109 research outputs found
Solvent Impregnated Resins (SIRs) for the recovery of low concentration ethers and phenols from water
Comparison of storm damage functions and their performance
Winter storms are the most costly natural hazard for European residential
property. We compare four distinct storm damage functions with respect to
their forecast accuracy and variability, with particular regard to the most
severe winter storms. The analysis focuses on daily loss estimates under
differing spatial aggregation, ranging from district to country level. We
discuss the broad and heavily skewed distribution of insured losses posing
difficulties for both the calibration and the evaluation of damage functions.
From theoretical considerations, we provide a synthesis between the
frequently discussed cubic wind–damage relationship and recent studies that
report much steeper damage functions for European winter storms. The
performance of the storm loss models is evaluated for two sources of wind
gust data, direct observations by the German Weather Service and ERA-Interim
reanalysis data. While the choice of gust data has little impact on the
evaluation of German storm loss, spatially resolved coefficients of variation
reveal dependence between model and data choice. The comparison shows that
the probabilistic models by Heneka et al. (2006) and Prahl et al.
(2012) both provide accurate loss predictions for moderate to extreme losses, with
generally small coefficients of variation. We favour the latter model in
terms of model applicability. Application of the versatile deterministic
model by Klawa and Ulbrich (2003) should be restricted to extreme loss, for which it
shows the least bias and errors comparable to the probabilistic model by
Prahl et al. (2012)
Linewidth of the Laser Optical Frequency Comb with Arbitrary Temporal Profile
For many applications Optical Frequency Combs (OFCs) require a high degree of
temporal coherence (narrow linewidth). Commonly OFCs are generated in nonlinear
media from a monochromatic narrow linewidth laser sources or from a mode-locked
laser pulses but in the all-important mid-infrared (MIR) and terahertz (THz)
regions of spectrum OFCs can be generated intrinsically by the free-running
quantum cascade lasers (QCLs) with high efficiency. These combs do not look
like conventional OFCs as the phases of each mode are different and in temporal
domain the OFC is a seemingly random combination of amplitude- and
phase-modulated signals rather than a short pulse. Despite this
pseudo-randomness, the experimental evidence suggests that the linewidth of the
QCL OFC is just as narrow as that of a QCL operating in the single mode. While
universally acknowledged, this seemingly observation is not fully understood.
In this work we rigorously prove this fact by deriving the expression for the
Schawlow-Townes linewidth of QCL OFC and offer a transparent physical
interpretation based on orthogonality of laser modes, indicating that despite
their very different temporal profiles MIR and THz QCL OFCs are just as good
for most applications as any other OFC
Selective recovery of a pyridine derivative from an aqueous waste stream containing acetic acid and succinonitrile with solvent impregnated resins
An Improved Search for the Neutron Electric Dipole Moment
A permanent electric dipole moment of fundamental spin-1/2 particles violates
both parity (P) and time re- versal (T) symmetry, and hence, also charge-parity
(CP) symmetry since there is no sign of CPT-violation. The search for a neutron
electric dipole moment (nEDM) probes CP violation within and beyond the Stan-
dard Model. The experiment, set up at the Paul Scherrer Institute (PSI), an
improved, upgraded version of the apparatus which provided the current best
experimental limit, dn < 2.9E-26 ecm (90% C.L.), by the RAL/Sussex/ILL
collaboration: Baker et al., Phys. Rev. Lett. 97, 131801 (2006). In the next
two years we aim to improve the sensitivity of the apparatus to sigma(dn) =
2.6E-27 ecm corresponding to an upper limit of dn < 5E-27 ecm (95% C.L.), in
case for a null result. In parallel the collaboration works on the design of a
new apparatus to further increase the sensitivity to sigma(dn) = 2.6E-28 ecm.Comment: APS Division for particles and fields, Conference Proceedings, Two
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Constraining interactions mediated by axion-like particles with ultracold neutrons
We report a new limit on a possible short range spin-dependent interaction
from the precise measurement of the ratio of Larmor precession frequencies of
stored ultracold neutrons and Hg atoms confined in the same volume. The
measurement was performed in a 1 T vertical magnetic holding field
with the apparatus searching for a permanent electric dipole moment of the
neutron at the Paul Scherrer Institute. A possible coupling between freely
precessing polarized neutron spins and unpolarized nucleons of the wall
material can be investigated by searching for a tiny change of the precession
frequencies of neutron and mercury spins. Such a frequency change can be
interpreted as a consequence of a short range spin-dependent interaction that
could possibly be mediated by axions or axion-like particles. The interaction
strength is proportional to the CP violating product of scalar and pseudoscalar
coupling constants . Our result confirms limits from complementary
experiments with spin-polarized nuclei in a model-independent way. Limits from
other neutron experiments are improved by up to two orders of magnitude in the
interaction range of m
Toward neuronal current spectroscopy at Ultra-Low field NMR
Centro Studi e Ricerche "E. Fermi", Rome, Italy. Email: [email protected] Physikalish-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin, Germany University of Leipzig, Leipzig, Germany Neurophysics Group, Dept. of Neurology, Campus Benjamin Franklin, Charite/University Medicine, Berlin, Germany Dip. di Fisica, Universita di Roma "La Sapienza", Piazzale Aldo Moro, 5, 00185, Rome, Ital
An Improved Neutron Electric Dipole Moment Experiment
A new measurement of the neutron EDM, using Ramsey's method of separated
oscillatory fields, is in preparation at the new high intensity source of
ultra-cold neutrons (UCN) at the Paul Scherrer Institute, Villigen, Switzerland
(PSI). The existence of a non-zero nEDM would violate both parity and time
reversal symmetry and, given the CPT theorem, might lead to a discovery of new
CP violating mechanisms. Already the current upper limit for the nEDM
(|d_n|<2.9E-26 e.cm) constrains some extensions of the Standard Model.
The new experiment aims at a two orders of magnitude reduction of the
experimental uncertainty, to be achieved mainly by (1) the higher UCN flux
provided by the new PSI source, (2) better magnetic field control with improved
magnetometry and (3) a double chamber configuration with opposite electric
field directions.
The first stage of the experiment will use an upgrade of the RAL/Sussex/ILL
group's apparatus (which has produced the current best result) moved from
Institut Laue-Langevin to PSI. The final accuracy will be achieved in a further
step with a new spectrometer, presently in the design phase.Comment: Flavor Physics & CP Violation Conference, Taipei, 200
Revised experimental upper limit on the electric dipole moment of the neutron
We present for the first time a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron. We have extended and enhanced our earlier analysis to include recent developments in the understanding of the effects of gravity in depolarizing ultracold neutrons; an improved calculation of the spectrum of the neutrons; and conservative estimates of other possible systematic errors, which are also shown to be consistent with more recent measurements undertaken with the apparatus. We obtain a net result of dn=−0.21±1.82×10−26 e cm, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of 3.0×10−26 e cm (90% C.L.) or 3.6×10−26 e cm (95% C.L.)
Measurement of the permanent electric dipole moment of the neutron
We present the result of an experiment to measure the electric dipole moment EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons (UCN). Our measurement stands in the long history of EDM experiments probing physics violating time reversal invariance. The salient features of this experiment
were the use of a Hg-199 co-magnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic field changes. The statistical analysis was performed on blinded datasets by two separate groups while the estimation of systematic effects profited from an
unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d_{\rm n} = (0.0\pm1.1_{\rm stat}\pm0.2_{\rmsys})\times10^{-26}e\,{\rm cm}
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