Aspirated capacitor measurements of air conductivity and ion mobility spectra

Measurements of ions in atmospheric air are used to investigate atmospheric electricity and particulate pollution. Commonly studied ion parameters are (1) air conductivity, related to the total ion number concentration, and (2) the ion mobility spectrum, which varies with atmospheric composition. The physical principles of air ion instrumentation are long-established. A recent development is the computerised aspirated capacitor, which measures ions from (a) the current of charged particles at a sensing electrode, and (b) the rate of charge exchange with an electrode at a known initial potential, relaxing to a lower potential. As the voltage decays, only ions of higher and higher mobility are collected by the central electrode and contribute to the further decay of the voltage. This enables extension of the classical theory to calculate ion mobility spectra by inverting voltage decay time series. In indoor air, ion mobility spectra determined from both the novel voltage decay inversion, and an established voltage switching technique, were compared and shown to be of similar shape. Air conductivities calculated by integration were: 5.3 +- 2.5 fS/m and 2.7 +- 1.1 fS/m respectively, with conductivity determined to be 3 fS/m by direct measurement at a constant voltage. Applications of the new Relaxation Potential Inversion Method (RPIM) include air ion mobility spectrum retrieval from historical data, and computation of ion mobility spectra in planetary atmospheres.Comment: To be published in Review of Scientific Instrument

Osmotic stress induces JNK-dependent embryo invasion in a model of implantation

In vitro culture during assisted reproduction technologies (ARTs) exposes pre-implantation embryos to environmental stressors, such as non-physiological nutritional, oxidative and osmotic conditions. The effects on subsequent implantation are not well understood but could contribute to poor ART efficiency and outcomes. We have used exposure to hyperosmolarity to investigate the effects of stress on the ability of embryos to interact with endometrial cells in an in vitro model. Culturing mouse blastocysts for 2 h in medium with osmolarity raised by 400 mosmol induced blastocoel collapse and re-expansion, but did not affect subsequent attachment to, or invasion of, the endometrial epithelial Ishikawa cell line. Inhibition of stress-responsive c-Jun N-terminal kinase (JNK) activity with SP600125 did not affect the intercellular interactions between these embryos and the epithelial cells. Four successive cycles of hyperosmotic stress at E5.5 had no effect on attachment, but promoted embryonic breaching of the epithelial cell layer by trophoblast giant cells in a JNK-dependent manner. These findings suggest that acute stress at the blastocyst stage may promote trophoblast breaching of the endometrial epithelium at implantation and implicates stress signalling through JNK in the process of trophectoderm differentiation into the invasive trophoblast necessary for the establishment of pregnancy. The data may lead to increased understanding of factors governing ART success rates and safety

Solar-driven variation in the atmosphere of Uranus

Long-term measurements (1972-2015) of the reflectivity of Uranus at 472 and 551 nm display variability that is incompletely explained by seasonal effects. Spectral analysis shows this non-seasonal variability tracks the 11-year solar cycle. Two mechanisms could cause solar modulation, (a) nucleation onto ions or electrons created by galactic cosmic rays (GCR), or (b) UV-induced aerosol colour changes. Ion-aerosol theory is used to identify expected relationships between reflectivity fluctuations and GCR flux, tested with multiple regression and compared to the linear response predicted between reflectivity and solar UV flux. The statistics show that 24% of the variance in reflectivity fluctuations at 472 nm is explained by GCR ion-induced nucleation, compared to 22% for a UV-only mechanism. Similar GCR-related variability exists in Neptune’s atmosphere, hence the effects found at Uranus provide the first example of common variability in two planetary atmospheres driven through energetic particle modulation by their host star

Late diagenesis of illite-smectite in the Podhale Basin, southern Poland: Chemistry, morphology, and preferred orientation

Well-characterized samples from the Podhale Basin, southern Poland, formed the basis for exploring and illuminating subtle diagenetic changes to a mudstone toward the upper end of the diagenetic window, prior to metamorphism.Transmission electron microscopy (TEM) performed on dispersed grains and ion-beam thinned preparations, selected area diffraction patterns,and chemistry by TEM-EDS (energy dispersive spectra) augmented mineralogy and fabric data. The deepest samples show no change in their percent illite in illite-smectite (I-S), yet I-S–phase octahedral Fe3+ and Al3+ are statistically different between samples. A decrease in the Fe3+ concentration in the octahedral sheet correlates with an increase in I-S fabric intensity and apparent crystallinity. The D-statistic from the Kolmogorov-Smirnov test on TEM- EDS data describes statistical differences in the I-S chemistry. Previous work on these samples showed a significant increase in the preferred orientation of the I-S phase across the smectite to illite transition and a significant slowdown in the rate of development of preferred orientation beyond the termination of smectite illitization. Lattice fringe images describe an I-S morphology that coalesces into larger and tighter packets with increasing burial temperature and a decrease in I-S packet contact angle, yet some evidence for smectite collapse structures is retained. The deepest sample shows the thickest, most coherent I-S packets. We propose that the deepest samples in the Podhale Basin describe the precursor stage in phyllosilicate fabric preferred orientation increase from diagenesis into metamorphism, where continued evolution of crystallite packets and associated crystallinity create higher I-S fabric intensities as the structural formulae of I-S approach an end-member composition