Theoretical calculation of equilibrium Mg isotope fractionation between silicate melt and its vapor

Isotope fractionation during the evaporation of silicate melt and condensation of vapor has been widely used to explain various isotope signals observed in lunar soils, cosmic spherules, calcium-aluminum-rich inclu- sions, and bulk compositions of planetary materials. During evaporation and condensation, the equilibrium isotope fractionation factor （α） between high-temperature silicate melt and vapor is a fundamental parameter that can con- strain the melt＇s isotopic compositions. However, equilib- rium a is difficult to calibrate experimentally. Here we used Mg as an example and calculated equilibrium Mg isotope fractionation in MgSiO3 and Mg2SiO4 melt-vapor systems based on first-principles molecular dynamics and the high- temperature approximation of the Bigeleisen-Mayer equation. We found that, at 2500 K, 625Mg values in the MgSiO3 and Mg2SiO4 melts were 0.141 ±0.004 and 0.143 ±0.003‰ more positive than in their respective vapors. The corresponding 626Mg values were 0.270 ± 0.008 and 0.274 ± 0.006‰ more positive than in vapors, respectively. The general α - T equations describing the equilibrium Mg α in MgSiO3 and Mg2SiO4 melt-vapor systems were： αMg（l）-Mg（g） = 1 ＋ 5.264×10^5/T^2 （1/m - 1/m＇） and αmg（l）-Mg（g） = 1 ＋ 5.340×10^5/T^2 （1/m - 1/m＇）, respectively, Where m is the mass of light isotope, ^25Mg or ^26Mg. These results offer a necessary parameter for mechanistic under- standing of Mg isotope fractionation during evaporation and condensation that commonly occurs during the early stages of planetary formation and evolution.

Seed amplification assay of nasal swab extracts for accurate and non-invasive molecular diagnosis of neurodegenerative diseases

Nasal swabs are non-invasive testing methods for detecting diseases by collecting samples from the nasal cavity or nasopharynx.Dysosmia is regarded as an early sign of coronavirus disease 2019(COVID-19),and nasal swabs are the gold standard for the detection.By nasal swabs,severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)nucleic acids can be cyclically amplified and detected using real-time reverse transcriptase-polymerase chain reaction after sampling.Similarly,olfactory dysfunction precedes the onset of typical clinical manifestations by several years in prion diseases and other neurodegenerative diseases,such as Alzheimer’s disease,Parkinson’s disease,dementia with Lewy bodies,and multiple system atrophy.In neurodegenerative diseases,nasal swab tests are currently being explored using seed amplification assay(SAA)of pathogenic misfolded proteins,such as prion,α-synuclein,and tau.These misfolded proteins can serve as templates for the conformational change of other copies from the native form into the same misfolded form in a prion-like manner.SAA for misfolded prion-like proteins from nasal swab extracts has been developed,conceptually analogous to PCR,showing high sensitivity and specificity for molecular diagnosis of degenerative diseases even in the prodromal stage.Cyclic amplification assay of nasal swab extracts is an attractive and feasible method for accurate and non-invasive detection of trace amount of pathogenic substances for screening and diagnosis of neurodegenerative disease.