MiR-9 facilitates cartilage regeneration of osteoarthritis in rabbits through regulating Notch signaling pathway.

OBJECTIVE: To explore the effect of micro ribonucleic acid (miR-9) on cartilage regeneration of osteoarthritis in rabbits through the regulation of the Notch signaling pathway. MATERIALS AND METHODS: A total of 30 specific pathogen-free Sprague-Dawley rabbits were randomly divided into control group (healthy rabbits, n=10), model group (osteoarthritis model, n=10) and miR-9 group (osteoarthritis model + miR-9 interference, n=10). The degeneration degree of rabbit knee articular cartilage in three groups was assessed through the Mankin's score. The morphology of cartilage tissues was observed under an optical microscope. Expressions of the Notch1, B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax) proteins, and collagen II (CII) in chondrocytes were detected via the immunohistochemical assay. RESULTS: In rabbits of control group, the articular cartilage had a smooth surface and complete structure, and the cells were arranged orderly with a clear tidal line. A large number of articular chondrocytes died in model group, while it was improved in miR-9 group. The Mankin's score was 3.52±0.79 points in control group, 6.73±0.95 points in model group, and 5.37±0.61 points in miR-9 group, showing significant differences among the three groups (p<0.05). Results of immunohistochemistry showed that the protein expressions of Notch1 and Bax were higher in model group, but lower in control group and miR-9 group (p<0.05). The protein expression of Bcl-2 was lower in model group but was upregulated in control group and miR-9 group (p<0.05). The results of Reverse Transcription-Polymerase Chain Reaction (RT-PCR) revealed that the expressions of Notch1 and Bax in control group were lower than those in model group and miR-9 group (p<0.05), while the expression of Bcl-2 in model group was lower than that in control group and miR-9 group (p<0.05). According to the results of immunohistochemistry, the CII optical density (OD) value was 0.18±0.013, 0.25±0.05 and 0.22±0.009 in control group, model group, and miR-9 group, respectively. It could be seen that the CII OD value was the highest in model group, indicating that the CII expression in articular cartilage in osteoarthritis was negatively correlated with the severity of osteoarthritis. CONCLUSIONS: MiR-9, through the down-regulation of the expressions of Notch and Bax, can activate the Bcl-2 to promote the differentiation and regeneration of chondrocytes. It can facilitate the cartilage regeneration of osteoarthritis in rabbits through the mediation of the CII expression.

Superconductivity in HfTe5 across weak to strong topological insulator transition induced via pressures.

Recently, theoretical studies show that layered HfTe5 is at the boundary of weak &strong topological insulator (TI) and might crossover to a Dirac semimetal state by changing lattice parameters. The topological properties of 3D stacked HfTe5 are expected hence to be sensitive to pressures tuning. Here, we report pressure induced phase evolution in both electronic &crystal structures for HfTe5 with a culmination of pressure induced superconductivity. Our experiments indicated that the temperature for anomaly resistance peak (Tp) due to Lifshitz transition decreases first before climbs up to a maximum with pressure while the Tp minimum corresponds to the transition from a weak TI to strong TI. The HfTe5 crystal becomes superconductive above ~5.5 GPa where the Tp reaches maximum. The highest superconducting transition temperature (Tc) around 5 K was achieved at 20 GPa. Crystal structure studies indicate that HfTe5 transforms from a Cmcm phase across a monoclinic C2/m phase then to a P-1 phase with increasing pressure. Based on transport, structure studies a comprehensive phase diagram of HfTe5 is constructed as function of pressure. The work provides valuable experimental insights into the evolution on how to proceed from a weak TI precursor across a strong TI to superconductors.

Superconductivity Bordering Rashba Type Topological Transition.

Strong spin orbital interaction (SOI) can induce unique quantum phenomena such as topological insulators, the Rashba effect, or p-wave superconductivity. Combining these three quantum phenomena into a single compound has important scientific implications. Here we report experimental observations of consecutive quantum phase transitions from a Rashba type topological trivial phase to topological insulator state then further proceeding to superconductivity in a SOI compound BiTeI tuned via pressures. The electrical resistivity measurement with V shape change signals the transition from a Rashba type topological trivial to a topological insulator phase at 2 GPa, which is caused by an energy gap close then reopen with band inverse. Superconducting transition appears at 8 GPa with a critical temperature TC of 5.3 K. Structure refinements indicate that the consecutive phase transitions are correlated to the changes in the Bi-Te bond and bond angle as function of pressures. The Hall Effect measurements reveal an intimate relationship between superconductivity and the unusual change in carrier density that points to possible unconventional superconductivity.

New Fluoride-arsenide Diluted Magnetic Semiconductor (Ba,K)F(Zn,Mn)As with Independent Spin and Charge Doping.

We report the discovery of a new fluoride-arsenide bulk diluted magnetic semiconductor (Ba,K)F(Zn,Mn)As with the tetragonal ZrCuSiAs-type structure which is identical to that of the "1111" iron-based superconductors. The joint hole doping via (Ba,K) substitution &spin doping via (Zn,Mn) substitution results in ferromagnetic order with Curie temperature up to 30 K and demonstrates that the ferromagnetic interactions between the localized spins are mediated by the carriers. Muon spin relaxation measurements confirm the intrinsic nature of the long range magnetic order in the entire volume in the ferromagnetic phase. This is the first time that a diluted magnetic semiconductor with decoupled spin and charge doping is achieved in a fluoride compound. Comparing to the isostructure oxide counterpart of LaOZnSb, the fluoride DMS (Ba,K)F(Zn,Mn)As shows much improved semiconductive behavior that would be benefit for further application developments.

In situ electron holography study of charge distribution in high-κ charge-trapping memory.

Charge-trapping memory with high-κ insulator films is a candidate for future memory devices. Many efforts with different indirect methods have been made to confirm the trapping position of the charges, but the reported results in the literatures are contrary, from the bottom to the top of the trapping layers. Here we characterize the local charge distribution in the high-κ dielectric stacks under different bias with in situ electron holography. The retrieved phase change induced by external bias strength is visualized with high spatial resolution and the negative charges aggregated on the interface between Al2O3 block layer and HfO2 trapping layer are confirmed. Moreover, the positive charges are discovered near the interface between HfO2 and SiO2 films, which may have an impact on the performance of the charge-trapping memory but were neglected in previous models and theory.

Wire network behavior in superconducting Nb films with diluted triangular arrays of holes.

We present results of transport measurements on superconducting Nb films with diluted triangular arrays (honeycomb and kagomé) of holes. The patterned films have large disk-shaped interstitial regions even when the edge-to-edge separations between nearest neighboring holes are comparable to the coherence length. Changes in the field interval of two consecutive minima in the field dependent resistance R(H) curves are observed. In the low field region, fine structures in the R(H) and T(c)(H) curves are identified in both arrays. Comparison of experimental data with calculation results reveals that these structures observed in honeycomb and kagomé hole arrays resemble those in wire networks with triangular and T(3) symmetries, respectively. The findings suggest that even in these specified periodic hole arrays with very large interstitial regions, the low field fine structures are determined by the connectivity of the nanostructures.

Energy gaps in Bi(2)Sr(2)CaCu(2)O(8+δ) cuprate superconductors.

The relationship between the cuprate pseudogap (Δ(p)) and superconducting gap (Δ(s)) remains an unsolved mystery. Here, we present a temperature- and doping-dependent tunneling study of submicron Bi(2)Sr(2)CaCu(2)O(8+δ) intrinsic Josephson junctions, which provides a clear evidence that Δ(s) closes at a temperature T(c) (0) well above the superconducting transition temperature T(c) but far below the pseudogap opening temperature T*. We show that the superconducting pairing first occurs predominantly on a limited Fermi surface near the node below T(c) (0), accompanied by a Fermi arc due to the lifetime effects of quasiparticles and Cooper pairs. The arc length has a linear temperature dependence, and as temperature decreases below T(c) it reduces to zero while pairing spreads to the antinodal region of the pseudogap leading to a d-wave superconducting gap on the entire Fermi surface at lower temperatures.

Metallic electrical transport in inter-graphitic planes of an individual tubular carbon nanocone.

Tubular carbon cones (TCCs) with a herring-bone-like graphitic structure are synthesized on gold wire via the bias-assisted hot filament chemical vapor deposition (HFCVD) method. The electrical transport properties of an individual TCC are studied in the temperature range from 300 to 500 K by using a double probe scanning electron microscopy (DPSEM) in situ electrical measurement system. The high-resistance I-V characteristics of W-TCC-Au back-to-back double junctions show that electrons tunnel through the W-TCC junction, while thermoionic transport through the Au-TCC junction contributes to low-resistance properties. Temperature dependence of the electrical characteristics indicates that inter-graphitic-plane electrical transport in TCC is metallic.

Formation of nanocrystalline copolymer thin film PVDF-TrFE and its ferroelectric electron emission property.

Ferroelectric copolymer thin film PVDF-TrFE was deposited by spin coating method, and then annealed for the improved crystallization. The XRD and AFM measurements showed that as-formed PVDF-TrFE thin film was composed of the nanocrystallines with 50-80 nm in size and some amorphous phases. Meanwhile, as-formed PVDF-TrFE thin films also show a good polarization inversion property with a switch current of approximately 2.0 microA at a coercive field 40 MV/m. Electron emission testing results showed that under a continuous excitation of applied voltage pulses, PVDF-TrFE thin films exhibited an expected electron emission ability with emission current range of 0.08-0.52 microA, and the related electron emission mechanism was discussed.

Bond-counting rule for carbon and its application to the roughness of diamond (001).

Despite that carbon is tetravalent identical to silicon, first-principles calculations reveal that stable step structures on diamond (001) are entirely different from those on silicon. Moreover, pristine Si(001) is flat; pristine diamond (001) could be rough due to negative step formation energies. A generic bond-counting rule is established, which should apply to most carbon structures where sp2 and sp3 hybrids coexist: e.g., it provides a qualitative account of the step energy order without detailed calculation. Our findings agree with experimental observations.

Low-temperature electronic transport in single K(0.27)MnO(2)·0.5H(2)O nanowires: enhanced electron-electron interaction.

The current-voltage (I-V) characteristics and electrical resistivity of isolated potassium manganese oxide (K(0.27)MnO(2)·0.5H(2)O) nanowires prepared by a simple hydrothermal method were investigated over a wide temperature range from 300 to 4 K. With lowering temperature, a transition from linear to nonlinear I-V curves was observed around 50 K, and a clear zero bias anomaly (i.e., Coulomb gap-like structure) appeared on the differential conductance (dI/dV) curves, possibly due to enhanced electron-electron interaction at low temperatures. The temperature dependence of resistivity, [Formula: see text], follows the Efros-Shklovskii (ES) law, as expected in the presence of a Coulomb gap. Here we note that both the ES law and Coulomb blockade can in principle lead to a reduced zero bias conductance at low temperatures; in this study we cannot exclude the possibility of Coulomb-blockade transport in the measured nanowires, especially in the low-temperature range. It is still an open question how to pin down the origin of the observed reduction to a Coulomb gap (ES law) or Coulomb blockade.

Observation of macroscopic quantum tunneling in a single Bi2Sr2CaCu2O8+delta surface intrinsic Josephson junction.

We report on the first unambiguous observation of macroscopic quantum tunneling (MQT) in a single submicron Bi(2)Sr(2)CaCu(2)O(8+delta) surface intrinsic Josephson junction (IJJ) by measuring its temperature-dependent switching current distribution. All relevant junction parameters were determined in situ in the classical regime and were used to predict the behavior of the IJJ in the quantum regime via MQT theory. Experimental results agree quantitatively with the theoretical predictions, thus confirming the MQT picture. Furthermore, the data also indicate that the surface IJJ, where the current flows along the c axis of the crystal, has the conventional sinphi current-phase relationship.

Growth and field emission properties of tubular carbon cones.

New forms of tubular carbon cone (TCC) were grown on gold wires by hot-filament chemical vapor deposition (HFCVD). They have a long-cone-shaped appearance with a herringbone hollow interior, surrounded by helical sheets of graphite that are coiled around it. It is considered that TCC formation results because the size of the catalyst particle located in the top of the TCC decreases continuously during growth, due to etching effects in the CVD plasma, reflecting competition between the growth and etching processes in the plasma. In addition, field emission measurements show that TCCs have a very low-threshold field of 0.27 V/microm, and that a stable macroscopic emitting current density of 1 mA/cm2 can be obtained at only 0.5 V/microm. TCCs have good field emission properties, compared to other forms of carbon field emitter, and may be good candidates for use in field emission display devices.

Multichannel ballistic transport in multiwall carbon nanotubes.

The electric transport properties of an individual vertical multiwall carbon nanotube (MWCNT) were studied in situ at room temperature in a scanning electron microscope chamber. It was found that the single MWCNT has a large current-carrying capacity, and the maximum current can reach 7.27 mA. At the same time, a very low resistance of about 34.4 ohms and a high conductance of about (460-490)G0 were obtained. The experimental observations imply a multichannel quasiballistic conducting behavior occurring in the MWCNTs with large diameter, which can be attributed to the participation of multiple walls in electrical transport and the large diameter of the MWCNTs.