Development of Freezing Nucleation Apparatus

[871049] Vali对冻结核特性的基本认识是大气科学和其他科学的一个重要问题。大气科学界认识到，云中冰的起源是理解云过程的主要不确定因素之一。这些过程反过来又是全球环流和水循环模式不确定性的最关键来源。在生物学领域，冰成核已被发现具有广泛的重要性。已经鉴定出细菌和真菌冰核，并且已经表明，冰核测量可以提供比微生物试验更有效的方法来鉴定食品中的细菌污染物。冰核被用于喷冰技术（包括人工造雪）。通过控制植物上的冰核细菌可以预防霜冻对农业植物的危害，虫害的生存也可以得到类似的控制。首席研究员将开发的新型冷冻核装置有可能大大加强这些领域的研究活动，因为缺乏简单可靠的测量方法经常被研究人员列为一个严重问题。该仪器将提供一个显著的改进，比常用的滴冷冻法测定冻结核的活度在水中。新仪器提供的主要进步将是保持样品完整性和高度可靠性。样品的完整性将通过将子样品放置在单独的密封小瓶中来实现。通过这种方式，每个子样品都可以通过任何所需的冷冻顺序或其他测试来保存，而不受持续时间的任何严重限制。同样的步骤也保证了没有可能将冰虚假地扩散到样品中，这是早期设备的主要限制。该仪器的成功开发有望导致与大气和生物冰形成有关的冻结成核的新研究，包括更好地测量溶质、抑制剂和活化剂的影响；原子核的稳定性；成分分析;云和降水样品的分析；以及生物冰核和大气冰核之间的联系。这些课题大多在以前的实验中得到了解决，但只能得到统计结果，而且由于早期仪器的缺点，一些结果仍然存在疑问。＊＊＊

9871049 Vali Fundamental understanding of the characteristics of freezing nuclei is an important problem for the atmospheric and other sciences. The atmospheric science community recognizes that the origins of ice in clouds is one of the major uncertainties in the understanding of cloud processes. Those processes in turn are the most critical source of uncertainties in global models of the general circulation and the water cycle. In the biological arena, ice nucleation has been found to have widespread importance. Bacterial and fungal ice nuclei have been identified and it has been shown that ice nucleation measurements can provide more effective ways than microbiological tests for the identification of bacterial contaminants in food. Ice nuclei are being used in spray ice technology (including artificial snow making). Prevention of frost damage to agricultural plants is possible via control of ice nucleating bacteria on plants, and insect pest survival may be controlled similarly. The new freezing nuclei apparatus that the Principal Investigator will develop has the potential to significantly enhance research activity in these areas, since the unavailability of simple and reliable measurement methods has been frequently cited by researchers as a serious problem. This apparatus will provide a significant improvement over the commonly used drop freezing method of determining the activity of freezing nuclei in water. The principal advances provided by the new instrument will be the preservation of sample integrity and a high degree of reliability. Sample integrity will be achieved by placing sub-samples in individual sealed vials. In this manner each sub-sample can be preserved through any desired sequence of freezing or other tests without any serious limitation on duration. This same step also assures that there is no possibility of spurious spread of ice into the sample which was a major limitation of earlier devices. Successful develo pment of this instrument is expected to lead to new research on freezing nucleation, in relation to atmospheric and biological ice formation including better measurements of the effects of solutes, inhibitors, and activators; the stability of nuclei; compositional analyses; the analyses of cloud and precipitation samples; and the connection between biogenic and atmospheric ice nuclei. Most of these topics have been addressed in previous experiments but only statistical results could be obtained, and some results remained in doubt because of shortcomings of earlier instruments. ***