Freezing behavior

Animal models of fear and anxiety have primarily used the rat, the mouse and, to a lesser extent, nonhuman primates. It is not particularly difficult to evoke or measure anxiety in these species. However, difficulties arise when one attempts to define exactly how a stimulus and resultant behavioral response are related to human behavior, i.e. when a mouse exhibits freezing behavior to an unfamiliar and threatening cue, what is the human equivalent Or, similarly, what stimulus could one present to a rat to best model the anxiety-inducing-experience of... 

Talsma et al. [1.34] described the freezing behavior of certain liposomes by DSC measurements. Besides the expected influences of freezing and rewarming speeds, and of the CPAs (mannitol and mannitol in Tris-buffer solutions) it was shown, that the heterogeneous and homogeneous crystallization in mannitol solutions exists and the nucleation of ice depends also on the liposome size In small liposomes (e. g. 0.14 pm) mannitol suppressed the heterogeneous crystallization more effectively than in large (0.87 pm) liposomes. If in certain substances no crystallization or eutectic mixtures can be found by DSC (cephalosporin, Williams [1.35]) with the used experimental conditions, one has to seek different conditions [1.32]. 

MacKenzie, A.P. 1977. Non-equilibrium freezing behavior of aqueous systems. Phil. Trans. R. Soc. LondB. 278, 167-189. 

Hashimoto S, Inoue T, Koyama T (1999) Effects of conditioned fear stress on serotonin neurotransmission and freezing behavior in rats. Eur J Pharmacol 378 23-30 Hayley S, Borowski T, Merali Z, Anisman H (2001) Central monoamine activity in genetically distinct strains of mice following a psychogenic stressor effects of predator exposure. Brain Res 892 293-300... 

Figure 2.1 Fear responses involve the activation of many brain areas. The hypothalamus controls physical changes in the body, such as increased blood pressure and dilated pupils. The central gray area causes freezing behavior, the reticular net triggers a reflex response, and norepinephrine increases attention.

Central gray— A region deep in the brain that suppresses motor activation and causes freezing behavior. 

Bertram, A. K., and J. J. Sloan, Temperature-Dependent Nucleation Rate Constants and Freezing Behavior of Submicron Nitric Acid Dihydrate Aerosol Particles under Stratospheric Conditions, J. Geophys. Res., 103, 3553-356f (f998a). 

Tabazadeh, A., O. B. Toon, and P. Hamill, Freezing Behavior of Stratospheric Sulfate Aerosols Inferred from Trajectory Studies, Geophys. Res. Lett., 22, 1725-1728 (1995). 

Just as the presence of a solute disrupts the rate of ice crystal formation, so does it disrupt the rate of ice microcrystal formation. As you should recall, it is the formation of microcrystals in fresh water that results in fresh water s expansion as it is cooled below 4°C. Without the formation of microcrystals, saltwater continues to contract all the way to its freezing temperature of about —18°C. Ocean water, therefore, is most dense just before it freezes, which makes its freezing behavior most different from that of fresh water. To see for yourself, place a cupful of saltwater next to a cupful of fresh water in your kitchen freezer. 

The freezing behaviors of ideal mixtures over the entire range of temperatures can be calculated readily. The method is explained for example by Walas (Phase Equilibria in Chemical Engineering, Butterworths, Stoneham, MA, 1985, Example 8.9). 

In addition to eutectic crystallization and glass formation (vitrification), there are other types of freezing behavior which may be observed... 

Contextual fear conditioning (CFC) that depends on fear memory has been established as an animal model of anxiety. During the postadolescent period, rats were exposed to CFC as shown in Fig. 2. Fear-related freezing behavior during... 

Tada, K., Kasamo, K., Suzuki, T., Matsuzaki, Y., and Kojima, T. (2004). Endogenous 5-HT inhibits firing activity of hippocampal CA1 pyramidal neurons during conditioned fear stress-induced freezing behavior through stimulating 5-HT1A receptors. Hippocampus 14, 143-147. 

Now the research effort goes toward experimental verification of the elevation phenomena in the simplest geometry, a slit. Our main interest is in the range of a few to several nanomenters. Some experimental studies have already reported freezing point elevation in slit pores [8-10], but the materials used were activated carbon fibers (ACFs), which have only micropores less than 2nm. In such small pores the first layer adjacent to the attractive pore wall, which is known to form a frozen phase at a temperature well above the bulk freezing point, will occupy most of the pore spaces, and the freezing behavior in the interior of the pore space is difficult to be detected. Further, there may still remain some controversy if a liquid confined in a larger nanopore would exhibit elevation unless an experimental verification is made over such sizes. 

Three kinds of liquids of analytical grade (Wako Pure Chemicals) were used. All liquids were desiccated with zeolite 4A molecular sieve for one week before experimental use. Cyclohexane, and octamethylcyclotetrasiloxane (OMCTS), whose bulk freezing point were 6.4°C and ISTl respectively were used for the examination of freezing behavior. The reasons of the choice were i)affinity to carbonaceous surface, ii)freezmg point near ambient temperature, and iii)almost spherical molecular shape. Methanol, with bulk freezing point of -98 C was also used as a reference. All the force measurement were done after confirming the stability of the temperature under control for at least 10 minutes The temperature was set at various values above the bulk freezing point. 

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