241 research outputs found
Cosmic-ray induced background intercomparison with actively shielded HPGe detectors at underground locations
The main background above 3\,MeV for in-beam nuclear astrophysics studies
with -ray detectors is caused by cosmic-ray induced secondaries. The
two commonly used suppression methods, active and passive shielding, against
this kind of background were formerly considered only as alternatives in
nuclear astrophysics experiments. In this work the study of the effects of
active shielding against cosmic-ray induced events at a medium deep location is
performed. Background spectra were recorded with two actively shielded HPGe
detectors. The experiment was located at 148\,m below the surface of the Earth
in the Reiche Zeche mine in Freiberg, Germany. The results are compared to data
with the same detectors at the Earth's surface, and at depths of 45\,m and
1400\,m, respectively.Comment: Minor errors corrected; final versio
Dynamic clamp with StdpC software
Dynamic clamp is a powerful method that allows the introduction of artificial electrical components into target cells to simulate ionic conductances and synaptic inputs. This method is based on a fast cycle of measuring the membrane potential of a cell, calculating the current of a desired simulated component using an appropriate model and injecting this current into the cell. Here we present a dynamic clamp protocol using free, fully integrated, open-source software (StdpC, for spike timing-dependent plasticity clamp). Use of this protocol does not require specialist hardware, costly commercial software, experience in real-time operating systems or a strong programming background. The software enables the configuration and operation of a wide range of complex and fully automated dynamic clamp experiments through an intuitive and powerful interface with a minimal initial lead time of a few hours. After initial configuration, experimental results can be generated within minutes of establishing cell recording
Progress of the Felsenkeller shallow-underground accelerator for nuclear astrophysics
Low-background experiments with stable ion beams are an important tool for
putting the model of stellar hydrogen, helium, and carbon burning on a solid
experimental foundation. The pioneering work in this regard has been done by
the LUNA collaboration at Gran Sasso, using a 0.4 MV accelerator. In the
present contribution, the status of the project for a higher-energy underground
accelerator is reviewed. Two tunnels of the Felsenkeller underground site in
Dresden, Germany, are currently being refurbished for the installation of a 5
MV high-current Pelletron accelerator. Construction work is on schedule and
expected to complete in August 2017. The accelerator will provide intense, 50
uA, beams of 1H+, 4He+, and 12C+ ions, enabling research on astrophysically
relevant nuclear reactions with unprecedented sensitivity.Comment: Submitted to the Proceedings of Nuclei in the Cosmos XIV, 19-24 June
2016, Niigata/Japa
Assignment of the group A rotavirus NSP4 gene into genotypes using a hemi-nested multiplex PCR assay: a rapid and reproducible assay for strain surveillance studies
The rotavirus non-structural protein NSP4 has been implicated in a number of biological functions during the rotavirus cellular cycle and pathogenesis, and has been addressed as a target for vaccine development. The NSP4 gene has been classified into six genotypes (A-F). A semi-nested triplex PCR was developed for genotyping the major human NSP4 genotypes (A-C), which are common in human rotavirus strains but are also shared among most mammalian rotavirus strains. A total of 192 previously characterized human strains representing numerous G and P type specificities (such as G1P[8], G1P[4], G2P[4], G3P[3], G3P[8], G3P[9], G4P[6], G4P[8], G6P[4], G6P[9], G6P[14], G8P[10], G8P[14], G9P[8], G9P[11], G10P[11], G12P[6] and G12P[8]) were tested for NSP4 specificity by the collaborating laboratories. An additional 35 animal strains, including the reference laboratory strains SA11 (simian, G3P[2]), NCDV (bovine, G6P[1]), K9 and CU-1 (canine, G3P[3]), together with 31 field isolates (canine, G3P[3]; feline, G3P[9]; porcine, G2P[23], G3P[6], G4P[6], G5P[6], G5P[7], G5P[26], G5P[27], G9P[6] and G9P[7]) were also successfully NSP4-typed. Four human G3P[9] strains and one feline G3P[9] strain were found to possess an NSP4 A genotype, instead of NSP4 C, suggesting a reassortment event between heterologous strains. Routine NSP4 genotyping may help to determine the genomic constellation of rotaviruses of man and livestock, and identify interspecies transmission of heterologous strain
Cosmic-ray-induced background intercomparison with actively shielded HPGe detectors at underground locations
The main background above 3 MeV for in-beam nuclear astrophysics studies with γ-ray detectors is caused by cosmic-ray induced secondaries. The two commonly used suppression methods, active and passive shielding, against this kind of background were formerly considered only as alternatives in nuclear astrophysics experiments. In this work the study of the effects of active shielding against cosmic-ray induced events at a medium deep location is performed. Background spectra were recorded with two actively shielded HPGe detectors. The experiment was located at 148 m below the surface of the Earth in the Reiche Zeche mine in Freiberg, Germany. The results are compared to data with the same detectors at the Earth’s surface, and at depths of 45 m and 1400 m, respectively
First Measurement of the 96Ru(p, γ)97Rh Cross Section for the p-Process with a Storage Ring
This work presents a direct measurement of the 96Ru(p, γ)97Rh cross section via a novel technique using a storage ring, which opens opportunities for reaction measurements on unstable nuclei. A proof-of-principle experiment was performed at the storage ring ESR at GSI in Darmstadt, where circulating 96 Ru ions interacted repeatedly with a hydrogen target. The 96Ru(p, γ)97Rh cross section between 9 and 11 MeV has been determined using two independent normalization methods. As key ingredients in Hauser-Feshbach calculations, the γ-ray strength function as well as the level density model can be pinned down with the measured (p, γ) cross section. Furthermore, the proton optical potential can be optimized after the uncertainties from the γ-ray strength function and the level density have been removed. As a result, a constrained 96 Ru(p, γ)97Rh reaction rate over a wide temperature range is recommended for p-process network calculations
Autonomous Bursting in a Homoclinic System
A continuous train of irregularly spaced spikes, peculiar of homoclinic
chaos, transforms into clusters of regularly spaced spikes, with quiescent
periods in between (bursting regime), by feeding back a low frequency portion
of the dynamical output. Such autonomous bursting results to be extremely
robust against noise; we provide experimental evidence of it in a CO2 laser
with feedback. The phenomen here presented display qualitative analogies with
bursting phenomena in neurons.Comment: Submitted to Phys. Rev. Lett., 14 pages, 5 figure
Neutron flux and spectrum in the Dresden Felsenkeller underground facility studied by moderated He counters
Ambient neutrons may cause significant background for underground
experiments. Therefore, it is necessary to investigate their flux and energy
spectrum in order to devise a proper shielding. Here, two sets of altogether
ten moderated He neutron counters are used for a detailed study of the
ambient neutron background in tunnel IV of the Felsenkeller facility,
underground below 45 meters of rock in Dresden/Germany. One of the moderators
is lined with lead and thus sensitive to neutrons of energies higher than 10
MeV. For each He counter-moderator assembly, the energy dependent neutron
sensitivity was calculated with the FLUKA code. The count rates of the ten
detectors were then fitted with the MAXED and GRAVEL packages. As a result,
both the neutron energy spectrum from 10 MeV to 300 MeV and the flux
integrated over the same energy range were determined experimentally.
The data show that at a given depth, both the flux and the spectrum vary
significantly depending on local conditions. Energy integrated fluxes of , , and cm
s, respectively, are measured for three sites within Felsenkeller tunnel
IV which have similar muon flux but different shielding wall configurations.
The integrated neutron flux data and the obtained spectra for the three sites
are matched reasonably well by FLUKA Monte Carlo calculations that are based on
the known muon flux and composition of the measurement room walls.Comment: 10 figures, 4 tables; to be published in Phys. Rev.
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