The BGOOD experimental setup at ELSA Alef, S.; Bauer, P.; Bayadilov, D. ...
The European physical journal. A, Hadrons and nuclei,
04/2020, Letnik:
56, Številka:
4
Journal Article
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The BGOOD experiment at the ELSA facility in Bonn has been commissioned within the framework of an international collaboration. The experiment pursues a systematic investigation of non-strange and ...strange meson photoproduction, in particular
t
-channel processes at low momentum transfer. The setup uniquely combines a central almost
4
π
acceptance BGO crystal calorimeter with a large aperture forward magnetic spectrometer providing excellent detection of both neutral and charged particles, complementary to other setups such as Crystal Barrel, Crystal Ball, LEPS and CLAS.
GEANT4-based calibration of an organic liquid scintillator Mauritzson, N.; Fissum, K.G.; Perrey, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2022, Letnik:
1023
Journal Article
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A light-yield calibration of an NE 213A organic liquid scintillator detector has been performed using both monoenergetic and polyenergetic gamma-ray sources. Scintillation light was detected in a ...photomultiplier tube, and the corresponding pulses were subjected to waveform digitization on an event-by-event basis. The resulting Compton edges have been analyzed using a GEANT4 simulation of the detector which models both the interactions of the ionizing radiation as well as the transport of scintillation photons. The simulation is calibrated and also compared to well-established prescriptions used to determine the Compton edges, resulting ultimately in light-yield calibration functions. In the process, the simulation-based method produced information on the gain and intrinsic pulse-height resolution of the detector. It also facilitated a previously inaccessible understanding of the systematic uncertainties associated with the calibration of the scintillation-light yield. The simulation-based method was also compared to well-established numerical prescriptions for locating the Compton edges. Ultimately, the simulation predicted as much as 17% lower light-yield calibrations than the prescriptions. These calibrations indicate that approximately 35% of the scintillation light associated with a given gamma-ray reaches the photocathode. It is remarkable how well two 50 year old prescriptions for calibrating scintillation-light yield in organic scintillators have stood the test of time.
The polarization observables T,E,P,H, and G in photoproduction of η mesons off protons are measured for photon energies from threshold to W=2400 MeV (T), 2280 MeV (E), 1620 MeV (P,H), or 1820 MeV ...(G), covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, JüBo, and BnGa partial-wave analyses. A refit within the BnGa approach including further data yields precise branching ratios for the Nη decay of nucleon resonances. A Nη-branching ratio of 0.33±0.04 for N(1650)1/2− is found, which reduces the large and controversially discussed Nη-branching ratio difference of the two lowest mass JP=1/2−-resonances significantly.
The γp→K+Σ0 differential cross section at extremely forward angles was measured at the BGOOD experiment. A three-quarter drop in strength over a narrow range in energy and a strong dependence on the ...polar angle of the K+ in the centre-of-mass of the reaction is observed at a centre-of-mass energy of 1900 MeV. Residing close to multiple open and hidden strangeness thresholds, the structure appears consistent with meson-baryon threshold effects which may contribute to the reaction mechanism.
γ
p
→
K
+
Λ
differential cross sections and recoil polarisation data from threshold for extremely forward angles are presented. The measurements were performed at the BGOOD experiment at ELSA, ...utilising the high angular and momentum resolution forward spectrometer for charged particle identification. The high statistics and forward angle acceptance enables the extraction of the cross section as the minimum momentum transfer to the recoiling hyperon is approached.
Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W = 1748 MeV to W = 2045 MeV). The data ...cover the full solid angle that allows for a precise moment analysis. For the first time, a strong cusp effect in a polarization observable has been observed that is an effect of a branch-point singularity at the pη′ threshold Eγ = 1447 MeV (W = 1896 MeV). The latest BnGa partial wave analysis includes the new beam asymmetry data and yields a strong indication for the N (1895)1/2− nucleon resonance, demonstrating the importance of including all singularities for a correct determination of partial waves and resonance parameters.
In the cultivation of stem cells in vitro, components of animal origin and/or chemically undefined extracts like human platelet lysate are still used for the formulation of culture media because the ...quality of the most common basal media is unsuitable for cell culture in chemically defined environments. Experimental evidence shows that the better the qualitative and quantitative composition of the basal medium, the fewer additives of animal origin or chemically undefined components are needed to achieve successful cultivation of stem cells.
The contribution deals with essential aspects concerning identity and quality of culture media components for pre-clinical and clinical research. It describes the development of physico-chemically defined micro-environments for cell cultures that modulate functions of the metabolism of human stem cells from adipose tissue (hASCs).
The development process consists of two parts. The first phase involves the development of fully defined cellular microenvironments capable of satisfying the essential physiological needs of the cell. For this purpose, a detailed analysis of the physical (pH, osmotic pressure) and chemical requirements (energy sources, amino acids, vitamins, precursors of fatty and nucleic acids, inorganic salts, trace elements and chemical impurities) of the cells is carried out, which are then selected for the second phase. The second phase involves the elimination of complex, chemically undefined variables such as fetal calf serum or human platelet lysate, which are to be considered as critical components in cell culture media. The selection of a suitable basal medium and relative preparation technique allows the achievement of the goal.
The results show that good knowledge of the variables that influence cellular growth processes has numerous advantages. The two-step strategy described above allows the identification of the essential physiological needs of the cells, thus favouring control and modulation of the main metabolic functions. This perspective becomes even more interesting as the omission of complex and expensive medium additives in clinical culture processes leads to a reduction of contamination risk and production costs.
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