Evaluating Hydration and Artificial Aging Effects on the Paleointensity in Natural Glass

Young natural volcanic glasses have been successfully used to recover Earth’s geomagnetic field intensity (paleointensity). However, the magnetic stability and reliability of volcanic glass as a paleomagnetic recorder over geologic time is unclear. Paleointensity estimates may be influenced by natural processes that alter magnetic mineralogy. Previous results from paleointensity and rock magnetic experiments suggest that post-emplacement hydrothermal alteration can alter the magnetic remanence and can possibly cause paleointensity experiments to fail. Low-temperature hydration and natural relaxation of the glass structure over time may also adversely impact paleointensity results. In this study, rhyolitic and basaltic glass specimens underwent artificial aging and artificial hydration treatments to observe how the magnetic mineralogy and resulting magnetic properties are affected. The fresh rhyolitic glass contained pseudo-single-domain to multidomain low-Ti titanomagnetite, and basaltic glass contained single-domain and superparamagnetic grains of medium to low-Ti titanomagnetite. Artificial aging took place by heating in air at 200-400°C under anhydrous conditions for up to 240 days. Hydration was induced at 200 MPa pressure with elevated temperatures of 300℃ and 450℃ at different time intervals. Before and after aging or hydration, samples underwent experimental procedures to assess the impact of the aging or hydration treatments on magnetic mineralogy and behavior during paleointensity experiments. Aged samples were subject to a modified Thellier-Thellier paleointensity experiment, isothermal remanent magnetization (IRM) acquisition experiments, hysteresis and first order reversal curve (FORC) experiments, and thermal demagnetization of a three-component IRM. Hydrated samples were subject to hysteresis and FORC experiments, and IRM acquisition experiments. IRM acquisition experiments on artificially aged samples showed increases in saturation IRM and a decrease in coercivity in both rhyolitic and basaltic glass specimens. These trends in magnetic properties are believed to have arisen from a growth of existing grains within the basaltic and rhyolitic glasses. Paleointensity experiments showed that with increased aging temperature, basaltic glasses experience more alteration during paleointensity laboratory reheating experiments. This is not seen in rhyolitic glasses. Hydration experiments resulted in inconsistent changes in coercivity and magnetization over treatment. Changes in coercivity and magnetization in basaltic glasses were much greater than rhyolitic glasses. These changes may be explained by magnetic grain growth, loss of material, select dissolution of the finest magnetic grains, and possible oxidation in basaltic glass samples based on IRM experiments. Hydration rims appeared prominently in nearly all hydrated samples, with some rhyolitic glasses experiencing a hydrated interior while only one basaltic sample showed hydration within the interior. While young volcanic glass could be used as a good paleomagnetic recorder, results of this study suggest that older material might pose several problems. Older material could be hydrated, rehydrated, or have a change in the glass structure that results in a change in the magnetic mineral assemblage and therefore incorrect paleointensity and paleomagnetic data. It is recommended that the glass properties and hydration states of older glasses should be further studied before carrying out paleomagnetic studies

Suicide and dementia: A systematic review and meta-analysis of prevalence and risk factors.

Dementia is a global health concern with increasing numbers of people living long enough to develop dementia. People with dementia (PwD) may be particularly vulnerable to suicidality. However, suicide in PwD has not been thoroughly explored. The objective of this review was to determine the prevalence and risk factors of suicide in PwD. Five databases were searched from inception to July 2023. Peer-reviewed publications reporting prevalence, risk factors or quantitative summary data for suicide outcomes in PwD were included. Random effects models were used to calculate the pooled prevalence and effect sizes. 54 studies met inclusion criteria. In PwD, the point prevalence of suicidal ideation was 10 % (95 %CI=6 %;16 %), 2-year period prevalence of suicide attempts was 0.8 % (95 %CI=0.3 %;2 %), 10-year period prevalence of suicide attempts was 8.7 % (95 %CI=6.0 %%;12.7 %) and the incidence of death by suicide 0.1 % (95 %CI=0.1 %;0.2 %). Compared to not having dementia, a diagnosis of dementia increased risk of suicidal ideation (OR=1.62[95 %CI=1.17;2.24]) but not risk of suicide attempt (OR=1.77 [95 %CI=0.85;3.69]) or death by suicide (OR=1.30 [95 %CI=0.81;2.10]). People with moderate dementia had significantly increased risk of suicidal ideation than those with mild dementia (OR=1.59[95 %CI=1.11;2.28]), younger PwD were at increased risk of dying by suicide (OR=2.82[95 %CI=2.16;3.68]) and men with dementia were more likely to attempt (OR=1.28[95 %CI=1.25;1.31]) and die by suicide (OR=2.88[95 %CI=1.54;5.39]) than women with dementia. This review emphasises the need for mental health support and suicide prevention in dementia care, emphasising tailored approaches based on age, symptoms, and being male

Paleomagnetism indicates that primary magnetite in zircon records a strong Hadean geodynamo.

Determining the age of the geomagnetic field is of paramount importance for understanding the evolution of the planet because the field shields the atmosphere from erosion by the solar wind. The absence or presence of the geomagnetic field also provides a unique gauge of early core conditions. Evidence for a geomagnetic field 4.2 billion-year (Gy) old, just a few hundred million years after the lunar-forming giant impact, has come from paleomagnetic analyses of zircons of the Jack Hills (Western Australia). Herein, we provide new paleomagnetic and electron microscope analyses that attest to the presence of a primary magnetic remanence carried by magnetite in these zircons and new geochemical data indicating that select Hadean zircons have escaped magnetic resetting since their formation. New paleointensity and Pb-Pb radiometric age data from additional zircons meeting robust selection criteria provide further evidence for the fidelity of the magnetic record and suggest a period of high geomagnetic field strength at 4.1 to 4.0 billion years ago (Ga) that may represent efficient convection related to chemical precipitation in Earth's Hadean liquid iron core

Paleomagnetism indicates that primary magnetite in zircon records a strong Hadean geodynamo.

Determining the age of the geomagnetic field is of paramount importance for understanding the evolution of the planet because the field shields the atmosphere from erosion by the solar wind. The absence or presence of the geomagnetic field also provides a unique gauge of early core conditions. Evidence for a geomagnetic field 4.2 billion-year (Gy) old, just a few hundred million years after the lunar-forming giant impact, has come from paleomagnetic analyses of zircons of the Jack Hills (Western Australia). Herein, we provide new paleomagnetic and electron microscope analyses that attest to the presence of a primary magnetic remanence carried by magnetite in these zircons and new geochemical data indicating that select Hadean zircons have escaped magnetic resetting since their formation. New paleointensity and Pb-Pb radiometric age data from additional zircons meeting robust selection criteria provide further evidence for the fidelity of the magnetic record and suggest a period of high geomagnetic field strength at 4.1 to 4.0 billion years ago (Ga) that may represent efficient convection related to chemical precipitation in Earth's Hadean liquid iron core

Functional ceramic materials database: an online resource for materials research

We present work on the creation of a ceramic materials database which contains data gleaned from literature data sets as well as new data obtained from combinatorial experiments on the London University Search Instrument. At the time of this writing, the database contains data related to two main groups of materials, mainly in the perovskite family. Permittivity measurements of electroceramic materials are the first area of interest, while ion diffusion measurements of oxygen ion conductors are the second. The nature of the database design does not restrict the type of measurements which can be stored; as the available data increase, the database may become a generic, publicly available ceramic materials resource

Genomic reconstruction of the SARS-CoV-2 epidemic in England

AbstractThe evolution of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus leads to new variants that warrant timely epidemiological characterization. Here we use the dense genomic surveillance data generated by the COVID-19 Genomics UK Consortium to reconstruct the dynamics of 71 different lineages in each of 315 English local authorities between September 2020 and June 2021. This analysis reveals a series of subepidemics that peaked in early autumn 2020, followed by a jump in transmissibility of the B.1.1.7/Alpha lineage. The Alpha variant grew when other lineages declined during the second national lockdown and regionally tiered restrictions between November and December 2020. A third more stringent national lockdown suppressed the Alpha variant and eliminated nearly all other lineages in early 2021. Yet a series of variants (most of which contained the spike E484K mutation) defied these trends and persisted at moderately increasing proportions. However, by accounting for sustained introductions, we found that the transmissibility of these variants is unlikely to have exceeded the transmissibility of the Alpha variant. Finally, B.1.617.2/Delta was repeatedly introduced in England and grew rapidly in early summer 2021, constituting approximately 98% of sampled SARS-CoV-2 genomes on 26 June 2021.</jats:p