The ecology of Bacillus thuringiensis on the Phylloplane: colonization from soil, plasmid transfer, and interaction with larvae of Pieris brassicae

Seedlings of clover (Triflorium hybridum) were colonized by Bacillus thuringiensis when spores and seeds were co-inoculated into soil. Both a strain isolated in the vegetative form from the phylloplane of clover, 2810-S-4, and a laboratory strain, HD-1, were able to colonize clover to a density of about 1000 CFU/g leaf when seeds were sown in sterile soil and to a density of about 300 CFU/g leaf in nonsterile soil. A strain lacking the characteristic insecticidal crystal proteins produced a similar level of colonization over a 5-week period as the wild type strain, indicating that crystal production was not a mitigating factor during colonization. A small plasmid, pBC16, was transferred between strains of B. thuringiensis when donor and recipient strains were sprayed in vegetative form onto leaves of clover and pak choi (Brassica campestris var. chinensis). The rate of transfer was about 0.1 transconjugants/recipient and was dependent on the plant species. The levels of B. thuringiensis that naturally colonized leaves of pak choi produced negligible levels of mortality in third instar larvae of Pieris brassicae feeding on the plants. Considerable multiplication occurred in the excreted frass but not in the guts of living insects. Spores in the frass could be a source of recolonization from the soil and be transferred to other plants. These findings illustrate a possible cycle, not dependent on insect pathology, by which B. thuringiensis diversifies and maintains itself in nature.

Entanglement between two superconducting qubits via interaction with nonclassical radiation

We propose a scheme to physically interface superconducting nanocircuits and quantum optics. We address the transfer of quantum information between systems having different physical natures and defined in Hilbert spaces of different dimensions. In particular, we investigate the transfer of the entanglement initially in a nonclassical state of an infinite dimensional system to a pair of superconducting charge qubits. This setup is able to drive an initially separable state of the qubits into an almost pure, highly entangled state suitable for quantum information processing.

Short pulse laser interaction with positive ions

The viability of using beams of molecular ions as a target for strong field fragmentation studies using intense ultra-short laser pulses is demonstrated. In this way the production mechanism for multiply charged ions in strong fields may be elucidated.

The human micro-vascular enclothelial cells in vitro interaction with atomic-nitrogen-doped diamond-like carbon thin films

This paper reports the initial response of atomic nitrogen doped diamond like carbon (DLC) to endothelial cells in vitro. The introduction of nitrogen atoms/molecules to the diamond like carbon structures leads to an atomic structural change favorable to the attachment of human micro-vascular enclothelial cells. Whilst the semi-conductivity induced by nitrogen in DLC is thought to play a part, the increase in the inion-bonded N atoms and N-2 molecules in the atomic doped species (with the exclusion of the charged species) seems to contribute to the improved attachment of human microvascular endothelial cells. The increased endothelial attachment is associated with a lower work function and slightly higher water contact angle in the atomic doped films, where the heavy charged particles are excluded. The films used in the study were synthesized by the RF PECVD technique followed by post deposition doping with nitrogen, and afterwards the films were characterized by XPS, Raman spectroscopy, SIMS and Kelvin probe. The water contact angles were measured, and the counts of the adherent endothelial cells on the samples were carried out. This study is relevant and contributory to improving biocompatibility of surgical implants and prostheses.

Plasma Jets Driven by Ultraintense-Laser Interaction with Thin Foils

Experimental evidence of plasma jets ejected from the rear side of thin solid targets irradiated by ultraintense (> 10(19) W cm(-2)) laser pulses is presented. The jets, detected by transverse interferometric measurements with high spatial and temporal resolutions, show collimated expansion lasting for several hundreds of picoseconds and have substantially steep density gradients at their periphery. The role played by radiation pressure of the laser in the jet formation process is highlighted analytically and by extensive two-dimensional particle-in-cell simulations.

MeV negative ion generation from ultra-intense laser interaction with a water spray

MeV negative oxygen ions are obtained from a water spray target irradiated by high intensity (5 x 10(19) W/cm(2)) and ultrashort (50 fs) laser pulses. Generation of negative ions is ascribed to electron-capture processes that the laser-accelerated high-energy positive ion experiences when it interacts with atoms in the spray. This mechanism implies the existence of a large number of MeV neutral oxygen atoms, which is consistent with indirect experimental evidence. (C) 2011 American Institute of Physics. [doi:10.1063/1.3622664]