H.Y. Li

Roles of FGF-2 and TGF-beta/FGF-2 on differentiation of human mesenchymal stem cells towards nucleus pulposus-like phenotype

Abstract Human mesenchymal stem cells (MSCs) are reported to have the capability of differentiating towards nucleus pulposus (NP)-like phenotype under specific culture conditions. So far, the effects of fibroblast growth factor (FGF)-2 and the cocktail effects of transforming growth factor (TGF)-beta and FGF-2 on MSCs remain unclear. Therefore, we designed this study to clarify these effects. MSCs were cultured in conditioned medium containing FGF-2 or TGF-beta/FGF-2, and compared with basal or TGF-beta medium. The groups with FGF-2 showed the increase of cell proliferation. Functional gene markers and novel NP markers decreased in FGF-2 group, together with functional protein expression. Pho-ERK1/2 and pho-Smad3 differed significantly in the two conditioned groups. All these results suggest FGF-2 promotes MSCs’ proliferation, synergistically with TGF-beta. However, FGF-2 plays a negative role in cartilage homeostasis. We also demonstrate that FGF-2 has no positive effect in differentiating MSCs into NP-like cells, but hinders the acceleration effect of TGF-beta.

Angle-dependent oscillations in valence-band photoemission intensity of C60

High-resolution angle-resolved photoelectron spectroscopy (ARPES) has been performed to investigate valence-band photoemission in C 60 single crystals, which were cleaved in ultra-high-vacuum systems. The results present angle-dependent modulations in intensities of valence-band photoemission of the C 60 single crystal. The observed intensity modulations are caused by polarization influence and photoelectron diffraction (PED) effects, of which the latter is also responsible for the similar oscillations produced by varying incident photon energies. The calculated results indicate that only photoelectrons scattered by the top hemisphere of C 60 molecules dominate the angle-dependent interference modulations.

Effect of geometric configuration on the electrocaloric properties of nanoscale ferroelectric materials

The electrocaloric properties of ferroelectrics are highly dependent on the domain structure in the materials. For nanoscale ferroelectric materials, the domain structure is greatly influenced by the geometric configuration of the system. Using a real-space phase field model based on the Ginzburg-Landau theory, we investigate the effect of geometric configurations on the electrocaloric properties of nanoscale ferroelectric materials. The ferroelectric hysteresis loops under different temperatures are simulated for the ferroelectric nano-metamaterials with square, honeycomb, and triangular Archimedean geometric configurations. The adiabatic temperature changes (ATCs) for three ferroelectric nano-metamaterials under different electric fields are calculated from the Maxwell relationship based on the hysteresis loops. It is found that the honeycomb specimen exhibits the largest ATC of Δ T = 4.3 °C under a field of 391.8u2009kV/cm among three geometric configurations, whereas the square specimen has the smallest ATC of Δ T = 2.7 u2009°C under the same electric field. The different electrocaloric properties for three geometric configurations stem from the different domain structures. There are more free surfaces perpendicular to the electric field in the square specimen than the other two specimens, which restrict more polarizations perpendicular to the electric field, resulting in a small ATC. Due to the absence of free surfaces perpendicular to the electric field in the honeycomb specimen, the change of polarization with temperature in the direction of the electric field is more easy and thus leads to a large ATC. The present work suggests a novel approach to obtain the tunable electrocaloric properties in nanoscale ferroelectric materials by designing their geometric configurations.The electrocaloric properties of ferroelectrics are highly dependent on the domain structure in the materials. For nanoscale ferroelectric materials, the domain structure is greatly influenced by the geometric configuration of the system. Using a real-space phase field model based on the Ginzburg-Landau theory, we investigate the effect of geometric configurations on the electrocaloric properties of nanoscale ferroelectric materials. The ferroelectric hysteresis loops under different temperatures are simulated for the ferroelectric nano-metamaterials with square, honeycomb, and triangular Archimedean geometric configurations. The adiabatic temperature changes (ATCs) for three ferroelectric nano-metamaterials under different electric fields are calculated from the Maxwell relationship based on the hysteresis loops. It is found that the honeycomb specimen exhibits the largest ATC of Δ T = 4.3 °C under a...

Piezoelectric Energy Harvester Array With Magnetic Tip Mass

Energy harvesting using piezoelectric materials is an alternative method for low power electronics, such as MEMS, wireless sensor network, portable devices, and nano structures, from extracting the ambient energy. Most piezoelectric energy harvesters are based on cantilever beams with laminated piezoelectric patches. To generate higher dynamic response of piezoelectric energy harvesters, tip mass is attached at the free end of the cantilever beams. Piezoelectric energy harvester array is another way to improve the power, i.e., installing a set of cantilever piezoelectric energy harvesters in close distance. In this research, a new design of piezoelectric energy harvester is proposed. The present design consists of an array of cantilever beams with permanent magnets at the free ends. The permanent magnets are introduced to transfer the excitation force to every cantilever beams. An experimental model is manufactured and experimental energy harvesting is carried out. Piezoelectric patches are laminated on clamped end of cantilever beams, and the permanent magnets are fixed at the free ends. All the magnets have opposite poles with each other to generate repelling force. Then these piezoelectric electric energy harvesters were connected to an AC/DC circuit and the power was measured. Also, the power of proposed piezoelectric energy harvester was compared with the piezoelectric harvesters without permanent magnets. The results show that, present design can generate higher power at the same excitation. Under the base excitation at the first natural frequency, the array of the cantilever beam show similar motion pattern, i.e., there is no phase difference between each other. At higher frequencies, the beams have a phase difference of π. Thus the crash between the cantilever beams can be effectively avoided. At lower excitation frequencies, the presented piezoelectric energy harvester vibration likes the first mode of a simple multi-degree-of-freedom system; and at higher excitation frequencies, the vibration of the presented piezoelectric vibrates like a second mode of a MDOF system.Copyright

Study of the initial adsorption state of tetracene on [Formula: see text].

Tetracene on the [Formula: see text] surface has been investigated by ultraviolet photoemission spectroscopy (UPS). The UPS results show features, from tetracene, between 2.0 and 10.0xa0eV below the Fermi level, and their shift in binding energy with increasing coverage. Angle-resolved UPS (ARUPS) results indicate that the molecular plane of tetracene near the interface is parallel to the substrate. Moreover, an abxa0initio calculation has also been carried out to determine the favourable adsorption structure. Temperature-dependent UPS measurements show that tetracene is stable on the [Formula: see text] surface up to 150u2009°C.

The orbital symmetry of carbon monoxide on a Cs-precovered Ru(1010) surface

The molecular orbitals of CO are rearranged under the strong influence of coadsorbed Cs atoms. The peak for CO on the clean surface, at 7.5 eV BE attributed to the and orbits, is split into two peaks; one is at 6.3 eV BE and the other 7.8 eV BE. The peak at 6.3 eV BE shows an anti-symmetry character about the plane parallel to the crystallographic direction in the surface.

High-resolution electron energy loss spectroscopy and angle-resolved ultra-violet photoemission spectroscopy studies of carbon monoxide on a Cs-precovered surface

There are two molecular adsorption states of CO in the system. One is , with lower C - O frequency, and the other is , with higher C - O frequency. The latter is similar to that on a clean surface. The two states of CO are occupied sequentially during the exposure to CO. The C - O stretch frequency of both states shifts to a higher value with the exposure to CO and to a lower value with higher Cs precoverage. The electronic structure of the molecule is different from that of the molecule and is of the same character as CO in a tilted mode.