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OBJECTIVE: To elucidate the function of MOTS-c in accelerating bone fracture healing by inducing BMSCs differentiation into osteoblasts, as well as its potential mechanism. MATERIALS AND METHODS: Primary BMSCs were extracted from rats and induced for osteogenesis. The highest dose of MOTS-c that did not affect BMSCs proliferation was determined by CCK-8 assay. After 7-day osteogenesis, the relative levels of ALP, Bglap, and Runx2 in MOTS-c-treated BMSCs influenced by FOXF1 were examined. ALP staining and alizarin red S staining in BMSCs were performed as well. The interaction between FOXF1 and TGF-β was analyzed by ChIP assay. At last, rescue experiments were performed to uncover the role of FOXF1/TGF-β axis in MOTS-c-induced osteogenesis. RESULTS: 1 μM MOTS-c was the highest dose that did not affect BMSCs proliferation. MOTS-c treatment upregulated the relative levels of ALP, Bglap, and Runx2, and stimulated mineralization ability in BMSCs, which were attenuated by the silence of FOXF1. TGF-β was proved to interact with FOXF1, and its level was positively mediated by FOXF1. The silence of FOXF1 attenuated the accelerated osteogenesis and TGF-β upregulation in BMSCs because of MOTS-c induction, and these trends were further reversed by the overexpression of TGF-β. CONCLUSIONS: MOTS-c treatment markedly induces osteogenesis in BMSCs. During MOTS-c-induced osteogenic progression, the upregulated FOXF1 triggers the activation of TGF-β pathway, thus accelerating bone fracture healing. [ABSTRACT FROM AUTHOR]

Correlation between the elastic modulus (B) and the Raman shift (Δω) of TiO2 and their responses to the variation of crystal size, applied pressure, and measuring temperature have been established as a function depending on the order, length, and energy of a representative bond for the entire specimen. In addition to the derived fundamental information of the atomic cohesive energy, binding energy density, Debye temperature and nonlinear compressibility, theoretical reproduction of the observations clarified that (i) the size effect arises from the under-coordination induced cohesive energy loss and the energy density gain in the surface up to skin depth; (ii) the thermally softened B and Δω results from bond expansion and bond weakening due to vibration; and, (iii) the mechanically stiffened B and Δω results from bond compression and bond strengthening due to mechanical work hardening. With the developed premise, one can predict the changing trends of the concerned properties with derivatives of quantitative information as such from any single measurement alone. [ABSTRACT FROM AUTHOR]

The functional dependence of stress, elastic modulus, melting point, and their interdependence on the identities (bond order, nature, length, and strength) of a representative bond of the specimen has been established for deeper insight into the transition from the conventional Hall-Petch relationship (HPR) to the inverse HPR (IHPR) for nanostructured TiO2. Theoretical reproduction of the observed inverse HPR suggests that the intrinsic competition between the energy-density gain (elastic modulus enhancement) and the cohesive-energy remnant (melting point depression) in the grain boundaries originates and the extrinsic competition between the activation and the inhibition of atomic dislocations activates the IHPR. [ABSTRACT FROM AUTHOR]

Germanium-doped silica films were prepared by magnetron cosputtering and postannealing. The photoluminescence properties and their dependence on the Ge contents and annealing temperature were investigated. Our experiments indicate that the observed light emission originates from the neutral oxygen vacancy defects. The substructures in the luminescence bands of the films were found to result from multiple-beam interferences of the emission in the optical cavity formed by the transparent films. [ABSTRACT FROM AUTHOR]

Magnetic Zn1-xCoxO nanorods were fabricated via direct hydrothermal synthesis. The measurements of x-ray diffraction, x-ray photoemission spectroscopy, and optical absorption spectra demonstrate the presence of cobalt in the +2 state in a tetrahedral crystal field, which indicates that Co ions have been doped into the nanorods. The observations of morphology and microstructure reveal that the Zn1-xCoxO nanorods grow along the [0002] direction through Ostwald ripening not only competing with but being assisted by oriented attachment. The field dependence of magnetization (M-H curves) of the Zn1-xCoxO nanorods measured at 300 K shows their ferromagnetic characteristics. The coercive fields (Hc) were obtained to be 98 and 36 Oe for nominal x=0.029 and 0.056, respectively. Our experimental results provide one effective method for fabrication of transition metal doped ZnO nanostructures with room-temperature ferromagnetism by direct chemical synthesis. [ABSTRACT FROM AUTHOR]

A low-frequency Raman vibration mode, whose peak position and linewidth are independent of the sizes of Ge nanocrystals and the polarization configuration of incident excitation light, was observed in silicon oxide films embedded with Ge nanocrystals which were prepared using magnetron cosputtering of SiO2–Ge–Si targets. The peak position of the Raman mode is sensitive to the content of Si in the matrix. After the sample is annealed above a special temperature that increases with the content of Si, the Raman mode disappears. Microstructural observations and spectral analyses disclose that this low-frequency Raman mode arises from a local structure which is positioned at the surfaces of Ge nanocrystals and consists of Ge, Si, and O atoms. High-temperature annealing leads to the removal of Ge atoms from the local structure. As a result, the local vibration mode vanishes. [ABSTRACT FROM AUTHOR]

Ge and Si nanocrystals (nc-Ge and nc-Si) with average sizes in the range of 2–7 nm, embedded in silica matrix, were fabricated for investigating their acoustic-phonon vibrational properties. The freely elastic sphere theory was found to be unsuitable for explaining the low-frequency phonon vibration character of both nc-Ge and nc-Si in our current experiments. We have assigned the observed low-frequency Raman peaks to “LA-like mode” and “TA-like mode” in terms of their polarization and depolarization behaviors. In addition, it is revealed that the lattice contraction phenomenon exists in nc-Ge and nc-Si with sizes smaller than 4 nm, which leads to a contrary effect against matrix traction on the phonon vibrational frequencies. [ABSTRACT FROM AUTHOR]

Mn-doped ZnO multileg nanostructures were synthesized via in situ thermal oxidation of Zn and MnO2 powder. Spectroscopic measurements show that Mn ions have been doped into the lattice positions of Zn ions, which strongly induce growth of the observed ZnO multileg nanostructure. It is revealed that the growth mechanism of this kind of multileg ZnO:Mn nanostructure is different from the traditional vapor–solid or vapor–liquid–solid nucleation model of ZnO nanostructures. A possible mechanism is discussed on the basis of the growth process of a tetrapod ZnO nanostructure. Furthermore, we report the observation of an additional Raman peak. This peak is considered to have an origin related to Mn dopant in the ZnO nanostructure. This Raman feature can be regarded as an indicator for the incorporation of Mn ions into the lattice positions of the multileg ZnO nanostructure. [ABSTRACT FROM AUTHOR]

The effect of bilayer thickness (L) reduction on the oxidation-induced strengthening of Zr/Nb nanoscale metallic multilayers (NMM) is investigated. Zr/Nb NMMs with L = 10 and 75 nm were annealed at 350 °C for a time ranging between 2 and 336 h, and the changes in structure and deformation behaviour were studied by nanoscale mechanical testing and analytical electron microscopy. Annealing led to the transformation of the Zr layers into ZrO2 after a few hours, while the Nb layers oxidised progressively at a much slower rate. The sequential oxidation of Zr and Nb layers was found to be key for the oxidation to take place without rupture of the multilayered structure and without coating spallation in all cases. However, the multilayers with the smallest bilayer thickness (L = 10 nm) presented superior damage tolerance and therefore structural integrity during the oxidation process, while for L = 75 nm the volumetric expansion associated with oxidation led to the formation of cracks at the interfaces and within the ZrO2 layers. As a result, the nanoindentation hardness increase after annealing was significantly higher for the nanolaminate with L = 10 nm. Comparison between nanoindentation and micropillar compression behaviour of the oxidised NMMs demonstrates that the hardness increase upon oxidation arises from the contribution of the residual stresses associated with the volume increase due to oxidation and to the higher strength of the oxides. [ABSTRACT FROM AUTHOR]

This paper investigated the effects of space-based laser irradiating small scale space debris by numerical simulation. Laser ablation impulse coupling models were established by selecting typical materials of small scale space debris. The velocity variation of the space debris ablating by space-based laser was analysed, and the orbit manoeuvre of the small scale space debris irradiating by laser was modelled and investigated. The variations of the orbital parameters of the space debris orbit under the irradiation of high-power pulsed laser were simulated and analysed, and the effects of the spinning angular velocity and impulse coupling coefficient of debris and the power density and repetition of laser on debris removal efficiency were analysed and discussed. The simulation results show that, the assumed space-based laser can complete the mission of removing debris successfully by irradiating in one pass and the effects of the debris removal using space-based laser was described, which validated the feasibility of space-based laser debris removal and provided the necessary theoretical basis for the application of space debris removal by using space-based laser. [ABSTRACT FROM AUTHOR]

Discusses a study which described heavily doped p-GaAs properties grown by low-pressure organometallic vapor phase epitaxy using liquid CCI[sub4]. Usefulness of a novel photoluminescence technique; Description of a p type dopant considered promising in AlGaAs/GaAs heterostructures; Properties of carbon as a dopant.

Focuses on a study that investigated a shallow palladium/germanium/titanium/platinum/ohmic contact for both n- and p-gallium arsenide. Condition of the p contact at higher temperatures; Problem for low melting point contacts; Requirement for the microstructure of the contacts for optimum device behavior; Concept in practical device processing.

The aim here was to address the influence rules in small-scale space debris with different laser pulse width and power density by simulation and experiment. A dynamic model of ground-based laser irradiating small-scale space debris was established to simulate the relation between speed increment and different power density, and the request of effective laser working time was obtained for typical power density. Further, the waveforms and arriving positions of shock wave propagation with different laser pulse widths were analysed, and the distributed rules of impulse coupling coefficient with different laser pulse widths and power densities were investigated by comparing the numerical simulation and experimental results. Finally, the orbit status of small-scale space debris and removing effect were described. The results indicated that the pulse number increases with the increase of altitude, and the remaining debris mass decreases obviously with the increase of pulse number and orbit. [ABSTRACT FROM AUTHOR]