850 research outputs found
Monte Carlo aided design of the inner muon veto detectors for the Double Chooz experiment
The Double Chooz neutrino experiment aims to measure the last unknown
neutrino mixing angle theta_13 using two identical detectors positioned at
sites both near and far from the reactor cores of the Chooz nuclear power
plant. To suppress correlated background induced by cosmic muons in the
detectors, they are protected by veto detector systems. One of these systems is
the inner muon veto. It is an active liquid scintillator based detector and
instrumented with encapsulated photomultiplier tubes. In this paper we describe
the Monte Carlo aided design process of the inner muon veto, that resulted in a
detector configuration with 78 PMTs yielding an efficiency of 99.978 +- 0.004%
for rejecting muon events and an efficiency of >98.98% for rejecting correlated
events induced by muons. A veto detector of this design is currently used at
the far detector site and will be built and incorporated as the muon
identification system at the near site of the Double Chooz experiment
Climate and structure of the 8.2 ka event reconstructed from three speleothems from Germany
The most pronounced climate anomaly of the Holocene was the 8.2 ka cooling
event. We present new 230Th/U-ages as well as high-resolution stable isotope
and trace element data from three stalagmitesfrom two different cave systems in
Germany, which provide important information about the structure and climate
variability of the 8.2 ka event in central Europe. In all three speleothems,
the 8.2 ka event is clearly recorded as a pronounced negative excursion of the
{\delta}18O values and can be divided into a 'whole event' and a 'central
event'. All stalagmites show a similar structure of the event with a short
negative excursion prior to the 'central event', which marks the beginning of
the 'whole event'. The timing and duration of the 8.2.ka event are different
for the individual records, which may, however, be related to dating
uncertainties. Whereas stalagmite Bu4 from Bunker Cave also shows a negative
anomaly in the {\delta}13C values and Mg content during the event, the two
speleothems from the Herbstlabyrinth cave system do not show distinct peaks in
the other proxies. This may suggest that the speleothem {\delta}18O values
recorded in the three stalagmites do not primarily reflect climate change at
the cave site, but rather large-scale changes in the North Atlantic. This is
supported by comparison with climate modelling data, which suggest that the
negative peak in the speleothem {\delta}18O values is mainly due to lower
{\delta}18O values of precipitation above the cave and that temperature only
played a minor role. Alternatively, the other proxies may not be as sensitive
as {\delta}18O values to record this centennial-scale cooling event. This may
particularly be the case for speleothem {\delta}13C values as suggested by
comparison with a climate modelling study simulating vegetation changes in
Europe during the 8.2 ka event. ..
The self-assembly and evolution of homomeric protein complexes
We introduce a simple "patchy particle" model to study the thermodynamics and
dynamics of self-assembly of homomeric protein complexes. Our calculations
allow us to rationalize recent results for dihedral complexes. Namely, why
evolution of such complexes naturally takes the system into a region of
interaction space where (i) the evolutionarily newer interactions are weaker,
(ii) subcomplexes involving the stronger interactions are observed to be
thermodynamically stable on destabilization of the protein-protein interactions
and (iii) the self-assembly dynamics are hierarchical with these same
subcomplexes acting as kinetic intermediates.Comment: 4 pages, 4 figure
The CRESST Dark Matter Search
We present first competitive results on WIMP dark matter using the
phonon-light-detection technique. A particularly strong limit for WIMPs with
coherent scattering results from selecting a region of the phonon-light plane
corresponding to tungsten recoils. The observed count rate in the neutron band
is compatible with the rate expected from neutron background. CRESST is
presently being upgraded with a 66 channel SQUID readout system, a neutron
shield and a muon veto system. This results in a significant improvement in
sensitivity.Comment: 6 pages, 3 figures, to be published in the proceedings of the 5th
International Workshop on the Identification and Detection of Dark Matter IDM
2004, Edinburgh, Sept. 2004, World Scientifi
- âŠ