Time-dependence of Heterogeneous Ice Nucleation by Ambient Aerosols: Laboratory Observations and a Formulation for Models

The time dependence of ice-nucleating particle (INP) activity is known to exist, yet for simplicity it is often omitted in atmospheric models as an approximation. Hitherto only limited experimental work has been done to quantify this time dependency, for which published data are especially scarce regarding ambient aerosol samples and longer time scales. In this study, the time dependence of INP activity is quantified experimentally for ambient environmental samples. The experimental approach includes a series of hybrid experiments with alternating constant cooling and isothermal experiments using a recently developed cold-stage setup called the Lund University Cold-Stage (LUCS). This approach of observing ambient aerosol samples provides the optimum realism for representing their time dependence in any model. Six ambient aerosol samples were collected representing aerosol conditions likely influenced by these types of INPs: marine, mineral dust, continental pristine, continental polluted, combustion-related and rural continental aerosol. Active INP concentrations were seen to be augmented by about 40 % to 100 % (or 70 % to 200 %), depending on the sample, over 2 (or 10) hours. This degree of time dependence observed was comparable to that seen in previous published works. Our observations show that the minority of active ice nuclei (IN) with strong time dependency on hourly time scales display only weak time dependence on short time scales of a few minutes. A general tendency was observed for the natural time scale of the freezing to dilate increasingly with time. The fractional freezing rate was observed to steadily declines exponentially with the order of magnitude (logarithm) of the time since the start of isothermal conditions. A representation of time dependence for incorporation into schemes of heterogeneous ice nucleation that currently omit time dependence is proposed.

Some living eukaryotes during and after scanning electron microscopy

Electron microscopy (EM) is an essential imaging method in biological sciences. Since biological specimens are exposed to radiation and vacuum conditions during EM observations, they die due to chemical bond breakage and desiccation. However, some organisms belonging to the taxa of bacteria, fungi, plants, and animals (including beetles, ticks, and tardigrades) have been reported to survive hostile scanning EM (SEM) conditions since the onset of EM. The surviving organisms were observed (i) without chemical fixation, (ii) after mounting to a precooled cold stage, (iii) using cryo-SEM, or (iv) after coating with a thin polymer layer, respectively. Combined use of these techniques may provide a better condition for preservation and live imaging of multicellular organisms for a long time beyond live-cell EM.

The late Matuyama glaciation in the southern European Alps

<p>The onset of Pleistocene glaciations in the European Alps represented a significant change in the palaeoenvironmental settings of this mountain range. The stratigraphy of the event was described in the subsoil of the Po Plain (Muttoni et al., 2003; Scardia et al., 2012) and is marked by a regional unconformity (namely “Red unconformity”, Muttoni et al., 2003) at 870 ka, in the final part of the Matuyama chron. Elsewhere, in the Alpine end-moraine systems the record of early stages of glaciations is scarce and cryptic. Spots of glacigenic deposits with reverse magnetic polarity were recognized only in the Ivrea (Carraro et al., 1991) and Garda (Cremaschi, 1987; Scardia et al., 2015) end-moraine systems, while deposits related to (peri)glacial environment were recorded along the Lombardian foothills (Scardia et al., 2010). The updated record of the Garda system shows the geometry of a late Matuyama glacier overrunning the piedmont plain with comparable size in respect to the LGM (Monegato et al., 2017). This indicates a fully glaciated Adige-Sarca catchment, one of the largest of the Alps, suggesting that the Alpine Ice Sheet reached one of its waxing climax during a late Matuyama cold stage (MIS20 or MIS22).</p><p> </p><p>References</p><p>Carraro et al. 1991, Boll. Museo Reg. Sc. Nat. Torino 9, 99-117.</p><p>Cremaschi 1987, Edizioni Unicopli, 306 pp.</p><p>Monegato et al. 2017, Scientific Reports 7, 2078.</p><p>Muttoni et al. 2003, Geology 31, 989-992.</p><p>Scardia et al. 2010, Quaternary Science Reviews 29, 832-846.</p><p>Scardia et al. 2012, Tectonics 31, TC6004.</p><p>Scardia et al. 2015, GSA Bulletin 127, 113-130.</p>

A Reduced-Cost Apparatus for Observing Ice Recrystallization Inhibition

This document contains instructions for building a low-cost apparatus to measure ice recrystallization and ice recrystallization inhibition. The supplies are commercially-available and total a fraction of the costs of a traditional microscope and cold-stage, thereby allowing more scientists the opportunity to become involved in this research as well as build the apparatus for possible use in chemical education.

A Reduced-Cost Apparatus for Observing Ice Recrystallization Inhibition

This document contains instructions for building a low-cost apparatus to measure ice recrystallization and ice recrystallization inhibition. The supplies are commercially-available and total a fraction of the costs of a traditional microscope and cold-stage, thereby allowing more scientists the opportunity to become involved in this research as well as build the apparatus for possible use in chemical education.