2,772 research outputs found

    Reconstruction of plasma density profiles by measuring spectra of radiation emitted from oscillating plasma dipoles

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    We suggest a new method for characterising non-uniform density distributions of plasma by measuring the spectra of radiation emitted from a localised plasma dipole oscillator excited by colliding electromagnetic pulses. The density distribution can be determined by scanning the collision point in space. Two-dimensional particle-in-cell simulations demonstrate the reconstruction of linear and nonlinear density profiles corresponding to laser-produced plasma. The method can be applied to a wide range of plasma, including fusion and low temperature plasmas. It overcomes many of the disadvantages of existing methods that only yield average densities along the path of probe pulses, such as interferometry and spectroscopy

    Cyanidiophyceae in Iceland: Plastid rbcL gene elucidates origin and dispersal of extremophilic Galdieria sulphuraria and G. maxima (Galdieriaceae, Rhodophyta)

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    The Cyanidiophyceae are a group of unicellular organisms that diverged from ancestral red algae around 1.3 billion years ago. Present-day species are restricted to hot springs and geothermal habitats from around the world. Because of discontinuous geothermal environments, the distribution patterns and dispersal modes of the cyanidiophycean species are poorly understood. Iceland is the third largest island in the Atlantic Ocean and has intense underground volcanic activity that generates broad hydrothermal areas with different ecological conditions that are excellent for thermoacidophilic microfloral development. We analyzed populations to address the Icelandic cyanidiophycean biodiversity and dispersal. A global rbcL phylogeny showed two main populations inhabiting Iceland, Galdieria sulphuraria and G. maxima. Their areas of distribution are not completely superimposed because they coexisted only in New Zealand, Kamchatka (Russia), Japan, and Iceland. Because of the strong monophyly of Icelandic species with Japanese and Russian species, we hypothesized an origin and dispersion of Icelandic G. suphuraria and G. maxima from northeastern Asia. On the basis of network analysis of rbcL haplotypes, it is likely that the southwestern region of Iceland is the diversity center of both G. sulphuraria and G. maxima

    CORRELATION BETWEEN SUPERHEATED LIQUID FRAGILITY AND ONSET TEMPERATURE OF CRYSTALLIZATION FOR Al-BASED AMORPHOUS ALLOYS

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    Amorphous alloys or metallic glasses have attracted significant interest in the materials science and engineering communities due to their unique physical, mechanical, and chemical properties. The viscous flow of amorphous alloys exhibiting high strain rate sensitivity and homogeneous deformation is considered to be an important characteristic in thermoplastic forming processes performed within the supercooled liquid region because it allows superplastic-like deformation behavior. Here, the correlation between the superheated liquid fragility, and the onset temperature of crystallization for Al-based alloys, is investigated. The activation energy for viscous flow of the liquid is also investigated. There is a negative correlation between the parameter of superheated liquid fragility and the onset temperature of crystallization in the same Al-based alloy system. The activation energy decreases as the onset temperature of crystallization increases. This indicates that the stability of a superheated liquid can affect the thermal stability of the amorphous alloy. It also means that a liquid with a large superheated liquid fragility, when rapidly solidified, forms an amorphous alloy with a low thermal stability.1111Ysciescopu

    Functional features of an ssi signal of plasmid pGKV21 in Escherichia coli

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    A single-strand initiation (ssi) signal was detected on the Lactococcus lactis plasmid pGKV21 containing the replicon of pWV01 by its ability to complement the poor growth of an M13 phage derivative (M13??lac182) lacking the complementary-strand origin in Escherichia coli. This ssi signal was situated at the 229-nucleotide (nt) DdeI-DraI fragment and located within the 109 nt upstream of the nick site of the putative plus origin. SSI activity is orientation specific with respect to the direction of replication. We constructed an ssi signal-deleted plasmid and then examined the effects of the ssi signal on the conversion of the single-stranded replication intermediate to double-stranded plasmid DNA in E. coli. The plasmid lacking an ssi signal accumulated much more plasmid single-stranded DNA than the wild-type plasmid did. Moreover, deletion of this region caused a great reduction in plasmid copy number or plasmid maintenance. These results suggest that in E. coli, this ssi signal directs its lagging-strand synthesis as a minus origin of plasmid pGKV21. Primer RNA synthesis in vitro suggests that E. coli RNA polymerase directly recognizes the 229-nt ssi signal and synthesizes primer RNA dependent on the presence of E. coli single-stranded DNA binding (SSB) protein. This region contains two stem-loop structures, stem-loop I and stem-loop II. Deletion of stem-loop I portion results in loss of priming activity by E. coli RNA polymerase, suggesting that stem-loop I portion is essential for priming by E. coli RNA polymerase on the SSB-coated single-stranded DNA template.open5

    Seed-layer mediated orientation evolution in dielectric Bi-Zn-Ti-Nb-O thin films

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    Highly (hhh) -oriented pyrochlore Bi-Zn-Ti-Nb-O (BZTN) thin films were fabricated via metal-organic decomposition using orientation template layers. The preferred orientation was ascribed to the interfacial layer, the lattice parameter of which is similar to BZTN. High-resolution transmission electron microscopy supported that the interfacial layer consists of Bi and Pt. The (hhh) -oriented thin films exhibited a highly insulating nature enabling feasible applications in electronic devices, particularly voltage tunable application. The BZTN thin films did not show any apparent dielectric anisotropy and the slightly enhanced dielectric properties were discussed in connection to the internal stress and the grain boundary effect. © 2007 American Institute of Physics

    High frequency plant regeneration from mature seedderived callus of Italian ryegrass (Lolium multiflorum) cultivars

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    In the present study, we have developed a high-frequency plant regeneration system for Italian ryegrass via callus culture using mature seeds as explants. Optimal embryogenic callus induction was found to occur in MS medium containing 5 mg l-1 2,4-D, 0.5 mg l-1 BA, 500 mg l-1 L-proline, 1 g l-1 casein hydrolysate, 30 g l-1 sucrose, 7 mg l-1 AgNO3, 2 mg l-1 CuSO4 and solidified with 3 g l-1 Gelrite. The highest regeneration rate was obtained in MS medium containing 1 mg l-1 2,4-D, 5 mg l-1 BA, 500 mg l-1 L-proline, 1 g l-1 casein hydrolysate, 1 mg l-1 thiamine-HCl, 30 g l-1 sucrose, 7 mg l-1 AgNO3, 2 mg l-1 CuSO4 and solidified with 3 g l-1 Gelrite. By using the most effective treatment determined for each parameter, the highest rates of embryogenic callus formation (48.9%) and regeneration (47.6%) were obtained with the Hwasan 101 cultivar. The overall plant regeneration rates of the examined cultivars ranged from 7.5 to 23.2%. Thus, optimization of regeneration frequency using mature seeds as explant material may offer a simple and efficient protocol for Italian ryegrass that may improve molecular breeding of this species

    Enhanced efficiency for better wastewater sludge hydrolysis conversion through ultrasonic hydrolytic pretreatment

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    © 2016 Taiwan Institute of Chemical Engineers The major requirements for accelerating the process of anaerobic digestion and energy production are breaking the structure of waste activated sludge (WAS), and transforming it into a soluble form suitable for biodegradation. This work investigated and analysed a novel bench-scale ultrasonic system for WAS disruption and hydrolysis using ultrasonic homogenization. Different commercial sonoreactors were used at low frequencies under a variety of operating conditions (intensity, density, power, sonication time, and total suspended solids) to evaluate the effects of the equipment on sludge hydrolysis and to generate new insights into the empirical models and mechanisms applicable to the real-world processing of wastewater sludge. A relationship was established between the operating parameters and the experimental data. Results indicated an increase in sonication time or ultrasonic intensity correlated with improved sludge hydrolysis rates, sludge temperature, and reduction rate of volatile solids (33.51%). It also emerged that ultrasonication could effectively accelerate WAS hydrolysis to achieve disintegration within 5–10 min, depending on the ultrasonic intensity. This study also determined multiple alternative parameters to increase the efficiency of sludge treatment and organic matter reduction, and establish the practicality of applying ultrasonics to wastewater sludge pretreatment

    Electrical conductivity and electromagnetic interference shielding of multiwalled carbon nanotube composites containing Fe catalyst

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    Thin and flexible composite films of raw or purified multiwalled carbon nanotube (MWCNT) with various mass fractions and poly(methylmethacrylate) (PMMA) were synthesized for electromagnetic interference (EMI) shielding material. From scanning electron microscopy and high-resolution transmission electron microscopy photographs, we observed the formation of a conducting network through MWCNTs in an insulating PMMA matrix and the existence of an Fe catalyst in MWCNTs. The dc conductivity (sigma(dc)) of the systems increased with increasing MWCNT mass fraction, showing typical percolation behavior. The measured EMI shielding efficiency (SE) of MWCNT-PMMA composites by using the extended ASTM D4935-99 method (50 MHz-13.5 GHz) increased with increasing MWCNT mass fraction as sigma(dc). The highest EMI SE for raw MWCNT-PMMA composites was similar to27 dB, indicating commercial use for far-field EMI shielding. The contribution of absorption to total EMI SE of the systems is larger than that of reflection. Based on magnetic permeability, we suggest raw MWCNTs and their composites can be used for near-field EMI shielding.open28629

    Molecular and genetic characterization of OSH6 (Oryza sativa Homeobox 6) using dissociation (Ds) insertion mutant rice

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    Genetic studies of dissociation (Ds) insertion mutant rice plants indicated that ectopic expression of truncated OSH6 (Oryza sativa Homeobox 6) mRNA may be responsible for the mutant phenotype of knotted leaf formation at the peduncle. Additionally, ectopic expression of truncated OSH6 mRNA in the OSH6-Ds mutant plant led to alteration of other homeobox genes including OSH15 in leaf tissues. The OSH6-Ds mutant plant exhibited altered expression of more than 118 genes on a 22K rice microarray in comparison with wild type plants. Of these genes, 20 were up- or down-regulated in both OSH6-Ds and OSH6-overexpressing (OSH6-35S) plants. Especially, OsDof3 was not expressed in floral organs, but was present in the panicles of both OSH6-Ds and OSH6-35S plants. It is assumed that truncated OSH6 transcript might be actively involved in the gene expression during organ development. The genetic relationship between OSH6-Ds and OSH15 suggested that the formation of the extra leaf is independent of OSH6-Ds or OSH15 expression. These results suggest that truncated OSH6 mRNA influences lateral organ growth and development by regulating the expression of specific gene groups.Key words: Oryza sativa Homeobox 6 (OSH6) genes, Ds insertion lines, OSH15 mutant
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