Direct Determination of the Kinetics of Oxygen Diffusion to the Photocytes of a Bioluminescent Elaterid Larva, Measurement of Gas- and Aqueous-Phase Diffusional Barriers and Modelling of Oxygen Supply

We describe the development and use of a direct kinetic technique to determine the time taken for oxygen to diffuse from the external environment into the light-producing cells (photocytes) in the prothorax of bioluminescent larvae of Pyrearinus termitilluminans. This was achieved by measuring the time course of the pseudoflash induced through sequential anoxia followed by normoxia. We have also determined the separate times taken for this oxygen diffusion in gaseous and tissue (predominantly aqueous) phases by using helium and nitrogen as the carrier gas. Of the total time taken for diffusion, that in the gas phase required 613+/-136 ms (mean +/- s.e. m., N=5) whilst that in the aqueous phase required 1313+/-187 ms. These values imply pathlengths of diffusion in the gaseous and aqueous phases of 4.80x10(-)(3)+/-0.53x10(-)(3) and 8. 89x10(-)(5)+/-0.61x10(-)(5 )m, respectively. In addition, the pathlength of gas-phase diffusion was used to derive a parameter relating to the tortuosity of the tracheal system. These values, together with those obtained upon bioluminescent oxygen consumption, have been used to model oxygen supply to the photocyte. From these studies, it would also appear that the modulation of tracheolar fluid levels might be a significant mechanism of control of tissue oxygen levels in at least some insects

Strangeness production in jets from p+p \sqrt{s} = 200 GeV collisions

Measurements of strangeness production in jets help illuminate the QCD mechanisms in fragmentation. Furthermore, they provide a crucial baseline for heavy-ion studies where modifications in jet chemistry have recently been predicted. We present new results on strange particle production in jets from p+p \sqrt{s} = 200 GeV collisions measured by the STAR experiment. The momentum distributions of the \Lambda, \bar{\Lambda} and K0Short particles are obtained using various jet finding algorithms, and then compared to various models. Strange particle ratios in jets are obtained and compared to values obtained from the inclusive spectra. Finally, we show jets tagged with leading strange baryons and mesons, in order to investigate whether gluon or quark jets can be isolated in this way.Comment: 5 pages, 4 figures, Winter Workshop on Nuclear Dynamics 2010, Jamaic

Firefly Flashing is Controlled by Gating Oxygen to Light-Emitting Cells

Although many aspects of firefly bioluminescence are understood, the mechanism by which adult fireflies produce light as discrete rapid flashes is not. Here we examine the most postulated theory, that flashing is controlled by gating oxygen access to the light-emitting cells (photocytes). According to this theory, the dark state represents repression of bioluminescence by limiting oxygen, which is required for bioluminescence; relief from this repression by transiently allowing oxygen access to the photocytes allows the flash. We show that normobaric hyperoxia releases the repression of light emission in the dark state of both spontaneously flashing and non-flashing fireflies, causing continual glowing, and we measure the kinetics of this process. Secondly, we determine the length of the barriers to oxygen diffusion to the photocytes in the aqueous and gas phases. Thirdly, we provide constraints upon the distance between any gas-phase gating structure(s) and the photocytes. We conclude from these data that the flash of the adult firefly is controlled by gating of oxygen to the photocytes, and demonstrate that this control mechanism is likely to act by modulating the levels of fluid in the tracheoles supplying photocytes, providing a variable barrier to oxygen diffusion

Measurement of Oxygen Partial Pressure, its Control During Hypoxia and Hyperoxia, and its Effect upon Light Emission in a Bioluminescent Elaterid Larva

This study investigates the respiratory physiology of bioluminescent larvae of Pyrearinus termitilluminans in relation to their tolerance to hypoxia and hyperoxia and to the supply of oxygen for bioluminescence. The partial pressure of oxygen (P(O2)) was measured within the bioluminescent prothorax by in vivo electron paramagnetic resonance (EPR) oximetry following acclimation of larvae to hypoxic, normoxic and hyperoxic (normobaric) atmospheres and during periods of bioluminescence (during normoxia). The P(O2) in the prothorax during exposure to an external P(O2) of 15.2, 160 and 760 mmHg was 10.3+/-2.6, 134+/-0.9 and 725+/-73 mmHg respectively (mean +/- s.d., N=5; 1 mmHg=0.1333 kPa). Oxygen supply to the larvae via gas exchange through the spiracles, measured by determining the rate of water loss, was also studied in the above atmospheres and was found not to be dependent upon P(O2). The data indicated that there is little to no active control of extracellular tissue P(O2) within the prothorax of these larvae. The reduction in prothorax P(O2) observed during either attack-response-provoked bioluminescence or sustained feeding-related bioluminescence in a normoxic atmosphere was variable, but fell within the range 10-25 mmHg. The effect of hypoxic atmospheres on bioluminescence was measured to estimate the intracellular P(O2) within the photocytes of the prothorax. Above a threshold value of 50-80 mmHg, bioluminescence was unaffected by P(O2). Below this threshold, an approximately linear relationship between P(O2) and bioluminescence was observed. Taken together with the extracellular P(O2) measurements, this suggests that control of P(O2) within the photocyte may occur. This work establishes that EPR oximetry is a valuable technique for long-term measurement of tissue P(O2) in insects and can provide valuable insights into their respiratory physiology. It also raises questions regarding the hypothesis that bioluminescence can have a significant antioxidative effect by reduction of prothorax P(O2 )through oxygen consumption

Fluctuation and flow probes of early-time correlations in relativistic heavy ion collisions

Fluctuation and correlation observables are often measured using multi-particle correlation methods and therefore mutually probe the origins of genuine correlations present in multi-particle distribution functions. We investigate the common influence of correlations arising from the spatially inhomogeneous initial state on multiplicity and momentum fluctuations as well as flow fluctuations. Although these observables reflect different aspects of the initial state, taken together, they can constrain a correlation scale set at the earliest moments of the collision. We calculate both the correlation scale in an initial stage Glasma flux tube picture and the modification to these correlations from later stage hydrodynamic flow and find quantitative agreement with experimental measurements over a range of collision systems and energies.Comment: Proceedings of the 28th Winter Workshop on Nuclear Dynamics, Dorado del Mar, Puerto Rico, April 7-14, 201

The Zel'dovich effect and evolution of atomic Rydberg spectra along the Periodic Table

In 1959 Ya. B. Zel'dovich predicted that the bound-state spectrum of the non-relativistic Coulomb problem distorted at small distances by a short-range potential undergoes a peculiar reconstruction whenever this potential alone supports a low-energy scattering resonance. However documented experimental evidence of this effect has been lacking. Previous theoretical studies of this phenomenon were confined to the regime where the range of the short-ranged potential is much smaller than Bohr's radius of the Coulomb field. We go beyond this limitation by restricting ourselves to highly-excited s states. This allows us to demonstrate that along the Periodic Table of elements the Zel'dovich effect manifests itself as systematic periodic variation of the Rydberg spectra with a period proportional to the cubic root of the atomic number. This dependence, which is supported by analysis of experimental and numerical data, has its origin in the binding properties of the ionic core of the atom.Comment: 17 pages, 12 figure

VHMPID: a new detector for the ALICE experiment at LHC

This article presents the basic idea of VHMPID, an upgrade detector for the ALICE experiment at LHC, CERN. The main goal of this detector is to extend the particle identification capabilities of ALICE to give more insight into the evolution of the hot and dense matter created in Pb-Pb collisions. Starting from the physics motivations and working principles the challenges and current status of development is detailed.Comment: 4 pages, 6 figures. To be published in EPJ Web of Conference

A wider Europe? The view from Russia, Belarus and Ukraine

On the evidence of national surveys conducted between 2000 and 2006, there is a declining sense of European self-identity in the three Slavic post-Soviet republics of Russia, Belarus and Ukraine. Attitudes towards the European Union and the possibility of membership are broadly supportive, but with a substantial proportion who find it difficult to express a view, and substantial proportions are poorly informed in comparison with the general public in EU member or prospective member countries. Those who are better informed are more likely to favour EU membership and vice versa. Generally, socioeconomic characteristics (except for age and region) are relatively poor predictors of support for EU membership as compared with attitudinal variables. But ‘Europeanness’ should not be seen as a given, and much will depend on whether EU member countries emphasize what is common to east and west or establish ‘new dividing lines’ in place of those of the cold war

Liquid membrane system for the removal and concentration of transuranic elements

The goal of this program is to develop an efficient, reliable, and radiation-resistant modified liquid membrane system (MLMS) for the selective removal and concentration of transuranic elements (TRUs) and strontium-90 from dissolved Hanford sludge wastes. The efforts are divided into three categories: (1) demonstration and optimization of the MLMS for the TRUEX and SREX processes using simulant waste solution; (2) development of a radiation-resistant microporous divider and membrane module for testing with actual waste solutions; and (3) demonstration of the MLMS for the TRUEX and SREX processes using actual Hanford waste. Successful completion of these development efforts will yield a compact, versatile, and reliable MLMS for implementation with the TRUEX and SREX processes. The MLMS is simple, stable, more efficient, and easier to control and operate than conventional solvent-extraction processes, such as those employing centrifugal contactors. In addition, the MLMS process offers operational cost savings over the conventional technology, by exhibiting at least a 10% reduction in the consumption of extractant chemicals