Photon Production from the Vacuum Close to the Superradiant Transition: Linking the Dynamical Casimir Effect to the Kibble-Zurek Mechanism

The dynamical Casimir effect (DCE) predicts the generation of photons from the vacuum due to the parametric amplification of the quantum fluctuations of an electromagnetic field. The verification of such an effect is still elusive in optical systems due to the very demanding requirements of its experimental implementation. We show that an ensemble of two-level atoms collectively coupled to the electromagnetic field of a cavity, driven at low frequencies and close to a quantum phase transition, stimulates the production of photons from the vacuum. This paves the way to an effective simulation of the DCE through a mechanism that has recently found experimental demonstration. The spectral properties of the emitted radiation reflect the critical nature of the system and allow us to link the detection of the DCE to the Kibble-Zurek mechanism for the production of defects when crossing a continuous phase transition.

Molecular Dynamics of HIV1-Integrase in Complex with 93del - A Structural Perspective on the Mechanism of Inhibition

HIV1 integrase is an important target for the antiviral therapy. Guanine-rich quadruplex, such as 93del, have been shown to be potent inhibitors of this enzyme and thus representing a new class of antiviral agents. Although X-ray and NMR structures of HIV1 integrase and 93del have been reported, there is no structural information of the complex and the mechanism of inhibition still remains unexplored. A number of computational methods including automated protein-DNA docking and molecular dynamics simulation in explicit solvent were used to model the binding of 93del to HIV1 integrase. Analysis of the dynamic behaviour of the complex using principal components analysis and elastic network modelling techniques allow us to understand how the binding of 93del aptamer and its interactions with key residues affect the intrinsic motions of the catalytic loops by stabilising them in catalytically inactive conformations. Such insights into the structural mechanism of inhibition can aid in improving the design of anti-HIV aptamers.

Design of a deployment rotation mechanism for microsatellite

Solar array rotation mechanism provides a hinged joint between the solar panel and satellite body, smooth rota-tion of the solar array into deployed position and its fixation in this position. After unlocking of solar panel (while in orbit), rotation bracket turns towards ready-to-work position under the action of driving spring. During deployment, once reached the required operating angle (defined by power subsystem engineer), the rotation bracket collides with the fixed bracket that is mounted on body of the satellite, to stop rotation. Due to the effect of collision force that may alter the rotation mechanism function, design of centrifugal brake is essential. At stoppage moment micro-switches activate final position sensor and a stopper locks the rotation bracket. Design of spring and centrifugal brake components, static finite element stress analysis of primary structure body of rotation mechanism at stoppage moment have been obtained. Last, reliability analysis of rotation mechanism is evaluated. The benefit of this study is to aid in the design of rotation mechanism that can be used in micro-satellite applications.

DESIGN, ANALYSIS, AND RELIABILTY OF SOLAR PANEL ROTATION MECHANISM FOR MICROSATELLITE

Solar array rotation mechanism provides a hinged joint between the solar panel and satellite body, smooth rotation of the solar array into deployed position and its fixation in this position. After unlocking of solar panel (while in orbit), rotation bracket turns towards ready-to-work position under the action of driving spring. During deployment, once reached the required operating angle (defined by power subsystem engineer), the rotation bracket collides with the fixed bracket that is mounted on body of the satellite, to stop rotation. Due to the effect of collision force that may alter the rotation mechanism function, design of centrifugal brake is essential. At stoppage moment micro-switches activate final position sensor and a stopper locks the rotation bracket. Design of spring and centrifugal brake components, static finite element stress analysis of primary structure body of rotation mechanism at stoppage moment have been obtained. Last, reliability analysis of rotation mechanism is evaluated. The benefit of this study is to aid in the design of rotation mechanism that can be used in micro-satellite applications.

Akt-Mediated Proinflammatory Response of Mononuclear Phagocytes Infected with Burkholderia cenocepacia Occurs by a Novel GSK3 beta-Dependent, I kappa B Kinase-Independent Mechanism

The environmental bacterium Burkholderia cenocepacia causes opportunistic lung infections in immunocompromised individuals, particularly in patients with cystic fibrosis. Infections in these patients are associated with exacerbated inflammation leading to rapid decay of lung function, and in some cases resulting in cepacia syndrome, which is characterized by a fatal acute necrotizing pneumonia and sepsis. B. cenocepacia can survive intracellularly in macrophages by altering the maturation of the phagosome, but very little is known on macrophage responses to the intracellular infection. In this study, we have examined the role of the PI3K/Akt signaling pathway in B. cenocepacia-infected monocytes and macrophages. We show that PI3K/Akt activity was required for NF-kappa B activity and the secretion of proinflammatory cytokines during infection with B. cenocepacia. In contrast to previous observations in epithelial cells infected with other Gram-negative bacteria, Akt did not enhance I kappa B kinase or NF-kappa B p65 phosphorylation, but rather inhibited GSK3 beta, a negative regulator of NF-kappa B transcriptional activity. This novel mechanism of modulation of NF-kappa B activity may provide a unique therapeutic target for controlling excessive inflammation upon B. cenocepacia infection. The Journal of Immunology, 2011, 187: 635-643.

The WTO’s Trade Policy Review Mechanism – An Effective Surveillance Mechanism for Aid for Trade?

There has always been a question mark over how best to integrate developing countries into the world trading system and traditionally the WTO has used special and differential treatment (S&D) to do so. However, since 1996 the WTO has been involved with the Aid for Trade (AfT) initiative typically co-ordinated by the OECD and UN. This article firstly outlines the background to AfT since 1996 under the numerous agencies working in the area, highlighting how importance has always been placed on the monitoring and effectiveness of the process. It then turns to assessing the various methods currently used and the proposal of the WTO’s Trade Policy Review Mechanism (TPRM) as a potential monitoring tool of AfT.

Substrate specificity of bacterial oligosaccharyltransferase suggests a common transfer mechanism for the bacterial and eukaryotic systems

The PglB oligosaccharyltransferase (OTase) of Campylobacter jejuni can be functionally expressed in Escherichia coli, and its relaxed oligosaccharide substrate specificity allows the transfer of different glycans from the lipid carrier undecaprenyl pyrophosphate to an acceptor protein. To investigate the substrate specificity of PglB, we tested the transfer of a set of lipid-linked polysaccharides in E. coli and Salmonella enterica serovar Typhimurium. A hexose linked to the C-6 of the monosaccharide at the reducing end did not inhibit the transfer of the O antigen to the acceptor protein. However, PglB required an acetamido group at the C-2. A model for the mechanism of PglB involving this functional group was proposed. Previous experiments have shown that eukaryotic OTases have the same requirement, suggesting that eukaryotic and prokaryotic OTases catalyze the transfer of oligosaccharides by a conserved mechanism. Moreover, we demonstrated the functional transfer of the C. jejuni glycosylation system into S. enterica. The elucidation of the mechanism of action and the substrate specificity of PglB represents the foundation for engineering glycoproteins that will have an impact on biotechnology.

Enhancing the Activity and Tuning the Mechanism of Formic acid Oxidation at Tetrahexahedral Pt Nanocrystals by Au Decoration

Tetrahexahedral Pt nanocrystals (THH Pt NCs), bound by high index facets, belong to an emerging class of nanomaterials that promise to bridge the gap between model and practical electrocatalysts. The atomically stepped surfaces of THH Pt NCs are extremely active for the electrooxidation of small organic molecules but they also readily accommodate the dissociative chemisorption of such species, resulting in poisoning by strongly adsorbed CO. Formic acid oxidation is an ideal reaction for studying the balance between these competing catalyst characteristics, since it can proceed by either a direct or a CO mediated pathway. Herein, we describe electrochemical and in situ FTIR spectroscopic investigations of formic acid electrooxidation at both clean and Au adatom modified THH Pt NC surfaces. The Au decoration leads to higher catalytic currents and enhanced CO2 production in the low potential range. As the CO oxidation behaviour of the catalyst is not changed by the presence of the Au, it is likely that the role of the Au is to promote the direct pathway. Beyond their fundamental importance, these results are significant in the development of stable, poison resistant anodic electrocatalysts for direct formic acid fuel cells.

A proposed mechanism for chlorpromazine jaundice--defective hepatic sulphoxidation combined with rapid hydroxylation

On the basis of previous experimental studies we postulated that individuals who were phenotypically good hydroxylators but poor sulphoxidisers would be susceptible to chlorpromazine jaundice. Sulphoxidation capacity was assessed in 12 subjects with a history of chlorpromazine jaundice, using S-carboxymethyl-L-cysteine as an in vivo probe. Following an oral dose of 750 mg, unchanged compound and sulphoxide metabolites were measured in urine. All 12 subjects (100%) were shown to be poor sulphoxidisers compared to 22% of normal controls (P less than 0.001) and 23.8% of liver disease controls (P less than 0.001). No subjects with a history of chlorpromazine jaundice had an impaired hydroxylation capacity as assessed by recovery of 4-hydroxydebrisoquine in urine following oral debrisoquine. The results support the hypothesis and demonstrate an inherent metabolic basis of susceptibility to chlorpromazine jaundice.

Multilevel election timing - A comparative overview

This article investigates the link between regionalization of the structure of government, regional elections and regionalism on the one hand, and the organization of state-wide political parties in Spain and the UK on the other. It particularly looks at two aspects of the relations between the central and regional levels of party organization: integration of the regional branches in central decision making and autonomy of the regional branches. It argues that the party factors are the most crucial elements explaining party change and that party leaders mediate between environmental changes and party organization. The parties' history and beliefs and the strength of the central leadership condition their ability or willingness to facilitate the emergence of meso-level elites. The institutional and electoral factors are facilitating factors that constitute additional motives for or against internal party decentralization.