A recirculating-flow fluorescent oxygen sensor

Abstract: An immersible oxygen sensor was constructed by circulating small quantities of ruthenium tris-(2,2'-bipyridyl) II dichloride oxygen-sensitive fluorescent dye through a loop of oxygen-permeable silicone tubing immersed in test medium. The fluroescence intensity of the dye was subsequently measured as it exited the flow loop and related to oxygen tension. This method of measuring the oxygen tension, through diffusive transport to a flowing stream of dye and recirculating it in the sensor, has been found to give a stable response and relatively long sensor lifetime without major recalibration. The sensor showed good stability over at least a week's duration and showed no degradation due to leaching of the dye through membranes or photobleaching that commonly affects fluorescent sensors with immobilized chemistries

The hard X-ray Photon Single-Shot Spectrometer of SwissFEL - Initial characterization

SwissFEL requires the monitoring of the photon spectral distribution at a repetition rate of 100 Hz for machine optimization and experiment online diagnostics. The Photon Single Shot Spectrometer has been designed for the photon energy range of 4 keV to 12 keV provided by the Aramis beamline. It is capable of measuring the spectrum in a non-destructive manner, with an energy resolution of Δ E/E = (2-5) × 10-5 over a bandwidth of 0.5% on a shot-to-shot basis. This article gives a detailed description about the technical challenges, structures, and considerations when building such a device, and to further enhance the performance of the spectrometer

Effective theories for real-time correlations in hot plasmas

We discuss the sequence of effective theories needed to understand the qualitative, and quantitative, behavior of real-time correlators in ultra-relativistic plasmas. We analyze in detail the case where A is a gauge-invariant conserved current. This case is of interest because it includes a correlation recently measured in lattice simulations of classical, hot, SU(2)-Higgs gauge theory. We find that simple perturbation theory, free kinetic theory, linearized kinetic theory, and hydrodynamics are all needed to understand the correlation for different ranges of time. We emphasize how correlations generically have power-law decays at very large times due to non-linear couplings to long-lived hydrodynamic modes.Comment: 28 pages, Latex, uses revtex, epsf macro packages [Revised version: t -> sqrt{t} in a few typos on p. 10.

Lifetime of quasiparticles in hot QED plasmas

The calculation of the lifetime of quasiparticles in a QED plasma at high temperature remains plagued with infrared divergences, even after one has taken into account the screening corrections. The physical processes responsible for these divergences are the collisions involving the exchange of very soft, unscreened, magnetic photons, whose contribution is enhanced by the thermal Bose-Einstein occupation factor. The self energy diagrams which diverge in perturbation theory contain no internal fermion loops, but an arbitrary number of internal magnetostatic photon lines. By generalizing the Bloch-Nordsieck model at finite temperature, we can resum all the singular contributions of such diagrams, and obtain the correct long time behaviour of the retarded fermion propagator in the hot QED plasma: $S_R(t)\sim \exp\{-\alpha T \, t\, \ln\omega_pt\}$, where $\omega_p=eT/3$ is the plasma frequency and $\alpha=e^2/4\pi$.Comment: 13 pages, LaTe

PrP-dependent association of prions with splenic but not circulating lymphocytes of scrapie-infected mice.

An intact immune system, and particularly the presence of mature B lymphocytes, is crucial for mouse scrapie pathogenesis in the brain after peripheral exposure. Prions are accumulated in the lymphoreticular system (LRS), but the identity of the cells containing infectivity and their role in neuroinvasion have not been determined. We show here that although prion infectivity in the spleen is associated with B and T lymphocytes and to a lesser degree with the stroma, no infectivity could be detected in lymphocytes from blood. In wild-type mice, which had been irradiated and reconstituted with PrP-deficient lymphohaematopoietic stem cells and inoculated with scrapie prions, infectivity in the spleen was present in the stroma but not in lymphocytes. Therefore, splenic B and T lymphocytes can either synthesize prions or acquire them from another source, but only when they express PrP

On the Quasiparticle Description of Lattice QCD Thermodynamics

We propose a novel quasiparticle interpretation of the equation of state of deconfined QCD at finite temperature. Using appropriate thermal masses, we introduce a phenomenological parametrization of the onset of confinement in the vicinity of the predicted phase transition. Lattice results of the energy density, the pressure and the interaction measure of pure SU(3) gauge theory are excellently reproduced. We find a relationship between the thermal energy density of the Yang-Mills vacuum and the chromomagnetic condensate _T. Finally, an extension to QCD with dynamical quarks is discussed. Good agreement with lattice data for 2, 2+1 and 3 flavour QCD is obtained. We also present the QCD equation of state for realistic quark masses.Comment: 20 pages, 10 eps figure

Two problems in thermal field theory

In this talk, I review recent progress made in two areas of thermal field theory. In particular, I discuss various approaches for the calculation of the quark gluon plasma thermodynamical properties, and the problem of its photon production rate.Comment: 10 pages Latex document, 15 postscript figures. Invited talk given at the 6th Workshop on High Energy Particle Physics, Chennai, India, 3-15 Jan 200

Contrast-enhanced ultrasound monitoring of perfusion changes in hepatic neuroendocrine metastases after systemic versus selective arterial ¹⁷⁷Lu/⁹⁰Y-DOTATOC and ²¹³Bi-DOTATOC radiopeptide therapy

Aim - radiopeptide therapy with beta emitter labeled ¹⁷⁷Lu/⁹⁰Y- DOTA(0)-Phe(1)-Tyr(3)-octreotide (DOTATOC) and more recently also alpha emitting ²¹³Bi-DOTATOC are promising new treatments for neuroendocrine tumors. No early predictors for treatment response have been recognized and tumor-shrinkage after radiation therapy appears slowly. In some solid tumors a decline in tumor perfusion was found predictive of final treatment response but the gold standard multiphase computed tomography (CT) has a high radiation burden. Therefore we evaluated the ability of contrast-enhanced ultrasound (CEUS) to evaluate tumor perfusion as a response criteria. 14 patients with hepatic neuroendocrine tumor (NET) metastases were enrolled in the retrospective study. Eleven patients were treated with beta-emitting ¹⁷⁷Lu/⁹⁰Y-DOTATOC, either intravenous (i.v.) (n = 5) or intra-arterial (i.a.) (n = 6) and three patients received alpha-emitting ²¹³Bi-DOTATOC (i.a.). CEUS and contrast-enhanced CT (CE-CT) were performed before and 3 months after treatment. CE-CT and CEUS presented comparable results in the baseline study and in the assessment of perfusion changes due to the different treatment regimes. A therapy related decrease in tumor perfusion is an early predictor of longterm morphologic response. Conclusion: CEUS is available and radiation free technique which showed comparable results for perfusion and diameter of liver metastases compared to CE-CT. Intensity reduction in an arterial phase CEUS can be seen as a positive sign indicating long term tumor response to treatment. Therefore CEUS may be considered as an imaging modality for monitoring early treatment after focal alpha and beta targeted therapy. Key Words: contrast-enhanced ultrasound, radionuclide therapy, treatment response, DOTATOC PET/CT

Transport Theory of Massless Fields

Using the Schwinger-Keldysh technique we discuss how to derive the transport equations for the system of massless quantum fields. We analyse the scalar field models with quartic and cubic interaction terms. In the $\phi^4$ model the massive quasiparticles appear due to the self-interaction of massless bare fields. Therefore, the derivation of the transport equations strongly resembles that one of the massive fields, but the subset of diagrams which provide the quasiparticle mass has to be resummed. The kinetic equation for the finite width quasiparticles is found, where, except the mean-field and collision terms, there are terms which are absent in the standard Boltzmann equation. The structure of these terms is discussed. In the massless $\phi^3$ model the massive quasiparticles do not emerge and presumably there is no transport theory corresponding to this model. It is not surprising since the $\phi^3$ model is anyhow ill defined.Comment: 32 pages, no macro

Bayesian calibration, comparison and averaging of six forest models, using data from Scots pine stands across Europe

Forest management requires prediction of forest growth, but there is no general agreement about which models best predict growth, how to quantify model parameters, and how to assess the uncertainty of model predictions. In this paper, we show how Bayesian calibration (BC), Bayesian model comparison (BMC) and Bayesian model averaging (BMA) can help address these issues. We used six models, ranging from simple parameter-sparse models to complex process-based models: 3PG, 4C, ANAFORE, BASFOR, BRIDGING and FORMIND. For each model, the initial degree of uncertainty about parameter values was expressed in a prior probability distribution. Inventory data for Scots pine on tree height and diameter, with estimates of measurement uncertainty, were assembled for twelve sites, from four countries: Austria, Belgium, Estonia and Finland. From each country, we used data from two sites of the National Forest Inventories (NFIs), and one Permanent Sample Plot (PSP). The models were calibrated using the NFI-data and tested against the PSP-data. Calibration was done both per country and for all countries simultaneously, thus yielding country-specific and generic parameter distributions. We assessed model performance by sampling from prior and posterior distributions and comparing the growth predictions of these samples to the observations at the PSPs. We found that BC reduced uncertainties strongly in all but the most complex model. Surprisingly, country-specific BC did not lead to clearly better within-country predictions than generic BC. BMC identified the BRIDGING model, which is of intermediate complexity, as the most plausible model before calibration, with 4C taking its place after calibration. In this BMC, model plausibility was quantified as the relative probability of a model being correct given the information in the PSP-data. We discuss how the method of model initialisation affects model performance. Finally, we show how BMA affords a robust way of predicting forest growth that accounts for both parametric and model structural uncertainty