Search

This study evaluates the coded aperture imaging method for pitch angle observations of magnetospheric energetic electrons in the solar, Earth, and planetary space environments. We present a review of key previous energetic electron instruments with pitch angle‐resolved observations across a range of electron energies. We describe the coded aperture imaging method, typically used for high angular resolution X‐ray and gamma ray observations, and evaluate design parameters in the context of energetic electron observations. We present the results of simulations of energetic electrons in Geant4 and evaluate the method's ability to resolve sources with high angular and temporal resolution. We also evaluate the impact of secondary radiation produced from electron interactions in the tungsten coded aperture, as well as the impact of artifacts from the decoding process. With these simulated results, we identify key areas in magnetospheric science that would benefit from high angular resolution observations of energetic electrons. We find that coded aperture imaging may be well‐suited for high‐resolution observations of intense localized structures, such as low energy (tens of eV to several keV) field‐aligned electron beams or the electron strahl wind. Key Points: We have developed a Geant4 model to simulate energetic electrons propagating through a coded aperture to a detectorWe show that for extended sources, careful design is necessary to account for artifacts from sources in the partially coded field of viewFor compact sources, such as field‐aligned electron beams, coded aperture imaging can provide high resolution pitch angle observations [ABSTRACT FROM AUTHOR]

Mica exhibits a relatively high Rb/Sr ratio and possesses a closure temperature for the Rb-Sr isotope system that is higher than the ore-forming temperature range of low- to medium-temperature deposits. Consequently, utilizing the laser ablation (LA) technique for in situ Rb-Sr dating in mica constitutes a significant methodology for resolving the mineralization chronology of low- to medium-temperature hydrothermal ore deposits. In this study, we employed a combination of a triple quadrupole inductively coupled plasma mass spectrometer (ICP-MS/MS) and 193 nm LA system with SF6 as the reaction gas to achieve interference removal of 87Rb+ on 87Sr+. We then developed an in situ Rb-Sr dating method for mica. In addition, an investigation was conducted to identify the factors that could influence the analytical accuracy of the method. Subsequently, we applied the developed method to carry out in situ Rb-Sr dating for the ZBH-25 biotite, a national primary reference material (GBW04439) for K-Ar dating, and yielded a younger age (ca. 12%, relative standard deviation, RSD) than the reference K-Ar age when using NIST SRM 610 as the reference material for external calibration. This finding indicated that in the process of determining Rb-Sr ages for mica by LA-ICP-MS/MS, there are significant matrix effects between the NIST SRM 610 and the mica samples, resulting in inaccurate Rb-Sr ages. In response to this issue, a two-step calibration method is proposed here. Based on external calibration using NIST SRM 610, ZBH-25 biotite is employed as a second external reference material to perform a second calibration of the sample data to correct the matrix effect between the glass standards and the natural mica samples, thereby improving the accuracy of Rb-Sr dating by LA-ICP-MS/MS. Using the proposed method, in situ Rb-Sr dating by LA-ICP-MS/MS was performed on mica samples from monzonite exposed in Mt. Dromedary, New South Wales, Australia, porphyritic granodiorite in Fangshan pluton and albionite granite in the Gyirong area of Tibet. The obtained Rb-Sr age results show agreement with the recommended values within the analytical uncertainty, which serves to validate the accuracy and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

We present zircon U–Pb ages, major and trace element analyses and zircon Hf isotope data on the Cretaceous mafic–felsic igneous rocks in the north‐eastern North China Craton (NCC) of NE China. These data have been used to discuss the petrogenesis of the mafic–felsic igneous rocks in order to constrain the geodynamical and magmatic evolution of the region. Zircon U–Pb dating results indicate that these igneous rocks crystallized during the Cretaceous (ca. 123–90 Ma). These mafic igneous rocks display low SiO2 contents, high MgO contents and marked enrichments in large‐ion lithophile elements (LILEs) and depletions in high‐field‐strength elements (HFSEs), combined with their εHf(t) values and La/Nb versus La/Ba diagram, suggesting they were derived from lithospheric mantle that experienced gradually increasing fluid metasomatism from 123 to 90 Ma. The felsic igneous rocks with high SiO2 values are metaluminous to weakly peraluminous and belong to the high–K calc–alkaline series. These felsic igneous rocks are all enriched in light rare earth elements (LREEs) and LILEs and relatively depleted in HFSEs, with barely negative Eu anomalies, combined with their εHf(t) values, these felsic igneous rocks were derived from partial melting of a lower crust. A synthesis of these new data with previous researches shows that the subduction and rollback of the Palaeo‐Pacific slab played a major role in the destruction of the north‐eastern NCC. The diagenetic temperatures of igneous rocks indicate that the mechanism of destruction of the NCC may be heterogeneous, most likely a thermal erosion mechanism in eastern Jilin area and a delamination mechanism in Liaodong Peninsula. [ABSTRACT FROM AUTHOR]

We study the dependence of the primordial nuclear abundances as a function of the electromagnetic fine-structure constant α , keeping all other fundamental constants fixed. We update the leading nuclear reaction rates, in particular the electromagnetic contribution to the neutron-proton mass difference pertinent to β -decays, and go beyond certain approximations made in the literature. In particular, we include the temperature-dependence of the leading nuclear reactions rates and assess the systematic uncertainties by using four different publicly available codes for Big Bang nucleosynthesis. Disregarding the unsolved so-called lithium-problem, we find that the current values for the observationally based 2 H and 4 He abundances restrict the fractional change in the fine-structure constant to less than 2 % , which is a tighter bound than found in earlier works on the subject. [ABSTRACT FROM AUTHOR]

In situ U‐Pb geochronology and hafnium, oxygen and zirconium isotope measurements in zircons using laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) and ion microprobe techniques can provide essential isotopic data to constrain geological evolutionary histories. Developing reliable zircon reference materials is the cornerstone for in situ zircon chronology and isotopic studies. In this study, the homogeneity of U‐Pb ages and Hf‐O‐Zr isotope ratios in three Sri Lankan zircon megacrysts (SLZA, SLZB and SLZC) were investigated using multiple analytical methods. The obtained U, Th, Pb and Hf mass fractions of the SLZA zircon were 839 ± 56 μg g‐1 (1s), 151 ± 15 μg g‐1 (1s), 198 ± 28 μg g‐1 (1s) and 8635 ± 286 μg g‐1 (1s), respectively. The mass fractions of U, Th, Pb and Hf in the SLZB zircon were 1106 ± 106 μg g‐1 (1s), 331 ± 61 μg g‐1 (1s), 376 ± 57 μg g‐1 (1s) and 9673 ± 976 μg g‐1 (1s), respectively. The U, Th, Pb and Hf mass fractions determined in the SLZC zircon were 551 ± 35 μg g‐1 (1s), 111 ± 8 μg g‐1 (1s), 129 ± 18 μg g‐1 (1s) and 7881 ± 393 μg g‐1 (1s), respectively. The chemical abrasion isotope dilution thermal ionisation mass‐spectrometry (CA‐ID‐TIMS) method yielded a Th‐corrected weighted mean 206Pb/238U age of 556.94 ± 1.29 Ma (95% conf., n = 5) for the SLZA zircon, 552.90 ± 1.29 Ma (95% conf., n = 7) for the SLZB zircon and 560.83 ± 1.29 Ma (95% conf., n = 7) for the SLZC zircon. The obtained Hf isotopic compositions of the SLZA, SLZB and SLZC zircons determined with the solution MC‐ICP‐MS method were 0.281651 ± 0.000014 (2s, n = 10), 0.281704 ± 0.000008 (2s, n = 10) and 0.281676 ± 0.000006 (2s, n = 10), respectively. The obtained O isotopes of the SLZA and SLZB zircons measured with the laser fluorination method were 12.14 ± 0.56‰ (2s, n = 4) and 11.91 ± 0.30‰ (2s, n = 4), respectively. The Zr isotopes of the SLZA, SLZB and SLZC zircons determined with double spike TIMS analysis yielded mean δ94/90ZrSRM3169 values of ‐0.03 ± 0.06‰ (2s, n = 10), ‐0.03 ± 0.04‰ (2s, n = 10) and 0.00 ± 0.07‰ (2s, n = 8), respectively. The SLZA zircon can be used as a primary reference or quality control material for microbeam U‐Pb, Hf and Zr isotope measurements because of its slight heterogeneity. The U‐Pb, Hf and Zr isotopic compositions of the SLZB and SLZC megacrysts were homogeneous. The O isotopic compositions in the SLZA and SLZB zircon were slightly dispersed, indicating that these two megacrysts can only serve as secondary reference materials for microbeam O isotope measurements. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations were applied to study primary damage formation in collision cascades initiated by the recoil of primary knock-on atoms (PKAs) with PKA energies = 5, 10, 15, 20, and 25 keV in α-Ti at temperature T = 100, 300, 600, and 900 K. A statistical sample of 24 collision cascades per set of parameters was generated in order to assure statistical reliability of the obtained results. The size of the sampling set was justified posteriori using a simple procedure. The number of Frenkel pairs, , and cascade relaxation time were obtained as functions of . It was found that the average values fit into ≈0.3NRT if the threshold displacement energy is selected in the range of 28–40 eV depending on the irradiation temperature. At high PKA energies/low temperatures, collision cascades in α-Ti tend to break up into subcascades elongated along the trajectories of high-energy recoil atoms and their relaxation time does not depend on . At low PKA energies/high temperatures, equiaxed collision cascades dominate and their relaxation time increases monotonically with increasing PKA energy . [ABSTRACT FROM AUTHOR]

Molecular diagnostic point-of-care (MDx POC) testing is gaining momentum and is increasingly important for infectious disease detection and monitoring, as well as other diagnostic areas such as oncology. Molecular testing has traditionally required high-complexity laboratories. Laboratory testing complexity is determined by utilizing the Clinical Laboratory Improvement Amendments of 1988 (CLIA) Categorization Criteria scorecard, utilizing seven criteria that are scored on a scale of one to three. Previously, most commercially available point-of-care (POC) tests use other analytes and technologies that were not found to be highly complex by the CLIA scoring system. However, during the COVID-19 pandemic, MDx POC testing became much more prominent. Utilization during the COVID-19 pandemic has demonstrated that MDx POC testing applications can have outstanding advantages compared to available non-molecular POC diagnostic tests. This article introduces MDx POC testing to students, technologists, researchers, and others, providing a general algorithm for MDx POC test development. This algorithm is an introductory, step-by-step decision tree for defining a molecular POC diagnostic device meeting the functional requirements for a desired application. The technical considerations driving the decision-making include nucleic acid selection method (DNA, RNA), extraction methods, sample preparation, number of targets, amplification technology, and detection method. The scope of this article includes neither higher-order multiplexing, nor quantitative molecular analysis. This article covers key application considerations, such as sensitivity, specificity, turnaround time, and shipping/storage requirements. This article provides an overall understanding of the best resources and practices to use when developing a MDx POC assay that may be a helpful resource for readers without extensive molecular testing experience as well as for those who are already familiar with molecular testing who want to increase MDx availability at the POC. © 2024 Wiley Periodicals LLC., (© 2024 Wiley Periodicals LLC.)

Aims. With this article, we aim to provide the sputtering yields for molecular species of potential astrophysical interest and in the electronic regime of interaction characteristic of cosmic rays. We specifically target molecules that are constitutive of interstellar ice mantles. Methods. We used a compendium of existing data on electronic sputtering to calculate the prefactors leading to the generalisation of the stopping-power-dependent sputtering yield for many species condensing at low temperature. In addition, we present new experimental results to constrain the yield for solid CH4, C6, and CH3CN. Results. Electronic sputtering is constrained using literature data for H2, HD, D2, Ne, N2, CO, Ar, O2, Kr, Xe, CO2, SO2, NH3, S, H2O, D2O, CH3OH, Leucine, C20H12, C24H12, and C60. A first-order relation with the sublimation enthalpy is derived, which allows us to predict the sputtering yield within an order of magnitude for most species. The fluctuations around the mean are partly assignable to the differences in resilience towards radiolysis for individual species, and partly to the micro-physics details of the energy transfer to the lattice. [ABSTRACT FROM AUTHOR]

Giant volcanic eruptions have the potential to overturn civilizations. Yet, the driving mechanism and timescale over which batholithic magma reservoirs transition from non‐eruptible crystal mush to mobile melt‐dominated stages and our capacity to detect a pending super‐eruption remain obscure. Here we show, using Sr isotope zonation in plagioclase crystals from three Andean large‐magnitude eruptions (Atana, Toconao, and Tara ignimbrites), that eruptible magma forms by amalgamation of isotopically diverse crystal populations and silicic melt without large‐scale reheating. In each case, crystals record large isotopic diversity in crystal cores, converging toward a common value in crystal rims that coincides with the composition of the rhyolitic carrier melt. Using diffusion chronometry, we show that the assembled magma resided pre‐eruptively in the crust for timescales of no more than decades to centuries for Atana and Tara, but up to several millennia for Toconao. These timescales and isotopic observations are consistent with the accumulation and destabilization of melt‐rich layers in crystal mush. While the prospect of capturing such melt lenses with most geophysical monitoring techniques is pessimistic, gravity modeling indicates that such structures are potentially resolvable. Our findings provoke a new assessment of the origin and hazards associated with large magnitude explosive eruptions. Plain Language Summary: Super‐eruptions are the largest manifestation of explosive volcanism on Earth. If such an event would occur today, it could deeply impact human civilization on a global scale. Yet, signals that may emerge prior to such eruptions are difficult to constrain. To gain greater understanding of the mechanisms and timescales over which giant, eruptible, reservoirs form, and to evaluate our capacity of capturing the evolution toward large eruptions, we studied plagioclase crystals, a mineral that is an excellent recorder of magmatic processes. For three large eruptions in the Central Andes, we analyzed strontium isotopes in traverses from crystal cores to rims to provide a temporal record of melt composition. Our results show that, in each case, the eruptible magma amalgamated from distinct pre‐existing magma pockets that merged prior to eruption. This merged state of the magma did not exist for longer than a few hundred to thousands of years based on the preservation of the crystal strontium‐isotope traverses at high temperatures. These results are consistent with the destabilization of melt‐rich layers on timescales comparable to human lifespans. Although most geophysical imaging methods are unlikely to capture this process, our calculations indicate that gravity monitoring of super‐volcanoes can potentially resolve such structures. Key Points: Sr‐isotopes in plagioclase record the emergence of eruptible magma through amalgamation of pre‐existing mush in the Central AndesThe amalgamated magma did not reside at depth for longer than centuries to millennia based on diffusion chronometryForward modeling indicates that high‐precision gravity monitoring has large potential to resolve eruptible magma amalgamation [ABSTRACT FROM AUTHOR]

Copyright of Rock & Mineral Analysis is the property of Editorial Board of Rock & Mineral Analysis and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In nanographite films, for the first time, when measuring the current–voltage characteristics, the Josephson current at room temperature has been detected, which confirms the earlier observations in nanographite films of the effects of weak superconductivity: zeroing of the temperature dependence at 650 K of the constant voltage on the sample when exposed to an alternating microwave voltage due to the inverse Josephson effect, as well as observation in a magnetic force microscope of local regions with the structure of magnetic vortices at room temperature. The obtained value of the critical current of 0.8 μA is significantly lower than the expected value for the superconducting gap, as well as for pinning at the Bean–Levingston barrier. Measures for increasing the critical current are proposed. [ABSTRACT FROM AUTHOR]

Utilizing three–parameter Morse function as model interaction describing the scattering between two alpha particles, and Coulomb potential in the form of erf() function, the resulting potentials for various channels have been constructed. The scattering phase shifts (SPS) are obtained by phase function method (PFM) in an iterative fashion, while varying the Morse parameters till the mean absolute percentage error (MAPE)-value w.r.t experimental data reach a minimum. The SPS from the optimized potentials for , and partial waves are matching with the experimental SPS, for experimental energies upto 25.5 MeV to MAPE-values of 1.17, 0.69 and 1.77 respectively. The partial cross sections at various energies for and channels have been determined and are in consonance with those obtained using Complex scaling method (CSM). [ABSTRACT FROM AUTHOR]

The Neoproterozoic granites along the western margin of the Yangtze Block are crucial for understanding the evolution of the Rodinia supercontinent and crust–mantle interaction. Based on a regional geological survey, this study analyses the zircon U–Pb geochronology, Lu–Hf isotope, whole‐rock Sr–Nd isotopes, and geochemistry of the Maoniushan granites along the western margin of the Yangtze Block and discusses the Neoproterozoic tectonic evolution history of the Mianning–Maoniushan belt. The results show that the Maoniushan granites belong to calc‐alkaline weak peraluminous monzogranite. The granites are enriched in large‐ion lithophile elements (i.e., Rb, Sr, Cs, and Ba) but relatively depleted in high‐field‐ strength elements (i.e., Nb, Ta, U, and Th). The zircon saturation temperature (TZr) ranges from 628 to 766°C, and the weighted average 206Pb/238U ages of zircon range from 771 ± 30 to 759 ± 26 Ma. The εHf(t) values range from −2.0 to +7.2, with TDM2 model ages ranging from 1,797 to 1,208 Ma. The whole‐rock Sr–Nd isotopic data show (87Sr/86Sr)i ratios of 0.7039–0.7093, and the εNd(t) values range from +1.25 to +1.76 with TDM2 model ages ranging from 1,303 to 1,344 Ma. These findings indicate the presence of deep Mesoproterozoic crustal materials in the source area. The Maoniushan monzogranites belong to I‐type granite, which is formed by the partial melting of the basic rocks and pelites in the ancient lower crust due to the metasomatism of fluids from the subducted oceanic crust. The Maoniushan monzogranites may be formed in the process of transformation from regional thickening to thinning under the oceanic crust subduction setting. [ABSTRACT FROM AUTHOR]