Fabrication and electrical characteristics of high-performance ZnO nanorod field-effect transistors

We report on fabrication and electrical characteristics of high-mobility field-effect transistors (FETs) using ZnO nanorods. For FET fabrications, single-crystal ZnO nanorods were prepared using catalyst-free metalorganic vapor phase epitaxy. Although typical ZnO nanorod FETs exhibited good electrical characteristics, with a transconductance of similar to140 nS and a mobility of 75 cm(2)/V s, the device characteristics were significantly improved by coating a polyimide thin layer on the nanorod surface, exhibiting a large turn-ON/OFF ratio of 10(4)-10(5), a high transconductance of 1.9 muS, and high electron mobility above 1000 cm(2)/V s. The role of the polymer coating in the enhancement of the devices is also discussed. (C) 2004 American Institute of Physics.X11333sciescopu

High water availability increases the negative impact of a native hemiparasite on its non-native host

Environmental factors alter the impacts of parasitic plants on their hosts. However, there have been no controlled studies on how water availability modulates stem hemiparasites' effects on hosts. A glasshouse experiment was conducted to investigate the association between the Australian native stem hemiparasite Cassytha pubescens and the introduced host Ulex europaeus under high (HW) and low (LW) water supply. Cassytha pubescens had a significant, negative effect on the total biomass of U. europaeus, which was more severe in HW than LW. Regardless of watering treatment, infection significantly decreased shoot and root biomass, nodule biomass, nodule biomass per unit root biomass, F-v/F-m, and nitrogen concentration of U. europaeus. Host spine sodium concentration significantly increased in response to infection in LW but not HW conditions. Host water potential was significantly higher in HW than in LW, which may have allowed the parasite to maintain higher stomatal conductances in HW. In support of this, the delta C-13 of the parasite was significantly lower in HW than in LW (and significantly higher than the host). C. pubescens also had significantly higher F-v/F-m and 66% higher biomass per unit host in the HW compared with the LW treatment. The data suggest that the enhanced performance of C. pubescens in HW resulted in higher parasite growth rates and thus a larger demand for resources from the host, leading to poorer host performance in HW compared with LW. C. pubescens should more negatively affect U. europaeus growth under wet conditions rather than under dry conditions in the field

An Analytic Theory for the Orbits of Circumbinary Planets

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On the Migration of the Galilean Satellites

Topic 67: Solar System: GeneralPoster PresentationThe migration of the Galilean satellites during formation due to interactions with the circumjovian disk is studied. In the gas-starved disk model proposed by Canup & Ward (2002, 2006), the Galilean satellites are the last generation of satellites formed in the circumjovian disk, and their migration and accretion depend on disk viscosity, opacity and material inflow rate. Relaxing the migration to non-isothermal type I regime (e.g. Paardekooper et al. 2010) allows the satellites to migrate outwards in optically-thick disk regions, and there is a position where the disk torque is zero. This contrasts with 278the results in the isothermal type I regime in which the satellites always migrate inwards. Including the effect of temperature dependence of disk opacity can produce multiple zero-torque positions in the circumjovian disk. As the disk depletes, these zero-torque positions shift towards Jupiter. Under this setting, a satellite at a range of initial locations will eventually converge to near one of these zero-torque positions, but stays at a fixed distance away (with the distance depending on satellite mass), so that it is moving inwards with the zero-torque position. However, if the satellite starts at a large-enough distance from Jupiter, it may move in a trajectory that does not converge to any of these zero-torque positions and survives to the end. The effect of satellite growth and variation of disk parameters on satellite migration will be discussed. The migration in multiple satellite system, and how these settings can possibly result in the Laplace resonance among the Galilean satellites, will be also investigated. This work is supported in part by Hong Kong RGC grant HKU 7030/11Ppublished_or_final_versio

Local P T symmetry violates the no-signaling principle

Bender et al. [Phys. Rev. Lett. 80, 5243 (1998)] have developed PT-symmetric quantum theory as an extension of quantum theory to non-Hermitian Hamiltonians. We show that when this model has a local PT symmetry acting on composite systems, it violates the nonsignaling principle of relativity. Since the case of global PT symmetry is known to reduce to standard quantum mechanics A. Mostafazadeh [J. Math. Phys. 43, 205 (2001)], this shows that the PT-symmetric theory is either a trivial extension or likely false as a fundamental theory. © 2014 American Physical Society

Magnetic Coupling in the Disks around Young Gas Giant Planets

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EMI due to electric field coupling on PCB

In switching converter circuits, EM noise can couple between PCB traces through the effect of electric field coupling. An experiment using a flyback converter verifies the severity of this effect. Further experiments and field plots confirm that a good PCB layout can significantly reduce conducted EMI due to unintentional E-field coupling.published_or_final_versio

Passive PT -symmetric couplers without complex optical potentials

© 2015 American Physical Society. In addition to the implementation of parity-time-(PT-) symmetric optical systems by carefully and actively controlling the gain and loss, we show that a 2×2 PT-symmetric Hamiltonian has a unitarily equivalent representation without complex optical potentials in the resulting optical coupler. Through the Naimark dilation in operator algebra, passive PT-symmetric couplers can thus be implemented with a refractive index of real values and asymmetric coupling coefficients. This opens up the possibility to implement general PT-symmetric systems with state-of-the-art asymmetric slab waveguides, dissimilar optical fibers, or cavities with chiral mirrors

Magnetic nanoparticle density mapping from the magnetically induced displacement data: a simulation study

<p>Abstract</p> <p>Background</p> <p>Magnetic nanoparticles are gaining great roles in biomedical applications as targeted drug delivery agents or targeted imaging contrast agents. In the magnetic nanoparticle applications, quantification of the nanoparticle density deposited in a specified region is of great importance for evaluating the delivery of the drugs or the contrast agents to the targeted tissues. We introduce a method for estimating the nanoparticle density from the displacement of tissues caused by the external magnetic field.</p> <p>Methods</p> <p>We can exert magnetic force to the magnetic nanoparticles residing in a living subject by applying magnetic gradient field to them. The nanoparticles under the external magnetic field then exert force to the nearby tissues causing displacement of the tissues. The displacement field induced by the nanoparticles under the external magnetic field is governed by the Navier's equation. We use an approximation method to get the inverse solution of the Navier's equation which represents the magnetic nanoparticle density map when the magnetic nanoparticles are mechanically coupled with the surrounding tissues. To produce the external magnetic field inside a living subject, we propose a coil configuration, the Helmholtz and Maxwell coil pair, that is capable of generating uniform magnetic gradient field. We have estimated the coil currents that can induce measurable displacement in soft tissues through finite element method (FEM) analysis.</p> <p>Results</p> <p>From the displacement data obtained from FEM analysis of a soft-tissue-mimicking phantom, we have calculated nanoparticle density maps. We obtained the magnetic nanoparticle density maps by approximating the Navier's equation to the Laplacian of the displacement field. The calculated density maps match well to the original density maps, but with some halo artifacts around the high density area. To induce measurable displacement in the living tissues with the proposed coil configuration, we need to apply the coil currents as big as 10⁴A.</p> <p>Conclusions</p> <p>We can obtain magnetic nanoparticle maps from the magnetically induced displacement data by approximating the Navier's equation under the assumption of uniform-gradient of the external magnetic field. However, developing a coil driving system with the capacity of up to 10⁴A should be a great technical challenge.</p