299 research outputs found
KADoNiS-: The astrophysical -process database
The KADoNiS- project is an online database for cross sections relevant to
the -process. All existing experimental data was collected and reviewed.
With this contribution a user-friendly database using the KADoNiS (Karlsruhe
Astrophysical Database of Nucleosynthesis in Stars) framework is launched,
including all available experimental data from (p,), (p,n),
(p,), (,), (,n) and (,p) reactions in
or close to the respective Gamow window with cut-off date of August 2012
(www.kadonis.org/pprocess).Comment: Proceedings Nuclear Data Conference 2013, published in Nuclear Data
Sheets 120 (2014) 19
The Karlsruhe Astrophysical Database of Nucleosynthesis in Stars Project - Status and Prospects
The KADoNiS (Karlsruhe Astrophysical Database of Nucleosynthesis in Stars) project is an astrophysical online database for cross sections relevant for nucleosynthesis in the s process and the γ process. The s-process database (http://www.kadonis.org) was started in 2005 and is presently facing its 4th update (KADoNiS v1.0). The γ-process database (KADoNiS-p, http://www.kadonis.org/pprocess) was recently revised and re-launched in March 2013. Both databases are compilations for experimental cross sections with relevance to heavy ion nucleosynthesis. For the s process recommended Maxwellian averaged cross sections for kT=5-100 keV are given for more than 360 isotopes between 1H and 210Bi. For the γ-process database all available experimental data from (p, γ), (p, n), (p, α), (α, γ), (α, n), and (α, p) reactions between 70Ge and 209Bi in or close to the respective Gamow window were collected and can be compared to theoretical predictions. The aim of both databases is a quick and user-friendly access to the available data in the astrophysically relevant energy regions. © 2014 Elsevier Inc.Peer reviewe
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
Cross section measurement of the astrophysically important 17O(p,gamma)18F reaction in a wide energy range
The 17O(p,g)18F reaction plays an important role in hydrogen burning
processes in different stages of stellar evolution. The rate of this reaction
must therefore be known with high accuracy in order to provide the necessary
input for astrophysical models.
The cross section of 17O(p,g)18F is characterized by a complicated resonance
structure at low energies. Experimental data, however, is scarce in a wide
energy range which increases the uncertainty of the low energy extrapolations.
The purpose of the present work is therefore to provide consistent and precise
cross section values in a wide energy range.
The cross section is measured using the activation method which provides
directly the total cross section. With this technique some typical systematic
uncertainties encountered in in-beam gamma-spectroscopy experiments can be
avoided.
The cross section was measured between 500 keV and 1.8 MeV proton energies
with a total uncertainty of typically 10%. The results are compared with
earlier measurements and it is found that the gross features of the 17O(p,g)18F
excitation function is relatively well reproduced by the present data.
Deviation of roughly a factor of 1.5 is found in the case of the total cross
section when compared with the only one high energy dataset. At the lowest
measured energy our result is in agreement with two recent datasets within one
standard deviation and deviates by roughly two standard deviations from a third
one. An R-matrix analysis of the present and previous data strengthen the
reliability of the extrapolated zero energy astrophysical S-factor.
Using an independent experimental technique, the literature cross section
data of 17O(p,g)18F is confirmed in the energy region of the resonances while
lower direct capture cross section is recommended at higher energies. The
present dataset provides a constraint for the theoretical cross sections.Comment: Accepted for publication in Phys. Rev. C. Abstract shortened in order
to comply with arxiv rule
Determination of gamma-ray widths in N using nuclear resonance fluorescence
The stable nucleus N is the mirror of O, the bottleneck in the
hydrogen burning CNO cycle. Most of the N level widths below the proton
emission threshold are known from just one nuclear resonance fluorescence (NRF)
measurement, with limited precision in some cases. A recent experiment with the
AGATA demonstrator array determined level lifetimes using the Doppler Shift
Attenuation Method (DSAM) in O. As a reference and for testing the
method, level lifetimes in N have also been determined in the same
experiment. The latest compilation of N level properties dates back to
1991. The limited precision in some cases in the compilation calls for a new
measurement in order to enable a comparison to the AGATA demonstrator data. The
widths of several N levels have been studied with the NRF method. The
solid nitrogen compounds enriched in N have been irradiated with
bremsstrahlung. The -rays following the deexcitation of the excited
nuclear levels were detected with four HPGe detectors. Integrated
photon-scattering cross sections of ten levels below the proton emission
threshold have been measured. Partial gamma-ray widths of ground-state
transitions were deduced and compared to the literature. The photon scattering
cross sections of two levels above the proton emission threshold, but still
below other particle emission energies have also been measured, and proton
resonance strengths and proton widths were deduced. Gamma and proton widths
consistent with the literature values were obtained, but with greatly improved
precision.Comment: Final published version, minor grammar changes, 10 pages, 4 figures,
8 tables; An addendum is published where the last section is revised: T.
Sz\"ucs and P. Mohr, Phys. Rev. C 92, 044328 (2015) [arXiv:1510.04956
Ultrasound-guided paravertebral puncture and placement of catheters in human cadavers: an imaging study
Background During paravertebral block, the anterolateral limit of the paravertebral space, which consists of the pleura, should preferably not be perforated. Also it is possible that, during the block, the constant superior costotransverse ligament can be missed in the loss-of-resistance technique. We therefore aimed to develop a new technique for an ultrasound-guided puncture of the paravertebral space. Methods We performed 20 punctures and catheter placements in 10 human cadavers. A sonographic view showing the pleura and the superior costotransverse ligament was obtained with a slightly oblique scan using a curved array transducer. After inline approach, injection of 10 ml normal saline confirmed the correct position of the needle tip, distended the space, and enabled catheter insertion. The spread of contrast dye injected through the catheters was assessed by CT scans. Results The superior costotransverse ligament and the paravertebral space were easy to identify. The needle tip reached the paravertebral space without problems under visualization. In contrast, the introduction of the catheter was difficult. The CT scan revealed a correct paravertebral spread of contrast in 11 cases. Out of the remaining, one catheter was found in the pleural space, in six cases there was an epidural, and in two cases there was a prevertebral spread of contrast dye. Conclusions We successfully developed a technique for an accurate ultrasound-guided puncture of the paravertebral space. We also showed that when a catheter is introduced through the needle with the tip lying in the paravertebral space, there is a high probability of catheter misplacement into the epidural, mediastinal, or pleural space
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
Alpha-induced reactions for the astrophysical p-process: the case of 151Eu
The cross sections of 151Eu(alpha,gamma)155Tb and 151Eu(alpha,n)154Tb
reactions have been measured with the activation method. Some aspects of the
measurement are presented here to illustrate the requirements of experimental
techniques needed to obtain nuclear data for the astrophysical p-process
nucleosynthesis. Preliminary cross section results are also presented and
compared with the predictions of statistical model calculations.Comment: Accepted for publication in Journal of Physics Conference Series,
proceeding of the Nuclear Physics in Astrophysics IV. conferenc
Measurement of the 91 Zr(p, Îł ) 92 m Nb cross section motivated by type Ia supernova nucleosynthesis
Abstract: The synthesis of heavy, proton rich isotopes is a poorly understood astrophysical process. Thermonuclear (type Ia) supernova explosions are among the suggested sites and the abundance of some isotopes present in the early Solar System may be used to test the models. 92Nb is such an isotope and one of the reactions playing a role in its synthesis is 91Zr(p,Îł)92Nb. As no experimental cross sections were available for this reaction so far, nucleosynthesis models had to solely rely on theoretical calculations. In the present work the cross section of 91Zr(p,Îł)92m Nb has been measured at astrophysical energies by activation. The results excellently confirm the predictions of cross sections and reaction rates for 91Zr(p,Îł)92Nb, as used in astrophysical simulations.Peer reviewe
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