Neural network predictions of (α,n) reaction cross sections at 18.5±3 MeV using the Levenberg-Marquardt algorithm

In recent developments, artificial neural networks (ANNs) have demonstrated their capability to predict reaction cross-sections based on experimental data. Specifically, for predicting (α,n) reaction cross-sections, we meticulously fine-tuned the neural network's performance by optimizing its parameters through the Levenberg-Marquardt algorithm. The effectiveness of this approach is corroborated by notable correlation coefficients; an R-value of 0.90928 for overall correlation, 0.98194 for validation, 0.99981 for testing, and 0.94116 for the comprehensive network prediction. We conducted a rigorous comparison between the results and theoretical computations derived from the TALYS 1.95 nuclear code to validate the predictive accuracy. The mean square error value for artificial neural network results is 7620.92, whereas for TALYS 1.95 calculations, it has been found to be 50,312.74. This comprehensive evaluation process validates the reliability of the ANN based on the Levenberg-Marquardt algorithm in approximating the reaction sections, thus demonstrating its potential for comprehensive investigations. These recent developments confirm the feasibility of using ANN models to gain insight into (α,n) reaction cross-sections.

Process optimization of broad ion beam milling for preparation of coating cross-sections

The application of Argon ion based broad ion beam milling in the preparation of coating cross-sections is systematically evaluated in this work. In order to reduce and eliminate defects and artefacts from the prepared sectional surface, the substrate side of the sample is found to be best facing the ion beams, and the milling time needs to be optimized to be not too long to introduce scratching of the obtained surface, while not too short to result in particle deposition. Further, the energy of the ion beams is found to have great effect on the etch rate of the sample, thus having a large impact on the process time and quality depending on the materials nature of the samples. It is found that by introducing a second low-energy polishing step after the high-energy milling step, the quality of the cross-section is greatly improved with the measured surface roughness down to the nanometer scale. The capability of broad ion beam milling method to provide smooth cross-sections for the subsequent microscopic investigations by e.g. scanning electron microscopy or atomic force microscopy is important to reveal morphological information of the coating systems with high level of details without distortions due to sample preparation.

Empirical formula for (n, f) reaction cross sections of Uranium isotopes at 1-20 MeV neutrons

This article describes how to calculate neutron-induced fission reaction cross sections using a proposed empirical formula and the EMPIRE 3.2.3 and TALYS 1.95 computer codes for Uranium isotopes up to the third fission plateau. In this study, the excitation functions of 232U (n, f), 233U (n, f), 234U (n, f), 235U (n, f), 236U (n, f), 237U (n, f) and 238U (n, f) nuclear reactions were calculated at 1-20 MeV neutron energies. The results were contrasted to measured values from the Experimental Nuclear Reaction Data (EXFOR) as well as the evaluated data from Evaluated Nuclear Data File (ENDF) such as (EAF-2010, JEFF-3.3, ENDF/B-VIII.0 and TENDL-2019). Overall, the calculated, experimental, and evaluated fission cross-sections are in concordance.

Can we reach suitable 161Tb purity for medical applications using the 160Gd(d,n) reaction?

Terbium is a chemical element that has several radioactive isotopes with suitable physical characteristics to be used in medical applications either for imaging or for therapy. This makes terbium a promising element to implement the theranostic approach. For therapeutic applications, 161Tb (T1/2 = 6.89 d) is suitable for targeted β-therapy. The main production route is through neutron capture reaction in nuclear reactors. In this work, we explored an alternative production route, the 160Gd(d,n)161Tb reaction. We have measured its production cross-section as well as those of possible co-produced contaminants, with a special focus on 160Tb (T1/2 = 72.3 d). To achieve this, cross-section measurements were made from natural gadolinium target. Production yields of 10.3 MBq/μA/h for the 161Tb and 1.5 MBq/μA/h for the 160Tb were obtained at 20 MeV. A161Tb radionuclidic purity of 86% was achieved over the 8 MeV-20 MeV energy range. The co-production of other terbium isotopes limits the interest of using higher energies. Based on the limited purity of 161Tb using the 160Gd(d,n)161Tb reaction, we conclude that it is not a production route suitable for medical applications. Although, this may be reconsidered when mass separation technique with high efficiency will be available.

Electronically excited states of formic acid investigated by theoretical and experimental methods

Absolute cross-section values are reported from high-resolution vacuum ultraviolet (VUV) photoabsorption measurements of gas-phase formic acid (HCOOH) in the photon energy range 4.7-10.8 eV (265-115 nm), together with quantum chemical calculations to provide vertical energies and oscillator strengths. The combination of experimental and theoretical methods has allowed a comprehensive assignment of the electronic transitions. The VUV spectrum reveals various vibronic features not previously reported in the literature, notably associated with (3pa'←10a'), (3p'a'←10a'), (3sa'←2a″) and (3pa'←2a″) Rydberg transitions. The assignment of vibrational features in the absorption bands reveal that the C=O stretching, v₃^'a', the H'-O-C' deformation, v₅^'a^', the C-O stretching, v₆^'a^', and the O=C-O' deformation, v₇^'a^' modes are mainly active. The measured absolute photoabsorption cross sections have also been used to estimate the photolysis lifetime of HCOOH in the upper stratosphere (30-50 km), showing that solar photolysis is an important sink at altitudes above 30 km but not in the troposphere. Potential energy curves for the lowest-lying electronic excited states, as a function of the C=O coordinate, are obtained employing time dependent density functional theory (TD-DFT). These calculations have shown the relevance of internal conversion from Rydberg to valence character governing the nuclear dynamics, yielding clear evidence of the rather complex multidimensional nature of the potential energy surfaces involved.

Confocal Laser Scanning Microscopy Approach to Investigate Plant-Fungal Interactions

Plants interact with a broad range of microorganisms, such as bacteria and fungi. In plant roots, complex microbial communities participate in plant nutrition and development as well as in the protection against stresses. The establishment of the root microbiota is a dynamic process in space and time regulated by abiotic (e.g., edaphic, climate, etc.) and biotic factors (e.g., host genotype, root exudates, etc.). In the last 20 years, the development of metabarcoding surveys, based on high-throughput next-generation sequencing methods, identified the main drivers of microbial community structuration. However, identification of plant-associated microbes by sequencing should be complemented by imaging techniques to provide information on the micrometric spatial organization and its impact on plant-fungal and fungal-fungal interactions. Laser scanning confocal microscopy can provide both types of information and is now used to investigate communities of endophytic, endomycorrhizal, and ectomycorrhizal fungi. In this chapter, we present a protocol enabling the detection of fungal individuals and communities associated to the plant root system.

Production cross-section measurements of proton-induced reactions on natural tantalum in the 0.3 GeV-1.7 GeV energy range

This work reports the production cross-section data for seventy-one radionuclides produced by 0.3 GeV-1.7 GeV protons impinging on thin tantalum targets. For that purpose, activation experiments were performed using the COSY synchrotron at FZ Jülich utilizing the stacked-foils technique and γ-ray spectrometry with high-purity germanium detectors. The Al-27(p,x)Na-24 reaction has been used as monitor reaction. All experimental data have been systematically compared with the existing literature. The excitation functions of Te-116, I-123, Dy-153 and Er-158 are reported for the first time.

Measurements of formation cross-sections of short-lived nuclei around the 14 MeV neutron induced reactions on 180Hf and 90Zr and theoretical calculation of excitation functions

The cross sections of the ¹⁸⁰Hf(n,p)¹⁸⁰Lu and ⁹⁰Zr(n,2n)^89mZr reactions were measured around the neutron energies of 13.5-14.8 MeV by using the activation technique. The excitation functions of the above reactions in the neutron energies from the threshold to 20 MeV were calculated by using the nuclear theoretical model program system Talys-1.9 with the adjusted relevant parameters. The measured results were discussed and compared with previous experiments by other researchers and with the evaluated data of ENDF/B-VIII.0, CENDL-3.1, JEFF-3.3, JENDL-4.0u2, BROND-3.1 as well as the theoretical values based on Talys-1.9. The obtained experimental values at some neutron energies, within experimental error, are consistent with those of the fitting line of the results of previous experiments and are also consistent with those of theoretical excitation curve at the corresponding energies. The obtained theoretical excitation curves match well with most of the experimental data.

Calculation of 89Y(p,x)86,88,89gZr, 86g,87g,88gY, 85gSr, and 84Rb reaction cross sections based on level density

Excitation functions based on level density were calculated for proton-induced on yttrium-89 using the TALYS-1.8 code. Hence, production cross-section of the ⁸⁹Y(p,x)^86,88,89gZr, ^86g,87g,88gY, ^85gSr, and ^84gRb were computed up to 50 MeV. In this study, the constant temperature model alongside the Fermi Gas model (CGCM) was employed as a default model. For this reason, the a-parameter as an essential parameter in the Fermi Gas formula was modified to obtain the best result. Besides, the Back-shifted Fermi Gas Model (BSFGM) and the Generalized Superfluid Model (GSM) are presented to the deliberation. The outcomes of cross-sections were compared with the experimental data approaching regarding desired consequences.

Exploring atmospheric stagnation during a severe particulate matter air pollution episode over complex terrain in Santiago, Chile

A severe air quality degradation event occurred in the Santiago Metropolitan Area (SMA), Chile, in June 2014. Meteorological and air quality measurements from 11 stations in the area as well as numerical simulations using the Weather and Research Forecasting (WRF) model were used to explain the main reasons for the occurrence of elevated particulate matter (PM) concentrations. The conditions were characterized with formation of a coastal low in central Chile between the southeastern anticyclone and a high-pressure system over Argentina. At a local scale, these conditions generated a depression at the base of the inversion layer, an increase in the vertical thermal stability, lower humidity and low-wind conditions, which were conducive to a decrease in pollutant dispersion and insufficient ventilation of the polluted air. Measurements and simulations using the WRF model revealed a vertical structure of the boundary layer during these stagnant conditions and provided a basis for a trajectory analysis. The back-trajectory calculation showed that the transport of air parcels was contained in the valley during the highest concentrations. The analysis also enabled the definition of the threshold values of a simple indicator of air pollution (ventilation coefficient, VC), which confirmed the evolution of the episode and divided the observed daily concentrations into two groups, with one including values above the limits prescribed by the national air quality standards (NAQS) and the other including values below these limits. For the SMA, the daily PM concentrations above the NASQ limits were associated with an overall mean threshold value of VC below 500 m² s^-1 (for PM_2.5) and 300 m² s^-1 (for PM₁₀). To apply the VC analysis to other pollutants and different geographic locations, different threshold values should be evaluated.

A neural network approach to analyze cross-sections of muscle fibers in pathological images

Morphological characteristics of muscle fibers, such as their cross-sections, are important indicators of the health and function of the musculoskeletal system. However, manual analysis of muscle fiber morphology is a labor-intensive and time-consuming process that is prone to errors. Overall, the procedure involves high inter- and intra-observer variability. Therefore, it is desirable for biologists to have a tool that can produce objective and reproducible analysis for muscle fiber images. In this work, we propose a deep convolutional neural network (DCNN) followed by post-processing for detecting and measuring the cross-sections of muscle fibers. We evaluate three segmentation networks for muscle boundary segmentation: (1) U-net, (2) FusionNet, and (3) a customized FusionNet. The customized FusionNet, which had the highest Dice coefficient on the test set, was used for subsequent morphological analysis of the muscle fibers. The proposed method was tested on microscopic images of the tibialis anterior muscles of a pre-clinical model of muscular dystrophy. The dataset contained four mosaic images, totalling more than 3400 fibers. Because of the severity of muscle injury in this pre-clinical model, its muscle fiber images present a challenge for quantitative analysis for several reasons. First, the muscle fibers had inhomogeneous spatial distribution and very different sizes. Second, the membranes of the muscle fibers had uneven signal intensity due to the loss of a membrane protein. Third, the shapes of intact muscle fibers were very different. All these factors contributed to the difficulty of acquiring good training data in the first place. Despite these difficulties, we achieved an average muscle fiber overlay precision of 0.65 and an average recall of 0.49. In this context, overlaid fibers are defined as fibers that have one or more pixels overlaying in the manual and DCNN cross-section segmentation. For the overlaid fibers, the proposed method achieved excellent segmentation accuracy of 94% ± 10.26%, as measured by the Dice-Sorensen coefficient.

Measurement of formation cross-section of 99Mo from the 98Mo(n,γ) and 100Mo(n,2n) reactions

The formation cross-section of medical isotope ⁹⁹Mo from the ⁹⁸Mo(n,γ) reaction at the neutron energy of 0.025eV and from the ¹⁰⁰Mo(n,2n) reaction at the neutron energies of 11.9 and 15.75MeV have been determined by using activation and off-line γ-ray spectrometric technique. The thermal neutron energy of 0.025eV was used from the reactor critical facility at BARC, Mumbai, whereas the average neutron energies of 11.9 and 15.75MeV were generated using ⁷Li(p,n) reaction in the Pelletron facility at TIFR, Mumbai. The experimentally determined cross-sections were compared with the evaluated nuclear data libraries of ENDF/B-VII.1, CENDL-3.1, JENDL-4.0 and JEFF-3.2 and are found to be in close agreement. The ¹⁰⁰Mo(n,2n)⁹⁹Mo reaction cross-sections were also calculated theoretically by using TALYS-1.8 and EMPIRE-3.2 computer codes and compared with the experimental data.

Production cross-sections of radionuclides from α-induced reactions on natural copper up to 50MeV

The excitation functions were measured for the (nat)Cu(α,x)(66,67)Ga,(65)Zn,(57,58,60)Co reactions in the energy range of 16.5 -50MeV. A conventional stacked-foil activation technique combined with HPGe γ-ray spectrometry was employed to determine cross-sections. The measured cross-sections were critically compared with relevant previous experimental data and also with the evaluated data in the TENDL-2014 library. Present results confirmed some of the previous experimental data, whereas only a partial agreement was found with the evaluated data. The measured data are useful for reducing the existing discrepancies in the literature, to improve the nuclear reaction model codes, and to enrich the experimental database towards various applications.

Rotationally inelastic dynamics of LiH (X(1)Σ(+), v = 0) in collisions with Ar: State-to-state inelastic rotational rate coefficients

A theoretical study of rotational collision of LiH(X(1)Σ(+),v = 0, J) with Ar has been carried out. The ab initio potential energy surface (PES) describing the interaction between the Ar atom and the rotating LiH molecule has been calculated very accurately and already discussed in our previous work [Computational and Theoretical Chemistry 993 (2012) 20-25]. This PES is employed to evaluate the de-excitation cross sections. The ab initio PES for the LiH(X(1)Σ(+))-Ar((1)S) Van der waals system is calculated at the coupled-cluster [CCSD(T)] approximation for a LiH length fixed to an experimental value of 3.0139 bohrs. The basis set superposition error (BSSE) is corrected and the bond functions are placed at mid-distance between the center of mass of LiH and the Ar atom. The cross sections are then derived in the close coupling (CC) approach and rate coefficients are inferred by averaging these cross sections over a Maxwell-Boltzmann distribution of kinetic energies. The 11 first rotational levels of rate coefficients are evaluated for temperatures ranging from 10 to 300 K. We notice that the de-excitation rate coefficients appear large in the order 10(-10) cm(-3) s(-1) and show very low temperature dependence. The rate coefficients magnify significantly the propensity toward ∆ J = -1 transitions. These results confirm the same propensity already noted for the cross sections.

Automated image segmentation of haematoxylin and eosin stained skeletal muscle cross-sections

The ability to accurately and efficiently quantify muscle morphology is essential to determine the physiological relevance of a variety of muscle conditions including growth, atrophy and repair. There is agreement across the muscle biology community that important morphological characteristics of muscle fibres, such as cross-sectional area, are critical factors that determine the health and function (e.g. quality) of the muscle. However, at this time, quantification of muscle characteristics, especially from haematoxylin and eosin stained slides, is still a manual or semi-automatic process. This procedure is labour-intensive and time-consuming. In this paper, we have developed and validated an automatic image segmentation algorithm that is not only efficient but also accurate. Our proposed automatic segmentation algorithm for haematoxylin and eosin stained skeletal muscle cross-sections consists of two major steps: (1) A learning-based seed detection method to find the geometric centres of the muscle fibres, and (2) a colour gradient repulsive balloon snake deformable model that adopts colour gradient in Luv colour space. Automatic quantification of muscle fibre cross-sectional areas using the proposed method is accurate and efficient, providing a powerful automatic quantification tool that can increase sensitivity, objectivity and efficiency in measuring the morphometric features of the haematoxylin and eosin stained muscle cross-sections.