Cooperative Institute for Research in Environmental Sciences and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States.
Published: October 2015
AI Article Synopsis
Article Abstract
In this study, we have explored the phase behavior and the ice nucleation properties of secondary organic aerosol made from aqueous processing (aqSOA). AqSOA was made from the dark reactions of methylglyoxal with methylamine in simulated evaporated cloud droplets. The resulting particles were probed from 215 to 250 K using Raman spectroscopy coupled to an environmental cell. We find these particles are in a semisolid or glassy state based upon their behavior when exposed to mechanical pressure as well as their flow behavior. Further, we find that these aqSOA particles are poor depositional ice nuclei, in contrast to previous studies on simple mixtures of glassy organics. Additionally, we have studied the effect of ammonium sulfate on the phase, morphology, and ice nucleation behavior of the aqSOA. We find that the plasticizing effect of ammonium sulfate lowers the viscosity of the aqSOA, allowing the ammonium sulfate to effloresce within the aqSOA matrix. Upon humidification, the aqSOA matrix liquefies before it can depositionally nucleate ice, and the effloresced ammonium sulfate can act as an immersion mode ice nucleus. This change in the mode of nucleation is accompanied by an increase in the overall ice nucleation efficiency of the aqSOA particles.
Ice-nucleating proteins (INPs) from bacteria like are among the most effective ice nucleators known. However, large INP aggregates with maximum ice nucleation activity (at approximately -2 °C) typically account for less than 1% of the overall ice nucleation activity in bacterial samples. This study demonstrates that polyols significantly enhance the assembly of INPs into large aggregates, dramatically improving bacterial ice nucleation efficiency.
We investigated the role of a nanoporous particle on the formation of macroscopic solid in the framework of equilibrium thermodynamics and from the free-energy perspective. The model particle has cylindrical pores with equidistant circular openings on the particle surface. We focused on two potentially limiting steps: (i) the solid nucleation from liquid inside a single pore and (ii) the bridging of multiple pores on the particle surface.
Amber is a fragile (in Angell's classification) natural glass that has performed maturation processes over geological time. The terahertz dynamics of Baltic amber that was about 40 million years old were studied by terahertz time-domain spectroscopy (THz-TDS) in the frequency range of 0.2 and 6.
Temperature monitoring has immediate relevance to many areas of research, from atmospheric environmental studies to biological sample and food preservation to chemical reactions. Here, we use a triple-barrel electrode to provide temperature readouts in bulk solution and microdroplets, as well as electrochemically monitor freezing events in a microdroplet. Using this method, we are able to identify distinct characteristics of a freezing aqueous droplet (supercooling, ice formation beginning and end, temperature change, and thawing) with greater temporal resolution than a standard thermocouple and without the use of microscopy.
* This study focused on measuring the ice nucleation rate of 2-methyltetrols (2-MT), a component of certain organic aerosols, and found that as the aerosol's viscosity increases, its ice nucleation ability also increases significantly, especially when transitioning from liquid to semisolid states.
* A new model based on classical nucleation theory was created to quantify the relationship between viscosity and ice nucleation rate, which can be used in climate models to better represent cir
