Synthesis and Thermoelectric Properties of C 60

Nanosized C60 powder was sufficiently incorporated with Cu2GeSe3 powder by ball milling and C60/Cu2GeSe3 composites were prepared by spark plasma sintering. C60 distributed uniformly in the form of clusters and the average size of cluster was lower than 1 μm. With the addition of C60 increasing, the electrical resistivity and Seebeck coefficient of C60/Cu2GeSe3 composites increased while the thermal conductivity decreased significantly which resulted from the phonon scattering by C60 clusters locating on the grain boundaries of Cu2GeSe3 matrix. The maximum ZT of 0.20 was achieved at 700 K for 0.9% C60/Cu2GeSe3 sample

Exceptional point-based ultrasensitive surface acoustic wave gas sensor

Exceptional points (EPs) refer to degeneracies in non-Hermitian systems where two or more eigenvalues and their corresponding eigenvectors coalesce. Recently, there has been growing interest in harnessing EPs to enhance the responsivity of sensors. Significant improvements in the sensitivity of sensors in optics and electronics have been developed. In this work, we present a novel ultrasensitive surface acoustic wave (SAW) gas sensor based on EP. We demonstrate its ability to significantly respond to trace amount of hydrogen sulfide (H2S) gas by tuning additional loss to approach the EP, thereby enhancing the responsivity compared to the conventional delay line gas sensors. In addition to high sensitivity, our sensor is robust to temperature variation and exclusive to H2S gas. We propose an innovative method for designing a new generation of ultrasensitive gas sensor

Acoustic Vortex in Waveguide with Chiral Gradient Sawtooth Metasurface

The acoustic vortex states with spiral phase dislocation that can carry orbital angular moment (OAM) have aroused many research interests in recent years. The mainstream methods of generating acoustic vortex are based on Huygens-Fresnel principle to modulate the wavefront to create spatial spiral phase dislocation. In this work, we propose an entirely new scenario to generate acoustic vortex in a waveguide with chiral gradient sawtooth metasurface. The physical mechanism of our method is to lift the degenerate dipole eigenmodes through the scattering effect of the chiral surface structure, and then the superposition of them will generate both and order vortices in place. Compared to the existing methods of acoustic vortex production, our design has many merits, such as easy to manufacture and control, the working frequency is broadband, sign of vortex order can be readily flipped. Both the full-wave simulations and experimental measurements validate the existence of the acoustic vortices. The torque effect of the acoustic vortices is also successfully performed by rotating a foam disk as a practical application. Our work opens up a new route for generating acoustic vortex and could have potential significances in microfluidics, acoustic tweezers and ultrasonic communication, etc

Expression of MDR1, HIF-1α and MRP1 in sacral chordoma and chordoma cell line CM-319

<p>Abstract</p> <p>Background</p> <p>Chordoma was a typically slow-growing tumor. The therapeutic approach to chordoma had traditionally relied mainly on surgical therapy. And the main reason for therapeutic failure was resistance to chemotherapy and radiotherapy. However the refractory mechanism was not clear. The aim of this study was to investigate the expression of three genes (<it>MDR1</it>, <it>HIF-1α</it> and <it>MRP1</it>) associated with resistance to chemotherapy and radiotherapy in chordoma and chordoma cell line CM-319.</p> <p>Materials and methods</p> <p>Using immunohistochemical techniques, the expression of MDR1, HIF-1α and MRP1 was investigated in 50 chordoma specimen. Using RT-PCR and Western blot, the expression of MDR1, HIF-1α and MRP1 was investigated in chordoma and chordoma cell line CM-319.</p> <p>Results</p> <p>Expression of MDR1, HIF-1α and MRP1 was observed in 10%, 80% and 74% of all cases, respectively. Expression of MRP1 was correlated with HIF-1α. On the other hand, expression of MDR1 was not correlated with the expression of HIF-1α or MRP1. The expression of HIF-1α and MRP1 was observed, but MDR1 was not observed in chordoma and CM-319.</p> <p>Conclusion</p> <p>Expression of HIF-1α and MRP1 was observed in most chordoma specimen and CM-319 cell line; expression of HIF-1α correlated with MRP1. HIF-1α and MRP1 may play a role in the multidrug resistance of chordoma to chemotherapy.</p

Thermal induced spin-polarized current protected by spin-momentum locking in nanowires

Spin-momentum locking arising from strong spin-orbit coupling is one of the key natures of topological materials. Since charge can induce a spin polarization due to spin-momentum locking, the search for materials that exhibit this feature has become one of the top priorities in the field of spintronics. In this paper, we report the electrical detection of the spin-transport properties of nanowires, using a nonlocal geometry measurement. A clear hysteresis voltage signal, which depends on the relative orientations between the magnetization of the ferromagnetic electrodes and the carrier spin polarization, has been observed. The hysteresis voltage states can be reversed by altering the electron movement direction, providing direct evidence of the spin-momentum locking feature of nanowires and revealing its topological nature. Furthermore, the current-dependent measurement suggests that the charge (spin) current is induced by thermal effect, which utilizes the thermoelectric properties of . Using the thermal effect to control the spin-polarized current protected by spin-momentum locking offers possibilities for small-sized devices based on the topological materials

Axonal Fiber Terminations Concentrate on Gyri

Convoluted cortical folding and neuronal wiring are 2 prominent attributes of the mammalian brain. However, the macroscale intrinsic relationship between these 2 general cross-species attributes, as well as the underlying principles that sculpt the architecture of the cerebral cortex, remains unclear. Here, we show that the axonal fibers connected to gyri are significantly denser than those connected to sulci. In human, chimpanzee, and macaque brains, a dominant fraction of axonal fibers were found to be connected to the gyri. This finding has been replicated in a range of mammalian brains via diffusion tensor imaging and high–angular resolution diffusion imaging. These results may have shed some lights on fundamental mechanisms for development and organization of the cerebral cortex, suggesting that axonal pushing is a mechanism of cortical folding

Efficient numerical methods for dislocation dynamics simulation

Dislocations are line defects in crystals. They are primary carries of crystal plasticity. The direct simulation of dynamics and interactions of dislocations, known as dislocation dynamics, provides a promising tool for investigations of plastic behaviors of crystalline materials. However, for the method of dislocation dynamics to be a practical engineering tool, significant efforts are needed to improve the efficiency of dislocation dynamics methods. In this thesis, we have developed efficient numerical methods for dislocation dynamics simulations. First, we apply new version of fast multipole method to calculate stress field of dislocation ensembles in infinite mediums. Numerical experiments show that for a dislocation ensemble discretized into N dislocation segments, the new version of the FMM is asymptotically O(N) with an optimized prefactor, and very efficient for prescribed accuracy requirements. Second, we derive accurate approximation formulas to compute the contribution to the stress of a curved dislocation segment containing or very close to the target point within the framework of distribution of dislocations in small tubes. Previously in the literature, lots of numerical grid points for accurate calculation of such contribution. Finally, we develop an efficient numerical method that employs the fast multipole accelerated boundary integral equation method to solve the complementary boundary value problem of the elasticity system. The boundary integral equation method reduces the unknowns to those only on the material boundaries. Then the new version of fast multipole method is employed to compute convolution of the Green’s functions and the unknowns in a very efficient way