The neutron inelastic scattering of carbon-12, populating the Hoyle state, is a reaction of interest for the triple-alpha process. The inverse process (neutron upscattering) can enhance the Hoyle ...state's decay rate to the bound states of
C, effectively increasing the overall triple-alpha reaction rate. The cross section of this reaction is impossible to measure experimentally but has been determined here at astrophysically-relevant energies using detailed balance. Using a highly-collimated monoenergetic beam, here we measure neutrons incident on the Texas Active Target Time Projection Chamber (TexAT TPC) filled with CO
gas, we measure the 3α-particles (arising from the decay of the Hoyle state following inelastic scattering) and a cross section is extracted. Here we show the neutron-upscattering enhancement is observed to be much smaller than previously expected. The importance of the neutron-upscattering enhancement may therefore not be significant aside from in very particular astrophysical sites (e.g. neutron star mergers).
We report the fabrication of high porous cellular material (HPCM) by a combination of spray-solution combustion synthesis (SSCS) and spark plasma sintering (SPS) approaches. It was shown that unique ...morphological features of the hollow nickel nanostructured spheres, produced by solution combustion, permit rapid (15 min) low temperature (763 K) sintering of the HPCM with porosity of 93%, which possesses high mechanical properties and thermal conductivity 70 times less than that for bulk nickel.
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•Combination of SSCS and SPS is a novel approach for fabrication of materials.•Unique morphological features of nanostructured hollow metallic spheres.•Extremely high porous cellular materials with high mechanical properties.•Thermal conductivity of produced foams 70 times smaller than that for balk Ni.
The triple-alpha process is a vital reaction in nuclear astrophysics, characterized by two consecutive reactions 2α ⇌ 8Be (α, γ) 12C that drive carbon formation. The second reaction occurs through ...the Hoyle state, a 7.65 MeV excited state in 12C with Jπ = 0+. The rate of the process depends on the radiative width, which can be determined by measuring the branching ratio for electromagnetic decay. Recent measurements by Kibédi et al. conflicted with the adopted value and resulted in a significant increase of nearly 50% in this branching ratio, directly affecting the triple-alpha reaction. Here, this work aims to utilize charged-particle spectroscopy with magnetic selection as a means to accurately measure the total radiative branching ratio (Γrad/Γ) of the Hoyle state in 12C.
The aim of the study was to assess the capabilities of age determination (age group) at death using classification techniques by histomorphometric characteristics of osseous and cartilaginous tissue ...aging. Materials and MethodsThe study material was a database containing the findings of morphometric researches of osseous and cartilaginous tissue histologic specimens from 294 categorized male corpses aged 10-93 years. For data analysis and classification we used modern machine learning methods: k-NN, SVM, logistic regression, CatBoost, SGD, naive Bayes, random forest, nonlinear dimensionality reduction methods (t-SNE and uMAP), and recursive feature elimination for feature selection. ResultsThe used techniques (algorithms) provided effective representation of a complex data set (76 histomorphometric features), allowing to reveal the cluster structure inside the low dimensional feature space, thus fitting the classifier becomes even more reasonable. During feature selection, we estimated their importance for age group classification and studied the relationship between classification quality and the number of features inside the feature space. Data pre-processing made it possible to get rid of noise and keep most informative features, thereby accelerating a learning process and improving the classification quality. Data projection showed more well-defined cluster structure in the space of selected features. The accuracy of establishing certain groups was equal to 90%. It proves high efficiency of machine learning techniques used for forensic age diagnostics based on histomorphometric findings.
The TexAT (Texas Active Target) detector is a new active-target time projection chamber (TPC) that was built at the Cyclotron Institute Texas A&M University. The detector is designed to be of general ...use for nuclear structure and nuclear astrophysics experiments with rare isotope beams. TexAT combines a highly segmented Time Projection Chamber (TPC) with two layers of solid state detectors. It provides high efficiency and flexibility for experiments with low intensity exotic beams, allowing for the 3D track reconstruction of the incoming and outgoing particles involved in nuclear reactions and decays.
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