91 research outputs found
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Removal of hazardous pharmaceutical from water by photocatalytic treatment
The photocatalytic abatement of hazardous pharmaceuticals has been investigated at very low concentration in the ppb range as found in wastewater and in environmental pollutants. Photocatalytic degradation of tetracycline as a model compound with titania catalysts has been studied using solarium UV-A and black light with differentially applied electric power, tetracycline and catalyst concentration. Abatement of up to 90% has been achieved after 1 hour. Adsorption of tetracycline and photochemical degradation contribute significantly to the abatement of tetracycline resulting in an immediate reduction during the initial period of treatment. Contribution of adsorption is high at very low concentration (500 ppb). Photocatalytic treatment with titania is even highly efficient in the abatement of very small concentrations of tetracycline in drinking water. © 2010 Versita Warsaw and Springer-Verlag Wien
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 Î E/E = (2-5) Ă 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
Numerical optimization of spherical variable-line-spacing grating X-ray spectrometers
Operation of an X-ray spectrometer based on a spherical variable-line-spacing grating is analyzed using dedicated ray-tracing software allowing fast optimization of the grating parameters and spectrometer geometry
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
Damping Rates and Mean Free Paths of Soft Fermion Collective Excitations in a Hot Fermion-Gauge-Scalar Theory
We study the transport coefficients, damping rates and mean free paths of
soft fermion collective excitations in a hot fermion-gauge-scalar plasma with
the goal of understanding the main physical mechanisms that determine transport
of chirality in scenarios of non-local electroweak baryogenesis. The focus is
on identifying the different transport coefficients for the different branches
of soft collective excitations of the fermion spectrum. These branches
correspond to collective excitations with opposite ratios of chirality to
helicity and different dispersion relations. By combining results from the hard
thermal loop (HTL) resummation program with a novel mechanism of fermion
damping through heavy scalar decay, we obtain a robust description of the
different damping rates and mean free paths for the soft collective excitations
to leading order in HTL and lowest order in the Yukawa coupling. The space-time
evolution of wave packets of collective excitations unambiguously reveals the
respective mean free paths. We find that whereas both the gauge and scalar
contribution to the damping rates are different for the different branches, the
difference of mean free paths for both branches is mainly determined by the
decay of the heavy scalar into a hard fermion and a soft collective excitation.
We argue that these mechanisms are robust and are therefore relevant for
non-local scenarios of baryogenesis either in the Standard Model or extensions
thereof.Comment: REVTeX, 19 pages, 4 eps figures, published versio
The Thermal Renormalization Group for Fermions, Universality, and the Chiral Phase-Transition
We formulate the thermal renormalization group, an implementation of the
Wilsonian RG in the real-time (CTP) formulation of finite temperature field
theory, for fermionic fields. Using a model with scalar and fermionic degrees
of freedom which should describe the two-flavor chiral phase-transition, we
discuss the mechanism behind fermion decoupling and universality at second
order transitions. It turns out that an effective mass-like term in the fermion
propagator which is due to thermal fluctuations and does not break chiral
symmetry is necessary for fermion decoupling to work. This situation is in
contrast to the high-temperature limit, where the dominance of scalar over
fermionic degrees of freedom is due to the different behavior of the
distribution functions. The mass-like contribution is the leading thermal
effect in the fermionic sector and is missed if a derivative expansion of the
fermionic propagator is performed. We also discuss results on the
phase-transition of the model considered where we find good agreement with
results from other methods.Comment: References added, minor typos correcte
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Advanced source apportionment of size-resolved trace elements at multiple sites in London during winter
Trace element measurements in PM10â2.5, PM2.5â1.0 and PM1.0â0.3 aerosol were performed with 2 h time resolution at kerbside, urban background and rural sites during the ClearfLo winter 2012 campaign in London. The environment-dependent variability of emissions was characterized using the Multilinear Engine implementation of the positive matrix factorization model, conducted on data sets comprising all three sites but segregated by size. Combining the sites enabled separation of sources with high temporal covariance but significant spatial variability. Separation of sizes improved source resolution by preventing sources occurring in only a single size fraction from having too small a contribution for the model to resolve. Anchor profiles were retrieved internally by analysing data subsets, and these profiles were used in the analyses of the complete data sets of all sites for enhanced source apportionment.
A total of nine different factors were resolved (notable elements in brackets): in PM10â2.5, brake wear (Cu, Zr, Sb, Ba), other traffic-related (Fe), resuspended dust (Si, Ca), sea/road salt (Cl), aged sea salt (Na, Mg) and industrial (Cr, Ni); in PM2.5â1.0, brake wear, other traffic-related, resuspended dust, sea/road salt, aged sea salt and S-rich (S); and in PM1.0â0.3, traffic-related (Fe, Cu, Zr, Sb, Ba), resuspended dust, sea/road salt, aged sea salt, reacted Cl (Cl), S-rich and solid fuel (K, Pb). Human activities enhance the kerb-to-rural concentration gradients of coarse aged sea salt, typically considered to have a natural source, by 1.7â2.2. These site-dependent concentration differences reflect the effect of local resuspension processes in London. The anthropogenically influenced factors traffic (brake wear and other traffic-related processes), dust and sea/road salt provide further kerb-to-rural concentration enhancements by direct source emissions by a factor of 3.5â12.7. The traffic and dust factors are mainly emitted in PM10â2.5 and show strong diurnal variations with concentrations up to 4 times higher during rush hour than during night-time. Regionally influenced S-rich and solid fuel factors, occurring primarily in PM1.0â0.3, have negligible resuspension influences, and concentrations are similar throughout the day and across the regions
Approximately self-consistent resummations for the thermodynamics of the quark-gluon plasma. I. Entropy and density
We propose a gauge-invariant and manifestly UV finite resummation of the
physics of hard thermal/dense loops (HTL/HDL) in the thermodynamics of the
quark-gluon plasma. The starting point is a simple, effectively one-loop
expression for the entropy or the quark density which is derived from the fully
self-consistent two-loop skeleton approximation to the free energy, but subject
to further approximations, whose quality is tested in a scalar toy model. In
contrast to the direct HTL/HDL-resummation of the one-loop free energy, in our
approach both the leading-order (LO) and the next-to-leading order (NLO)
effects of interactions are correctly reproduced and arise from kinematical
regimes where the HTL/HDL are justifiable approximations. The LO effects are
entirely due to the (asymptotic) thermal masses of the hard particles. The NLO
ones receive contributions both from soft excitations, as described by the
HTL/HDL propagators, and from corrections to the dispersion relation of the
hard excitations, as given by HTL/HDL perturbation theory. The numerical
evaluations of our final expressions show very good agreement with lattice data
for zero-density QCD, for temperatures above twice the transition temperature.Comment: 62 pages REVTEX, 14 figures; v2: numerous clarifications, sect. 2C
shortened, new material in sect. 3C; v3: more clarifications, one appendix
removed, alternative implementation of the NLO effects, corrected eq. (5.16
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Kerb and urban increment of highly time-resolved trace elements in PM10, PM2.5 and PM1.0 winter aerosol in London during ClearfLo 2012
Ambient concentrations of trace elements with 2 h time resolution were measured in PM10â2.5, PM2.5â1.0 and PM1.0â0.3 size ranges at kerbside, urban background and rural sites in London during winter 2012. Samples were collected using rotating drum impactors (RDIs) and subsequently analysed with synchrotron radiation-induced X-ray fluorescence spectrometry (SR-XRF). Quantification of kerb and urban increments (defined as kerb-to-urban and urban-to-rural concentration ratios, respectively), and assessment of diurnal and weekly variability provided insight into sources governing urban air quality and the effects of urban micro-environments on human exposure. Traffic-related elements yielded the highest kerb increments, with values in the range of 10.4 to 16.6 for SW winds (3.3â6.9 for NE) observed for elements influenced by brake wear (e.g. Cu, Sb, Ba) and 5.7 to 8.2 for SW (2.6â3.0 for NE) for other traffic-related processes (e.g. Cr, Fe, Zn). Kerb increments for these elements were highest in the PM10â2.5 mass fraction, roughly twice that of the PM1.0â0.3 fraction. These elements also showed the highest urban increments (~ 3.0), although no difference was observed between brake wear and other traffic-related elements. All elements influenced by traffic exhibited higher concentrations during morning and evening rush hours, and on weekdays compared to weekends, with the strongest trends observed at the kerbside site, and additionally enhanced by winds coming directly from the road, consistent with street canyon effects. Elements related to mineral dust (e.g. Al, Si, Ca, Sr) showed significant influences from traffic-induced resuspension, as evidenced by moderate kerb (3.4â5.4 for SW, 1.7â2.3 for NE) and urban (~ 2) increments and increased concentrations during peak traffic flow. Elements related to regional transport showed no significant enhancement at kerb or urban sites, with the exception of PM10â2.5 sea salt (factor of up to 2), which may be influenced by traffic-induced resuspension of sea and/or road salt. Heavy-duty vehicles appeared to have a larger effect than passenger vehicles on the concentrations of all elements influenced by resuspension (including sea salt) and wearing processes. Trace element concentrations in London were influenced by both local and regional sources, with coarse and intermediate fractions dominated by traffic-induced resuspension and wearing processes and fine particles influenced by regional transport
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