of Class Polyplacophora; Yangtzemerisma rarum Yu and Y.? cancellatum Yu of Class Merismoconchia; Yangtzeconus priscus Yu, Huangshandongoconus pileus Yu, Obtusoconus paucicostatus Yu, O. rostriptutea (Qian) and Spatuloconus rudis Yu of Class Monoplacophora; Bemella simplex Yu, Latouchlla of. memmorabilis Missarzhevsky, L. sanxiaesis Yu and L. lauta Yu of Class uncertain; Archaeospira ornata Yu, A. imbricata Yu and Cambrospira sinensis Yu of Class Gastropoda; Heraultipegma yunnanense He et Yang of Class Rostroconcbia: hyolithids and some other uncertain skeletal fossils. Although the systematic position of this peculiar fossil is unknown at present, it is inferred that this genus may be one of the typical primitive animal groups based on the characters of the shell and the spe cial spines. The shell is bilaterally symmetrical, elliptical in apical view; the dorsal side is roundly convex with three different forms of dorsal spines and several pairs of marginal spines on the anterior margin. Judged from the general morphological characters of the bilaterally symmetrical shell, these lower animals, generally speaking, have adapted themselves readily to different circumstances, and reduced resistance to any directional movement necessary for varied physiological activities. As to the function of the shell’s characteristics, the narrowly rounded side may serve as the anterior. Such a model of the body helps these animals go on with their benthonic creeping or swimming life. On the other hand, the dorsal spines are different from each other in shape, size, mode of arrangement and in number; especially, the end of the hook-shaped spines is generally curved outward, while the geniculate spines are oblique outward, and curved posteriorly all of a sudden. These structures of mechanism also provide us with the evidence that the narrowly rounded side serves as the anterior, while the opposite end as the posterior.It is of particular interest that this genus is somewhat similar to Phylum Mollusca, especially to the tryblidiids of Class Monoplacophora, in some morphological characters, such as: 1) the bilateral symmetry of the shell, 2) the outline elliptical in apical view and cap shaped in lateral view and 3) the dorsal side generally roundly convex. After careful study, it has been found that since this genus is strikingly different from monoplacopharans, may be it belongs to another interesting group of skeletal fossils. The reasons for this are: 1) in the former, there are many pairs of marginal spines on the anterior margin, while in monoplacophorans, no marginal spines can be seen; and 2) in this genus, the sculptures are different from each other in different areas, not only in shape and number, but also in the mode of arrangement, whereas in monoplacophorans, they are identical with each other in the same type and shape. Judged from the different forms of dorsal sculptures, this genus is comparatively similar to such uncertain shelly fossils as Lepidites Zhong, 1977 emend. Yu, 1987 and Xiadongoconus Yu, 1979 from the same horizon in the Yangtze Region of China, but differs from the latter two genera in the presence of marginal spines on the anterior margin. In addition, this new genus also differs from brachiopods and other skeletal fossils in the peculiar type of the shell. According to the above comparison, this genus is entirely different from all the classes of Phylum Mollusca, possibly representing another interesting group of skeletal fossils. It is impossible to determine the exact taxonomic position of this genus until more materials are available.     

Accumulation characteristics of biomass and nitrogen and critical nitrogen concentration dilution model of cotton reproductive organ

Several nitrogen (N) field experiments were carried out in Nanjing and Anyang, China, to study the dynamic characteristics of biomass accumulation and N uptake, and to define the dilution curve for critical N concentration in cotton reproductive organ over the growth period. The results show that the total biomass and N accumulation were affected significantly by the rate of N application, exhibiting a sigmoid curve over time. The beginning time of fast N accumulation was 1–5 d earlier than that of biomass accumulation. The cotton lint yield was correlated with N concentration in the reproductive organ and fluctuated with varying N concentration, indicating the existence of luxurious N consumption in the cotton reproductive organ. The N concentration increased with increasing N application rates, and decreased gradually during the growth period. The relationship between biomass and N concentration can be described with a power equation. The patterns of the N concentration dilution model were consistent at both experimental sites, but the model parameter values of a differed. The results presented in this paper indicate that a critical N concentration dilution curve for cotton reproductive organ is independent of ecological region and can be described with a power equation.     

Impacts of small hydropower plants on macroinvertebrate communities

Several nitrogen (N) field experiments were carried out in Nanjing and Anyang, China, to study the dynamic characteristics of biomass accumulation and N uptake, and to define the dilution curve for critical N concentration in cotton reproductive organ over the growth period. The results show that the total biomass and N accumulation were affected significantly by the rate of N application, exhibiting a sigmoid curve over time. The beginning time of fast N accumulation was 1–5 d earlier than that of biomass accumulation. The cotton lint yield was correlated with N concentration in the reproductive organ and fluctuated with varying N concentration, indicating the existence of luxurious N consumption in the cotton reproductive organ. The N concentration increased with increasing N application rates, and decreased gradually during the growth period. The relationship between biomass and N concentration can be described with a power equation. The patterns of the N concentration dilution model were consistent at both experimental sites, but the model parameter values of a differed. The results presented in this paper indicate that a critical N concentration dilution curve for cotton reproductive organ is independent of ecological region and can be described with a power equation.     

Accumulation characteristics of biomass and nitrogen and critical nitrogen concentration dilution model of cotton reproductive organ

Several nitrogen (N) field experiments were carried out in Nanjing and Anyang, China, to study the dynamic characteristics of biomass accumulation and N uptake, and to define the dilution curve for critical N concentration in cotton reproductive organ over the growth period. The results show that the total biomass and N accumulation were affected significantly by the rate of N application, exhibiting a sigmoid curve over time. The beginning time of fast N accumulation was 1–5 d earlier than that of biomass accumulation. The cotton lint yield was correlated with N concentration in the reproductive organ and fluctuated with varying N concentration, indicating the existence of luxurious N consumption in the cotton reproductive organ. The N concentration increased with increasing N application rates, and decreased gradually during the growth period. The relationship between biomass and N concentration can be described with a power equation. The patterns of the N concentration dilution model were consistent at both experimental sites, but the model parameter values of a differed. The results presented in this paper indicate that a critical N concentration dilution curve for cotton reproductive organ is independent of ecological region and can be described with a power equation.     

Bionic Photovoltaic Panels Bio-Inspired by Green Leaves

In strong solar light, silicon solar panels can heat up by 70℃ and, thereby, loose approximately one third of their efficiencyfor electricity generation. Leaf structures of plants on the other hand, have developed a series of technological adaptations,which allow them to limit their temperature to 40-45℃ in full sunlight, even if water evaporation is suppressed. This is accomplishedby several strategies such as limitation of leaf size, optimization of aerodynamics in wind, limitation of absorbedsolar energy only to the useful fraction of radiation and by efficient thermal emission. Optical and infrared thermographicmeasurements under a solar simulator and in a streaming channel were used to investigate the corresponding properties of leavesand to identify suitable bionic model systems. Experiments started with the serrated structure of ordinary green leaves distributedover typical twig structures and finally identified the Australian palm tree Licuala ramsayi as a more useful bionic model. Itcombines a large area for solar energy harvesting with optimized aerodynamic properties for cooling and is able to restructureitself as a protection against strong winds. The bionic models, which were constructed and built, are analyzed and discussed.     

Distribution and characteristics of telocytes as nurse cells in the architectural organization of engineered heart tissues

Interstitial Cajal-like cells are a distinct type of interstitial cell with a wide distribution in mammalian organs and tissues,and have been given the name"telocytes".Recent studies have demonstrated the potential roles of telocytes in heart development,renewal,and repair.However,further research on the functions of telocytes is limited by the complicated in vivo environment.This study was designed to construct engineered heart tissue(EHT)as a three-dimensional model in vitro to better understand the role of telocytes in the architectural organization of the myocardium.EHTs were constructed by seeding neonatal cardiomyocytes in collagen/Matrigel scaffolds followed by culture under persistent static stretch.Telocytes in EHTs were identified by histology,toluidine blue staining,immunofluorescence,and transmission electron microscopy.The results from histology and toluidine blue staining demonstrated widespread putative telocytes with compact toluidine blue-stained nuclei,which were located around cardiomyocytes.Prolongations from the cell bodies showed a characteristic dichotomous branching pattern and formed networks in EHTs.Immunofluorescence revealed positive staining of telocytes for CD34 and vimentin with typical moniliform prolongations.A series of electron microscopy images further showed that typical telocytes embraced the cardiomyocytes with their long prolongations and exhibited a marked appearance of nursing cardiomyocytes during the construction of EHTs.This finding highlights the great importance of telocytes in the architectural organization of EHTs.It also suggests that EHT is an appropriate physical and pathological model system in vitro to study the roles of telocytes during heart development and regeneration.     

Treatment of chronical myocardial ischemia by adenovirus-mediated hepatocyte growth factor gene transfer in minipigs

Growth factor gene transfer-induced therapeutic angiogenesis has become a novel approach for the treatment of myocardial ischemia. In order to provide a basis for the clinical application of an adeno- virus with hepatocyte growth factor gene (Ad-HGF) in the treatment of myocardial ischemia, we estab- lished a minipig model of chronically ischemic myocardium in which an Ameroid constrictor was placed around the left circumflex branch of the coronary artery (LCX). A total of 18 minipigs were ran- domly divided into 3 groups: a surgery control group, a model group and an Ad-HGF treatment group implanted with Ameroid constrictor. Ad-HGF or the control agent was injected directly into the ischemic myocardium, and an improvement in heart function and blood supply were evaluated. The results showed that myocardial perfusion remarkably improved in the Ad-HGF group compared with that in both the control and model groups. Four weeks after the treatment, the density of newly formed blood vessels was higher and the number of collateral blood vessels was greater in the Ad-HGF group than in the model group. The area of myocardial ischemia reduced evidently and the left ventricular ejection fraction improved significantly in the Ad-HGF group. These results suggest that HGF gene therapy may become a novel approach in the treatment of chronically ischemic myocardium.     

Numerical solution of generalized DPL model using wavelet method during thermal therapy applications

In this paper, generalized dual-phase-lag (DPL) model has been studied for the numerical analysis of spatial variation of temperature within living biological tissues during thermal therapy applications. A new hybrid numerical scheme based on finite difference scheme and Chebyshev wavelet Galerkin method are used to solve the generalized DPL model with constant heat flux boundary condition. Multi-resolution and multi-scale computational property of Chebyshev wavelet in the present case localizes small scale variations of solution and fast switching of functional bases. Our study demonstrates that due to presence of coupling factor (convection–perfusion), generalized DPL model predicts lower temperature than classical DPL and Pennes model at the tumor position. Higher values of phase lag times results in lower temperature at the tumor position. But, in case of variation of phase lag time due to temperature gradient, the nature of temperature profile also depends on the spatial coordinate. The effect of the blood temperature, porosity and interfacial convective heat transfer on temperature distribution has been investigated. It is found that larger values of porosity and interfacial convective heat transfer results in lower temperature at the tumor position. Also, both porosity and interfacial convective heat transfer are pronounced more at higher values. The whole analysis is presented in dimensionless form.     

Numerical solution of generalized DPL model using wavelet method during thermal therapy applications

In this paper, generalized dual-phase-lag (DPL) model has been studied for the numerical analysis of spatial variation of temperature within living biological tissues during thermal therapy applications. A new hybrid numerical scheme based on finite difference scheme and Chebyshev wavelet Galerkin method are used to solve the generalized DPL model with constant heat flux boundary condition. Multi-resolution and multi-scale computational property of Chebyshev wavelet in the present case localizes small scale variations of solution and fast switching of functional bases. Our study demonstrates that due to presence of coupling factor (convection–perfusion), generalized DPL model predicts lower temperature than classical DPL and Pennes model at the tumor position. Higher values of phase lag times results in lower temperature at the tumor position. But, in case of variation of phase lag time due to temperature gradient, the nature of temperature profile also depends on the spatial coordinate. The effect of the blood temperature, porosity and interfacial convective heat transfer on temperature distribution has been investigated. It is found that larger values of porosity and interfacial convective heat transfer results in lower temperature at the tumor position. Also, both porosity and interfacial convective heat transfer are pronounced more at higher values. The whole analysis is presented in dimensionless form.