Study of electron-beam propagation through preionized dense foam plasmas

The transport of an intense electron-beam produced by the Vulcan petawatt laser through dense plasmas has been studied by imaging with high resolution the optical emission due to electron transit through the rear side of coated foam targets. It is observed that the MeV-electron beam undergoes strong filamentation and the filaments organize themselves in a ringlike structure. This behavior has been modeled using particle-in-cell simulations of the laser-plasma interaction as well as of the transport of the electron beam through the preionized plasma. In the simulations the filamentary structures are reproduced and attributed to the Weibel instability.

Towards agent-oriented model-driven architecture

Model Driven Architecture supports the transformation from reusable models to executable software. Business representations, however, cannot be fully and explicitly represented in such models for direct transformation into running systems. Thus, once business needs change, the language abstractions used by MDA (e.g. Object Constraint Language / Action Semantics), being low level, have to be edited directly. We therefore describe an Agent-oriented Model Driven Architecture (AMDA) that uses a set of business models under continuous maintenance by business people, reflecting the current business needs and being associated with adaptive agents that interpret the captured knowledge to behave dynamically. Three contributions of the AMDA approach are identified: 1) to Agent-oriented Software Engineering, a method of building adaptive Multi-Agent Systems; 2) to MDA, a means of abstracting high level business-oriented models to align executable systems with their requirements at runtime; 3) to distributed systems, the interoperability of disparate components and services via the agent abstraction.

A novel structural class of photoswitchable oligonucleotide

Directed Michaelis–Arbuzov reactions of support-bound internucleotide O-benzyl- or O-methyl-phosphite triesters with meta-phenylazobenzylamine or alkane-/glycol-linked a,x-diamines were effected in the presence of iodine. The corresponding tritylated phosphoramidate-linked 11-mers were fully deprotected and released from the support under standard conditions and the fast- and slow-diastereoisomers of both the E- and the Z-meta-phenylazobenzyl-appended oligomers were readily resolved by RP-HPLC. The primary amine-functionalised oligonucleotides were either purified, detritylated and then finally treated with Nhydroxysuccinimidyl carboxylic acid ester derivatives of photoswitchable moieties (Route A) or first derivatised and then subsequently purified and detritylated (Route B). This latter route enabled resolution of fast- and slow-isomers of the trityl-on oligomers bearing novel photoswitchable azopyridine or 9-alkoxyanthracene moieties using RP-HPLC, following which the pure diastereoisomers were detritylated and characterised by MALDI-MS.

Analysis of DNA processing reactions in bacterial conjugation by using suicide oligonucleotides

Protein TrwC is the conjugative relaxase responsible for DNA processing in plasmid R388 bacterial conjugation. TrwC has two catalytic tyrosines, Y18 and Y26, both able to carry out cleavage reactions using unmodified oligonucleotide substrates. Suicide substrates containing a 30-Sphosphorothiolate linkage at the cleavage site displaced TrwC reaction towards covalent adducts and thereby enabled intermediate steps in relaxase reactions to be investigated. Two distinct covalent TrwC–oligonucleotide complexes could be separated from noncovalently bound protein by SDS–PAGE. As observed by mass spectrometry, one complex contained a single, cleaved oligonucleotide bound to Y18, whereas the other contained two cleaved oligonucleotides, bound to Y18 and Y26. Analysis of the cleavage reaction using suicide substrates and Y18F or Y26F mutants showed that efficient Y26 cleavage only occurs after Y18 cleavage. Strand-transfer reactions carried out with the isolated Y18–DNA complex allowed the assignment of specific roles to each tyrosine. Thus, only Y18 was used for initiation. Y26 was specifically used in the second transesterification that leads to strand transfer, thus catalyzing the termination reaction that occurs in the recipient cell.

Prediction and Verification of miRNA Expression in Human and Rat Retinas.

PURPOSE: MicroRNAs (miRNAs) play a global role in regulating gene expression and have important tissue-specific functions. Little is known about their role in the retina. The purpose of this study was to establish the retinal expression of those miRNAs predicted to target genes involved in vision. METHODS: miRNAs potentially targeting important "retinal" genes, as defined by expression pattern and implication in disease, were predicted using a published algorithm (TargetScan; Envisioneering Medical Technologies, St. Louis, MO). The presence of candidate miRNAs in human and rat retinal RNA was assessed by RT-PCR. cDNA levels for each miRNA were determined by quantitative PCR. The ability to discriminate between miRNAs varying by a single nucleotide was assessed. The activity of miR-124 and miR-29 against predicted target sites in Rdh10 and Impdh1 was tested by cotransfection of miRNA mimics and luciferase reporter plasmids. RESULTS: Sixty-seven miRNAs were predicted to target one or more of the 320 retinal genes listed herein. All 11 candidate miRNAs tested were expressed in the retina, including miR-7, miR-124, miR135a, and miR135b. Relative levels of individual miRNAs were similar between rats and humans. The Rdh10 3'UTR, which contains a predicted miR-124 target site, mediated the inhibition of luciferase activity by miR-124 mimics in cell culture. CONCLUSIONS: Many miRNAs likely to regulate genes important for retinal function are present in the retina. Conservation of miRNA retinal expression patterns from rats to humans supports evidence from other tissues that disruption of miRNAs is a likely cause of a range of visual abnormalities.

Performance of a Sequential Reactive Barrier for Bioremediation of Coal Tar Contaminated Groundwater

Following a thorough site investigation, a biological Sequential Reactive Barrier (SEREBAR), designed to remove Polycyclic Aromatic Hydrocarbons (PAHs) and BTEX compounds, was installed at a Former Manufactured Gas Plant (FMGP) site. The novel design of the barrier comprises, in series, an interceptor and six reactive chambers. The first four chambers (2 nonaerated-2 aerated) were filled with sand to encourage microbial colonization. Sorbant Granular Activated Carbon (GAC) was present in the final two chambers in order to remove any recalcitrant compounds. The SEREBAR has been in continuous operation for 2 years at different operational flow rates (ranging from 320 L/d to 4000 L/d, with corresponding residence times in each chamber of 19 days and 1.5 days, respectively). Under low flow rate conditions (320-520 L/d) the majority of contaminant removal (>93%) occurred biotically within the interceptor and the aerated chambers. Under high flow rates (1000-4000 L/d) and following the installation of a new interceptor to prevent passive aeration, the majority of contaminant removal (>80%) again occurred biotically within the aerated chambers. The sorption zone (GAC) proved to be an effective polishing step, removing any remaining contaminants to acceptable concentrations before discharge down-gradient of the SEREBAR (overall removals >95%).