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Tsinghua Science and Technology

Issue 4 • Date Aug. 2007

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  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • Contents

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    Freely Available from IEEE
  • In vitro cytotoxicity and protein drug release properties of chitosan/heparin microspheres

    Page(s): 361 - 365
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (745 KB)  

    Chitosan/heparin microspheres were prepared using the water-in-oil emulsification solvent evaporation technique. The microsphere diameters were controlled by selecting the fabrication process parameters. Scanning electron micrographs showed that the chitosan/heparin microspheres were regular and the surface morphology was smooth. Fourier transform infrared showed that the chitosan amino groups reacted with heparin carboxylic groups to form acylamides in the microspheres. Analysis of the microsphere cytotoxicity showed that they had no cytotoxic effect and behaved very similar to the negative control (polystyrene). To analyze the protein drug release profiles of the microspheres, bovine serum albumin was loaded as a model drug into the microspheres and released in vitro. Marked retardation was observed in the BSA release profiles. The results show that chitosan/heparin microspheres may provide a useful controlled release protein drug system for used in pharmaceutics. View full abstract»

    Open Access
  • Effects of quenching temperature and time on pore diameter of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) porous scaffolds and MC3T3-El osteoblast response to the scaffolds

    Page(s): 366 - 371
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    Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) scaffolds were prepared by thermally inducing phase separation (TIPS) for bone reconstruction. Scanning electron microscopy and porosity measurements were used to analyze the structure and properties of the scaffolds. The pore diameter of the scaffolds could be easily controlled by changing the quenching temperature and time. The biocompatibility was assessed by examining the proliferation and morphology of MC 3T3-E1 osteoprogenitor cells seeded on the scaffolds. Cultures grown in the presence of a source of phosphate ions showed the formation of a mineralized extracellular matrix. The results indicate that PHBHHx scaffolds prepared using TIPS are a promising candidate for bone reconstruction. View full abstract»

    Open Access
  • Effects of genistein on cell cycle and apoptosis of two murine melanoma cell lines

    Page(s): 372 - 380
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    The effects of genistein on several tumor cell lines were investigated to study the effects of genistein on cell growth, cell cycle, and apoptosis of two murine melanoma cell lines, 816 and K1735M2. These two closely related murine melanoma cell lines, however, have different responses to the genistein treatment. Genistein inhibits the growth of both the 816 and K 1735M2 cell lines and arrests the growth at the G2/M phase. After treatment with 60 μmol/L, genistein for 72 h, apoptosis and caspase activities were detected in B16 cells, while such effects were not found in K1735M2. Further tests showed that after genistein treatment the protein content and mRNA levels of p53 increased in 816, but remained the same in K1735M2. The protein content and mRNA levels of p21WAF1/CIP1 increased in both cell lines after treatment. The results show that genistein might induce apoptosis in 816 cells by damaging the DNA, inhibiting topoisomerase II, increasing p53 expression, releasing cytochrome c from the mitochondria, and activating the caspases which will lead to apoptosis. View full abstract»

    Open Access
  • Cloning and characterization of an mRNA encoding F1-ATPase beta-subunit abundant in epithelial cells of mantle and gill of pearl oyster, pinctada fucata

    Page(s): 381 - 388
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    In oyster biomineralization, large amounts of calcium are absorbed from external media, transported to the mineralization site, and finally deposited via a matrix-mediated process. All these activities are very energy intensive; therefore, investigations of the energy metabolism pathways of different oyster tissues will facilitate understanding of oyster biomineralization physiology. A full-length cDNA encoding the F1ATPase beta-subunit (the F1-β-subunit, a major calalytic subunit of F-ATPase) from the pearl oyster (Pinc­ tada fucata) was cloned using the homology strategy with a pair of degenerated primers based on the conserved regions of other animals' F1-β-subunit genes. Sequencing and structural analyses showed that the obtained sequence shared high identity with other animals' F1-β-subunits, and had a unique phosphorylation site of PKC and CK lion the external surface of the putative protein. Results from semi-quantitative reverse transcription-polymerase chain reaction and in situ hybridization demonstrated this oyster F1-β-subunit mRNA is abundant in the gill and mantle, and distributed widely in the periostracal groove, the outer folder, and the dorsal region of the mantle and in the gill epithelial cells. These tissues were the main regions that participate in biomineralization processes such as calcium uptake, transport, and matrix secretion. The results indicate that tissues involved in biomineralization have stronger energy metabolic processes and that F1-ATPase might play an important role in oyster biomineralization by providing energy transport. View full abstract»

    Open Access
  • Determination of polysaccharide in radix pseudostellariae extract by size-exclusion high-performance liquid chromatography

    Page(s): 389 - 393
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    A simple size-exclusion high-performance liquid chromatographic method was developed for rapid molecular mass screening to determine the average molecular mass, polydispersity, and quantity of Taizishen polysaccharides extract. The screening used a TOSOH TSK-GEL G3000SW high-performance liquid chromatographic column with 0.1 mol/L NaNO3 buffer as the mobile phase and refractive index detector. The molecular mass calibration curve was linear for polysaccharide standards from 10 to 100 kDa with a correlation coefficient of 0.9991. The method can be used to analyze the quantity, average molecular mass, and polydispersity of polysaccharides. In addition, the screening method is suitable for quality control of polysaccharide preparations in Chinese medicines and pharmaceutical products. View full abstract»

    Open Access
  • Different kinetics of puerarin in plasma of normal and depressed rats after oral administration of Chinese medicine TZ18

    Page(s): 394 - 399
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    The objective of this study is to quantify the puerarin in rat plasma following oral administration of TZ18 and compare the pharmacokinetics characteristics of puerarin in normal rats with that in depression model rats. A high performance liquid chromatography method was used to quantify the puerarin due to its good selectivity and linearity (coefficient correlation, r2=0.9991) within the tested range (0.028–0.889 μg • mL−1). Intra- and inter-day precision coefficients of variation and accuracy bias were acceptable (Maximum coefficient of variation was 5.740/0 for intra-day and 3.090/0 for inter-day) over the entire range. The recoveries were found to be 98.30/0, 101.40/0, and 103.40/0 for concentrations of 0.028,0.222, and 0.444 μg • mL−1, respectively. The concentration-time curves for both normal rats and depression model rats were fit to a twocompartment model with the first order absorption. The results show significant differences in the main pharmacokinetic parameters of peak time, peak concentration, and the area under the concentration-time curve between the two kinds of rats. View full abstract»

    Open Access
  • Inhibitory kinetics of p-substituted benzaldehydes on polyphenol oxidase from the fifth instar of Pieris rapae L

    Page(s): 400 - 404
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    Polyphenol oxidase (PPO) is the enzyme responsible for enzymatic browning during the growth of insects. It is also involved in defense reactions and is related with immunities in insects. PPO, a metalloenzyme oxidase, catalyzes the oxidation of o-diphenol to o-quinone. The present paper describes the effects of benzaldehyde and its p-substituted derivatives on the activity of PPO from the fifth instar of Pieris rapae L. PPO from the fifth instar of Pieris rapae L. was purified using ammonium sulfate fractionation and chromatography on Sephadex G-100. The enzyme kinetics was characterized using L-3,4-dihydroxyphenylalanine (L-DOPA) as substrate. The results show that benzaldehyde, p­ hydroxybenzaldehyde, p-chlorobenzaldehyde, and p-cyanobenzaldehyde can inhibit the PPO activity for the oxidation of L-DOPA. The inhibitor concentration leading to 500/0 activity lost, IC50, was estimated to be 5.90, 5.62, 2.83, and 2.91 mmol/L for the four tested inhibitors, respectively. Kinetic analyses show that the inhibitory effects of these compounds are reversible. Benzaldehyde, p­ hydroxybenzaldehyde, and p-chlorobenzaldehyde are noncompetitive inhibitors while p-cyano­ benzaldehyde is a mixed-type inhibitor. The inhibition constants were determined for all four inhibitors. p-chlorobenzaldehyde and p-cyanobenzaldehyde were more potent inhibitors than the other compounds. These results provide a basis for developing PPO inhibition-based pesticides. View full abstract»

    Open Access
  • Cloning, characterization, and distribution of an mRNA encoding a H+-ATPaseα subunit in the mantle of pearl oyster, pinetada fueata

    Page(s): 405 - 412
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    Mitochondrial ATP synthase is responsible for the production of the majority of the cellular ATP, which is composed of two major units: F0 and F1. Although much is known about the active complex (5 subunits (αβγδ∊)), the role of the α subunit in the catalytic mechanism remains unclear, particularly in bivalve animals. This study first cloned and identified the full-length sequence of the mitochondrial H+-ATP synthase α subunit cDNA gene in Pinctada fucata using the reverse transcriptase polymerase chain reaction (RT-PCR) technique. The Pinctada fucata mitochondrial H+-ATP synthase α subunit contains 1991 nucleotides, with the translation start site at nt 48 (ATG) and the stop codon at nt 1660 (TAA), encoding a polypeptide 553 amino acids in length, which shares high similarity to that of other animals (81% identity to fruit fly, 82% to carp, and 83% to humans). Alignment analysis of the well-conserved amino acid domains in the ATP ase α subunit, the α/β signal transduction domain, showed that two residues (Asp358 and Asn359) differ from any other ATP synthase α subunit. In situ hybridization analysis was used to reveal the wide-spread distribution of mitochondrial H+-ATP synthase in various tissues in Pinctada fucata. This work will help further research on pearl energy metabolism to increase the output and quality of pearls to more efficiently utilize our rich pearl oyster resources. View full abstract»

    Open Access
  • Vegetation spatial heterogeneity of different soil regions in inner mongolia, China

    Page(s): 413 - 423
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    The vegetation spatial heterogeneity and ecological characteristics in different soil regions were analyzed by surveying the vegetation in 12 different soil regions of Inner Mongolia, China, including coniferous-broadleaf deciduous forests, shrub, grassland, and desert regions with 1122 large 2 cm × 2 cm quadrats (actual size 30 km × 30 km, referred to as L-quadrat hereafter) in about 1.18 million krn2. Each Lquadrat was divided into four small 1 cm × 1 cm quadrats (actual size 15 km × 15 km, S-quadrat). The vegetation was analyzed based on the beta-binomial distribution to describe the frequency of occurrence and spatial heterogeneity for each kind of vegetation. The weighted average of the heterogeneity of all vegetation in the same soil region provides a measure of the soil regional landscape level heterogeneity which describes the spatial complexity of the regional landscape composition of the existing vegetation. Comparison of the vegetation characteristics in the 12 soil regions shows that, the calcic gray soil has the highest average vegetation type per quadrat. The largest soil region is calcic chestnut soil and has the most vegetation types. Every soil region has its own dominant vegetation sequence which dominates in occurrence and dominant vegetation types which dominates in spatial heterogeneity. For the Inner Mongolian vegetation, the weighted average of the heterogeneity is 0.60 and the vegetation diversity index is 4.47. View full abstract»

    Open Access
  • Spatial heterogeneity of vegetation in China

    Page(s): 424 - 434
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    The spatial heterogeneity and ecological characteristics of 74 vegetation types and the lack of vegetation type within the 9.6 million km2 of Chinese territory were studied using data from the China vegetation map. The analysis used 877 large quadrats 10 mn × 10mm (actual size 100 km × 100 km), which covered about 8.77 million km2, Each large-quadrat was divided into four small 5 mm × 5 mm quadrats (actual size 50 km × 50 km). The frequency of occurrence of all vegetation types was recorded in each small quadrat. The survey using the Shiyomi method of vegetation analysis based on the beta-binomial distribution was adopted to describe the frequency of occurrence and spatial heterogeneity for each kind of vegetation. The weighted average heterogeneity of all the vegetation types in the landscape provides a measure of the landscape level heterogeneity which describes the spatial intricacy of the existing vegetation composition. The maximum spatial vegetation heterogeneity was 0.8620 in the frigid-temperate coniferous forest of Larix (V1), which dominates cold moist northeast China. The minimum spatial heterogeneity with a low occurrence was the Caragana tibetica in the gravel desert in the western Yellow River Hetao area. The minimum occurrence with a low spatial heterogeneity was the Monsoon rainforest on rock in Guangxi and Yunnan Provinces. The vegetation types on the Qing-Zang Plateau were found to be representative of Chinese vegetation because of the very high occurrence and spatial heterogeneity of these vegetation types. The weighted average of the heterogeneity was 0.677, while the vegetation diversity index was 3.29. View full abstract»

    Open Access
  • Prospects of anaerobic digestion technology in China

    Page(s): 435 - 440
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    As the world's largest developing country, China must face the problem of managing municipal solid waste, and the challenge of organic waste disposal is even more serious. Considering the characteristics of traditional waste disposal technologies and the subsequent secondary pollution, anaerobic digestion has various advantages such as reduction in the land needed for disposal and preservation of environmental quality. In light of the energy crisis, this paper focuses on the potential production of biogas from biowaste through anaerobic digestion processes, the problems incurred by the waste collection system, and the efficiency of the anaerobic digestion process. Use of biogas in a combined heat and power cogeneration system is also discussed. Finally, the advantages of anaerobic digestion technology for the Chinese market are summarized. The anaerobic digestion is suggested to be a promising treating technology for the organic wastes in China. View full abstract»

    Open Access
  • FFT and wavelet-based analysis of the influence of machine vibrations on hard turned surface topographies

    Page(s): 441 - 446
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    With hard turning, which is an attractive alternative to existing grinding processes, surface quality is of great importance. Signal processing techniques were used to relate workpiece surface topography to the dynamic behavior of the machine tool. Spatial domain frequency analyses based on fast Fourier transform were used to analyze the tool behavior. Wavelet reconstruction was used for profile filtering. The results show that machine vibration remarkably affects the surface topography at small feed rates, but has negligible effect at high feed rates. The analyses also show how to control the surface quality during hard turning. View full abstract»

    Open Access
  • Automatic fiber orientation detection for sewed carbon fibers

    Page(s): 447 - 452
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    Automatic production and precise positioning of carbon fiber reinforced plastics (FRP) require precise detection of the fiber orientations. This paper presents an automatic method for detecting fiber orientations of sewed carbon fibers in the production of FRP. Detection was achieved by appropriate use of regional filling, edge detection operators, autocorrelation methods, and the Hough transformation. Regional filling was used to reduce the influence of the sewed regions, autocorrelation was used to clarify the fiber directions, edge detection operators were used to extract the edge features for the fiber orientations, and the Hough transformation was used to calculate the angles. Results for two kinds of carbon fiber materials show that the method is relatively quick and precise for detecting carbon fiber orientations. View full abstract»

    Open Access
  • Impulse capacitor discharge welding of hollow structure made of nickel-base alloy

    Page(s): 453 - 458
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    Future steam turbines will use hollow structures so that the turbine inlet temperature can be increased to improve the thermal efficiency. These hollow structures are made of the nickel-base alloy Nicrofer 6025 HT and consist of a wire mesh between two cover sheets. The cover sheets can be joined to the wire mesh by capacitor discharge welding due to its extremely short welding duration. The goal of this research is to investigate suitable welding parameters so that the weld spots form in an optimum way to increase the tensile shear strength and reduce spattering. Tensile shear tests, three-point bending tests, and micrographs were used to judge the joint quality of structures made with various welding parameters. The results show that the best welds are obtained with a transmission ratio of 1 :200, welding energy of 70% to 95%, and electrode force of 7 to 9 MPa. View full abstract»

    Open Access
  • Two-level genetic algorithm for clustered traveling salesman problem with application in large-scale TSPs

    Page(s): 459 - 465
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (294 KB)  

    Let G = (V, E) be a complete undirected graph with vertex set V, edge set E, and edge weights /(e) satisfying the triangle inequality. The vertex set V is partitioned into clusters V1, V2, …, Vk. The clustered traveling salesman problem (CTSP) seeks to compute the shortest Hamiltonian tour that visits all the vertices, in which the vertices of each cluster are visited consecutively. A two-level genetic algorithm (TLGA) was developed for the problem, which favors neither intra-cluster paths nor inter-cluster paths, thus realized integrated evolutionary optimization for both levels of the CTSP. Results show that the algorithm is more effective than known algorithms. A large-scale traveling salesman problem (TSP) can be converted into a CTSP by clustering so that it can then be solved by the algorithm. Test results demonstrate that the clustering TLGA for large TSPs is more effective and efficient than the classical genetic algorithm. View full abstract»

    Open Access
  • Information sharing in a multi-echelon inventory system

    Page(s): 466 - 474
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (314 KB)  

    The influence of different information sharing scenarios in a single supplier-single retailer supply chain is analyzed. The five information sharing scenarios are centralized information sharing, full information sharing, supplier-dominated information sharing, retailer-dominated information sharing, and noninformation sharing. Iterative procedures are developed to obtain the inventory policies and the system costs at equilibrium points. Numerical examples show that the cost of a centralized inventory system is about 20%–40% lower than that of a decentralized system with non-information sharing. Furthermore, a higher information sharing level does not always lead to a lower system cost in a decentralized supply chain due to inventory competition. View full abstract»

    Open Access
  • Infinite family of imaginary cyclic fields of degree p-1 with the p-rank p-rank of the ideal class groups of at least two

    Page(s): 475 - 478
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    Imaginary cyclic fields of degree p-1 which have two distinct unramified cyclic extensions of degree p are produced using elementary properties of the Lucas sequences. An infinite family of imaginary cyclic fields of degree p-1 are then given with the p-rank of the ideal class groups of at least two. View full abstract»

    Open Access
  • A note on trace polynomial

    Page(s): 479 - 484
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    In this paper, we mainly study the relation of two cyclically reduced words wand w' on the condition they have the same trace polynomial (i.e., tr w = trw'). By defining an equivalence relation through such operators on words as inverse, cyclically left shift, and mirror, it is straightforward to get that w∼w' implies tr w = trw'. We show by a counter example that tr w = tr w' does not imply w ∼ w'. And in two special cases, we prove that tr w = tr w' if and only if w ∼ w'. View full abstract»

    Open Access
  • Kinetics of Cd2+ and Cr3+ sorption from aqueous solutions using mercaptoacetic acid modified and unmodified oil palm fruit fibre(Elaeis guineensis) adsorbents

    Page(s): 485 - 492
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    The kinetics of the sorption of Cd 2+ and Cr3+ from aqueous solutions by mercaptoacetic acid modified and unmodified oil palm fruit fibre adsorbents were investigated. The results indicate that sorption equilibrium was reached within 60 min for both metals. Also, the removal efficiency of the three adsorbents was observed to increase for both metals with stronger treatments with mercaptoacetic acid. This may be attributed to the influence of the thiolation of the adsorbents. Furthermore, Cr 3+ had higher removal percentages than Cd2+ for all the adsorbents. The sorption mechanism based on the intraparticle diffusion model shows that Cd2+ sorption is better described than Cr3+. The intraparticle diffusion rate constants, Kid, for Cd2+ are 62.04 min−1 (untreated), 67.01 rnm−1 (treated with 0.5 mol/L mercaptoacetic acid), and 71.43 rnm−1 (treated with 1.0 mol/L mercaptocacetic acid) while those for Cr3+ are 63.41 min:−1 (untreated), 65.79 min:' (0.5 mol/L acid treated), and 66.25 min (1.0 mol/L acid treated). View full abstract»

    Open Access
  • Preparation and characterization of polymeric micelles from poly(D, L-lactide) and methoxypolyethylene glycol block copolymers as potential drug carriers

    Page(s): 493 - 496
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    Amphiphilic diblock copolymers composed of methoxy polyethylene glycol (MePEG) and poly(D, Llactide) (PDLLA) were prepared for the preparation of polymeric micelles. The use of MePEG-PDLLA as drug carriers has been reported in the open literature, but there are only few data on the application of a series of MePEG-PDLLA copolymers with different lengths in the medical field. The shape of the polymeric micelles is also important in drug delivery. Studies on in vitro drug release profiles require a good sink condition. The critical micelle concentration of a series of MePEG-PDLLA has a significant role in drug release. To estimate their feasibility as a drug carrier, polymeric micelles made of MePEG-PDLLA block copolymer were prepared by the oil in water (O/W) emulsion method. From dynamic light scattering (DLS) measurements, the size of the micelle formed was less than 200 nm. The critical micelle concentration of polymeric micelles with various compositions was determined using pyrene as a fluorescence probe. The critical micelle concentration decreased with increasing number of hydrophobic segments. MePEG-PDLLA micelles have a considerably low critical micelle concentration (0.4–0.5 μg/mL), which is apparently an advantage in utilizing these micelles as drug carriers. The morphology of the polymeric micelles was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The micelles were found to be nearly spherical. The yield of the polymeric micelles obtained from the O/W method is as high as 850/0. View full abstract»

    Open Access

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Tsinghua Science and Technology (Tsinghua Sci Technol) aims to highlight scientific achievements in computer science, electronic engineering, and other IT fields. Contributions all over the world are welcome.

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