Improvement of dielectric loss of doped Ba0.5Sr0.5TiO3 thin films for tunable microwave devices

Al2O3-Ba0.5Sr0.5TiO3 (Al2O3-BST) thin films, with different Al2O3 contents, were deposited on (100) LaAlO3 substrate by pulsed laser deposition (PLD) technique. The Al2O3-BST films was demosnstrated to be a suitable systems to fabricate ferroelectric thin films with low dielectric loss and higher figure of merit for tunable microwave devices. Pure BST thin films were also fabricated for comparison purpose. The films' structure and morphology were analyzed by X-ray diffractiopn and scanning electron microscopy, respectively; nad showed that the surface roughness for the Al2O3-BST films increased with the Al2O3 content. Apart from that, the broadening in the intensity peak in XRD result indicating the grain size of the Al2O3-BST films reduced with the increasing of Al2O3 dopant. We measured the dielctric properties of Al2O3-BST films with a home-made non-destructive dual resonator method at frequency ~ 7.7 GHZ. The effect of doped Al2O3 into BST thin films significantly reduced the dielectric constant, dielectric loss and tunability compare to pure BST thin film. Our result shows the figure of merit (K), used to compare the films with varied dielectric properties, increased with the Al2O3 content. Therefore Al2O3-BST films show the potential to be exploited in tunable microwave devices.Comment: 8 pages, 4 figures, 1 table. Accepted & tentatively for Feb 15 2004 issue, Journal of Applied Physic

Explaining actual online shopping behavior: evidences from two distinct national cultures

With increased population of online shoppers, research into online shopping behavior is starting to emerge. Much of the literature has used the technology acceptance model, innovation diffusion theory and the theory of planned behavior to study this phenomenon. This has shed light on the behavior of consumers when they shop online. However, prior research has placed little emphasis on cultural differences in online shopping. Despite wide acknowledgements that the online environment is characterized by a high level of uncertainty and an increasing number of international customers, there are only a few studies that describe how cultural differences may impact on the online shopping behavior of consumers. These have focused on intention to transact and not actual purchasing behaviour. The aim of this paper is to extend prior research by integrating national culture into the theory of planned behavior to better understand actual online shopping behaviour across two cultures. National culture dimensions of long-/short-term orientation and individualism/collectivism are found to have significant effects on both intended and actual behaviours

Electric Springs for Reducing Power Imbalance in Three-Phase Power Systems

published_or_final_versio

Chromosomal DNA deletion confers phage resistance to Pseudomonas aeruginosa.

Bacteria develop a broad range of phage resistance mechanisms, such as prevention of phage adsorption and CRISPR/Cas system, to survive phage predation. In this study, Pseudomonas aeruginosa PA1 strain was infected with lytic phage PaP1, and phage-resistant mutants were selected. A high percentage (~30%) of these mutants displayed red pigmentation phenotype (Red mutant). Through comparative genomic analysis, one Red mutant PA1r was found to have a 219.6 kb genomic fragment deletion, which contains two key genes hmgA and galU related to the observed phenotypes. Deletion of hmgA resulted in the accumulation of a red compound homogentisic acid; while A galU mutant is devoid of O-antigen, which is required for phage adsorption. Intriguingly, while the loss of galU conferred phage resistance, it significantly attenuated PA1r in a mouse infection experiment. Our study revealed a novel phage resistance mechanism via chromosomal DNA deletion in P. aeruginosa

The nature of Ho magnetism in multiferroic HoMnO3

Using x-ray resonant magnetic scattering and x-ray magnetic circular dichroism, techniques that are element specific, we have elucidated the role of Ho3+ in multiferroic HoMnO3. In zero field, Ho3+ orders antiferromagnetically with moments aligned along the hexagonal c direction below 40 K, and undergoes a transition to another magnetic structure below 4.5 K. In applied electric fields of up to 1x10^7 V/m, the magnetic structure of Ho3+ remains unchanged.Comment: 4 pages, 3 figures Manuscript accepted for publication in Phys. Rev. Lett. 200

Evolution of normal and superconducting properties of single crystals of Na1−δ_{1-\delta}FeAs upon interaction with environment

Iron-arsenide superconductor Na$_{1-\delta}$FeAs is highly reactive with the environment. Due to the high mobility of Na ions, this reaction affects the entire bulk of the crystals and leads an to effective stoichiometry change. Here we use this effect to study the doping evolution of normal and superconducting properties of \emph{the same} single crystals. Controlled reaction with air increases the superconducting transition temperature, $T_c$, from the initial value of 12 K to 27 K as probed by transport and magnetic measurements. Similar effects are observed in samples reacted with Apiezon N-grease, which slows down the reaction rate and results in more homogeneous samples. In both cases the temperature dependent resistivity, $\rho_a(T)$, shows a dramatic change with exposure time. In freshly prepared samples, $\rho_a(T)$ reveals clear features at the tetragonal-to-orthorhombic ($T_s$ $\approx$ 60 K) and antiferromagnetic ($T_m$=45 K) transitions and superconductivity with onset $T_{c,ons}$=16 K and offset $T_{c,off}$=12 K. The exposed samples show $T-$linear variation of $\rho_a(T)$ above $T_c,ons$=30 K ($T_{c,off}$=26 K), suggesting bulk character of the observed doping evolution and implying the existence of a quantum critical point at the optimal doping. The resistivity for different doping levels is affected below $\sim$200 K suggesting the existence of a characteristic energy scale that terminates the $T-$linear regime, which could be identified with a pseudogap

Broadband Radio Spectral Observations of Solar Eclipse on 2008-08-01 and Implications on the Quiet Sun Atmospheric Model

Based on the joint-observations of the radio broadband spectral emissions of solar eclipse on August 1, 2008 at Jiuquan (total eclipse) and Huairou (partial eclipse) at the frequencies of 2.00 -- 5.60 GHz (Jiuquan), 2.60 -- 3.80 GHZ (Chinese solar broadband radiospectrometer, SBRS/Huairou), and 5.20 -- 7.60 GHz (SBRS/Huairou), the authors assemble a successive series of broadband spectrum with a frequency of 2.60 -- 7.60 GHz to observe the solar eclipse synchronously. This is the first attempt to analyze the solar eclipse radio emission under the two telescopes located at different places with broadband frequencies in the periods of total and partial eclipse. With these analyses, the authors made a new semiempirical model of the coronal plasma density of the quiet Sun and made a comparison with the classic models.Comment: 10 pages, 4 figures, published on Sci. China Ser. G, 2009, Vol.52, page 1765-177

Quantitative phospho-proteomics reveals the Plasmodium merozoite triggers pre-invasion host kinase modification of the red cell cytoskeleton

The invasive blood-stage malaria parasite - the merozoite - induces rapid morphological changes to the target erythrocyte during entry. However, evidence for active molecular changes in the host cell that accompany merozoite invasion is lacking. Here, we use invasion inhibition assays, erythrocyte resealing and high-definition imaging to explore red cell responses during invasion. We show that although merozoite entry does not involve erythrocyte actin reorganisation, it does require ATP to complete the process. Towards dissecting the ATP requirement, we present an in depth quantitative phospho-proteomic analysis of the erythrocyte during each stage of invasion. Specifically, we demonstrate extensive increased phosphorylation of erythrocyte proteins on merozoite attachment, including modification of the cytoskeletal proteins beta-spectrin and PIEZO1. The association with merozoite contact but not active entry demonstrates that parasite-dependent phosphorylation is mediated by host-cell kinase activity. This provides the first evidence that the erythrocyte is stimulated to respond to early invasion events through molecular changes in its membrane architecture.</p

Evolving temporal association rules with genetic algorithms

A novel framework for mining temporal association rules by discovering itemsets with a genetic algorithm is introduced. Metaheuristics have been applied to association rule mining, we show the efficacy of extending this to another variant - temporal association rule mining. Our framework is an enhancement to existing temporal association rule mining methods as it employs a genetic algorithm to simultaneously search the rule space and temporal space. A methodology for validating the ability of the proposed framework isolates target temporal itemsets in synthetic datasets. The Iterative Rule Learning method successfully discovers these targets in datasets with varying levels of difficulty