A procedure to optimize the geometrical model of an n-type detector is described. Sixteen lines from seven point sources ((241)Am, (133)Ba, (22)Na, (60)Co, (57)Co, (137)Cs and (152)Eu) placed at three different source-to-detector distances (10, 20 and 30 cm) were used to calibrate a low-background gamma spectrometer between 26 and 1408 keV. Direct Monte Carlo techniques using the MCNPX 2.6 and GEANT 4 9.2 codes, and a semi-empirical procedure were performed to obtain theoretical efficiency curves. Since discrepancies were found between experimental and calculated data using the manufacturer parameters of the detector, a detail study of the crystal dimensions and the geometrical configuration is carried out. The relative deviation with experimental data decreases from a mean value of 18-4%, after the parameters were optimized.
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http://dx.doi.org/10.1016/j.apradiso.2010.06.018 | DOI Listing |
J Chem Phys
January 2025
Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
In this work, we propose a path integral Monte Carlo approach based on discretized continuous degrees of freedom and rejection-free Gibbs sampling. The ground state properties of a chain of planar rotors with dipole-dipole interactions are used to illustrate the approach. Energetic and structural properties are computed and compared to exact diagonalization and numerical matrix multiplication for N ≤ 3 to assess the systematic Trotter factorization error convergence.
View Article and Find Full Text PDFACS Nano
January 2025
Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401, United States.
Colloids can be used either as model systems for directed assembly or as the necessary building blocks for making functional materials. Previous work primarily focused on assembling colloids under a single external field, where controlling particle-particle interactions is limited. This work presents results under a combination of electric and magnetic fields.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Bernal Institute and Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Ireland.
2D and 3D porous coordination networks (PCNs) as exemplified by metal-organic frameworks, MOFs, have garnered interest for their potential utility as sorbents for molecular separations and storage. The inherent modularity of PCNs has enabled the development of crystal engineering strategies for systematic fine-tuning of pore size and chemistry in families of related PCNs. The same cannot be said about one-dimensional (1D) coordination polymers, CPs, which are understudied with respect to porosity.
View Article and Find Full Text PDFJ Chem Theory Comput
January 2025
Department of Electrical & Computer Engineering, Stony Brook University, Stony Brook, New York 11794, United States.
In this work, we develop a novel Bayesian approach to study the adsorption and desorption of CO onto a Pd(111) surface, a process of great importance in natural sciences. The motivation for this work comes from the recent availability of time-resolved infrared spectroscopy data and the need for model interpretability and uncertainty quantification in chemical processes. The objective is to learn the relevant parameters that characterize the process: coverage with time, rate constants, activation energies, and pre-exponential factors.
View Article and Find Full Text PDFEcotoxicol Environ Saf
December 2024
Chinese Academy of Geological Sciences, China Geology Survey, Ministry of Natural Resources, Beijing 100037, China.
This study investigates the pollution characteristics, spatial patterns, causes, and ecological risks of heavy metals in the soils of the southeastern Hubei polymetallic mining areas, specifically the Jilongshan (JLS) and Tonglushan (TLS) regions, located in the middle and lower reaches of the Yangtze River. The main findings are as follows: (1) Among the heavy metals present in the soil, copper (Cu) has the highest average concentration at 278.54 mg/kg, followed by zinc (Zn) at 161.
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