Supercooling

At high latitudes and altitudes, ice formation is a major variable affecting survival of freshwater fauna and hence the abundance and composition of invertebrate communities. Freezing, but also desiccation and anoxia, are lethal threats to all life stages of aquatic insects, from the eggs to the adults. During cold periods, the aquatic stages commonly remain in or move to a

This paper describes anchor ice formation in the Laramie River, a small river in Wyoming. Anchor ice in the Laramie River forms predominately in riffles at night, although minor amounts also form on sand substrates. Anchor ice crystals are large, indicating that in situ thermal growth is important. Anchor ice forms on the river’s bed, and, when released from the bed, rafts bed sediment downstream. The floating, released anchor ice is a major contributor to the river’s surface ice cover. A conceptual model for anchor ice formation is developed. This model suggests that water supercooled in pools supplies a heat sink that absorbs the latent heat of fusion of anchor ice growing in riffles. The net result is a non-uniform distribution of anchor ice on the bed. We discuss flow parameters important for determining anchor ice growth, and show how a substantial set of parameters influence anchor ice formation.

The longevity of Asian citrus psyllid, Diaphorina citri, infected by an entomopathogenic fungus, Isaria fumosorosea, was studied by microcalorimetry. Experimental results of microcalorimetry suggest that in the process of metabolism of D. citri heat or heat flow declined exponentially. The metabolism of D. citri inhibited by increasing temperature, and the longevity of D. citri decreased gradually with respect to temperature. The long-evity of D. citri almost reaches 500 h at 25 °C and D. citri died within 130 h at 41 °C under high-temperature exposure. The same phenomenon, decrease in longevity and metabolism inhibition, was observed under the low-temperature exposure. The supercooling point of insects can be derived from a cooling curve plotting the temperature versus time by using microcalorimetry. The heat released due to phase change can be determined by using microcalorimeter. Our results indicated that microcalorimetry can be used to measure the metabolism of herbivore insects.

We demonstrate some recent progress in understanding the anomalous behavior of liquid water, by combining information provided by recent experiments and simulations on water in bulk, nanoconfined, and biological environments. We interpret evidence from recent experiments designed to test the hypothesis that liquid water may display 'polymorphism' in that it can exist in two different phases--and discuss recent work on water's transport anomalies as well as the unusual behavior of water in biological environments. Finally, we will discuss how the general concept of liquid polymorphism may prove useful in understanding anomalies in other liquids, such as silicon, silica, and carbon, as well as metallic glasses which have in common that they are characterized by two characteristic length scales in their interactions.

Time to maximum supercooling is a parameter that can be easily measured during experiments on the dynamic, nonequilibrium stage of frazil ice formation. Mercier has determined an analytical expression for the time to maximum supercooling that depends only on the four basic system parameters: the rates of heat loss, seeding, turbulent dissipation and secondary nucleation. Mercier's analytical expression is applied to a number of experiments, the heat loss rate and turbulent dissipation rate were reported or could be determined from the experiment description. The secondary nucleation was set at the value of 4x10 to the 10th power nuclei/erg suggested by Mercier, and the seeding rate optimized to reproduce the experimental results, An inverse relationship was found between the coldroom temperature at which, the experiment was conducted and the seeding rate. The optimized seeding rates varied from 2.7. to 7.5x.00001 crystals/sq cm s. The implications for frazil ice formation in riv...

Water in confined geometries has obvious relevance in biology, geology, and other areas where the material properties are strongly dependent on the amount and behavior of water in these types of materials. Another reason to restrict the size of water domains by different types of geometrical confinements has been the possibility to study the structural and dynamical behavior of water in the deeply supercooled regime (e.g., 150-230 K at ambient pressure), where bulk water immediately crystallizes to ice. In this paper we give a short review of studies with this particular goal. However, from these studies it is also clear that the interpretations of the experimental data are far from evident. Therefore, we present three main interpretations to explain the experimental data, and we discuss their advantages and disadvantages. Unfortunately, none of the proposed scenarios is able to predict all the observations for supercooled and glassy bulk water, indicating that either the structural...

In this paper we study the four point correlation function $\chi_4$ of collective density fluctuations in a nonequilibrium liquid. The equilibration is controlled by a modified stretched exponential behavior ( $\exp [-{(t_\mathrm{w}/\tau)}^\beta]$ ) having the relaxation time $\tau$ dependent on the aging time $t_\mathrm{w}$. Similar aging behavior has been seen experimentally in supercooled liquids. The basic equations of fluctuating nonlinear hydrodynamics (FNH) are solved here numerically to obtain $\chi_4$ for equilibrium and non equilibrium states. We also identify a dynamic length scale $\xi$ from the equilibrated function. $\xi(T)$ grows with fall of temperature $T$. From a broader perspective, we demonstrate here that the characteristic signatures of dynamical heterogeneities in a supercooled liquid, observed previously in computer simulations of the dynamics of a small number of particles, are also present in the coarse grained equations of generalized hydrodynamics.

In this paper, a new type of sensor for in-line measurements of antifreeze mass fraction in aqueous solutions is described. Its principles of operation are based on the exploitation of the temperature rise that accompanies the freezing of an undercooled solution. ...

Deschampsia antarctica Desv. (Poaceae) and Colobanthus quitensis (Kunth) Bartl. (Cariophyllaceae) are the only two vascular plants that have colonized the Maritime Antarctic. The primary purpose of the present work was to determine cold resistance mechanisms in these two Antarctic plants. This was achieved by comparing thermal properties of leaves and the lethal freezing temperature to 50% of the tissue (LT50). The grass D. antarctica was able to tolerate freezing to a lower temperature than C. quitensis. The main freezing resistance mechanism for C. quitensis is supercooling. Thus, the grass is mainly a freezing-tolerant species, while C. quitensis avoids freezing. D. antarctica cold acclimated; thus, reducing its LT50. C. quitensis showed little cold-acclimation capacity. Because day length is highly variable in the Antarctic, the effect of day length on freezing tolerance, growth, various soluble carbohydrates, starch, and proline contents in leaves of D. antarctica growing in the laboratory under cold-acclimation conditions was studied. During the cold-acclimation treatment, the LT50 was lowered more effectively under long day (21/3 h light/dark) and medium day (16/8) light periods than under a short day period (8/16). The longer the day length treatment, the faster the growth rate for both acclimated and non-acclimated plants. Similarly, the longer the day treatment during cold acclimation, the higher the sucrose content (up to 7-fold with respect to non-acclimated control values). Oligo and polyfructans accumulated significantly during cold acclimation only with the medium day length treatment. Oligofructans accounted for more than 80% of total fructans. The degrees of polymerization were mostly between 3 and 10. C. quitensis under cold acclimation accumulated a similar amount of sucrose than D. antarctica, but no fructans were detected. The suggestion that survival of Antarctic plants in the Antarctic could be at least partially explained by accumulation of these substances is discussed.