Rice is the principal food for over half of the population of the world. With its genome size of 430 megabase pairs (Mb), the cultivated rice species Oryza sativa is a model plant for genome research. Here we report the sequence analysis of chromosome 4 of O. sativa, one of the first two rice chromosomes to be sequenced completely. The finished sequence spans 34.6 Mb and represents 97.3% of the chromosome. In addition, we report the longest known sequence for a plant centromere, a completely sequenced contig of 1.16 Mb corresponding to the centromeric region of chromosome 4. We predict 4,658 protein coding genes and 70 transfer RNA genes. A total of 1,681 predicted genes match available unique rice expressed sequence tags. Transposable elements have a pronounced bias towards the euchromatic regions, indicating a close correlation of their distributions to genes along the chromosome. Comparative genome analysis between cultivated rice subspecies shows that there is an overall syntenic relationship between the chromosomes and divergence at the level of single-nucleotide polymorphisms and insertions and deletions. By contrast, there is little conservation in gene order between rice and Arabidopsis.

Streamer-to-filament transition is a general feature of nanosecond discharges at elevated pressure. The transition is observed in different discharges by different groups: in the nanosecond surface dielectric barrier discharges (nSDBDs) in a single shot regime at high pressure (2-15 bar), in the point-to-point or point-to-plane open electrodes discharges at high repetitive frequency (so-called nanosecond repetitive pulsed discharges, NRPDs) at atmospherics pressure. The present paper contains experimental analysis of plasma properties in the filamentary nSDBD: the electrical current, the specific deposited energy, the electron density and the electron temperature were measured for a wide range of pressures and voltages. A model explaining plasma properties in filamentary nanosecond discharges and the role of excited species in streamer-to-filament transition is suggested and discussed.

Streamer-to-filament transition is a general feature of high pressure high voltage nanosecond surface dielectric barrier discharges (nSDBDs) for mixtures containing molecular gases. The transition is observed at high pressures and voltages in a single-shot experiment a few nanoseconds after the start of the discharge. A set of experimental results comparing streamer-to-filament transition and properties of plasma in the filaments for the identical high voltage pulses of negative and positive polarity is presented. The transition curves in voltage-pressure coordinates are obtained for N 2 :O 2 mixtures with different content of molecular oxygen, from 0 to 20%, at the pressure range 1-12 bar. Continuous optical spectra are compared for both polarities in 6 bar synthetic air. Electron density is calculated from Stark broadening of H α line at λ = 656.5 nm in the discharge and in early afterglow, 40 nanoseconds after the end of the high voltage pulse. Hydrodynamic perturbations are measured using schlieren imaging in 1-6 bar air for streamer and filamentary mode for both polarities. The review of common and distinctive features of the filamentary single-shot nSDBD for two polarities of the applied pulse is provided.

A control strategy of combining H control and feedback linearization was applied to the model of a highly nonlinear, three Degrees-Of-Freedom (DOF) electromagnetic actuator, which was recently designed for non-contact suspension of a large payload. The new electromagnetic actuator has the advantage of passive gravity compensation based on permanent magnets with low stiffness and high force density. But the nonlinearity is so high that the stability status along each DOF changes while the translator is traveling within the working range. Feedback linearization method was used to compensate the nonlinearity, a stabilizing controller was employed to eliminate the slow-varying calculation error of the passive force, and an H controller was designed for vibration isolation. Simulation results show that the proposed control strategy has robust vibration isolation performance within a working range in which the relation between the magnetic force and the relative position is highly nonlinear.

The fine structure of a streamer–to–filament transition in a single–shot high–voltage nanosecond surface dielectric barrier discharge (nSDBD) in molecular nitrogen at pressure $P = 6$~bar was studied with the help of ICCD microimaging. An intermediate discharge structure, existing for only a few nanoseconds, was observed in the time interval between two discharge modes: streamer discharge, with a typical electron density of $n_e \sim 10^{15}$~cm$^{-3}$, and filamentary discharge, with $n_e \sim 10^{19}$~cm$^{-3}$. The structure was observed for both polarities of the high–voltage electrode. The structure can be briefly described as a stochastic appearance of thin channels propagating a bit faster than the main ionization front of merged surface streamers, transforming in a few nanoseconds in a bi–directional ionization wave. One wave, which we associate with a feather–like structure in optical emission, propagates further away from the high–voltage electrode, and another, a backward wave of emission, propagates back towards the edge of the high–voltage electrode. When the backward wave of emission almost reaches the high–voltage electrode, the filament appears. Plasma properties of the observed structure were studied to better understand the nature of a streamer–to–filament transition. Theoretical analysis suggests that the instability of a flat front of ionization wave (Laplacian instability) triggers the streamer–to–filament transition, and that a surface stem (a tiny region with enhanced electron density) should be in the origin of the bi-directional ionization wave.

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This work describes the characterization of an optical pulse-slicer for performing electric field measurements using the Electric Field Induced Second Harmonic generation (or E-FISH) method. This laser-based diagnostic generally favors ultrashort (sub-nanosecond) pulses, given their intrinsically higher intensities and superior measurement time resolution. However, such laser systems can often prove inaccessible due to their high costs. Our response to this problem is to develop a Pockels-cell-based pulse slicing scheme, compatible with the more affordable and ubiquitous class of nanosecond laser sources. Using such a slicer, we demonstrate the ability to slice a 35 mJ, 20 ns (FWHM), 1064 nm pulse from a conventional Nd:YAG laser down to about 3 ns (FWHM) with an energy of 2 mJ. These shorter pulses are in turn used to make electric field measurements in an electrostatic field (at 5 bar) using E-FISH. Measurements performed with these sliced pulses not only have the expected benefit of improving the time resolution of the field measurement, but also reduce the possibility of laser-plasma interactions due to the lower laser pulse energy required. The current pulse slicer incorporates an off-optimum design Pockels cell, which limits the minimum pulse width and maximum energy that may be realized. It is anticipated that higher energies and a reduction in the pulse width to around 100 ps may be achieved with further optimization, and could present a cost-effective approach to extending the applicability of the E-FISH method.

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