A long-term evaluation of osteoinductive HA/β-TCP ceramics in vivo: 4.5 years study in pigs

It has been proved that some material-dependent calcium phosphate ceramics have intrinsic potentials to induce osteogenesis. But there is little literature concerning about the tissue response in long-term. The aim of this study is to evaluate the safety of the osteoinductive biocreamics and the stability of the newly formed bone after long-term tissue response. Porous calcium phosphate ceramics rods which contain hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) were implanted in the dorsal muscles of Banna Minipig Inbreding Line. After 4.5 years, all the implanted rods with surrounding tissues were harvested and stained with hematoxylin and eosin for histological observation. The 7 months’ rods were also harvested as short-term comparison. The histological results showed that compared with the short-term rods, amount of bone tissue formed after 4.5 years. And the newly formed bone in this bioceramics neither disappeared nor gave rise to uncontrolled growth. The bone growth in this bioceramics seemed to be self-confined. The surrounding soft tissues were normal and no tumor cell was found. We conclude that instead of disappearing or giving rise to out of control, the induced bone tissue trends to be further matured. And this bioceramics thus might have potentials in future clinical use.     

Determination of the natural frequency of a cantilevered ZnO nanowire resonantly excited by a sinusoidal electric field

The electric-field-induced mechanical resonance of an individual nanotube (NT) or nanowire (NW) has been utilized as a versatile technique for in situ measurement of the Young's modulus of the NT/NW in electron microscopes. The key step of this technique is to determine the fundamental natural frequency of the NT/NW. However, the emergence of super-?and/or sub-harmonic resonances might make the determination uncertain. This paper investigates the resonance behaviour of ZnO NWs in a nanotip-nanowire system in order to clarify this obscurity. It is found that forced and parametric resonance are two basic modes of the observed multi-frequency resonances and that each mode exhibits a distinct characteristic. By controlling the driving force exerted on the NW to be either lateral or axial, the two otherwise entangled modes are clearly separated. Based on this resonance mode separation, a criterion for identifying the natural frequency of ZnO NWs is proposed.     

Nano-scale compositional oscillation and phase intergrowth in Cu2S0.5Se0.5 and their role in thermal transport

Solid solution alloying is a promising strategy to establish high performance thermoelectrics.By alloying different elements,phase structures and phase compositions may vary accompanied by appearance of variety of interesting microstructures including mass fluctuation,lattice strain,nano-scale defects and spinodal decomposition,all of which may greatly influence the electrical and specifically the thermal transport of the material.In the present study,atomic structures of Cu2S0.5Se0.5 solid solution have been examined by using atom-resolved electron microscopy in order to investigate the structure-correlated physical insights for the abnormal thermal transport in this solid solution.Then the exceptional inter-growth nanostructures were observed.The solid solution consists of two high symmetrical phases,i.e.the hexagonal and cubic phase,which alternately intergrow to form highly oriented ultra-thin lamel-lae of nano or even,unit cell scales.The compositional oscillation in Se/S atomic ratio during alloying is responsible for the phase stability and intergrowth nanostructures.The unique binary phase intergrowth nanostructures make great contribution to the ultra-low lattice thermal conductivity comparable to glass and extremely short phonon mean free path of only 1.04 (A),peculiar continuous hexagonal-to-cubic struc-tural transformation without a critical transition temperature and its corresponding abnormal changes of thermal characters with temperatures.The present study further evokes the unlimited possibilities and potentials for tailoring nanostructures by alloying for improved thermoelectric performance.     

China’s bioenergy industry development roadmap

Positive development of renewable energy, saving and substitution of fossil energy, promotion of the energy structure adjustment are the inevitable strategy choices of China’s sustainable development. This paper discussed the China’s bioenergy resources status, development targets and technology development roadmaps. China has 136.140 million hm2 of marginal land, which distribute mainly in western and northern regions. There are 1 billion tons of crop residues and forestry waste annually, and 300 million tons can be used to produce different kinds of bioenergies. And organic waste and manure can generate 50 billion m3 of biogas. The discussed development target indicated that it can construct a Biomass Oilfield with a 100 million tons/year of capacity and reduce 200 million tons of CO2 emission by 2020. The bioenergy technology development roadmap indicated that the bioethanol mainly uses non grain starch and hemicellulose products as raw materials in the near-term (2006-2010). The biodiesel technology will focus on the advanced production technology, FT diesel, liquefaction of biomass and raw material production technology.     

Aqueous Cr(VI) reduction by electrodeposited zero-valent iron at neutral pH: acceleration by organic matters

This work investigated the effect of co-existing organic matters on aqueous Cr(VI) reduction by electrodeposited zero-valent iron (ED Fe(0)) at neutral pH. The ED Fe(0) prepared in a solution containing mixture of saccharin, L-ascorbic acid and sodium dodecyl sulfate showed higher activity in reducing the aqueous Cr(VI) at neutral pH than that prepared without any organic presence. XRD and SEM indicated that the structure of ED Fe(0) was significantly improved to nano-scale by the presence of organic mixture in the preparation solution. Further, the ED Fe(0) activity in the Cr(VI) reduction at neutral pH was increased by the co-existence of citric acid or oxalic acid in the chromate solution. Electrochemical impedance spectroscopy (EIS) demonstrated that the corrosive current increased with the concentration of organic matter in the reaction solution. With the co-existing organic matters in the preparation solution, the ED Fe(0) corroded more rapidly due to its nano-size, thus the Cr(VI) reduction by the ferrous iron was accelerated. With the co-existing organic matters in the reaction solution, the Cr(VI) reduction was accelerated by a Fe(II) complex as the main electron donor, and a prevention of the passivation due to the Fe(III) and Cr(III) complexes also accelerated the Cr(VI) reduction.     

A versatile current-mode biquad using operational amplifiers

A versatile current-mode biquadratic filter using three operational amplifiers and nine passive elements is proposed. By suitably choosing the output branch, lowpass, bandpass, highpass, bandstop and allpass transfer functions are realized simultaneously without changing the circuit configuration and elements. Two circuits, one is for low frequency application and the other for high frequency, are proposed. The center frequency, quality factor and gain constants of the circuit can be tuned independently. Simulated results show that the circuits work successfully.     

COMPUTER SIMULATION OF EFFECT OF ORIENTATION DIFFERENCE ON MECHANICAL PROPERTIES OF BICRYSTALLINE SPECIMENS

Based on the experimental results of the work-hardening processes of single crystals,the ac-commodation processes of polycrvstal deformation and the assumption of idealizedpolycrystal,the stress-strain relation of elasto-plastic deformation crystal was derived.Theeffect of orientation difference on the mechanical properties of the bicrvstalline specimens ofaluminum was simulated by means of the finite element method(FEM)of elasto-plasticcrystal.The results are in good agreement with the experimental results made by Clark andChalmers in 1954.     

MgO intercalation and crystallization between epitaxial graphene and Ru(0001)

Graphene on insulator is the foundation of its practical applications in electronic information technology.However,fabrication of graphene on insulating substrates suffers from small size and limited quality by direct growth of graphene on dielectric substrates,and the method of transferring graphene onto insulating substrates is not so compatible with the large-scale production in industry.Here,we report the fabrication of high-quality,large-area,single-crystal graphene on crystalline magnesium oxide(MgO),which has a dielectric constant of 7–10.Magnesium and oxygen are intercalated at the interface of epitaxial graphene/Ru(0001)and form crystalline structure after high-temperature annealing.The graphene/MgO/Ru(0001)sample was characterized by low energy electron diffraction(LEED),scanning tunneling microscopy(STM),X-ray photoelectron spectroscopy(XPS),and scanning transmission electron microscopy(STEM).LEED pattern shows that the magnesium oxide displays crystalline structure,and STM studies show clearly that the top layer is graphene.STEM characterization of as-intercalated sample demonstrates that the MgO intercalation layer,with a thickness of up to 2.3 nm,has a crystal structure of rock salt MgO,and the out-of-plane crystal orientation is[001].Our work provides a new route for fabrication of graphene on high dielectric constant insulators,which may have potential applications in future electronics.