We report a size dependence of Young's modulus in [0001] oriented ZnO nanowires (NWs) with diameters ranging from 17 to 550 nm for the first time. The measured modulus for NWs with diameters smaller than about 120 nm is increasing dramatically with the decreasing diameters, and is significantly higher than that of the larger ones whose modulus tends to that of bulk ZnO. A core-shell composite NW model in terms of the surface stiffening effect correlated with significant bond length contractions occurred near the {1010} free surfaces (which extend several layers deep into the bulk and fade off slowly) is proposed to explore the origin of the size dependence, and present experimental result is well explained. Furthermore, it is possible to estimate the size-related elastic properties of GaN nanotubes and relative nanostructures by using this model.
The magnetic field effects on excitons in an InAs nano-ring are studied theoretically. By numerically diagonalizing the effective-mass Hamiltonian of the problem, which can be separated into terms in centre-of-mass and relative coordinates, we calculate the low-lying exciton energy levels and oscillator strengths as a function of the width of the ring and the strength of the external magnetic field. The analytical results are obtained for a narrow-width nano-ring in which the radial motion is the fastest one and adiabatically decoupled from the azimuthal motions. It is shown that in the presence of Coulomb correlation, the so called Aharonov-Bohm effect of excitons exists in a finite (but small) width nano-ring. However, when the ring width becomes large, the non-simply-connected geometry of nano-rings is destroyed and in turn yields the suppression of Aharonov-Bohm effect. The conditional probability distribution calculated for the low-lying exction states allows identification of the presence of Aharonov-Bohm effect. The linear optical susceptibility is also calculated as a function of the magnetic field, to be confronted with the future measurements of optical emission experiments on InAs nano-rings.
The fracture strain, strength, and flexibility of ZnO nanowires (NWs) with a large range of diameters (85–542nm) are investigated at a quantitative level. Large strains up to 4%–7% have been obtained before the final elastic fracture, corresponding to fracture strengths close to the theoretical strength. The flexibility of a NW is discussed quantitatively in terms of the diameter and fracture strain. The fundamental mechanisms responsible for the observed exceptional properties are discussed.
Abstract. Long non-coding RNAs (lncRNAs) have recently emerged as a major class of regulatory molecules involved in a broad range of biological processes and complex diseases. Our aim was to identify important lncRNAs that might play an important role in contributing to glioblastoma (GBM) pathogenesis by conducting lncRNA and mRNA profile comparison between GBM and normal brain tissue. The differentially expressed lncRNA and mRNA profiles of the tissue between GBM patient and age-matched donor without GBM diseases were analyzed using microarrays. We propose a novel model for the identification of lncRNA-mRNA targeting relationships that combine the potential targets of the differentially expressed lncRNAs with the differentially expressed mRNA abundance data. Bioinformatic analysis of the predicted target genes (gene ontology, pathway and network analysis) was performed for further research. The lncRNA microarray reveals differentially expressed lncRNAs between GBM and normal brain tissues. In the GBM group, 654 lncRNAs were upregulated and 654 were downregulated (fold change ≥4.0 or ≤0.25, P<0.01). We found 104 matched lncRNAmRNA pairs for 91 differentially expressed lncRNAs and 84 differentially expressed genes. Target gene-related pathway analysis showed significant changes in PPAR pathways in the GBM group compared with the normal brain group (P<0.05).
Ultra-broad
spectral detection is critical for several technological
applications in imaging, sensing, spectroscopy, and communication.
Carbon nanotube (CNT) films are a promising material for ultra-broadband
photodetectors because their absorption spectra cover the entire ultraviolet
to the terahertz range. However, because of the high binding energy
of excitons, photodetectors based on CNT films always require a strong
electric field, asymmetric electrical contacts, or hybrid structures
with other materials. Here, we report an ultra-broadband bolometric
photodetector based on a suspended CNT film. With an abundant distribution
of tube diameters and an appropriate morphology (spider web-like),
the CNT films display a strong absorption spectrum from the ultraviolet
up to the terahertz region. Under illumination, heat generated from
the electron–photon interaction dominates the photoresponse
of our devices. For small changes in temperature, the photocurrent
shows a convincing linear dependence with the absorbed light’s
power across 3 orders of magnitude. When the channel length is reduced
to 100 μm, the device demonstrates a high performance with an
ultraviolet responsivity of up to 0.58 A/W with a bias voltage of
0.2 V and a short response time of ∼150 μs in vacuum,
which is better than that of many other photodetectors based on CNTs.
Moreover, this performance could be further enhanced by optimization.
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