Estimation of the shear viscosity at finite net-baryon density from A+A collision data at sNN=7.7−200\sqrt{s_\mathrm{NN}} = 7.7-200 GeV

Hybrid approaches based on relativistic hydrodynamics and transport theory have been successfully applied for many years for the dynamical description of heavy ion collisions at ultrarelativistic energies. In this work a new viscous hybrid model employing the hadron transport approach UrQMD for the early and late non-equilibrium stages of the reaction, and 3+1 dimensional viscous hydrodynamics for the hot and dense quark-gluon plasma stage is introduced. This approach includes the equation of motion for finite baryon number, and employs an equation of state with finite net-baryon density to allow for calculations in a large range of beam energies. The parameter space of the model is explored, and constrained by comparison with the experimental data for bulk observables from SPS and the phase I beam energy scan at RHIC. The favored parameter values depend on energy, but allow to extract the effective value of the shear viscosity coefficient over entropy density ratio $\eta/s$ in the fluid phase for the whole energy region under investigation. The estimated value of $\eta/s$ increases with decreasing collision energy, which may indicate that $\eta/s$ of the quark-gluon plasma depends on baryochemical potential $\mu_B$.Comment: minor changes in the text, results for constant eta*T/w added. Version accepted for publication in Phys. Rev.

Model system studies with a phase separated membrane bioreactor

The operation and evaluation of a bioreactor designed for high intensity oxygen transfer in a microgravity environment is described. The reactor itself consists of a zero headspace liquid phase separated from the air supply by a long length of silicone rubber tubing through which the oxygen diffuses in and the carbon dioxide diffuses out. Mass transfer studies show that the oxygen is film diffusion controlled both externally and internally to the tubing and not by diffusion across the tube walls. Methods of upgrading the design to eliminate these resistances are proposed. Cell growth was obtained in the fermenter using Saccharomyces cerevisiae showing that this concept is capable of sustaining cell growth in the terrestial simulation

Activation of nonselective cation channels by physiological cholecystokinin concentrations in mouse pancreatic acinar cells

The activation of the nonselective cation channels in mouse pancreatic acinar cells has been assessed at low agonist concentrations using patch-clamp whole cell, cell-attached patch, and isolated inside-out patch recordings. Application of acetylcholine (ACh) (25-1,000 nM) and cholecystokinin (CCK) (2-10 pM) evoked oscillatory responses in both cation and chloride currents measured in whole cell experiments. In cell-attached patch experiments we demonstrate CCK and ACh evoked opening of single 25-pS cation channels in the basolateral membrane. Therefore, at least a component of the whole cell cation current is due to activation of cation channels in the basolateral acinar cell membrane. To further investigate the reported sensitivity of the cation channel to intracellular ATP and calcium we used excised inside-out patches. Micromolar Ca2+ concentrations were required for significant channel activation. Application of ATP and ADP to the intracellular surface of the patch blocked channel opening at concentrations between 0.2 and 4 mM. The nonmetabolizable ATP analogue, 5'- adenylylimidodiphosphate (AMP-PNP, 0.2-2 mM), also effectively blocked channel opening. The subsequent removal of ATP caused a transient increase in channel activity not seen with the removal of ADP or AMP- PNP. Patches isolated into solutions containing 2 mM ATP showed channel activation at micromolar Ca2+ concentrations. Our results show that ATP has two separate effects. The continuous presence of the nucleotide is required for operation of the cation channels and this action seems to depend on ATP hydrolysis. ATP can also close the channel and this effect can be demonstrated in excised inside-out patches when ATP is added to the bath after a period of exposure to an ATP-free solution. This action does not require ATP hydrolysis. Under physiological conditions hormonal stimulation can open the nonselective cation channels and this can be explained by the rise in the intracellular free Ca2+ concentration

Magnetometry with entangled atomic samples

We present a theory for the estimation of a scalar or a vector magnetic field by its influence on an ensemble of trapped spin polarized atoms. The atoms interact off-resonantly with a continuous laser field, and the measurement of the polarization rotation of the probe light, induced by the dispersive atom-light coupling, leads to spin-squeezing of the atomic sample which enables an estimate of the magnetic field which is more precise than that expected from standard counting statistics. For polarized light and polarized atoms, a description of the non-classical components of the collective spin angular momentum for the atoms and the collective Stokes vectors of the light-field in terms of effective gaussian position and momentum variables is practically exact. The gaussian formalism describes the dynamics of the system very effectively and accounts explicitly for the back-action on the atoms due to measurement and for the estimate of the magnetic field. Multi-component magnetic fields are estimated by the measurement of suitably chosen atomic observables and precision and efficiency is gained by dividing the atomic gas in two or more samples which are entangled by the dispersive atom-light interaction.Comment: 8 pages, 11 figure