External Ice Research Articles

Optimal Control Policy of the Microwave Primary Freeze Drying of Random Solids

The optimal strategy of microwave energy input in freeze drying is proposed to keep the temperature of the material external surface, ice core, and sublimation interface as high as possible. This should ensure maximum process efficiency without violating the set constraints. The safety factors are introduced on electric field strength to avoid corona discharge. The microwave power is considered either constant or time variable during the process. A mathematical model of the microwave freeze-drying process is formulated with time-varying transport and dielectric properties of the frozen and dried layers. This model takes into account unknown a priori sublimation front temperature T S and mass concentration of water vapor C S at moving ice front. Comparative analysis of the various process operation conditions is performed to determine the optimal control policy for microwave freeze drying. It is demonstrated that applying an optimal control strategy for limiting process conditions significantly reduces the total microwave freeze-drying time in the primary stage.

Sea-ice thickness variability in Storfjorden, Svalbard

AbstractResults from electromagnetic induction surveys of sea-ice thickness in Storfjorden, Svalbard, reveal large interannual ice-thickness variations in a region which is typically characterized by a reoccurring polynya. the surveys were performed in March 2003, May 2006 and March 2007 with helicopter- and ship-based sensors. the thickness distributions are influenced by sea-ice and atmospheric boundary conditions 2 months prior to the surveys, which are assessed with synthetic aperture radar (SAR) images, regional QuikSCAT backscatter maps and wind information from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis dataset. Locally formed thin ice from the Storfjorden polynya was frequently observed in 2003 and 2007 (mean thickness 0.55 and 0.37 m, respectively) because these years were characterized by prevailing northeasterly winds. In contrast, the entire fjord was covered with thick external sea ice in 2006 (mean thickness 2.21 m), when ice from the Barents Sea was driven into the fjord by predominantly southerly winds. the modal thickness of this external ice in 2006 increased from 1.2m in the northern fjord to 2.4 m in the southern fjord, indicating stronger deformation in the southern part. This dynamically thickened ice was even thicker than multi-year ice advected from the central Arctic Ocean in 2003 (mean thickness 1.83 m). the thermodynamic ice thickness of fast ice as boundary condition is investigated with a one-dimensional sea-ice growth model (1DICE) forced with meteorological data from the weather station at the island of Hopen, southeast of Storfjorden. the model results are in good agreement with the modal thicknesses of fast-ice measurements in all years.

Low temperature survival of post-eclosion stages of the potato rot nematode <i>Ditylenchus destructor</i> Thorne (Tylenchida: Anguinidae)

AbstractThe potato rot nematode, Ditylenchus destructor, may experience extreme environmental stress caused by freezing temperatures when overwintering in the field. A series of laboratory experiments were conducted in order to clarify overwintering strategies of the nematode. The current study aimed to examine the cold tolerance of this species in various aqueous environments as well as in plant tissues in order to determine its ability to survive 24 h exposure to subzero temperatures. Cold tolerance of adults and fourth-stage juveniles was significantly lower than that of younger juveniles. The lower lethal temperature of adults was –15°C. Although external ice formation affects all life stages, a few second-stage juveniles were able to survive temperatures as low as –30°C. The results expand the current understanding of freezing survival in the potato rot nematode and will lead to better comprehension of its ability to withstand subzero temperature conditions.

The overwintering physiology of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae)

Ability to survive cold is an important factor in determining northern range limits of insects. The emerald ash borer ( Agrilus planipennis) is an invasive beetle introduced from Asia that is causing extensive damage to ash trees in North America, but little is known about its cold tolerance. Herein, the cold tolerance strategy and mechanisms involved in the cold tolerance of the emerald ash borer were investigated, and seasonal changes in these mechanisms monitored. The majority of emerald ash borers survive winter as freeze-intolerant prepupae. In winter, A. planipennis prepupae have low supercooling points (∼−30 °C), which they achieve by accumulating high concentrations of glycerol (∼4 M) in their body fluids and by the synthesis of antifreeze agents. Cuticular waxes reduce inoculation from external ice. This is the first comprehensive study of seasonal changes in cold tolerance in a buprestid beetle.

Freeze avoidance: a dehydrating moss gathers no ice

Using cryo-SEM with EDX fundamental structural and mechanical properties of the moss Ceratodon purpureus (Hedw.) Brid. were studied in relation to tolerance of freezing temperatures. In contrast to more complex plants, no ice accumulated within the moss during the freezing event. External ice induced desiccation with the response being a function of cell type; water-filled hydroid cells cavitated and were embolized at -4 °C while parenchyma cells of the inner cortex exhibited cytorrhysis, decreasing to ∼ 20% of their original volume at a nadir temperature of -20 °C. Chlorophyll fluorescence showed that these winter acclimated mosses displayed no evidence of damage after thawing from -20 °C while GCMS showed that sugar concentrations were not sufficient to confer this level of freezing tolerance. In addition, differential scanning calorimetry showed internal ice nucleation occurred in hydrated moss at ∼-12 °C while desiccated moss showed no evidence of freezing with lowering of nadir temperature to -20 °C. Therefore the rapid dehydration of the moss provides an elegantly simple solution to the problem of freezing; remove that which freezes.

Freezing in the Antarctic limpet, Nacella concinna

The process of organismal freezing in the Antarctic limpet, Nacella concinna, is complicated by molluscan biology. Internal ice formation is, in particular, mediated by two factors: (a) the provision of an inoculative target for ice formation in the exposed mucus-secreting foot; and (b) osmoconformity to the marine environment. With regard to the first, direct observations of the independent freezing of pedal mucus support the hypothesis that internal ice formation is delayed by the mucal film. As to the second, ice nucleation parametrics of organismal tissue (head, midgut, gonad, foot) and mucus in both inter- and subtidal populations were characterized by high melting points (range = −4.61 to −6.29 °C), with only c.50% of a given sample osmotically active. At this stage it would be premature to ascribe a cryo-adaptive function to the mucus as the protective effects are more readily attributed to the physical properties of the secretion (i.e. viscosity) and their corresponding effects on the rate of heat transfer. As it is difficult to thermally distinguish between the freezing of mucus and the rest of the animal, the question as to whether it is tolerant of internal as well as external ice formation remains problematic, although it may be well suited to the osmotic stresses of organismal freezing.

The Temperature and Type of Intracellular Ice Formation in Preimplantation Mouse Embryos as a Function of the Developmental Stage1

Our studies the past 5 yr have concentrated on intracellular ice formation (IIF) in mature mouse oocytes at the metaphase stage of meiosis II. Here we report an analogous investigation of the temperature of intracellular ice nucleation in preimplantation embryo stages from one-cell to early morula suspended in 1 M ethylene glycol/PBS and cooled at 20 degrees C/min to -70 degrees C. Physical modeling indicates that oocytes and preimplantation embryos undergo very little osmotic shrinkage at that cooling rate. As a consequence, their interior becomes increasingly supercooled until the supercooling is abruptly terminated by IIF. Four categories of IIF were observed. The first two were 1) those undergoing IIF at temperatures well below the temperature of external ice formation (EIF; -7.2 degrees C) vs. 2) those undergoing IIF within 1 degrees C of the EIF temperature. The other two categories were those multicellular stages in which 3) all the blastomeres underwent IIF simultaneously vs. 4) those in which blastomeres underwent IIF sequentially. Embryos in categories 1 and 3 constituted the majority (80-90%), and for them, the mean IIF temperatures of one-cell, two-cell, four- to six-cell, and early eight-cell ranged from -37 degrees C to -43 degrees C, temperatures that indicate that IIF is a consequence of homogeneous nucleation. However, the IIF nucleation temperature of early morulae in categories 1 and 3 was markedly higher; namely, -23.1 +/- 1.5 degrees C. This marked rise in nucleation temperature coincides with the appearance of aquaporin 3 and gap junctions in early morulae (compacted eight-cell), and is presumably causally related.

Development of computer program for simulation of an ice bank system operation, Part I: Mathematical modelling

Since the use of standard engineering methods in the process of an ice bank performance evaluation offers neither adequate flexibility nor accuracy, the aim of this research was to provide a powerful tool for an industrial design of an ice storage system allowing to account for the various design parameters and system arrangements over a wide range of time varying operating conditions. In this paper the development of a computer application for the prediction of an ice bank system operation is presented. Static, indirect, cool thermal storage systems with external ice on coil building/melting were considered. The mathematical model was developed by means of energy and mass balance relations for each component of the system and is basically divided into two parts, the model of an ice storage system and the model of a refrigeration unit. Heat transfer processes in an ice silo were modelled by use of empirical correlations while the performance of refrigeration unit components were based on manufacturers data. Programming and application design were made in Fortran 95 language standard. Input of data is enabled through drop down menus and dialog boxes, while the results are presented via figures, diagrams and data (ASCII) files. In addition, to demonstrate the necessity for development of simulation program a case study was performed. Simulation results clearly indicate that no simple engineering methods or rule of thumb principles could be utilised in order to validate performance of an ice bank system properly.

S0601-1-3 マイクロ波デハイドロフリージングに対する解凍条件の影響(食と熱工学(1))

Effect of thawing rate on the food quality has been studied by using the mackerel. The samples were frozen at temperature -20℃ and -80℃. Three different conditions were supplied for the thawing, i.e. microwave irradiation of 100W, warming by room temperature at 25℃ and in the refrigerator at 8℃. The results indicated that drip production decreases with the decreasing thawing rates. The microwave pre-dehydration can also reduce the drip loss. The microscopic observation indicated that the muscle fibers were melted first then followed by the melting of the external ice. The melted ice (water) gradually was absorbed by the muscle fibers. The results give evidence to hypothesis that the thawing conditions affect the amount of drip loss because the cells need time for re-absorption of the extracellular water.

Evaluation of a comprehensive slip, trip and fall prevention programme for hospital employees**

In 2007, the Bureau of Labor Statistics reported that the incidence rate of lost workday injuries from slips, trips and falls (STFs) on the same level in hospitals was 35.2 per 10,000 full-time equivalents (FTE), which was 75% greater than the average rate for all other private industries combined (20.2 per 10,000 FTEs). The objectives of this 10-year (1996–2005) longitudinal study were to: 1) describe occupational STF injury events in hospitals; 2) evaluate the effectiveness of a comprehensive programme for reducing STF incidents among hospital employees. The comprehensive prevention programme included analysis of injury records to identify common causes of STFs, on-site hazard assessments, changes to housekeeping procedures and products, introduction of STF preventive products and procedures, general awareness campaigns, programmes for external ice and snow removal, flooring changes and slip-resistant footwear for certain employee subgroups. The hospitals' total STF workers’ compensation claims rate declined by 58% from the pre-intervention (1996–1999) rate of 1.66 claims per 100 FTE to the post-intervention (2003–2005) time period rate of 0.76 claims per 100 FTE (adjusted rate ratio = 0.42, 95% CI: 0.33–0.54). STFs due to liquid contamination (water, fluid, slippery, greasy and slick spots) were the most common cause (24%) of STF claims for the entire study period 1996–2005. Food services, transport/emergency medical service and housekeeping staff were at highest risk of a STF claim in the hospital environment. Nursing and office administrative staff generated the largest numbers of STF claims. STF injury events in hospitals have a myriad of causes and the work conditions in hospitals are diverse. This research provides evidence that implementation of a broad-scale prevention programme can significantly reduce STF injury claims.

Crystallized Water: Internal and External Ice Fragments in Polycyclic Hosts

Two crystal structures of cyclic water hexamers are reported, one with a bicyclic cryptand and the other with a tricyclic host. In the bicycle structure, the water molecules lie between the cryptands. In the tricycle structure, the hexameric water cluster is almost totally encapsulated within the host framework.

Freezing resistance of antifreeze-deficient larval Antarctic fish

Antarctic notothenioids, along with many other polar marine fishes, have evolved biological antifreeze proteins (AFPs) to survive in their icy environments. The larvae of Antarctic notothenioid fish hatch into the same frigid environment inhabited by the adults, suggesting that they must also be protected by sufficient AFPs, but this has never been verified. We have determined the contribution of AFPs to the freezing resistance of the larvae of three species: Gymnodraco acuticeps, Pagothenia borchgrevinki and Pleuragramma antarcticum. Of the three, only P. borchgrevinki larvae are protected by high, adult levels of AFPs. Hatchling G. acuticeps and P. antarcticum have drastically inadequate AFP concentrations to avoid freezing at the ambient seawater temperature (-1.91 degrees C). We raised G. acuticeps larvae and measured the AFP levels in their blood for approximately 5 months post hatching. Larval serum freezing point was -1.34+/-0.04 degrees C at the time of hatch; it began to decrease only after 30 days post hatch (d.p.h.), and finally reached the adult value (-2.61+/-0.03 degrees C) by 147 d.p.h. Additionally, AFP concentrations in their intestinal fluids were very low at hatching, and did not increase with age throughout a sampling period of 84 d.p.h. Surviving in a freezing environment without adequate AFP protection suggests that other mechanisms of larval freezing resistance exist. Accordingly, we found that G. acuticeps hatchlings survived to -3.6+/-0.1 degrees C while in contact with external ice, but only survived to -1.5+/-0.0 degrees C when ice was artificially introduced into their tissues. P. antarcticum larvae were similarly resistant to organismal freezing. The gills of all three species were found to be underdeveloped at the time of hatch, minimizing the risk of ice introduction through these delicate structures. Thus, an intact integument, underdeveloped gill structures and other physical barriers to ice propagation may contribute significantly to the freezing resistance and survival of these larval fishes in the icy conditions of the Southern Ocean.

Inoculative freezing promotes winter survival in hatchling diamondback terrapin,Malaclemys terrapin

We investigated the hibernation ecology and cold hardiness of hatchling diamondback terrapins, Malaclemys terrapin (Schoepf, 1793), an estuarine species that reaches 42°N along the Atlantic Ocean. During 3 years of study, about 50% of the nests we monitored harboured hatchlings during winter, and the majority (87%) of these individuals survived despite being intermittently exposed to subfreezing temperatures. Most such exposures were brief (ca. 12 h) and mild (minimum temperature: ca. –1.2 °C); however, turtles were occasionally subjected to longer chilling episodes and lower temperatures. In laboratory experiments, hatchlings supercooled extensively, attaining ca. –15 °C before spontaneously freezing. However, they were highly susceptible to inoculative freezing through contact with external ice and (or) ice-nucleating agents, which occur in nesting soil. Therefore, freeze avoidance through supercooling does not appear to be a viable cold-hardiness strategy in these turtles. Hatchlings subjected to experimental freezing survived exposure to temperatures as low as –3.0 °C, suggesting that freeze tolerance may account for the high winter survival observed in natural nests. We conclude that freeze tolerance in hatchling M. terrapin is promoted by high susceptibility to inoculation, which is known to moderate freezing, allowing cells time to adapt to the attendant physical and osmotic stresses.

A possible additional role of mineral oil in successful flash cooling

Traditional explanations for the efficacy of mineral oil in successful flash cooling of a protein crystal correctly point to the removal of excess liquid around the crystal to prevent external ice formation. Based on the physics of the well known Leidenfrost phenomenon, an additional role that mineral oil possibly plays in aiding vitrification is suggested: that of improving cooling rates for a protein crystal plunged into liquid nitrogen. The full potential of liquid heat transfer when using liquid nitrogen is not realized in conventional cooling techniques due to film boiling that occurs around larger protein crystals. However, a thin layer of an insulating material, such as a mineral oil, around the protein crystal can prevent this vapor film from forming by raising the Leidenfrost temperature. Surface cooling then occurs in the more efficient nucleate boiling regime where liquid nitrogen is in contact with the crystal throughout the quench. Using bare and coated thermocouples, the validity of a predictive Leidenfrost temperature equation for use in liquid-nitrogen plunge cooling of protein crystals is demonstrated.

Use of External Abdominal Ice to Complete External Cephalic Version in Term Breech Pregnancy

A 36-year-old multiparous woman with fetus in the breech position applied ice to the fundus of the uterus and achieved successful cephalic version. No other reports of using ice to induce cephalic version are found with MEDLINE search; however, it has been used as a folk remedy. Further research to evaluate the efficacy and safety of ice is needed to determine whether it increases cephalic vaginal birth.

Extra- and intracellular ice formation in mouse oocytes

The occurrence of intracellular ice formation (IIF) during freezing, or the lack there of, is the single most important factor determining whether or not cells survive cryopreservation. One important determinant of IIF is the temperature at which a supercooled cell nucleates. To avoid intracellular ice formation, the cell must be cooled slowly enough so that osmotic dehydration eliminates nearly all cell supercooling before reaching that temperature. This report is concerned with factors that determine the nucleation temperature in mouse oocytes. Chief among these is the concentration of cryoprotective additive (here, glycerol or ethylene glycol). The temperature for IIF decreases from −14 °C in buffered isotonic saline (PBS) to −41 °C in 1 M glycerol/PBS and 1.5 M ethylene glycol/PBS. The latter rapidly permeates the oocyte; the former does not. The initial extracellular freezing at −3.9 to −7.8 °C, depending on the CPA concentration, deforms the cell. In PBS that deformation often leads to IIF; in CPA it does not. The oocytes are surrounded by a zona pellucida. That structure appears to impede the growth of external ice through it, but not to block it. In most cases, IIF is characterized by an abrupt blackening or flashing during cooling. But in some cases, especially with dezonated oocytes, a pale brown veil abruptly forms during cooling followed by slower blackening during warming. Above −30 °C, flashing occurs in a fraction of a second. Below −30 °C, it commonly occurs much more slowly. We have observed instances where flashing is accompanied by the abrupt ejection of cytoplasm. During freezing, cells lie in unfrozen channels between the growing external ice. From phase diagram data, we have computed the fraction of water and solution that remains unfrozen at the observed flash temperatures and the concentrations of salt and CPA in those channels. The results are somewhat ambiguous as to which of these characteristics best correlates with IIF.

A measurement method of ice layer thickness based on resistance-capacitance circuit for closed loop external melt ice storage tank

The measurement of the ice layer thickness in closed loop external melt ice storage tank not only affects the optimal operation of the ice storage system but also directly determines the safety of the system. The traditional methods could not satisfy the needs of rapidity and accuracy very well. A measurement method to quickly and accurately predict the thickness of ice layer is presented in this paper. Based on the differences of permittivity and resistivity between ice and water, the frequency response principle of resistance–capacitance circuit is applied to develop a measuring unit of ice layer thickness. The interpolation method is used in the transducer to increase the precision of this device. Experimental and analytic results show that the sensor is accurate enough for industrial application and has remarkable rapidity and stability in measuring the ice thickness on the plate or ice on the coil, which can be used to calculate the ice packing factor (IPF) of the ice storage system.

Cold tolerance of Littorinidae from southern Africa: intertidal snails are not constrained to freeze tolerance

All intertidal gastropods for which cold tolerance strategies have been assessed have been shown to be freeze tolerant. Thus, freeze tolerance is considered an adaptation to the intertidal environment. We investigated the cold tolerance strategies of three species of subtropical and temperate snails (Gastropoda: Littorinidae) to determine whether this group is phylogenetically constrained to freeze tolerance. We exposed 'dry' acclimated and 'wet' rehydrated snails to low temperatures to determine temperature of crystallisation (Tc), lower lethal temperature and LT(50) and to examine the relationship between ice formation and mortality. Tc was lowest in dry Afrolittorina knysnaensis (-13.6+/-0.4 degrees C), followed by dry Echinolittorina natalensis (-10.9+/-0.2 degrees C) and wet A. knysnaensis (-10.2+/-0.2 degrees C) . The Tc of both A. knysnaensis and E. natalensis increased with rehydration, whereas Tc of dry and wet Afrolittorina africana did not differ (-9.6+/-0.2 and -9.0+/-0.2 degrees C respectively). Wet snails of all species exhibited no or low survival of inoculative freezing, whereas dry individuals of A. knysnaensis could survive subzero temperatures above -8 degrees C when freezing was inoculated with ice . In the absence of external ice, Afrolittorina knysnaensis employs a freeze-avoidance strategy of cold tolerance, the first time this has been reported for an intertidal snail, indicating that there is no family-level phylogenetic constraint to freeze tolerance. Echinolittorina natalensis and A. africana both showed pre-freeze mortality and survival of some internal ice formation, but were not cold hardy in any strict sense.

Ice Nucleation, Propagation, and Deep Supercooling in Woody Plants

Summary The response of woody plants to freezing temperatures is complex. Species vary greatly in their ability to survive freezing temperatures and the resulting dehydrative and mechanical stresses that occur as a result from the presence of ice. Initially, this is presented by the ability to inhibit the formation of ice (ice nucleation) by supercooling. Significant questions exist about the role of internal and external ice nucleating agents in determining the extent to which any particular plant can supercool. Additionally, little is known about how plant structure can affect ice nucleation and propagation. In this review, the ability of high-resolution infrared thermography to reveal significant details about the freezing process is demonstrated. In general, the presence of effective, intrinsic nucleators appear to be common in woody plants. The nucleators appear to be as effective as external ice nucleators and induce stems to freeze at warm, subzero temperatures. Barriers appear to exist, however, that prevent ice propagation into lateral appendages such as buds, or newly extended primary tissues. Deep supercooling represents a unique adaptation of woody plants to avoid freezing injury by dramatically suppressing ice formation in specific tissues. The extent of suppression is limited by the homogeneous nucleation temperature of water (-38°C) and therefore deep supercooling is characteristic of moderately hardy woody plants. In contrast, it has been proposed that the most cold-hardy woody plants have the ability to form glassed solutions. These solutions are very stable as long as the cell remains below the melting temperature of the glass and so allows tissues to become relatively impervious to the stresses associated with extremely low temperatures.

Cold-hardiness and dehydration resistance of hatchling Blanding's turtles (Emydoidea blandingii): implications for overwintering in a terrestrial habitat

The overwintering habits of hatchling Blanding's turtles, Emydoidea blandingii (Holbrook, 1838), are not well understood. To ascertain whether these turtles are well suited to hibernation on land, we examined susceptibility to dehydration, supercooling capacity, resistance to inoculative freezing, capacity for freeze tolerance, and physiological responses to somatic freezing in laboratory-reared, hatchling E. blandingii. Rates of evaporative water loss (mean ± SE = 4.1 ± 0.2 mg·g–1·d–1) were intermediate to rates previously reported for the hatchlings of species known to hibernate on land and in water. Supercooled hatchlings recovered from a 1-h exposure to –8 °C or a 7-d exposure to –4 °C. Additional turtles supercooled to –14.3 ± 1.2 °C (mean ± SE) before spontaneously freezing. However, when immersed in frozen soil, their capacity to supercool was severely limited by an inability to resist inoculative freezing following contact with external ice and ice nuclei. Therefore, hatchlings likely do not use supercooling as a winter survival strategy. Hatchlings tolerated a 72-h period of somatic freezing to –3.5 °C and responded to somatic freezing by increasing plasma concentrations of the putative cryoprotectants lactate and glucose. Our results suggest that hatchling E. blandingii could overwinter in moist, terrestrial hibernacula where risk of dehydration is reduced and freeze tolerance is promoted.