A study of carbon-nanotube-based nanoelectromechanical resonators tuned by shear strain

This paper has investigated, using a classical molecular dynamics simulation method based on the Tersoff-Brenner potential, the resonance-frequency changes of single-walled carbon-nanotube resonators originating from the purely mechanical response of single-walled carbon nanotubes. The tension decreased with increasing rotation angle, so the resonance frequencies could be changed by controlling the rotation angles of the single-walled carbon nanotubes. The resonance frequencies decreased with increasing angle, and when the rotation angle was greater than 60°, the changes were marked. For nanotubes of similar length, the bandwidth for the (3, 3) single-walled carbon nanotube was higher than for the (5, 0) single-walled carbon nanotube. Because properties arising from the shear-strain-induced tension response can affect the electromechanical behavior of carbon nanotubes, the shear-strain-induced tension response should be given serious consideration in the application of embedded carbon nanotubes in nanoelectromechanical systems.     

Enhanced carrier transport along edges of graphene devices

The relation between macroscopic charge transport properties and microscopic carrier distribution is one of the central issues in the physics and future applications of graphene devices (GDs). We find strong conductance enhancement at the edges of GDs using scanning gate microscopy. This result is explained by our theoretical model of the opening of an additional conduction channel localized at the edges by depleting accumulated charge by the tip.     

NMR studies of artificial double-crossover DNA tiles

This report documents the design and characterization of DNA molecular nanoarchitectures consisting of artificial double crossover DNA tiles with different geometry and chemistry. The Structural characterization of the unit tiles, including normal, biotinylated and hairpin loop structures, are morphologically studied by atomic force microscopy. The specific proton resonance of the individual tiles and their intra/inter nucleotide relationships are verified by proton nuclear magnetic resonance spectroscopy and 2-dimensional correlation spectral studies, respectively. Significant up-field and down-field shifts in the resonance signals of the individual residues at various temperatures are discussed. The results suggest that with artificially designed DNA tiles it is feasible to obtain structural information of the relative base sequences. These tiles were later fabricated into 2D DNA lattice structures for specific applications such as protein arrangement by biotinylated bulged loops or pattern generation using a hairpin structure.     

Replication of a thin polydimethylsiloxane stamp and its application to dual-nanoimprint lithography for 3D hybrid nano/micropatterns

This paper presents the fabrication of a thin and flexible polydimethylsiloxane (PDMS) stamp with a thickness of a few tens of um and its application to nanoimprint lithography (NIL). The PDMS material generally has a low elastic modulus and high adhesive characteristics. Therefore, after being treated, the thin PDMS stamp is easily deformed and torn, adhering to itself and other materials. This paper introduces the use of a metal ring around the flange of a thin PDMS stamp to assist with the handling of this material. A PDMS stamp with a motheye pattern in nanometer scale was inserted between a substrate and a microstamp with concave patterns in micrometer scale. Subsequently, three-dimensional (3D) hybrid nano/micropatterns were fabricated by pressing these two stamps and curing the resist. The fabricated hybrid patterns were measured and verified in both the microscale and nanoscale. The process, termed "dual NIL," can be applied to the fabrication of optical components or bio-sensors that require repetitive nanopatterns on micropatterns.     

Evaluation of multi-layered graphene surface plasmon resonance-based transmission type fiber optic sensor

Graphene is a zero band-gap semi-metal with remarkable electromagnetic and mechanical characteristics. This study is the first ever attempt to use graphene in the surface plasmon resonance (SPR) sensor as replacement material for gold/silver. Graphene, comprised of a single atomic layer of carbon, is a purely two-dimensional material and it is an ideal candidate for use as a biosensor because of its high surface-to-volume ratio. This sensor is based on the resonance occasion of the surface plasmon wave (SPW) according to the dielectric constants of each metal film and detected material in gas or aqueous phase. Graphene in the SPR sensor is expected to enlarge the range of analyte to bio-aerosols based on the superior electromagnetic properties of graphene. In this study, a SPR-based fiber optic sensor coated with multi-layered graphene is described. The multi-layered graphene film synthesized by chemical vapor deposition (CVD) on Ni substrate was transferred on the sensing region of an optical fiber. The graphene coated SPR sensor is used to analyze the interaction between structured DNA biotin and Streptavidin is analyzed. Transmitted light after passing through the sensing region is measured by a spectrometer and multimeter. As the light source, blue light which of 450 to 460 nm in wavelength was used. We observed the SPR phenomena in the sensor and show the contrary trends between bare fiber and graphene coated fiber. The fabricated graphene based fiber optic sensor shows excellent detection sensitivity of the interaction between structured DNA and Streptavidin.     

A novel method for large area graphene transfer on the polymer optical fiber

We develop two simple methods-the dip coat stamping and lift-off methods-to transfer large area, high quality graphene films onto the top and side faces of the polymer optical fiber. The graphene films can be synthesized using chemical vapor deposition method on large Cu foils. After synthesis, the graphene films are characterized by scanning electron microscopy, atomic force microscopy and Raman spectroscopy. The polymer optical fiber probe with the transferred graphene film can be used as a chemical sensor for the detection of various organic aerosols.     

从化学角度探讨载重轮胎的爆破和爆炸

加拿大魁北克省职业健康及安全委员会（Commission de la santet de la scuritdutravail,CSST）网站上的文献表明,在魁北克地区,1990～2004年期间,每3年就有2起死亡事故可直接归因于载重轮胎爆破和爆炸。CSST中央和区域数据库中有更多的与轮胎爆破和爆炸有关的突发事故的信息。在有关这些事故的文献中可以发现一些证据,如OTRACO公司提供的有关在1981～2001年期间发生的18起工程机械轮胎爆炸的不完全列表。     

Physical/chemical properties of tin oxide thin film transistors prepared using plasma-enhanced atomic layer deposition

Thin film transistors (TFTs) with tin oxide films as the channel layer were fabricated by means of plasma enhanced atomic layer deposition (PE-ALD). The as-deposited tin oxide films show n-type conductivity and a nano-crystalline structure of SnO₂. Notwithstanding the relatively low deposition temperatures of 70, 100, and 130 °C, the bottom gate tin oxide TFTs show an on/off drain current ratio of 10⁶ while the device mobility values were increased from 2.31 cm²/V s to 6.24 cm²/V s upon increasing the deposition temperature of the tin oxide films.     

Long memory retention time and high contrast ratio in a tristate liquid crystal display device

We propose a method to obtain long memory retention time and high contrast ratio in a tristate liquid crystal display device. The proposed device has three unique liquid crystal (LC) states that are known as splay, π twist, and bend, with different operating schemes for the two modes of operation, which are the memory (M) mode or dynamic (D) mode. A form of selective vertical or horizontal switching changes the optically compensated π twist LC as a common black state in both the M and D modes into a bend LC state for the D mode or into the splay LC state for the M mode, respectively.     

On the capacity of Rayleigh fading cooperative systems under adaptive transmission

In this letter, the use of adaptive source transmission with amplify-and-forward relaying is proposed. Three different adaptive techniques are considered: (i) optimal simultaneous power and rate adaptation; (ii) constant power with optimal rate adaptation; (iii) channel inversion with fixed rate. The capacity upper bounds of these adaptive protocols are derived for the amplify-and-forward cooperative system over both independent and identically distributed (i.i.d.) Rayleigh fading and non-i.i.d. Rayleigh fading environments. The capacity analysis is based on an upper bound on the effective received signal-to-noise ratio (SNR). The tightness of the upper bound is validated by the use of a lower bound and by Monte Carlo simulation. It is shown that at high SNR the optimal simultaneous power and rate adaptation and the optimal rate adaptation with constant power provide roughly the same capacity. Channel inversion is shown to suffer from a deterioration in capacity relative to the other adaptive techniques.