Freeze-drying of nanosuspensions, 1: freezing rate versus formulation design as critical factors to preserve the original particle size distribution.

PubMed

Beirowski, Jakob; Inghelbrecht, Sabine; Arien, Albertina; Gieseler, Henning

2011-05-01

It has been recently reported in the literature that using a fast freezing rate during freeze-drying of drug nanosuspensions is beneficial to preserve the original particle size distribution. All freezing rates studied were obtained by utilizing a custom-made apparatus and were then indirectly related to conventional vial freeze-drying. However, a standard freeze-dryer is only capable of achieving moderate freezing rates in the shelf fluid circulation system. Therefore, it was the purpose of the present study to evaluate the possibility to establish a typical freezing protocol applicable to a standard freeze-drying unit in combination with an adequate choice of cryoprotective excipients and steric stabilizers to preserve the original particle size distribution. Six different drug nanosuspensions containing itraconazole as a drug model were studied using freeze-thaw experiments and a full factorial design to reveal major factors for the stabilization of drug nanosuspensions and the corresponding interactions. In contrast to previous reports, the freezing regime showed no significant influence on preserving the original particle size distribution, suggesting that the concentrations of both the steric stabilizer and the cryoprotective agent are optimized. Moreover, it could be pinpointed that the combined effect of steric stabilizer and cryoprotectant clearly contribute to nanoparticle stability. Copyright © 2010 Wiley-Liss, Inc.

Freeze Technology for Nuclear Applications - 13590

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rostmark, Susanne C.; Knutsson, Sven; Lindberg, Maria

2013-07-01

Freezing of soil materials is a complicated process of a number of physical processes: - freezing of pore water in a thermal gradient, - cryogenic suction causing water migration and - ice formation expanding pores inducing frost heave. Structural changes due to increase of effective stress during freezing also take place. The over consolidation gives a powerful dewatering/drying effect and the freeze process causes separation of contaminates. Artificial ground freezing (AGF is a well established technique first practiced in south Wales, as early as 1862. AGF is mostly used to stabilize tunnels and excavations. During the last ten years underwatermore » applications of freeze technologies based on the AGF have been explored in Sweden. The technology can, and has been, used in many different steps in a remediation action. Freeze Sampling where undisturbed samples are removed in both soft and hard sediment/sludge, Freeze Dredging; retrieval of sediment with good precision and minimal redistribution, and Freeze Drying; volume reduction of contaminated sludge/sediment. The application of these technologies in a nuclear or radioactive environment provides several advantages. Sampling by freezing gives for example an advantage of an undisturbed sample taken at a specified depth, salvaging objects by freezing or removal of sludges is other applications of this, for the nuclear industry, novel technology. (authors)« less

Summer Freezing Resistance: A Critical Filter for Plant Community Assemblies in Mediterranean High Mountains

PubMed Central

Pescador, David S.; Sierra-Almeida, Ángela; Torres, Pablo J.; Escudero, Adrián

2016-01-01

Assessing freezing community response and whether freezing resistance is related to other functional traits is essential for understanding alpine community assemblages, particularly in Mediterranean environments where plants are exposed to freezing temperatures and summer droughts. Thus, we characterized the leaf freezing resistance of 42 plant species in 38 plots at Sierra de Guadarrama (Spain) by measuring their ice nucleation temperature, freezing point (FP), and low-temperature damage (LT50), as well as determining their freezing resistance mechanisms (i.e., tolerance or avoidance). The community response to freezing was estimated for each plot as community weighted means (CWMs) and functional diversity (FD), and we assessed their relative importance with altitude. We established the relationships between freezing resistance, growth forms, and four key plant functional traits (i.e., plant height, specific leaf area, leaf dry matter content (LDMC), and seed mass). There was a wide range of freezing resistance responses and more than in other alpine habitats. At the community level, the CWMs of FP and LT50 responded negatively to altitude, whereas the FD of both traits increased with altitude. The proportion of freezing-tolerant species also increased with altitude. The ranges of FP and LT50 varied among growth forms, and only leaf dry matter content was negatively correlated with freezing-resistance traits. Summer freezing events represent important abiotic filters for assemblies of Mediterranean high mountain communities, as suggested by the CWMs. However, a concomitant summer drought constraint may also explain the high freezing resistance of species that thrive in these areas and the lower FD of freezing resistance traits at lower altitudes. Leaves with high dry matter contents may maintain turgor at lower water potential and enhance drought tolerance in parallel to freezing resistance. This adaptation to drought seems to be a general prerequisite for plants found in xeric mountains. PMID:26941761

Survival mechanisms of vertebrate ectotherms at subfreezing temperatures: applications in cryomedicine.

PubMed

Costanzo, J P; Lee, R E; DeVries, A L; Wang, T; Layne, J R

1995-03-01

Various marine fishes, amphibians, and reptiles survive at temperatures several degrees below the freezing point of their body fluids by virtue of adaptive mechanisms that promote freeze avoidance or freeze tolerance. Freezing is avoided by a colligative depression of the blood freezing point, supercooling of the body fluids, or the biosynthesis of unique antifreeze proteins that inhibit the propagation of ice within body fluids. Conversely, freeze tolerance is an adaptation for the survival of tissue freezing under ecologically relevant thermal and temporal conditions that is conferred by the biosynthesis of permeating carbohydrate cryoprotectants and an extensive dehydration of tissues and organs. Such cryoprotective responses, invoked by the onset of freezing, mitigate the osmotic stress associated with freeze-concentration of cytoplasm, attendant metabolic perturbations, and physical damage. Cryomedical research has historically relied on mammalian models for experimentation even though endotherms do not naturally experience subfreezing temperatures. Some vertebrate ectotherms have "solved" not only the problem of freezing individual tissues and organs, but also that of simultaneously freezing all organ systems. An emerging paradigm in cryomedicine is the application of principles governing natural cold hardiness to the development of protocols for the cryopreservation of mammalian tissues and organs.

Hepatitis B vaccine freezing in the Indonesian cold chain: evidence and solutions.

PubMed

Nelson, Carib M; Wibisono, Hariadi; Purwanto, Hary; Mansyur, Isa; Moniaga, Vanda; Widjaya, Anton

2004-02-01

To document and characterize freezing temperatures in the Indonesian vaccine cold chain and to evaluate the feasibility of changes designed to reduce the occurrence of freezing. Data loggers were used to measure temperatures of shipments of hepatitis B vaccine from manufacturer to point of use. Baseline conditions and three intervention phases were monitored. During each of the intervention phases, vaccines were removed progressively from the standard 2-8 degrees C cold chain. Freezing temperatures were recorded in 75% of baseline shipments. The highest rates of freezing occurred during transport from province to district, storage in district-level ice-lined refrigerators, and storage in refrigerators in health centres. Interventions reduced freezing, without excessive heat exposure. Inadvertent freezing of freeze-sensitive vaccines is widespread in Indonesia. Simple strategies exist to reduce freezing - for example, selective transport and storage of vaccines at ambient temperatures. The use of vaccine vial monitors reduces the risk associated with heat-damaged vaccines in these scenarios. Policy changes that allow limited storage of freeze-sensitive vaccines at temperatures >2-8 degrees C would enable flexible vaccine distribution strategies that could reduce vaccine freezing, reduce costs, and increase capacity.

Repeated freeze-thaw cycles induce embolism in drought stressed conifers (Norway spruce, stone pine).

PubMed

Mayr, Stefan; Gruber, Andreas; Bauer, Helmut

2003-07-01

Freezing and thawing lead to xylem embolism when gas bubbles caused by ice formation expand during the thaw process. However, previous experimental studies indicated that conifers are resistant to freezing-induced embolism, unless xylem pressure becomes very negative during the freezing. In this study, we show that conifers experienced freezing-induced embolism when exposed to repeated freeze-thaw cycles and simultaneously to drought. Simulating conditions at the alpine timberline (128 days with freeze-thaw events and thawing rates of up to 9.5 K h(-1) in the xylem of exposed twigs during winter), young trees of Norway spruce [Picea abies (L.) Karst.] and stone pine (Pinus cembra L.) were exposed to 50 and 100 freeze-thaw cycles. This treatment caused a significant increase in embolism rates in drought-stressed samples. Upon 100 freeze-thaw cycles, vulnerability thresholds (50% loss of conductivity) were shifted 1.8 MPa (Norway spruce) and 0.8 MPa (stone pine) towards less negative water potentials. The results demonstrate that freeze-thaw cycles are a possible reason for winter-embolism in conifers observed in several field studies. Freezing-induced embolism may contribute to the altitudinal limits of conifers.

Freezing of gait in Parkinson's disease: the paradoxical interplay between gait and cognition.

PubMed

Ricciardi, Lucia; Bloem, Bastiaan R; Snijders, Anke H; Daniele, Antonio; Quaranta, Davide; Bentivoglio, Anna Rita; Fasano, Alfonso

2014-08-01

Freezing of gait is a disabling episodic gait disturbance common in patients with Parkinson's disease. Recent evidences suggest a complex interplay between gait impairment and executive functions. Aim of our study was to evaluate whether specific motor conditions (sitting or walking) influence cognitive performance in patients with or without different types of freezing. Eight healthy controls, eight patients without freezing, nine patients with levodopa-responsive and nine patients with levodopa-resistant freezing received a clinical and neuropsychological assessment during two randomly performed conditions: at rest and during walking. At rest, patients with levodopa-resistant freezing performed worse than patients without freezing on tests of phonological fluency (p = 0.01). No differences among the four groups were detected during walking. When cognitive performances during walking were compared to the performance at rest, there was a significant decline of verbal episodic memory task (Rey Auditory Verbal Learning Test) in patients without freezing and with levodopa-responsive freezing. Interestingly, walking improved performance on the phonological fluency task in patients with levodopa-resistant freezing (p = 0.04). Compared to patients without freezing, patients with levodopa-resistant freezing perform worse when tested while seated in tasks of phonological verbal fluency. Surprisingly, gait was associated with a paradoxical improvement of phonological verbal fluency in the patients with levodopa-resistant freezing whilst walking determined a worsening of episodic memory in the other patient groups. Copyright © 2014 Elsevier Ltd. All rights reserved.

Freezing during tapping tasks in patients with advanced Parkinson's disease and freezing of gait.

PubMed

Delval, Arnaud; Defebvre, Luc; Tard, Céline

2017-01-01

Parkinson's disease patients with freezing of gait also experience sudden motor blocks (freezing) during other repetitive motor tasks. We assessed the proportion of patients with advanced PD and freezing of gait who also displayed segmental "freezing" in tapping tasks. Fifteen Parkinson's disease patients with freezing of gait were assessed. Freezing of gait was evaluated using a standardized gait trajectory with the usual triggers. Patients performed repetitive tapping movements (as described in the MDS-UPDRS task) with the hands or the feet in the presence or absence of a metronome set to 4 Hz. Movements were recorded with a video motion system. The primary endpoint was the occurrence of segmental freezing in these tapping tasks. The secondary endpoints were (i) the relationship between segmental episodic phenomena and FoG severity, and (ii) the reliability of the measurements. For the upper limbs, freezing was observed more frequently with a metronome (21% of trials) than without a metronome (5%). For the lower limbs, the incidence of freezing was higher than for the upper limbs, and was again observed more frequently in the presence of an auditory cue (47%) than in its absence (14%). Although freezing of the lower limbs was easily assessed during an MDS-UPDRS task with a metronome, it was not correlated with the severity of freezing of gait (as evaluated during a standardized gait trajectory). Only this latter was a reliable measurement in patients with advanced Parkinson's disease.

Short-term and practice effects of metronome pacing in Parkinson's disease patients with gait freezing while in the 'on' state: randomized single blind evaluation.

PubMed

Cubo, Esther; Leurgans, Sue; Goetz, Christopher G

2004-12-01

In a randomized single blind parallel study, we tested the efficacy of an auditory metronome on walking speed and freezing in Parkinson's disease (PD) patients with freezing gait impairment during their 'on' function. No pharmacological treatment is effective in managing 'on' freezing in PD. Like visual cues that can help overcome freezing, rhythmic auditory pacing may provide cues that help normalize walking pace and overcome freezing. Non-demented PD patients with freezing during their 'on' state walked under two conditions, in randomized order: unassisted walking and walking with the use of an audiocassette with a metronome recording. The walking trials were randomized and gait variables were rated from videotapes by a blinded evaluator. Outcome measures were total walking time (total trial time-total freezing time), which was considered the time over a course of specified length, freezing time, average freeze duration and number of freezes. All outcomes were averaged across trials for each person and then compared across conditions using Signed Rank tests. Twelve non-demented PD patients with a mean age of 65.8 +/- 11.2 years, and mean PD duration of 12.4 +/- 7.3 years were included. The use of the metronome slowed ambulation and increased the total walking time (P < 0.0005) only during the first visit, without affecting any freezing variable. In the nine patients who took the metronome recording home and used it daily for 1 week while walking, freezing remained unimproved. Though advocated in prior publications as a walking aid for PD patients, auditory metronome pacing slows walking and is not a beneficial intervention for freezing during their 'on' periods.

Freezing Injury in Onion Bulb Cells

PubMed Central

Palta, Jiwan P.; Levitt, Jacob; Stadelmann, Eduard J.

1977-01-01

Onion (Allium cepa L.) bulbs were subjected for 12 days to either a moderate freeze (−4 C) or a severe freeze (−11 C). They were then thawed slowly over ice. During 7 to 12 days following the thaw, the injury progressed with time in the severely frozen bulbs, but appeared completely repaired in the moderately frozen bulbs. This was shown by the following post-thawing changes. Infiltration of the intercellular spaces increased from 80 to 90% to 100% after the severe freeze, and decreased from 30 to 50% to zero after the moderate freeze. All of the cells were alive immediately after thawing whether the freeze was moderate or severe. Corresponding to the infiltration results 7 to 12 days later, many to most were dead following the severe freeze, all were alive following the moderate freeze. The conductivity of the effusate from pieces of bulb tissue increased after the severe freezing, and decreased after the moderate freezing. The concentration of K+, total solutes, and sugars in the effusate paralleled the conductivity changes. Neither the pH of the effusate nor the permeability of the cells (as long as cells were living) to water was changed following either the severe or the moderate freezes. Some treatments of the thawed tissue following the severe freeze halted the progress of injury. The above results indicate that the semipermeable properties of the cell are uninjured but that the ion and sugar transport mechanism is damaged by freezing. Most likely the primary injury is to the active transport mechanism involved in their transport. It must be concluded that the final injury following freezing and thawing cannot be evaluated from the degree of infiltration or the conductivity of the effusate immediately after thawing, since injury may progress or recede following the thawing. PMID:16660101

Effects of Pressure-shift Freezing on the Structural and Physical Properties of Gelatin Hydrogel Matrices

PubMed Central

Kim, Byeongsoo; Gil, Hyung Bae; Min, Sang-Gi; Lee, Si-Kyung; Choi, Mi-Jung

2014-01-01

This study investigates the effects of the gelatin concentration (10-40%, w/v), freezing temperatures (from -20℃ to -50℃) and freezing methods on the structural and physical properties of gelatin matrices. To freeze gelatin, the pressure-shift freezing (PSF) is being applied at 0.1 (under atmospheric control), 50 and 100 MPa, respectively. The freezing point of gelatin solutions decrease with increasing gelatin concentrations, from -0.2℃ (10% gelatin) to -6.7℃ (40% gelatin), while the extent of supercooling did not show any specific trends. The rheological properties of the gelatin indicate that both the storage (G') and loss (G") moduli were steady in the strain amplitude range of 0.1-10%. To characterize gelatin matrices formed by the various freezing methods, the ice crystal sizes which were being determined by the scanning electron microscopy (SEM) are affected by the gelatin concentrations. The ice crystal sizes are affected by gelatin concentrations and freezing temperature, while the size distributions of ice crystals depend on the freezing methods. Smaller ice crystals are being formed with PSF rather than under the atmospheric control where the freezing temperature is above -40℃. Thus, the results of this study indicate that the PSF processing at a very low freezing temperature (-50℃) offers a potential advantage over commercial atmospheric freezing points for the formation of small ice crystals. PMID:26760743

Evaluation of combined effects of ageing period and freezing rate on quality attributes of beef loins.

PubMed

Kim, Yuan H Brad; Liesse, Charlotte; Kemp, Robert; Balan, Prabhu

2015-12-01

The objective of our study was to evaluate the combined effects of ageing period and different freezing rates on meat quality attributes of beef loins. Pairs of loins (M. longissimus at 1 day post mortem) from 12 carcasses were divided into four equal portions and randomly assigned to four ageing/freezing treatments (aged only, frozen only, and 3 or 4 weeks ageing at -1.5°C then frozen). Two freezing methods (fast freezing by calcium chloride immersion or slow freezing by air freezer at -18°C) were applied to the loin sections. Fast freezing had no effect on shear force (P>0.05), but significantly improved the water-holding capacity of the aged/frozen loins by reducing purge and drip losses. Ageing-then-freezing significantly improved shear force values of loins compared to both the aged only and frozen only loins. These observations suggest that fast freezing will add more value to the aged/frozen/thawed meat by minimising the amount of water-loss due to the freezing/thawing process. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of different freezing methods on calcium enriched papaya (Carica papaya L.).

PubMed

Lovera, Nancy N; Ramallo, Laura; Salvadori, Viviana O

2018-06-01

The effect of calcium impregnation on drip loss, colour, mechanical properties, sensory perception and freezing time on frozen-thawed papaya was studied, evaluating different freezing methods: cryogenic, tunnel and household freezer freezing. Osmotic dehydration as pre-treatment was also evaluated. Freezing in liquid nitrogen was considered an inappropriate method for papaya preservation due to cracking. Calcium impregnation and osmotic dehydration increased tissue firmness and decreased freezing time (freezing time for fresh, calcium impregnated and osmo-dehydrated fruit was 23, 17 and 5 min in a tunnel and 118, 83 and 60 min in a household freezer, respectively). Calcium lactate was the most effective way to protect tissue's firmness before and after a freeze-thaw cycle (maximum stress values approx. 300-400% of the raw tissue for tunnel freezing and 260% for household freezer). Microstructure analysis showed better tissue integrity retention in papaya samples impregnated with calcium lactate than in those with calcium gluconate, after a freezing-thawing cycle, in agreement with the drip loss results. In spite of these results, consumers preferred frozen papaya without pre-treatment or impregnated with calcium gluconate.

Response of shoal grass, Halodule wrightii, to extreme winter conditions in the Lower Laguna Madre, Texas

USGS Publications Warehouse

Hicks, D.W.; Onuf, C.P.; Tunnell, J.W.

1998-01-01

Effects of a severe freeze on the shoal grass, Halodule wrightii, were documented through analysis of temporal and spatial trends in below-ground biomass. The coincidence of the second lowest temperature (-10.6??C) in 107 years of record, 56 consecutive hours below freezing, high winds and extremely low water levels exposed the Laguna Madre, TX, to the most severe cold stress in over a century. H. wrightii tolerated this extreme freeze event. Annual pre- and post-freeze surveys indicated that below-ground biomass estimated from volume was Unaffected by the freeze event. Nor was there any post-freeze change in biomass among intertidal sites directly exposed to freezing air temperatures relative to subtidal sites which remained submerged during the freezing period.

The effect of undissolved air on isochoric freezing.

PubMed

Perez, Pedro A; Preciado, Jessica; Carlson, Gary; DeLonzor, Russ; Rubinsky, Boris

2016-06-01

This study evaluates the effect of undissolved air on isochoric freezing of aqueous solutions. Isochoric freezing is concerned with freezing in a constant volume thermodynamic system. A possible advantage of the process is that it substantially reduces the percentage of ice in the system at every subzero temperature, relative to atmospheric freezing. At the pressures generated by isochoric freezing, or high pressure isobaric freezing, air cannot be considered an incompressible substance and the presence of undissolved air substantially increases the amount of ice that forms at any subfreezing temperature. This effect is measurable at air volumes as low as 1%. Therefore eliminating the undissolved air, or any separate gaseous phase, from the system is essential for retaining the properties of isochoric freezing. Copyright © 2016. Published by Elsevier Inc.

Visual Indicators on Vaccine Boxes as Early Warning Tools to Identify Potential Freeze Damage.

PubMed

Angoff, Ronald; Wood, Jillian; Chernock, Maria C; Tipping, Diane

2015-07-01

The aim of this study was to determine whether the use of visual freeze indicators on vaccines would assist health care providers in identifying vaccines that may have been exposed to potentially damaging temperatures. Twenty-seven sites in Connecticut involved in the Vaccine for Children Program participated. In addition to standard procedures, visual freeze indicators (FREEZEmarker ® L; Temptime Corporation, Morris Plains, NJ) were affixed to each box of vaccine that required refrigeration but must not be frozen. Temperatures were monitored twice daily. During the 24 weeks, all 27 sites experienced triggered visual freeze indicator events in 40 of the 45 refrigerators. A total of 66 triggered freeze indicator events occurred in all 4 types of refrigerators used. Only 1 of the freeze events was identified by a temperature-monitoring device. Temperatures recorded on vaccine data logs before freeze indicator events were within the 35°F to 46°F (2°C to 8°C) range in all but 1 instance. A total of 46,954 doses of freeze-sensitive vaccine were stored at the time of a visual freeze indicator event. Triggered visual freeze indicators were found on boxes containing 6566 doses (14.0% of total doses). Of all doses stored, 14,323 doses (30.5%) were of highly freeze-sensitive vaccine; 1789 of these doses (12.5%) had triggered indicators on the boxes. Visual freeze indicators are useful in the early identification of freeze events involving vaccines. Consideration should be given to including these devices as a component of the temperature-monitoring system for vaccines.

Influence of the freezing method on the changes that occur in grape samples after frozen storage.

PubMed

Santesteban, Luis G; Miranda, Carlos; Royo, José B

2013-09-01

Sample freezing is frequently used in oenological laboratories as a compromise solution to increase the number of samples that can be analysed, despite the fact that some grape characteristics are known to change after frozen storage. However, freezing is usually performed using standard freezers, which provide a slow freezing. The aim of this work was to evaluate whether blast freezing would decrease the impact of standard freezing on grape composition. Grape quality parameters were assessed in fresh and in frozen stored samples that had been frozen using three different procedures: standard freezing and blast freezing using either a blast freezer or an ultra-freezer. The implications of frozen storage in grape samples reported in earlier research were observed for the three freezing methods evaluated. Although blast freezing improved repeatability for the most problematic parameters (tartaric acidity, TarA; total phenolics, TP), the improvement was not important from a practical point of view. However, TarA and TP were relatively repeatable among the three freezing procedures, which suggests that freezing had an effect on these parameters independently of the method used . According to our results, the salification potential of the must is probably implied in the changes observed for TarA, whereas for TP the precipitation of protoanthocyanins after association with cell wall material is hypothesized to cause the lack of repeatability between fresh and frozen grapes. Blast freezing would not imply a great improvement if implemented in oenological laboratories, at least for the parameters included in this study. © 2013 Society of Chemical Industry.

The Adsorption and Desorption of Pb(2+) and Cd(2+) in Freeze-Thaw Treated Soils.

PubMed

Li, Linhui; Ma, Jincai; Xu, Meng; Li, Xu; Tao, Jiahui; Wang, Guanzhu; Yu, Jitong; Guo, Ping

2016-01-01

Adsorption and desorption are important processes that influence the potential toxicity and bioavailability of heavy metals in soils. However, information regarding adsorption and desorption behavior of heavy metals in soils subjected to freeze-thaw cycles is poorly understood. In the current study, the effect of freeze-thaw cycles with different freezing temperature (-15, -25, -35°C) on soil properties was investigated. Then the adsorption and desorption behavior of Pb(2+) and Cd(2+) in freeze-thaw treated soils was studied. The adsorption amounts of Pb(2+) and Cd(2+) in freeze-thaw treated soils were smaller than those in unfrozen soils (p < 0.05), due to the fact that pH, cation exchange capacity, organic matter content, free iron oxide content, and CaCO3 content in freeze-thaw treated soils were smaller than those in unfrozen soils. The adsorption amounts of Pb(2+) and Cd(2+) in soils treated with lower freezing temperatures were higher than those in soils treated with higher freezing temperatures. Desorption percentages of Pb(2+) and Cd(2+) in unfrozen soils were smaller than those in freeze-thaw treated soils (p < 0.05). The desorption percentages of Pb(2+) and Cd(2+) were smaller in soils treated with lower freezing temperatures than those in soils treated with higher freezing temperatures. The results obtained highlight the change of the adsorption and desorption behavior of typical heavy metals in freeze-thaw treated soils located in seasonal frozen soils zone in northeast China.

Evaluating Long-Term Impacts of Soil-Mixing Source-Zone Treatment using Cryogenic Core Collection

DTIC Science & Technology

2017-06-01

to (a) coring equipment freezing downhole, (b) freezing or binding of the core sample in barrel, and ( c ) running out of LN in the vicinity of sampling...encountered due to (a) coring equipment freezing downhole, (b) freezing or binding of the core sample in barrel, and ( c ) running out of LN in the...equipment freezing downhole, (b) freezing or binding of the core sample in barrel, and ( c ) running out of LN in the vicinity of sampling. Downhole

Insufficiency of copper ion homeostasis causes freeze-thaw injury of yeast cells as revealed by indirect gene expression analysis.

PubMed

Takahashi, Shunsuke; Ando, Akira; Takagi, Hiroshi; Shima, Jun

2009-11-01

Saccharomyces cerevisiae is exposed to freeze-thaw stress in commercial processes, including frozen dough baking. Cell viability and fermentation activity after a freeze-thaw cycle were dramatically decreased due to freeze-thaw injury. Because this type of injury involves complex phenomena, the injury mechanisms are not fully understood. We examined freeze-thaw injury by indirect gene expression analysis during postthaw incubation after freeze-thaw treatment using DNA microarray profiling. The results showed that genes involved in the homeostasis of metal ions were frequently contained in genes that were upregulated, depending on the freezing period. We assessed the phenotype of deletion mutants of the metal ion homeostasis genes that exhibited freezing period-dependent upregulation and found that the strains with deletion of the MAC1 and CTR1 genes involved in copper ion homeostasis exhibited freeze-thaw sensitivity, suggesting that copper ion homeostasis is required for freeze-thaw tolerance. We found that supplementation with copper ions during postthaw incubation increased intracellular superoxide dismutase activity and intracellular levels of reactive oxygen species were decreased. Moreover, cell viability was increased by supplementation with copper ions. These results suggest that insufficiency of copper ion homeostasis may be one of the causes of freeze-thaw injury.

Application of the Quality by Design Approach to the Freezing Step of Freeze-Drying: Building the Design Space.

PubMed

Arsiccio, Andrea; Pisano, Roberto

2018-06-01

The present work shows a rational method for the development of the freezing step of a freeze-drying cycle. The current approach to the selection of freezing conditions is still empirical and nonsystematic, thus resulting in poor robustness of control strategy. The final aim of this work is to fill this gap, describing a rational procedure, based on mathematical modeling, for properly choosing the freezing conditions. Mechanistic models are used for the prediction of temperature profiles during freezing and dimension of ice crystals being formed. Mathematical description of the drying phase of freeze-drying is also coupled with the results obtained by freezing models, thus providing a comprehensive characterization of the lyophilization process. In this framework, deep understanding of the phenomena involved is required, and according to the Quality by Design approach, this knowledge can be used to build the design space. The step-by-step procedure for building the design space for freezing is thus described, and examples of applications are provided. The calculated design space is validated upon experimental data, and we show that it allows easy control of the freezing process and fast selection of appropriate operating conditions. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Freezing curve-based monitoring to quickly evaluate the viability of biological materials subject to freezing or thermal injury.

PubMed

Liu, Jing; Zhou, Yi-Xin

2003-09-01

This paper is aimed at investigating the roles of freezing dynamics of a liquid droplet to characterize the properties of the material. In particular, freezing curve-based monitoring was proposed to quickly evaluate the viability of biological materials subject to freezing, re-warming, or other kinds of injury, which is an extremely important issue in practices such as cryobiology, hyperthermia, or freshness evaluation of bio-samples. An integrated micro analysis device was fabricated which is simple in structure and cheap to make. Preliminary freezing results demonstrated that minor changes in a biological material due to freezing or warming injury might result in a significant deviation of its freezing curve from that of the intact biomaterials. Several potential thermal indexes to quantify the material features were pointed out. Further, experiments were performed on some freezing and thawing processes of small amount of water on a cooling surface to test the effects of droplet sizes, measurement sites, cooling strength, and cooling geometry, etc., on the freezing responses of a water droplet. Their implementation in developing a new micro analysis system were suggested. This freezing curve-based monitoring method may open a new strategy for the evaluation of biomaterials subject to destruction in diverse fields.

Recent developments in smart freezing technology applied to fresh foods.

PubMed

Xu, Ji-Cheng; Zhang, Min; Mujumdar, Arun S; Adhikari, Benu

2017-09-02

Due to the increased awareness of consumers in sensorial and nutritional quality of frozen foods, the freezing technology has to seek new and innovative technologies for better retaining the fresh like quality of foods. In this article, we review the recent developments in smart freezing technology applied to fresh foods. The application of these intelligent technologies and the associated underpinning concepts have greatly improved the quality of frozen foods and the freezing efficiency. These technologies are able to automatically collect the information in-line during freezing and help control the freezing process better. Smart freezing technology includes new and intelligent technologies and concepts applied to the pretreatment of the frozen product, freezing processes, cold chain logistics as well as warehouse management. These technologies enable real-time monitoring of quality during the freezing process and help improve product quality and freezing efficiency. We also provide a brief overview of several sensing technologies used to achieve automatic control of individual steps of freezing process. These sensing technologies include computer vision, electronic nose, electronic tongue, digital simulation, confocal laser, near infrared spectroscopy, nuclear magnetic resonance technology and ultrasound. Understanding of the mechanism of these new technologies will be helpful for applying them to improve the quality of frozen foods.

Freezing tolerance of winter wheat as influenced by extended growth at low temperature and exposure to freeze-thaw cycles

USDA-ARS?s Scientific Manuscript database

As the seasons progress, autumn-planted winter wheat plants (Triticum aestivum L.) first gain, then progressively lose freezing tolerance. Exposing the plants to freeze-thaw cycles of -3/3°C results in increased ability to tolerate subsequent freezing to potentially damaging temperatures. This stu...

Host-mediated shift in the cold tolerance of an invasive insect

Treesearch

Amy C. Morey; Robert C. Venette; Erica C. Nystrom Santacruz; Laurel A. Mosca; W. D. Hutchison

2016-01-01

While many insects cannot survive the formation of ice within their bodies, a few species can. On the evolutionary continuum from freeze-intolerant (i.e., freeze-avoidant) to freeze-tolerant insects, intermediates likely exist that can withstand some ice formation, but not enough to be considered fully freeze tolerant. Theory suggests that freeze tolerance should be...

Freezing pattern and frost killing temperature of apple (Malus domestica) wood under controlled conditions and in nature.

PubMed

Pramsohler, Manuel; Hacker, Jürgen; Neuner, Gilbert

2012-07-01

The freezing pattern and frost killing temperatures of apple (Malus domestica Borkh.) xylem were determined by differential thermal analysis and infrared differential thermal analysis (IDTA). Results from detached or attached twigs in controlled freezing experiments and during natural field freezing of trees were compared. Non-lethal freezing of apoplastic water in apple xylem as monitored during natural winter frosts in the field occurred at -1.9 ± 0.4 °C and did not change seasonally. The pattern of whole tree freezing was variable and specific to the environmental conditions. On detached twigs high-temperature freezing exotherms (HTEs) occurred 2.8 K below the temperature observed under natural frosts in the field with a seasonal mean of -4.7 ± 0.5 °C. Microporous apple xylem showed freezing without a specific pattern within a few seconds in IDTA images during HTEs, which is in contrast to macroporous xylem where a 2D freezing pattern mirrors anatomical structures. The pith tissue always remained unfrozen. Increasing twig length increased ice nucleation temperature; for increased twig diameter the effect was not significant. In attached twigs frozen in field portable freezing chambers, HTEs were recorded at a similar mean temperature (-4.6 ± 1.0 °C) to those for detached twigs. Upon lethal intracellular freezing of apple xylem parenchyma cells (XPCs) low-temperature freezing exotherms (LTEs) can be recorded. Low-temperature freezing exotherms determined on detached twigs varied significantly between a winter minimum of -36.9 °C and a summer maximum -12.7 °C. Within the temperature range wherein LTEs were recorded by IDTA in summer (-12.7 ± 0.5 to -20.3 ± 1.1 °C) various tiny clearly separated discontinuous freezing events could be detected similar to that in other species with contrasting XPC anatomy. These freezing events appeared to be initially located in the primary and only later in the secondary xylem. During the LTE no freezing events in the bark and central pith tissue were recorded. Attached twigs were exposed to various freezing temperatures at which LTEs occur. Even if 60% of XPCs were frost-damaged twigs were able to recuperate and showed full re-growth indicating a high regeneration capacity even after severe frost damage to XPCs.

Defensive freezing links Hypothalamic-Pituitary-Adrenal-axis activity and internalizing symptoms in humans.

PubMed

Niermann, Hannah C M; Figner, Bernd; Tyborowska, Anna; van Peer, Jacobien M; Cillessen, Antonius H N; Roelofs, Karin

2017-08-01

The Hypothalamic-Pituitary-Adrenal (HPA)-axis plays an important role in the expression of defensive freezing. Adaptive freezing reactivity, characterized by an immediate increase in acute stress and timely termination upon threat offset or need to act, is essential for adequate stress coping. Blunted HPA-axis activity in animals is associated with blunted freezing reactivity and internalizing symptoms. Despite their potential relevance, it remains unknown whether these mechanisms apply to humans and human psychopathology. Using a well-established method combining electrocardiography and posturography, we assessed freezing before, immediately after, and one hour after a stress induction in 92 human adolescents. In line with animal models, human adolescents showed stress-induced freezing, as quantified by relative reductions in heart rate and body sway after, as compared to before, stress. Moreover, relatively lower basal cortisol was associated with reduced stress-induced freezing reactivity (i.e., less immediate freezing and less recovery). Path analyses showed that decreased freezing recovery in individuals with reduced cortisol levels was associated with increased levels of internalizing symptoms. These findings suggest that reduced freezing recovery may be a promising marker for the etiology of internalizing symptoms. Copyright © 2017 Elsevier Ltd. All rights reserved.

Improving survival and storage stability of bacteria recalcitrant to freeze-drying: a coordinated study by European culture collections.

PubMed

Peiren, Jindrich; Buyse, Joke; De Vos, Paul; Lang, Elke; Clermont, Dominique; Hamon, Sylviane; Bégaud, Evelyne; Bizet, Chantal; Pascual, Javier; Ruvira, María A; Macián, M Carmen; Arahal, David R

2015-04-01

The objective of this study is to improve the viability after freeze-drying and during storage of delicate or recalcitrant strains safeguarded at biological resource centers. To achieve this objective, a joint experimental strategy was established among the different involved partner collections of the EMbaRC project ( www.embarc.eu ). Five bacterial strains considered as recalcitrant to freeze-drying were subjected to a standardized freeze-drying protocol and to seven agreed protocol variants. Viability of these strains was determined before and after freeze-drying (within 1 week, after 6 and 12 months, and after accelerated storage) for each of the protocols. Furthermore, strains were exchanged between partners to perform experiments with different freeze-dryer-dependent parameters. Of all tested variables, choice of the lyoprotectant had the biggest impact on viability after freeze-drying and during storage. For nearly all tested strains, skim milk as lyoprotectant resulted in lowest viability after freeze-drying and storage. On the other hand, best freeze-drying and storage conditions were strain and device dependent. For Aeromonas salmonicida CECT 894(T), best survival was obtained when horse serum supplemented with trehalose was used as lyoprotectant, while Aliivibrio fischeri LMG 4414(T) should be freeze-dried in skim milk supplemented with marine broth in a 1:1 ratio. Freeze-drying Campylobacter fetus CIP 53.96(T) using skim milk supplemented with trehalose as lyoprotectant resulted in best recovery. Xanthomonas fragariae DSM 3587(T) expressed high viability after freeze-drying and storage for all tested lyoprotectants and could not be considered as recalcitrant. In contrary, Flavobacterium columnare LMG 10406(T) did not survive the freeze-drying process under all tested conditions.

State transitions and physicochemical aspects of cryoprotection and stabilization in freeze-drying of Lactobacillus rhamnosus GG (LGG).

PubMed

Pehkonen, K S; Roos, Y H; Miao, S; Ross, R P; Stanton, C

2008-06-01

The frozen and dehydrated state transitions of lactose and trehalose were determined and studied as factors affecting the stability of probiotic bacteria to understand physicochemical aspects of protection against freezing and dehydration of probiotic cultures. Lactobacillus rhamnosus GG was frozen (-22 or -43 degrees C), freeze-dried and stored under controlled water vapour pressure (0%, 11%, 23% and 33% relative vapour pressure) conditions. Lactose, trehalose and their mixture (1 : 1) were used as protective media. These systems were confirmed to exhibit relatively similar state transition and water plasticization behaviour in freeze-concentrated and dehydrated states as determined by differential scanning calorimetry. Ice formation and dehydrated materials were studied using cold-stage microscopy and scanning electron microscopy. Trehalose and lactose-trehalose gave the most effective protection of cell viability as observed from colony forming units after freezing, dehydration and storage. Enhanced cell viability was observed when the freezing temperature was -43 degrees C. State transitions of protective media affect ice formation and cell viability in freeze-drying and storage. Formation of a maximally freeze-concentrated matrix with entrapped microbial cells is essential in freezing prior to freeze-drying. Freeze-drying must retain a solid amorphous state of protectant matrices. Freeze-dried matrices contain cells entrapped in the protective matrices in the freezing process. The retention of viability during storage seems to be controlled by water plasticization of the protectant matrix and possibly interactions of water with the dehydrated cells. Highest cell viability was obtained in glassy protective media. This study shows that physicochemical properties of protective media affect the stability of dehydrated cultures. Trehalose and lactose may be used in combination, which is particularly important for the stabilization of probiotic bacteria in dairy systems.

Experimental analysis and modeling of ultrasound assisted freezing of potato spheres.

PubMed

Kiani, Hossein; Zhang, Zhihang; Sun, Da-Wen

2015-09-01

In recent years, innovative methods such as ultrasound assisted freezing have been developed in order to improve the freezing process. During freezing of foods, accurate prediction of the temperature distribution, phase ratios, and process time is very important. In the present study, ultrasound assisted immersion freezing process (in 1:1 ethylene glycol-water solution at 253.15K) of potato spheres (0.02 m diameter) was evaluated using experimental, numerical and analytical approaches. Ultrasound (25 kHz, 890 W m(-2)) was irradiated for different duty cycles (DCs=0-100%). A finite volume based enthalpy method was used in the numerical model, based on which temperature and liquid fraction profiles were simulated by a program developed using OpenFOAM® CFD software. An analytical technique was also employed to calculate freezing times. The results showed that ultrasound irradiation could decrease the characteristic freezing time of potatoes. Since ultrasound irradiation increased the heat transfer coefficient but simultaneously generated heat at the surface of the samples, an optimum DC was needed for the shortest freezing time which occurred in the range of 30-70% DC. DCs higher than 70% increased the freezing time. DCs lower than 30% did not provide significant effects on the freezing time compared to the control sample. The numerical model predicted the characteristic freezing time in accordance with the experimental results. In addition, analytical calculation of characteristic freezing time exhibited qualitative agreement with the experimental results. As the numerical simulations provided profiles of temperature and water fraction within potatoes frozen with or without ultrasound, the models can be used to study and control different operation situations, and to improve the understanding of the freezing process. Copyright © 2015 Elsevier B.V. All rights reserved.

Numerical simulation of the effect of groundwater salinity on artificial freezing wall in coastal area

NASA Astrophysics Data System (ADS)

Hu, Rui; Liu, Quan

2017-04-01

During the engineering projects with artificial ground freezing (AFG) techniques in coastal area, the freezing effect is affected by groundwater salinity. Based on the theories of artificially frozen soil and heat transfer in porous material, and with the assumption that only the variations of total dissolved solids (TDS) impact on freezing point and thermal conductivity, a numerical model of an AFG project in a saline aquifer was established and validated by comparing the simulated temperature field with the calculated temperature based on the analytic solution of rupak (reference) for single-pipe freezing temperature field T. The formation and development of freezing wall were simulated with various TDS. The results showed that the variety of TDS caused the larger temperature difference near the frozen front. With increasing TDS in the saline aquifer (1 35g/L), the average thickness of freezing wall decreased linearly and the total formation time of the freezing wall increased linearly. Compared with of the scenario of fresh-water (<1g/L), the average thickness of frozen wall decreased by 6% and the total formation time of the freezing wall increased by 8% with each increasing TDS of 7g/L. Key words: total dissolved solids, freezing point, thermal conductivity, freezing wall, numerical simulation Reference D.J.Pringel, H.Eicken, H.J.Trodahl, etc. Thermal conductivity of landfast Antarctic and Arctic sea ice[J]. Journal of Geophysical Research, 2007, 112: 1-13. Lukas U.Arenson, Dave C.Sego. The effect of salinity on the freezing of coarse- grained sand[J]. Canadian Geotechnical Journal, 2006, 43: 325-337. Hui Bing, Wei Ma. Laboratory investigation of the freezing point of saline soil[J]. Cold Regions Science and Technology, 2011, 67: 79-88.

Mechanisms of deterioration of nutrients phase 1

NASA Technical Reports Server (NTRS)

Karel, M.; Flink, J. M.

1972-01-01

Experimental methods are studied by which freeze-dried foods of improved quality are produced. Considered are: (1) Factors effecting the loss of butanol from frozen aqueous food solutions during storage; (2) a freeze-drying microscope system for observing solidification processes in organic mixtures and aqueous inorganic salt solutions; (3) browning of high quality freeze-dried foods with minimal organoleptic and nutritional detoriation; (4) retention of PVP-n-propanol in freeze-dried food models; and (5) effects of freezing rate and sucrose immersion on taste and texture of freeze-dried apple slices.

Effect of moisture content on the invertase activity of freeze-dried S. cerevisiae.

PubMed

Pitombo, R N; Spring, C; Passos, R F; Tonato, M; Vitolo, M

1994-08-01

The invertase activity of intact Saccharomyces cerevisiae submitted to freezing-thawing was affected by pH, the chemical nature of the buffer, and the freezing cooling rate (CR), leading in some cases to a complete invertase inactivation (acetate buffer, pH 4.0, CR = 0.5 degree C/min). Once established under adequate freezing conditions the invertase activity remained unchanged after freeze-drying. Nevertheless, in some cases the cell-growing capability after freeze-drying diminished around 70%, mainly if the frozen cell suspension was attained through freezing carried out at CR = 0.5 degree C/min. Water sorption isotherms of freeze-dried samples (freeze-dryer Edwards L-4KR; 30 degrees C and 0.1 mB) were determined at 10 and 25 degrees C. The monolayer moisture content (MMC) at each temperature (12.7 and 3.71 for 10 and 25 degrees C, respectively) was calculated from isotherms by applying BET and GAB models. Freeze-dried yeast with water activity (Aw) between 0 and 0.33 (about the MMC value) maintained at 25 degrees C for 235 days and at 89 degrees C for 15 min retained at least 85% of its original invertase activity (IA), whereas samples with Aw > MMC lost at least 60% of its IA. X ray diffraction showed that the freeze-dried cake before and after storage presented an amorphous structure.

Ice-Binding Proteins in Plants

PubMed Central

Bredow, Melissa; Walker, Virginia K.

2017-01-01

Sub-zero temperatures put plants at risk of damage associated with the formation of ice crystals in the apoplast. Some freeze-tolerant plants mitigate this risk by expressing ice-binding proteins (IBPs), that adsorb to ice crystals and modify their growth. IBPs are found across several biological kingdoms, with their ice-binding activity and function uniquely suited to the lifestyle they have evolved to protect, be it in fishes, insects or plants. While IBPs from freeze-avoidant species significantly depress the freezing point, plant IBPs typically have a reduced ability to lower the freezing temperature. Nevertheless, they have a superior ability to inhibit the recrystallization of formed ice. This latter activity prevents ice crystals from growing larger at temperatures close to melting. Attempts to engineer frost-hardy plants by the controlled transfer of IBPs from freeze-avoiding fish and insects have been largely unsuccessful. In contrast, the expression of recombinant IBP sequences from freeze-tolerant plants significantly reduced electrolyte leakage and enhanced freezing survival in freeze-sensitive plants. These promising results have spurred additional investigations into plant IBP localization and post-translational modifications, as well as a re-evaluation of IBPs as part of the anti-stress and anti-pathogen axis of freeze-tolerant plants. Here we present an overview of plant freezing stress and adaptation mechanisms and discuss the potential utility of IBPs for the generation of freeze-tolerant crops. PMID:29312400

Ice-Binding Proteins in Plants.

PubMed

Bredow, Melissa; Walker, Virginia K

2017-01-01

Sub-zero temperatures put plants at risk of damage associated with the formation of ice crystals in the apoplast. Some freeze-tolerant plants mitigate this risk by expressing ice-binding proteins (IBPs), that adsorb to ice crystals and modify their growth. IBPs are found across several biological kingdoms, with their ice-binding activity and function uniquely suited to the lifestyle they have evolved to protect, be it in fishes, insects or plants. While IBPs from freeze-avoidant species significantly depress the freezing point, plant IBPs typically have a reduced ability to lower the freezing temperature. Nevertheless, they have a superior ability to inhibit the recrystallization of formed ice. This latter activity prevents ice crystals from growing larger at temperatures close to melting. Attempts to engineer frost-hardy plants by the controlled transfer of IBPs from freeze-avoiding fish and insects have been largely unsuccessful. In contrast, the expression of recombinant IBP sequences from freeze-tolerant plants significantly reduced electrolyte leakage and enhanced freezing survival in freeze-sensitive plants. These promising results have spurred additional investigations into plant IBP localization and post-translational modifications, as well as a re-evaluation of IBPs as part of the anti-stress and anti-pathogen axis of freeze-tolerant plants. Here we present an overview of plant freezing stress and adaptation mechanisms and discuss the potential utility of IBPs for the generation of freeze-tolerant crops.

Changes in Ultrastructure and Sensory Characteristics on Electro-magnetic and Air Blast Freezing of Beef during Frozen Storage

PubMed Central

2015-01-01

The ultrastructure in the beef muscle of the electro-magnetic resonance and air blast freezing during the frozen storage, and the changes in the quality characteristics after thawing were evaluated. The size of ice crystal was small and evenly formed in the initial freezing period, and it showed that the size was increased as the storage period was elapsed (p<0.05). The beef stored by the electro-magnetic resonance freezing showed the size of ice crystal with a lower rate of increase than the air blast freezing during the frozen storage. The thawing loss of beef stored by the electro-magnetic resonance freezing was significantly lower than the air blast freezing during frozen storage (p<0.05), and it showed that the thawing loss of the round was higher than the loin. Water holding capacity decreased as the storage period became longer while the electro-magnetic resonance freezing was higher than the air blast on 8 month (p<0.05). As a result of sensory evaluation, the beef stored by the electro-magnetic resonance freezing did not show the difference until 4 months, and it showed higher acceptability in comparison with the beef stored by the air blast freezing. Thus, it is considered that the freezing method has an effect on the change in the ultrastructure and quality characteristics of the beef. PMID:26761797

Freeze-thaw durability of concrete: Ice formation process in pores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, H.; Liu, X.

1998-09-01

Freeze-thaw durability of concrete is of great importance to hydraulic structures in cold areas. Study of ice formation process in concrete pores is necessary to evaluate the damages in concrete caused by freezing. In this paper, freezing of pore solution in concrete exposed to a freeze-thaw cycle is studied by following the change of concrete electrical conductivity with freezing temperatures. Concretes were subjected to freeze-thaw cycles with temperature varying between {minus}0 C and {minus}20 C. In the freezing process, the changing rate of concrete electrical conductivity obviously decreases at about {minus}10 C, indicating that more pore solution in concrete freezesmore » above {minus}10 C than below {minus}10C. According to Powers` static hydraulic pressure hypothesis, it is thought that frost damage mainly occurs between 0 C and {minus}100 C. To ordinary concrete, frost damages below {minus}10 C are negligible.« less

Fish antifreeze protein and the freezing and recrystallization of ice.

PubMed

Knight, C A; DeVries, A L; Oolman, L D

Antifreeze glycopeptide and peptides from the blood of polar fishes prevent the growth of ice crystals in water at temperatures down to approximately 1 degree C below freezing point, but do not appreciably influence the equilibrium freezing point. This freezing point hysteresis must be a disequilibrium effect, or it would violate Gibbs' phase rule, but the separate freezing and melting points are experimentally very definite: ice neither melts nor freezes perceptibly within the 'hysteresis gap', for periods of hours or days. We report here unusual crystal faces on ice crystals grown from solutions of very low concentrations of the anti-freeze glycopeptides and peptides. This is a clue to the mechanism of freezing inhibition, and it may be the basis of a simple, very sensitive test for antifreeze material. Very low concentrations of the antifreeze protein are also remarkably effective in preventing the recrystallization of ice.

Increased spring freezing vulnerability for alpine shrubs under early snowmelt.

PubMed

Wheeler, J A; Hoch, G; Cortés, A J; Sedlacek, J; Wipf, S; Rixen, C

2014-05-01

Alpine dwarf shrub communities are phenologically linked with snowmelt timing, so early spring exposure may increase risk of freezing damage during early development, and consequently reduce seasonal growth. We examined whether environmental factors (duration of snow cover, elevation) influenced size and the vulnerability of shrubs to spring freezing along elevational gradients and snow microhabitats by modelling the past frequency of spring freezing events. We sampled biomass and measured the size of Salix herbacea, Vaccinium myrtillus, Vaccinium uliginosum and Loiseleuria procumbens in late spring. Leaves were exposed to freezing temperatures to determine the temperature at which 50% of specimens are killed for each species and sampling site. By linking site snowmelt and temperatures to long-term climate measurements, we extrapolated the frequency of spring freezing events at each elevation, snow microhabitat and per species over 37 years. Snowmelt timing was significantly driven by microhabitat effects, but was independent of elevation. Shrub growth was neither enhanced nor reduced by earlier snowmelt, but decreased with elevation. Freezing resistance was strongly species dependent, and did not differ along the elevation or snowmelt gradient. Microclimate extrapolation suggested that potentially lethal freezing events (in May and June) occurred for three of the four species examined. Freezing events never occurred on late snow beds, and increased in frequency with earlier snowmelt and higher elevation. Extrapolated freezing events showed a slight, non-significant increase over the 37-year record. We suggest that earlier snowmelt does not enhance growth in four dominant alpine shrubs, but increases the risk of lethal spring freezing exposure for less freezing-resistant species.

Controlled crystallization of the lipophilic drug fenofibrate during freeze-drying: elucidation of the mechanism by in-line Raman spectroscopy.

PubMed

de Waard, Hans; De Beer, Thomas; Hinrichs, Wouter L J; Vervaet, Chris; Remon, Jean-Paul; Frijlink, Henderik W

2010-12-01

We developed a novel process, "controlled crystallization during freeze-drying" to produce drug nanocrystals of poorly water-soluble drugs. This process involves freeze-drying at a relatively high temperature of a drug and a matrix material from a mixture of tertiary butyl alcohol and water, resulting in drug nanocrystals incorporated in a matrix. The aim of this study was to elucidate the mechanisms that determine the size of the drug crystals. Fenofibrate was used as a model lipophilic drug. To monitor the crystallization during freeze-drying, a Raman probe was placed just above the sample in the freeze-dryer. These in-line Raman spectroscopy measurements clearly revealed when the different components crystallized during freeze-drying. The solvents crystallized only during the freezing step, while the solutes only crystallized after the temperature was increased, but before drying started. Although the solutes crystallized only after the freezing step, both the freezing rate and the shelf temperature were critical parameters that determined the final crystal size. At a higher freezing rate, smaller interstitial spaces containing the freeze-concentrated fraction were formed, resulting in smaller drug crystals (based on dissolution data). On the other hand, when the solutes crystallized at a lower shelf temperature, the degree of supersaturation is higher, resulting in a higher nucleation rate and consequently more and therefore smaller crystals. In conclusion, for the model drug fenofibrate, a high freezing rate and a relatively low crystallization temperature resulted in the smallest crystals and therefore the highest dissolution rate.

Effect of three cueing devices for people with Parkinson's disease with gait initiation difficulties.

PubMed

McCandless, Paula J; Evans, Brenda J; Janssen, Jessie; Selfe, James; Churchill, Andrew; Richards, Jim

2016-02-01

Freezing of gait (FOG) remains one of the most common debilitating aspects of Parkinson's disease and has been linked to injuries, falls and reduced quality of life. Although commercially available portable cueing devices exist claiming to assist with overcoming freezing; their immediate effectiveness in overcoming gait initiation failure is currently unknown. This study investigated the effects of three different types of cueing device in people with Parkinson's disease who experience freezing. Twenty participants with idiopathic Parkinson's disease who experienced freezing during gait but who were able to walk short distances indoors independently were recruited. At least three attempts at gait initiation were recorded using a 10 camera Qualisys motion analysis system and four force platforms. Test conditions were; Laser Cane, sound metronome, vibrating metronome, walking stick and no intervention. During testing 12 of the 20 participants had freezing episodes, from these participants 100 freezing and 91 non-freezing trials were recorded. Clear differences in the movement patterns were seen between freezing and non-freezing episodes. The Laser Cane was most effective cueing device at improving the forwards/backwards and side to side movement and had the least number of freezing episodes. The walking stick also showed significant improvements compared to the other conditions. The vibration metronome appeared to disrupt movement compared to the sound metronome at the same beat frequency. This study identified differences in the movement patterns between freezing episodes and non-freezing episodes, and identified immediate improvements during gait initiation when using the Laser Cane over the other interventions. Copyright © 2015. Published by Elsevier B.V.

Role of glucose-6-phosphate dehydrogenase in freezing-induced freezing resistance of Populus suaveolens.

PubMed

Lin, Shan-Zhi; Zhang, Zhi-Yi; Liu, Wen-Feng; Lin, Yuan-Zhen; Zhang, Qian; Zhu, Bao-Qing

2005-02-01

To explore the role of glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) in the enhancement of freezing resistance induced by freezing acclimation, G6PDH was purified from the leaves of 8-week-old Populus suaveolens cuttings. The G6PDH activity in the absence or the presence of reduced dithiothreitol (DTT(red)) were determined, and the changes in superoxide dismutase (SOD), peroxides (POD) and cytosolic G6PDH activities, malondial-dehyde (MDA) content as well as freezing resistance (expressed as LT(50)) of P. suaveolens cuttings during freezing acclimation at -20 degrees C were investigated. The results showed that the purified G6PDH was probably located in the cytosol of P. suaveolens. Freezing acclimation increased the activities of SOD, POD and cytosolic G6PDH, and decreased the MDA content and LT(50) of cuttings, while 2 d of de-acclimation at 25 degrees C resulted in a decrease in SOD, POD and cytosolic G6PDH activities, and caused an increase in MDA content and LT(50). The change in cytosolic G6PDH activity was found to be closely correlated to the levels of SOD, POD and MDA, and to the degree of freezing resistance of cuttings during freezing acclimation. It is suggested that the enhancement of freezing resistance of cuttings induced by freezing acclimation is related to the distinct increase in cytosolic G6PDH activity, which may be involved in the activation of SOD and POD, and the induction of freezing resistance of cuttings.

Differential freezing resistance and photoprotection in C3 and C4 eudicots and grasses

PubMed Central

Liu, Mei-Zhen; Osborne, Colin P.

2013-01-01

Globally, C4 plants dominate hot, open environments, but this general pattern is underpinned by important differences in the biogeography of C4 lineages. In particular, the species richness of C4 Poaceae (grasses) increases strongly with increasing temperature, whereas that of the major C4 eudicot group Chenopodiaceae correlates positively with aridity. Freezing tolerance is a crucial determinant of biogeographical relationships with temperature and is mediated by photodamage and cellular disruption by desiccation, but little is known about differences between C4 families. This study hypothesized that there is a greater risk of freezing damage via these mechanisms in C4 Poaceae than Chenopodiaceae, that freezing protection differs between the taxonomic groups, and that freezing tolerance of species is linked to arid habitat preference. Chlorophyll fluorescence, water relations, and freezing injury were compared in four C3 and six C4 species of Poaceae and Chenopodiaceae from the same Mongolian flora. Contrary to expectations, freezing-induced leaf mortality and photodamage were lower in Poaceae than Chenopodiaceae species, and unrelated to photosynthetic pathway. The freezing resistance of Poaceae species resulted from constitutive protection and cold acclimation and an ability to protect the photosynthetic apparatus from photodamage. Freezing protection was associated with low osmotic potential and low tissue elasticity, and freezing damage was accompanied by electrolyte leakage, consistent with cell-membrane disruption by ice. Both Chenopodiaceae and Poaceae had the potential to develop cold acclimation and withstand freezing during the growing season, which conflicted with the hypothesis. Instead, freezing tolerance was more closely associated with life history and ecological preference in these Mongolian species. PMID:23599273

Embolism Formation during Freezing in the Wood of Picea abies1

PubMed Central

Mayr, Stefan; Cochard, Hervé; Améglio, Thierry; Kikuta, Silvia B.

2007-01-01

Freeze-thaw events can cause embolism in plant xylem. According to classical theory, gas bubbles are formed during freezing and expand during thawing. Conifers have proved to be very resistant to freeze-thaw induced embolism, because bubbles in tracheids are small and redissolve during thawing. In contrast, increasing embolism rates upon consecutive freeze-thaw events were observed that cannot be explained by the classical mechanism. In this study, embolism formation during freeze-thaw events was analyzed via ultrasonic and Cryo-scanning electron microscope techniques. Twigs of Picea abies L. Karst. were subjected to up to 120 freeze-thaw cycles during which ultrasonic acoustic emissions, xylem temperature, and diameter variations were registered. In addition, the extent and cross-sectional pattern of embolism were analyzed with staining experiments and Cryo-scanning electron microscope observations. Embolism increased with the number of freeze-thaw events in twigs previously dehydrated to a water potential of −2.8 MPa. In these twigs, acoustic emissions were registered, while saturated twigs showed low, and totally dehydrated twigs showed no, acoustic activity. Acoustic emissions were detected only during the freezing process. This means that embolism was formed during freezing, which is in contradiction to the classical theory of freeze-thaw induced embolism. The clustered pattern of embolized tracheids in cross sections indicates that air spread from a dysfunctional tracheid to adjacent functional ones. We hypothesize that the low water potential of the growing ice front led to a decrease of the potential in nearby tracheids. This may result in freezing-induced air seeding. PMID:17041033

Contact freezing of supercooled cloud droplets on collision with mineral dust particles: effect of particle size

NASA Astrophysics Data System (ADS)

Hoffmann, Nadine; Duft, Denis; Kiselev, Alexei; Leisner, Thomas

2013-04-01

The contact freezing of supercooled cloud droplets is one of the potentially important and the least investigated heterogeneous mechanism of ice formation in the tropospheric clouds [1]. On the time scales of cloud lifetime the freezing of supercooled water droplets via contact mechanism may occur at higher temperature compared to the same IN immersed in the droplet. However, the laboratory experiments of contact freezing are very challenging due to the number of factors affecting the probability of ice formation. In our experiment we study single water droplets freely levitated in the laminar flow of mineral dust particles acting as the contact freezing nuclei. By repeating the freezing experiment sufficient number of times we are able to reproduce statistical freezing behavior of large ensembles of supercooled droplets and measure the average rate of freezing events. We show that the rate of freezing at given temperature is governed only by the rate of droplet -particle collision and by the properties of the contact ice nuclei. In this contribution we investigate the relationship between the freezing probability and the size of mineral dust particle (represented by illite) and show that their IN efficiency scales with the particle size. Based on this observation, we discuss the similarity between the freezing of supercooled water droplets in immersion and contact modes and possible mechanisms of apparent enhancement of the contact freezing efficiency. [1] - K.C. Young, The role of contact nucleation in ice phase initiation in clouds, Journal of the Atmospheric Sciences 31, 1974

Ice nucleation temperature influences recovery of activity of a model protein after freeze drying.

PubMed

Cochran, Teresa; Nail, Steven L

2009-09-01

The objective of this study was to determine whether a relationship exists between ice nucleation temperature and recovery of activity of a model protein, lactate dehydrogenase, after freeze drying. Aqueous buffer systems containing 50 microg/mL of protein were frozen in vials with externally mounted thermocouples on the shelf of a freeze dryer, then freeze dried. Various methods were used to establish a wide range of ice nucleation temperatures. An inverse relationship was found between the extent of supercooling during freezing and recovery of activity in the reconstituted solution. The data are consistent with a mechanism of inactivation resulting from adsorption of protein at the ice/freeze-concentrate interface during the freezing process.

Predictive modeling of freezing and thawing of frost-susceptible soils.

DOT National Transportation Integrated Search

2015-09-01

Frost depth is an essential factor in design of various transportation infrastructures. In frost : susceptible soils, as soils freezes, water migrates through the soil voids below the freezing line : towards the freezing front and causes excessive he...

Cognitive Contributions to Freezing of Gait in Parkinson Disease: Implications for Physical Rehabilitation

PubMed Central

King, Laurie A.; Cohen, Rajal G.; Horak, Fay B.

2016-01-01

People with Parkinson disease (PD) who show freezing of gait also have dysfunction in cognitive domains that interact with mobility. Specifically, freezing of gait is associated with executive dysfunction involving response inhibition, divided attention or switching attention, and visuospatial function. The neural control impairments leading to freezing of gait have recently been attributed to higher-level, executive and attentional cortical processes involved in coordinating posture and gait rather than to lower-level, sensorimotor impairments. To date, rehabilitation for freezing of gait primarily has focused on compensatory mobility training to overcome freezing events, such as sensory cueing and voluntary step planning. Recently, a few interventions have focused on restitutive, rather than compensatory, therapy. Given the documented impairments in executive function specific to patients with PD who freeze and increasing evidence of overlap between cognitive and motor function, incorporating cognitive challenges with mobility training may have important benefits for patients with freezing of gait. Thus, a novel theoretical framework is proposed for exercise interventions that jointly address both the specific cognitive and mobility challenges of people with PD who freeze. PMID:26381808

Cognitive Contributions to Freezing of Gait in Parkinson Disease: Implications for Physical Rehabilitation.

PubMed

Peterson, Daniel S; King, Laurie A; Cohen, Rajal G; Horak, Fay B

2016-05-01

People with Parkinson disease (PD) who show freezing of gait also have dysfunction in cognitive domains that interact with mobility. Specifically, freezing of gait is associated with executive dysfunction involving response inhibition, divided attention or switching attention, and visuospatial function. The neural control impairments leading to freezing of gait have recently been attributed to higher-level, executive and attentional cortical processes involved in coordinating posture and gait rather than to lower-level, sensorimotor impairments. To date, rehabilitation for freezing of gait primarily has focused on compensatory mobility training to overcome freezing events, such as sensory cueing and voluntary step planning. Recently, a few interventions have focused on restitutive, rather than compensatory, therapy. Given the documented impairments in executive function specific to patients with PD who freeze and increasing evidence of overlap between cognitive and motor function, incorporating cognitive challenges with mobility training may have important benefits for patients with freezing of gait. Thus, a novel theoretical framework is proposed for exercise interventions that jointly address both the specific cognitive and mobility challenges of people with PD who freeze. © 2016 American Physical Therapy Association.

Representative Values of Icing-Related Variables Aloft in Freezing Rain and Freezing Drizzle

DOT National Transportation Integrated Search

1996-03-01

Radiosonde and surface observations in freezing rain (ZR) and freezing drizzle (ZL), and a limited number of aircraft measurements in ZR, have been examined for information on the magnitude and altitude dependence of meteorological variables associat...

Effects of Artificial Supercooling Followed by Slow Freezing on the Microstructure and Qualities of Pork Loin

PubMed Central

2016-01-01

This study investigated the effects of artificial supercooling followed by still air freezing (SSF) on the qualities of pork loin. The qualities of pork frozen by SSF were compared with the fresh control (CT, stored at 4℃ for 24 h), slow freezing (SAF, still air freezing) and rapid freezing (EIF, ethanol immersion freezing) treatments. Compared with no supercooling phenomena of SAF and EIF, the extent of supercooling obtained by SSF treatment was 1.4℃. Despite that SSF was conducted with the same method with SAF, application of artificial supercooling accelerated the phase transition (traverse from -0.6℃ to -5℃) from 3.07 h (SAF) to 2.23 h (SSF). The observation of a microstructure indicated that the SSF prevented tissue damage caused by ice crystallization and maintained the structural integrity. The estimated quality parameters reflected that SSF exhibited superior meat quality compared with slow freezing (SAF). SSF showed better water-holding capacity (lower thawing loss, cooking loss and expressible moisture) and tenderness than SAF, and these quality parameters of SSF were not significantly different with ultra-fast freezing treatment (EIF). Consequently, the results demonstrated that the generation of supercooling followed by conventional freezing potentially had the advantage of minimizing the quality deterioration caused by the slow freezing of meat. PMID:27857541

Fundamental Technical Elements of Freeze-fracture/Freeze-etch in Biological Electron Microscopy

EPA Science Inventory

Freeze-fracture/freeze-etch describes a process whereby specimens, typically biological or nanomaterial in nature, are frozen, fractured, and replicated to generate a carbon/platinum "cast" intended for examination by transmission electron microscopy. Specimens are subjected to u...

Demonstrating Functional Equivalence of Pilot and Production Scale Freeze-Drying of BCG

PubMed Central

ten Have, R.; Reubsaet, K.; van Herpen, P.; Kersten, G.; Amorij, J.-P.

2016-01-01

Process analytical technology (PAT)-tools were used to monitor freeze-drying of Bacille Calmette-Guérin (BCG) at pilot and production scale. Among the evaluated PAT-tools, there is the novel use of the vacuum valve open/close frequency for determining the endpoint of primary drying at production scale. The duration of primary drying, the BCG survival rate, and the residual moisture content (RMC) were evaluated using two different freeze-drying protocols and were found to be independent of the freeze-dryer scale evidencing functional equivalence. The absence of an effect of the freeze-dryer scale on the process underlines the feasibility of the pilot scale freeze-dryer for further BCG freeze-drying process optimization which may be carried out using a medium without BCG. PMID:26981867

Demonstrating Functional Equivalence of Pilot and Production Scale Freeze-Drying of BCG.

PubMed

Ten Have, R; Reubsaet, K; van Herpen, P; Kersten, G; Amorij, J-P

2016-01-01

Process analytical technology (PAT)-tools were used to monitor freeze-drying of Bacille Calmette-Guérin (BCG) at pilot and production scale. Among the evaluated PAT-tools, there is the novel use of the vacuum valve open/close frequency for determining the endpoint of primary drying at production scale. The duration of primary drying, the BCG survival rate, and the residual moisture content (RMC) were evaluated using two different freeze-drying protocols and were found to be independent of the freeze-dryer scale evidencing functional equivalence. The absence of an effect of the freeze-dryer scale on the process underlines the feasibility of the pilot scale freeze-dryer for further BCG freeze-drying process optimization which may be carried out using a medium without BCG.

Research on strength attenuation law of concrete in freezing - thawing environment

NASA Astrophysics Data System (ADS)

Xiao, qianhui; Cao, zhiyuan; Li, qiang

2018-03-01

By rapid freezing and thawing method, the experiments of concrete have been 300 freeze-thaw cycles specimens in the water. The cubic compression strength value under different freeze-thaw cycles was measured. By analyzing the test results, the water-binder ratio of the concrete under freeze-thaw environments, fly ash and air entraining agent is selected dosage recommendations. The exponential attenuation prediction model and life prediction model of compression strength of concrete under freezing-thawing cycles considering the factors of water-binder ratio, fly ash content and air-entraining agent dosage were established. The model provides the basis for predicting the durability life of concrete under freezing-thawing environment. It also provides experimental basis and references for further research on concrete structures with antifreeze requirements.

Experimental research on durability of recycled aggregate concrete under freeze- thaw cycles

NASA Astrophysics Data System (ADS)

Cheng, Yanqiu; Shang, Xiaoyu; Zhang, Youjia

2017-07-01

The freeze-thaw durability of recycled aggregate concrete has significance for the concrete buildings in the cold region. In this paper, the rapid freezing and thawing cycles experience on recycle aggregate concrete was conducted to study on the effects of recycle aggregate amount, water-binder ratio and fly ash on freeze-thaw durability of recycle aggregate concrete. The results indicates that recycle aggregate amount makes the significant influence on the freeze-thaw durability. With the increase of recycled aggregates amount, the freeze-thaw resistance for recycled aggregate concrete decreases. Recycled aggregate concrete with lower water cement ratio demonstrates better performance of freeze-thaw durability. It is advised that the amount of fly ash is less than 30% for admixture of recycled aggregates in the cold region.

MAL62 overexpression and NTH1 deletion enhance the freezing tolerance and fermentation capacity of the baker's yeast in lean dough.

PubMed

Sun, Xi; Zhang, Cui-Ying; Wu, Ming-Yue; Fan, Zhi-Hua; Liu, Shan-Na; Zhu, Wen-Bi; Xiao, Dong-Guang

2016-04-04

Trehalose is related to several types of stress responses, especially freezing response in baker's yeast (Saccharomyces cerevisiae). It is desirable to manipulate trehalose-related genes to create yeast strains that better tolerate freezing-thaw stress with improved fermentation capacity, which are in high demand in the baking industry. The strain overexpressing MAL62 gene showed increased trehalose content and cell viability after prefermention-freezing and long-term frozen. Deletion of NTH1 in combination of MAL62 overexpression further strengthens freezing tolerance and improves the leavening ability after freezing-thaw stress. The mutants of the industrial baker's yeast with enhanced freezing tolerance and leavening ability in lean dough were developed by genetic engineering. These strains had excellent potential industrial applications.

Freeze/Thaw-Induced Embolism: Probability of Critical Bubble Formation Depends on Speed of Ice Formation

DOE PAGES

Sevanto, Sanna; Holbrook, N. Michele; Ball, Marilyn C.

2012-06-06

Bubble formation in the conduits of woody plants sets a challenge for uninterrupted water transportation from the soil up to the canopy. Freezing and thawing of stems has been shown to increase the number of air-filled (embolized) conduits, especially in trees with large conduit diameters. Despite numerous experimental studies, the mechanisms leading to bubble formation during freezing have not been addressed theoretically. We used classical nucleation theory and fluid mechanics to show which mechanisms are most likely to be responsible for bubble formation during freezing and what parameters determine the likelihood of the process. Our results confirm the common assumptionmore » that bubble formation during freezing is most likely due to gas segregation by ice. If xylem conduit walls are not permeable to the salts expelled by ice during the freezing process, osmotic pressures high enough for air seeding could be created. The build-up rate of segregated solutes in front of the ice-water interface depends equally on conduit diameter and freezing velocity. Therefore, bubble formation probability depends on these variables. The dependence of bubble formation probability on freezing velocity means that the experimental results obtained for cavitation threshold conduit diameters during freeze/thaw cycles depend on the experimental setup; namely sample size and cooling rate. The velocity dependence also suggests that to avoid bubble formation during freezing trees should have narrow conduits where freezing is likely to be fast (e.g., branches or outermost layer of the xylem). Avoidance of bubble formation during freezing could thus be one piece of the explanation why xylem conduit size of temperate and boreal zone trees varies quite systematically.« less

Optimizing the Protocol for Pulmonary Cryoablation: A Comparison of a Dual- and Triple-Freeze Protocol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hinshaw, J. Louis, E-mail: jhinshaw@uwhealth.or; Littrup, Peter J.; Durick, Nathan

2010-12-15

The purpose of this study was to compare a double freeze-thaw protocol to a triple freeze-thaw protocol for pulmonary cryoablation utilizing an in vivo porcine lung model. A total of 18 cryoablations were performed in normal porcine lung utilizing percutaneous technique with 9 each in a double- (10-5-10) and triple-freeze (3-3-7-7-5) protocol. Serial noncontrast CT images were obtained during the ablation. CT imaging findings and pathology were reviewed. No imaging changes were identified during the initial freeze cycle with either protocol. However, during the first thaw cycle, a region of ground glass opacity developed around the probe with both protocols.more » Because the initial freeze was shorter with the triple freeze-thaw protocol, the imaging findings were apparent sooner with this protocol (6 vs. 13 min). Also, despite a shorter total freeze time (15 vs. 20 min), the ablation zone identified with the triple freeze-thaw protocol was not significantly different from the double freeze-thaw protocol (mean diameter: 1.67 {+-} 0.41 cm vs. 1.66 {+-} 0.21 cm, P = 0.77; area: 2.1 {+-} 0.48 cm{sup 2} vs. 1.99 {+-} 0.62 cm{sup 2}, P = 0.7; and circularity: 0.95 {+-} 0.04 vs. 0.96 {+-} 0.03, P = 0.62, respectively). This study suggests that there may be several advantages of a triple freeze-thaw protocol for pulmonary cryoablation, including earlier identification of the imaging findings associated with the ablation, the promise of a shorter procedure time or larger zones of ablation, and theoretically, more effective cytotoxicity related to the additional freeze-thaw cycle.« less

Rapid freezing without cooling equilibration in canine sperm.

PubMed

Kim, Suhee; Lee, Yongcheol; Yang, Honghyun; Kim, Yong-Jun

2012-01-01

The aim of this study was to develop a rapid method of canine semen freezing without cooling equilibration using treatment with different cryoprotectant agents (CPAs) and freezing in liquid nitrogen (LN(2)) vapor in a 0.5-mL straw via modifying vitrification. Ejaculates from eight beagle dogs were frozen with different CPAs (CPA-free, 5% glycerol, 5% ethylene glycol, and 10% ethylene glycol) and freezing times (direct plunging into LN(2) or freezing for 1, 2, 3, or 10 min in LN(2) vapor before plunging into LN(2)). Frozen-thawed sperm were evaluated for motility, viability, normal morphology, and plasma- and acrosome-membrane integrities. The 5% glycerol treatment resulted in improved sperm motility, plasma-membrane integrity and acrosome-membrane integrity (P<0.05). Freezing in LN(2) vapor showed improved sperm motility, viability, and plasma membrane integrity (P<0.05), and freezing for more than 2 min in LN(2) vapor increased acrosome-membrane integrity compared with direct plunging into LN(2) (P<0.05). The direct plunging into LN(2) showed no motile sperm. However, freezing for more than 2 min in LN(2) vapor increased the total abnormalities compared to direct plunging into LN(2) (P<0.05). In conclusion, use of 5% glycerol and freezing in LN(2) vapor were essential for the rapid freezing of canine sperm without cooling equilibration. In particular, holding for 2 min in LN(2) vapor was sufficient to yield successful rapid freezing. This rapid freezing method is simple and effective in canine sperm and would be helpful to offer information for trial of vitrification in large volumes of canine sperm. Copyright © 2012 Elsevier B.V. All rights reserved.

Freeze/Thaw-induced embolism: probability of critical bubble formation depends on speed of ice formation.

PubMed

Sevanto, Sanna; Holbrook, N Michele; Ball, Marilyn C

2012-01-01

Bubble formation in the conduits of woody plants sets a challenge for uninterrupted water transportation from the soil up to the canopy. Freezing and thawing of stems has been shown to increase the number of air-filled (embolized) conduits, especially in trees with large conduit diameters. Despite numerous experimental studies, the mechanisms leading to bubble formation during freezing have not been addressed theoretically. We used classical nucleation theory and fluid mechanics to show which mechanisms are most likely to be responsible for bubble formation during freezing and what parameters determine the likelihood of the process. Our results confirm the common assumption that bubble formation during freezing is most likely due to gas segregation by ice. If xylem conduit walls are not permeable to the salts expelled by ice during the freezing process, osmotic pressures high enough for air seeding could be created. The build-up rate of segregated solutes in front of the ice-water interface depends equally on conduit diameter and freezing velocity. Therefore, bubble formation probability depends on these variables. The dependence of bubble formation probability on freezing velocity means that the experimental results obtained for cavitation threshold conduit diameters during freeze/thaw cycles depend on the experimental setup; namely sample size and cooling rate. The velocity dependence also suggests that to avoid bubble formation during freezing trees should have narrow conduits where freezing is likely to be fast (e.g., branches or outermost layer of the xylem). Avoidance of bubble formation during freezing could thus be one piece of the explanation why xylem conduit size of temperate and boreal zone trees varies quite systematically.

Mutagenic effect of freezing on mitochondrial DNA of Saccharomyces cerevisiae.

PubMed

Stoycheva, T; Venkov, P; Tsvetkov, Ts

2007-06-01

Although suggested in some studies, the mutagenic effect of freezing has not been proved by induction and isolation of mutants. Using a well-defined genetic model, we supply in this communication evidence for the mutagenic effect of freezing on mitochondrial DNA (mtDNA) of the yeast Saccharomyces cerevisiae. The cooling for 2 h at +4 degrees C, followed by freezing for 1 h at -10 degrees C and 16 h at -20 degrees C resulted in induction of respiratory mutations. The immediate freezing in liquid nitrogen was without mutagenic effect. The study of the stepwise procedure showed that the induction of respiratory mutants takes place during the freezing at -10 and -20 degrees C of cells pre-cooled at +4 degrees C. The genetic crosses of freeze-induced mutants evidenced their mitochondrial rho- origin. The freeze-induced rho- mutants are most likely free of simultaneous nuclear mutations. The extracellular presence of cryoprotectants did not prevent the mutagenic effect of freezing while accumulation of cryoprotectors inside cells completely escaped mtDNA from cryodamage. Although the results obtained favor the notion that the mutagenic effect of freezing on yeast mtDNA is due to formation and growth of intracellular ice crystals, other reasons, such as impairment of mtDNA replication or elevated levels of ROS production are discussed as possible explanations of the mutagenic effect of freezing. It is concluded that: (i) freezing can be used as a method for isolation of mitochondrial mutants in S. cerevisiae and (ii) given the substantial development in cryopreservation of cells and tissues, special precautions should be made to avoid mtDNA damage during the cryopreservation procedures.

SENSITIVE TO FREEZING2 Aids in Resilience to Salt and Drought in Freezing-Sensitive Tomato

DOE PAGES

Wang, Kun; Hersh, Hope Lynn; Benning, Christoph

2016-09-06

SENSITIVE TO FREEZING2 (SFR2) is crucial for protecting chloroplast membranes following freezing in Arabidopsis (Arabidopsis thaliana). It has been shown that SFR2 homologs are present in all land plants, including freezing-sensitive species, raising the question of SFR2 function beyond freezing tolerance. Similar to freezing, salt and drought can cause dehydration. Thus, it is hypothesized that in freezing-sensitive plants SFR2 may play roles in their resilience to salt or drought. To test this hypothesis, SlSFR2 RNAi lines were generated in the cold/freezing-sensitive species tomato (Solanum lycopersicum [M82 cv]). Hypersensitivity to salt and drought of SlSFR2-RNAi lines was observed. Higher tolerance ofmore » wild-type tomatoes was correlated with the production of trigalactosyldiacylglycerol, a product of SFR2 activity. Tomato SFR2 in vitro activity is Mg 2+-dependent and its optimal pH is 7.5, similar to that of Arabidopsis SFR2, but the specific activity of tomato SFR2 in vitro is almost double that of Arabidopsis SFR2. When salt and drought stress were applied to Arabidopsis, no conditions could be identified at which SFR2 was induced prior to irreversibly impacting plant growth, suggesting that SFR2 protects Arabidopsis primarily against freezing. Discovery of tomato SFR2 function in drought and salt resilience provides further insights into general membrane lipid remodeling-based stress tolerance mechanisms and together with protection against freezing in freezing-resistant plants such as Arabidopsis, it adds lipid remodeling as a possible target for the engineering of abiotic stress-resilient crops.« less

SENSITIVE TO FREEZING2 Aids in Resilience to Salt and Drought in Freezing-Sensitive Tomato

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Kun; Hersh, Hope Lynn; Benning, Christoph

SENSITIVE TO FREEZING2 (SFR2) is crucial for protecting chloroplast membranes following freezing in Arabidopsis (Arabidopsis thaliana). It has been shown that SFR2 homologs are present in all land plants, including freezing-sensitive species, raising the question of SFR2 function beyond freezing tolerance. Similar to freezing, salt and drought can cause dehydration. Thus, it is hypothesized that in freezing-sensitive plants SFR2 may play roles in their resilience to salt or drought. To test this hypothesis, SlSFR2 RNAi lines were generated in the cold/freezing-sensitive species tomato (Solanum lycopersicum [M82 cv]). Hypersensitivity to salt and drought of SlSFR2-RNAi lines was observed. Higher tolerance ofmore » wild-type tomatoes was correlated with the production of trigalactosyldiacylglycerol, a product of SFR2 activity. Tomato SFR2 in vitro activity is Mg 2+-dependent and its optimal pH is 7.5, similar to that of Arabidopsis SFR2, but the specific activity of tomato SFR2 in vitro is almost double that of Arabidopsis SFR2. When salt and drought stress were applied to Arabidopsis, no conditions could be identified at which SFR2 was induced prior to irreversibly impacting plant growth, suggesting that SFR2 protects Arabidopsis primarily against freezing. Discovery of tomato SFR2 function in drought and salt resilience provides further insights into general membrane lipid remodeling-based stress tolerance mechanisms and together with protection against freezing in freezing-resistant plants such as Arabidopsis, it adds lipid remodeling as a possible target for the engineering of abiotic stress-resilient crops.« less

SENSITIVE TO FREEZING2 Aids in Resilience to Salt and Drought in Freezing-Sensitive Tomato1[OPEN

PubMed Central

Hersh, Hope Lynn

2016-01-01

SENSITIVE TO FREEZING2 (SFR2) is crucial for protecting chloroplast membranes following freezing in Arabidopsis (Arabidopsis thaliana). It has been shown that SFR2 homologs are present in all land plants, including freezing-sensitive species, raising the question of SFR2 function beyond freezing tolerance. Similar to freezing, salt and drought can cause dehydration. Thus, it is hypothesized that in freezing-sensitive plants SFR2 may play roles in their resilience to salt or drought. To test this hypothesis, SlSFR2 RNAi lines were generated in the cold/freezing-sensitive species tomato (Solanum lycopersicum [M82 cv]). Hypersensitivity to salt and drought of SlSFR2-RNAi lines was observed. Higher tolerance of wild-type tomatoes was correlated with the production of trigalactosyldiacylglycerol, a product of SFR2 activity. Tomato SFR2 in vitro activity is Mg2+-dependent and its optimal pH is 7.5, similar to that of Arabidopsis SFR2, but the specific activity of tomato SFR2 in vitro is almost double that of Arabidopsis SFR2. When salt and drought stress were applied to Arabidopsis, no conditions could be identified at which SFR2 was induced prior to irreversibly impacting plant growth, suggesting that SFR2 protects Arabidopsis primarily against freezing. Discovery of tomato SFR2 function in drought and salt resilience provides further insights into general membrane lipid remodeling-based stress tolerance mechanisms and together with protection against freezing in freezing-resistant plants such as Arabidopsis, it adds lipid remodeling as a possible target for the engineering of abiotic stress-resilient crops. PMID:27600812

Arginine and proline applied as food additives stimulate high freeze tolerance in larvae of Drosophila melanogaster.

PubMed

Koštál, Vladimír; Korbelová, Jaroslava; Poupardin, Rodolphe; Moos, Martin; Šimek, Petr

2016-08-01

The fruit fly Drosophila melanogaster is an insect of tropical origin. Its larval stage is evolutionarily adapted for rapid growth and development under warm conditions and shows high sensitivity to cold. In this study, we further developed an optimal acclimation and freezing protocol that significantly improves larval freeze tolerance (an ability to survive at -5°C when most of the freezable fraction of water is converted to ice). Using the optimal protocol, freeze survival to adult stage increased from 0.7% to 12.6% in the larvae fed standard diet (agar, sugar, yeast, cornmeal). Next, we fed the larvae diets augmented with 31 different amino compounds, administered in different concentrations, and observed their effects on larval metabolomic composition, viability, rate of development and freeze tolerance. While some diet additives were toxic, others showed positive effects on freeze tolerance. Statistical correlation revealed tight association between high freeze tolerance and high levels of amino compounds involved in arginine and proline metabolism. Proline- and arginine-augmented diets showed the highest potential, improving freeze survival to 42.1% and 50.6%, respectively. Two plausible mechanisms by which high concentrations of proline and arginine might stimulate high freeze tolerance are discussed: (i) proline, probably in combination with trehalose, could reduce partial unfolding of proteins and prevent membrane fusions in the larvae exposed to thermal stress (prior to freezing) or during freeze dehydration; (ii) both arginine and proline are exceptional among amino compounds in their ability to form supramolecular aggregates which probably bind partially unfolded proteins and inhibit their aggregation under increasing freeze dehydration. © 2016. Published by The Company of Biologists Ltd.

Evidence of cyclical light/dark-regulated expression of freezing tolerance in young winter wheat plants.

PubMed

Skinner, Daniel Z; Bellinger, Brian; Hiscox, William; Helms, Gregory L

2018-01-01

The ability of winter wheat (Triticum aestivum L.) plants to develop freezing tolerance through cold acclimation is a complex rait that responds to many environmental cues including day length and temperature. A large part of the freezing tolerance is conditioned by the C-repeat binding factor (CBF) gene regulon. We investigated whether the level of freezing tolerance of 12 winter wheat lines varied throughout the day and night in plants grown under a constant low temperature and a 12-hour photoperiod. Freezing tolerance was significantly greater (P<0.0001) when exposure to subfreezing temperatures began at the midpoint of the light period, or the midpoint of the dark period, compared to the end of either period, with an average of 21.3% improvement in survival. Thus, freezing survival was related to the photoperiod, but cycled from low, to high, to low within each 12-hour light period and within each 12-hour dark period, indicating ultradian cyclic variation of freezing tolerance. Quantitative real-time PCR analysis of expression levels of CBF genes 14 and 15 indicated that expression of these two genes also varied cyclically, but essentially 180° out of phase with each other. Proton nuclear magnetic resonance analysis (1H-NMR) showed that the chemical composition of the wheat plants' cellular fluid varied diurnally, with consistent separation of the light and dark phases of growth. A compound identified as glutamine was consistently found in greater concentration in a strongly freezing-tolerant wheat line, compared to moderately and poorly freezing-tolerant lines. The glutamine also varied in ultradian fashion in the freezing-tolerant wheat line, consistent with the ultradian variation in freezing tolerance, but did not vary in the less-tolerant lines. These results suggest at least two distinct signaling pathways, one conditioning freezing tolerance in the light, and one conditioning freezing tolerance in the dark; both are at least partially under the control of the CBF regulon.

Comparison of Cryopreserved Human Sperm between Ultra Rapid Freezing and Slow Programmable Freezing: Effect on Motility, Morphology and DNA Integrity.

PubMed

Tongdee, Pattama; Sukprasert, Matchuporn; Satirapod, Chonticha; Wongkularb, Anna; Choktanasiri, Wicham

2015-05-01

Cryopreservation of sperm is common methods to preserve male fertility. Sperm freezing, suggest slow programmable freezing caused lower change of sperm morphology than sperm freezing in vapor of liquid nitrogen. Ultra rapid freezing is easy to be worked on, less time, low cost and does not need high experience. To compare the effect on sperm motility, morphology and DNA integrity of post-thawed sperm after ultra rapid freezing and slow programmable freezing methods. Experimental study at laboratory of infertility unit, Department of Obstetrics and Gynecology, Faculty of Medicine Ramathibodi Hospital. Thirty-seven semen samples with normal semen analysis according to World Health Organization (WHO) 1999 [normal sperm volume ( 2 ml) and normal sperm concentration (≥ 20 x10(6)/ml) and sperm motility (≥ 50%)]. Semen samples were washed. Then each semen sample was divided into six cryovials. Two cryovials, 0.5 ml each, were cryopreserved by slow programmable freezing. Four 0.25 ml containing cryovials, were cryopreserved by ultra rapidfreezing method. After cryopreservationfor 1 month, thawedprocess was carried out at room temperature. Main outcomes are sperm motility was determined by Computer-Assisted Semen Analysis (CASA), sperm morphology was determined by eosin-methylene blue staining and sperm DNA integrity was assessed by TUNEL assay. Sperm motility was reduced significantly by both methods, from 70.4 (9.0)% to 29.1 (12.3)% in slowprogrammable freezing and to 19.7 (9.8)% in ultra rapid freezing (p < 0.05). Sperm motility decreased significantly more by ultra rapid freezing (p < 0.001). The percentage of normal sperm morphology and DNA integrity were also reduced significantly by both methods. However, no significant difference between the two methods was found (p > 0.05). Cryopreservation of human sperm for 1 month significantly decreased sperm motility, morphology and DNA integrity in both methods. However sperm motility was decreased more by ultra rapid freezing.

A study of the impact of freezing on the lyophilization of a concentrated formulation with a high fill depth.

PubMed

Liu, Jinsong; Viverette, Todd; Virgin, Marlin; Anderson, Mitch; Paresh, Dalal

2005-01-01

The objective of this study was to evaluate the impact of freezing on the lyophilization of a concentrated formulation with a high fill depth. A model system consisting of a 15-mL fill of 15% (w/w) sulfobutylether 7-beta-cyclodextrin (SBECD) solution in a 30-mL vial was selected for this study. Various freezing methods including single-step freezing, two-step freezing with a super-cooling holding, annealing, vacuum-induced freezing, changing ice habit using tert-butyl-alcohol (TBA), ice nucleation with silver iodide (AgI), as well as combinations of some of the methods, were used in the lyophilization of this model system. This work demonstrated that the freezing process had a significant impact on primary drying rate and product quality of a concentrated formulation with a high fill depth. Annealing, vacuum-induced freezing, and addition of either TBA or an ice nucleating agent (AgI) to the formulation accelerated the subsequent ice sublimation process. Two-step freezing or addition of TBA improved the product quality by eliminating vertical heterogeneity within the cake. The combination of two-step freezing in conjunction with an annealing step was shown to be a method of choice for freezing in the lyophilization of a product with a high fill depth. In addition to being an effective method of freezing, it is most applicable for scaling up. An alternative approach is to add a certain amount of TBA to the formulation, if the TBA-formulation interaction or regulatory concerns can be demonstrated as not being an issue. An evaluation of vial size performed in this study showed that although utilizing large-diameter vials to reduce the fill depth can greatly shorten the cycle time of a single batch, it will substantially decrease the product throughput in a large-scale freeze-dryer.

A freeze-stable formulation for DTwP and DTaP vaccines.

PubMed

Xue, Honggang; Yang, Bangling; Kristensen, Debra D; Chen, Dexiang

2014-01-01

Inadvertent vaccine freezing often occurs in the cold chain and may cause damage to freeze‑sensitive vaccines. Liquid vaccines that contain aluminum salt adjuvants are particularly vulnerable. Polyol cryoprotective excipients have been shown to prevent freeze damage to hepatitis B vaccine. In this study, we examined the freeze-protective effect of propylene glycol on diphtheria-tetanus-pertussis-whole-cell (DTwP) and acellular (DTaP) vaccines. Pilot lots of DTwP and DTaP formulated with 7.5% propylene glycol underwent 3 freeze-thaw treatments. The addition of propylene glycol had no impact on pH, particle size distribution, or potency of the vaccines prior to freeze-thaw treatment; the only change noted was an increase in osmolality. The potencies and the physical properties of the vaccines containing cryoprotectant were maintained after freeze-thawing and for 3 months in accelerated stability studies. The results from this study indicate that formulating vaccines with propylene glycol can protect diphtheria-tetanus-pertussis vaccines against freeze damages.

Indirect contact freeze water desalination for an ice maker machine - CFD simulation

NASA Astrophysics Data System (ADS)

Jayakody, Harith; Al-Dadah, Raya; Mahmoud, Saad

2017-11-01

To offer for potable water shortages, sea water desalination is a potential solution for the global rising demand for fresh water. The latent heat of fusion is about one-seventh the latent heat of vaporisation, thus indicating the benefit of lower energy consumption for the freeze desalination process. Limited literature is reported on computational fluid dynamics (CFD) on freeze desalination. Therefore, analysing and investigating thermodynamic processes are easily conducted by the powerful tool of CFD. A single unit of ice formation in an ice maker machine was modelled using ANSYS Fluent software three-dimensionally. Energy, species transport and solidification/melting modules were used in building the CFD model. Parametric analysis was conducted using the established CFD model to predict the effects of freezing temperature and the geometry of the ice maker machine; on ice production and the freezing time. Lower freezing temperatures allowed more ice production and faster freezing. Increasing the diameter and the length of the freezing tube enabled more ice to be produced.

Freeze-drying of tert-butyl alcohol/water cosolvent systems: effects of formulation and process variables on residual solvents.

PubMed

Wittaya-Areekul, S; Nail, S L

1998-04-01

The objective of this study was to identify significant formulation and processing variables affecting levels of tert-butyl alcohol (TBA) and isopropyl alcohol (IPA) in freeze-dried solids prepared from TBA/water cosolvent systems. The variables examined were the physical state of the solute (crystalline vs amorphous), initial TBA concentration, freezing rate, cake thickness, and the temperature and duration of secondary drying. Sucrose and glycine were used as models for noncrystallizing and crystallizing solutes, respectively. The TBA concentration above which eutectic crystallization takes place was determined by differential scanning calorimetry. Model formulations were subjected to extremes of freezing rate by either dipping in liquid nitrogen or by slowly freezing on the shelf of a freeze-dryer. Dynamics of solvent loss during secondary drying was determined by withdrawing samples as a function of time at different shelf temperatures using a thief system. On the basis of these studies, the most important determinant of residual TBA level is the physical state of the solute. Freeze-dried glycine contained very low levels of residual TBA (0.01-0.03%) regardless of freezing rate or initial TBA concentration. For freeze-dried sucrose, residual TBA levels were approximately 2 orders of magnitude higher and were significantly affected by initial TBA concentration and freezing rate. For the sucrose/TBA/water system, relatively low residual TBA levels were obtained when the initial TBA level was above the threshold concentration for eutectic crystallization of TBA, whereas samples freeze-dried from solutions containing TBA concentrations below this threshold contained significantly higher levels of TBA. Residual IPA levels increased continuously with initial concentration of TBA in the sucrose/TBA/water system. Formulations of sucrose/TBA/water which were frozen rapidly contained residual TBA levels which were approximately twice those measured in the same formulation after slow freezing and drying under the same conditions. For the sucrose/TBA/water system, the temperature and time of secondary drying had only minimal influence on residual TBA in the freeze-dried solid. At low initial TBA concentrations (2%), residual TBA increases with increased cake thickness, perhaps because of the influence of depth of fill on effective freezing rate.

Characterization of freezing precipitation events through other meteorological variables and their recent changes over Northern Extratropics

NASA Astrophysics Data System (ADS)

Groisman, P. Y.; Yin, X.; Bulygina, O.

2017-12-01

Freezing precipitation events intertwine with agriculture, recreation, energy consumption, and seasonal transportation cycles of human activities. Using supplementary synoptic reports at 1,500 long-term stations of North America and Northern Eurasia, we created climatology of freezing precipitation near the surface and found significant changes (increases) in these occurrences in the past decade at high latitudes/elevations (Groisman et al. 2016; updated). Firstly, we document narrow boundaries of near surface temperature and humidity fields when freezing precipitation events occur; these are necessary but insufficient conditions of their occurrence. Secondly, using the upper air data at the sites collocated with in situ observations of freezing events, we quantify the typical pattern of lower troposphere temperature anomalies during freezing events: At the same locations and Julian days, the presence of freezing event at the surface is associated with significantly warmer temperatures in the lower troposphere; comparison of temperatures at nearest days before and after the freezing events with days during these events also shows statistically significant positive temperature anomalies in the lower troposphere to 500 hPa (on average, +3 to 4 °C) In the days with freezing events, vertical air temperature gradients between surface and 850 hPa become less than usual with frequent inversions, when the tropospheric air is warmer than at the surface. The above features of the lower tropospheric temperature, near-surface temperature and humidity represent a combination of weather conditions conducive for precipitation, if it happens, falling in the freezing rain form. The in situ reports of freezing events at synoptic stations allow us to estimate temporary and spatial distributions of such "special weather conditions". Thus, a posteriori high probability of freezing events under these weather conditions invokes similar probabilities of freezing rain over the ungauged terrain, where we do not have special synoptic reports but can reproduce these "special weather conditions" from less sophisticated observational networks and/or reanalyses. Reference: Groisman et al. 2016: Recent changes in the frequency of freezing precipitation in North America and Northern Eurasia. Environ Res Lett 11 045007.

Cryopreservation of Iberian pig spermatozoa. Comparison of different freezing extenders based on post-thaw sperm quality.

PubMed

De Mercado, Eduardo; Rodríguez, Ana; Gómez, Emilio; Sanz, Elena

2010-03-01

The aim of this study was to evaluate the cryoprotective effect of different freezing extenders against cryopreservation injuries on Iberian boar sperm. The sperm-rich fraction was collected and pooled from six sexually mature Iberian boars, and was frozen in different extenders containing glucose, lactose or fructose as sugar source and including Orvus ES Paste only in the freezing extender-2 (Glucose; Lactose and Fructose) or in both freezing extenders (Glucose2; Lactose2 and Fructose2). During the cryopreservation process, the supernatant was removed after the centrifugation step, then was extended with freezing extender-1 for the equilibration period and with freezing extender-2 immediately before freezing. Post-thaw sperm characteristics, such as plasma membrane integrity (SYBR-14/PI), mitochondrial function (Rhodamine 123) and acrosome integrity (NAR), were monitored. Overall sperm motility and the individual kinematic parameters of motile spermatozoa (assessed by the computer-aided sperm analysis system Sperm Class Analyzer [SCA]) were recorded in the different experimental treatments. Measurements were taken at 30 and 150 min post-thaw. The state of the acrosome after thawing did not show significant differences between the freezing extenders studied. Freezing-thawing caused a significant decrease (P<0.001) in plasma membrane integrity and in mitochondrial activity in the spermatozoa frozen with Orvus ES Paste in both freezing extenders. Furthermore, spermatozoa frozen with Orvus ES Paste in both freezing extenders exhibited lower (P<0.05) motility and kinematic parameters than those frozen in the absence of Orvus ES Paste in the first freezing extender. The spermatozoa frozen with the Lactose extender and with Orvus ES Paste only in the second freezing extender showed a better evolution of the motility and kinematic characteristics (P<0.05) over time. The deterioration in post-thaw sperm motility and kinematic parameters were concurrent with reduced sperm characteristics. It can be suggested that in the Iberian pig, the beneficial effects of Orvus ES Paste during the freezing process of spermatozoa is time dependent. The analysis of different sperm characteristics such as motility, plasma membrane integrity and mitochondrial function, determined that the extenders studied in the present experiment affected the quality of frozen-thawed semen in Iberian boar.

Care during freeze-drying of bovine pericardium tissue to be used as a biomaterial: a comparative study.

PubMed

Polak, Roberta; Pitombo, Ronaldo N M

2011-10-01

Bovine pericardium (BP) tissue is widely used in the manufacture of bioprosthetics. The effects of freeze-drying on the BP tissue have been studied by some researchers in order to decrease their cytotoxicity due to preservation in formaldehyde solution, and to increase the lifetime of the product in storage. This study was undertaken in order to study the effect of freeze-drying in the structure of BP. To perform this study BP samples were freeze-dried in two different types of freeze-dryers available in our laboratory: a laboratory freeze-dryer, in which it was not possible to control parameters and a pilot freeze-dryer, wherein all parameters during freezing and drying were controlled. After freeze-drying processes, samples were analyzed by SEM, Raman spectroscopy, tensile strength, water uptake tests and TEM. In summary, it has been demonstrated that damages occur in collagen fibers by the loss of bulk water of collagen structure implicating in a drastic decreasing of BP mechanical properties due to its structural alterations. Moreover, it was proven that the collagen fibrils suffered breakage at some points, which can be attributed to the uncontrolled parameters during drying. Copyright © 2011 Elsevier Inc. All rights reserved.

Perspective: Surface freezing in water: A nexus of experiments and simulations

NASA Astrophysics Data System (ADS)

Haji-Akbari, Amir; Debenedetti, Pablo G.

2017-08-01

Surface freezing is a phenomenon in which crystallization is enhanced at a vapor-liquid interface. In some systems, such as n-alkanes, this enhancement is dramatic and results in the formation of a crystalline layer at the free interface even at temperatures slightly above the equilibrium bulk freezing temperature. There are, however, systems in which the enhancement is purely kinetic and only involves faster nucleation at or near the interface. The first, thermodynamic, type of surface freezing is easier to confirm in experiments, requiring only the verification of the existence of crystalline order at the interface. The second, kinetic, type of surface freezing is far more difficult to prove experimentally. One material that is suspected of undergoing the second type of surface freezing is liquid water. Despite strong indications that the freezing of liquid water is kinetically enhanced at vapor-liquid interfaces, the findings are far from conclusive, and the topic remains controversial. In this perspective, we present a simple thermodynamic framework to understand conceptually and distinguish these two types of surface freezing. We then briefly survey fifteen years of experimental and computational work aimed at elucidating the surface freezing conundrum in water.

Three-Dimensional Microstructure of Biological Tissues during Freezing and Thawing

NASA Astrophysics Data System (ADS)

Ishiguro, Hiroshi; Horimizu, Takashi; Kataori, Akinobu; Kajigaya, Hiroshi

Three-dimensional behavior of ice crystals and cells during the freezing and thawing of biological tissues was investigated microscopically in real time by using a confocal laser scanning microscope(CLSM) and a fluorescent dye, acridine orange (AO). Fresh tender meat (2nd pectoral muscles) of chicken was stained with the AO in physiological saline to distinguish ice crystals and cells by their different colors, and then frozen and thawed under two different thermal protocols: a) slow-cooling and rapid-warming and b) rapid-cooling and rapid-warming. The CLSM noninvasively produced optical tomograms of the tissues to clarify the pattern of freezing, morphology of ice crystals in the tissues, and the interaction between ice crystals and cells. Also, the tissues were morphologically investigated by pathological means after the freezing and thawing. Typical freezing pattern during the slow-cooling was extracellular-freezing, and those during the rapid-cooling were extracellular-freezing and intracellular freezing with a lot of fine ice crystals in the cells. Cracks caused by the extracellular and intracellular ice crystals remained in the muscle tissues after the thawing. The results obtained by using the CLSM/dye method were consistent with pathologically morphological changes in the tissues through freezing and thawing.

Cold tolerance and freeze-induced glucose accumulation in three terrestrial slugs.

PubMed

Slotsbo, Stine; Hansen, Lars Monrad; Jordaens, Kurt; Backeljau, Thierry; Malmendal, Anders; Nielsen, Niels Chr; Holmstrup, Martin

2012-04-01

Cold tolerance and metabolic responses to freezing of three slug species common in Scandinavia (Arion ater, Arion rufus and Arion lusitanicus) are reported. Autumn collected slugs were cold acclimated in the laboratory and subjected to freezing conditions simulating likely winter temperatures in their habitat. Slugs spontaneously froze at about -4 °C when cooled under dry conditions, but freezing of body fluids was readily induced at -1 °C when in contact with external ice crystals. All three species survived freezing for 2 days at -1 °C, and some A. rufus and A. lusitanicus also survived freezing at -2 °C. (1)H NMR spectroscopy revealed that freezing of body fluids resulted in accumulation of lactate, succinate and glucose. Accumulation of lactate and succinate indicates that ATP production occurred via fermentative pathways, which is likely a result of oxygen depletion in frozen tissues. Glucose increased from about 6 to 22 μg/mg dry tissue upon freezing in A. rufus, but less so in A. ater and A. lusitanicus. Glucose may thus act as a cryoprotectant in these slugs, although the concentrations are not as high as reported for other freeze tolerant invertebrates. Copyright © 2012 Elsevier Inc. All rights reserved.

To freeze or not to freeze embryos: clarity, confusion and conflict.

PubMed

Goswami, Mohar; Murdoch, Alison P; Haimes, Erica

2015-06-01

Although embryo freezing is a routine clinical practice, there is little contemporary evidence on how couples make the decision to freeze their surplus embryos, or of their perceptions during that time. This article describes a qualitative study of 16 couples who have had in vitro fertilisation (IVF) treatment. The study question was 'What are the personal and social factors that patients consider when deciding whether to freeze embryos?' We show that while the desire for a baby is the dominant drive, couples' views revealed more nuanced and complex considerations in the decision-making process. It was clear that the desire to have a baby influenced couples' decision-making and that they saw freezing as 'part of the process'. However, there were confusions associated with the term 'freezing' related to concerns about the safety of the procedure. Despite being given written information, couples were confused about the practical aspects of embryo freezing, which suggests they were preoccupied with the immediate demands of IVF. Couples expressed ethical conflicts about freezing 'babies'. We hope the findings from this study will inform clinicians and assist them in providing support to couples confronted with this difficult decision-making.

Silicon-based Porous Ceramics via Freeze Casting of Preceramic Polymers

NASA Astrophysics Data System (ADS)

Naviroj, Maninpat

Freeze casting is a technique for processing porous materials that has drawn significant attention for its effectiveness in producing a variety of tailorable pore structures for ceramics, metals, and polymers. With freeze casting, pores are generated based on a solidification process where ice crystals act as a sacrificial template which can eventually be sublimated to create pores. While the majority of freeze-casting studies have been performed using conventional ceramic suspensions, this work explores an alternative processing route by freeze casting with preceramic polymer solutions. Significant differences exist between freeze casting of a particulate suspension and a polymeric solution. These changes affect the processing method, solidification behavior, and pore structure, thereby introducing new challenges and possibilities for the freeze-casting technique. The first part of this study explored the processing requirements involved with freeze casting of preceramic polymers, along with methods to control the resulting pore structure. Solvent choice, freezing front velocity, and polymer concentration were used as processing variables to manipulate the pore structures. A total of seven organic solvents were freeze cast with a polymethylsiloxane preceramic polymer to produce ceramics with isotropic, dendritic, prismatic, and lamellar pore morphologies. Changes in freezing front velocity and polymer concentration were shown to influence pore size, shape, and connectivity. Differences between suspension- and solution-based samples freeze cast under equivalent conditions were also investigated. Certain solidification microstructures were strongly affected by the presence of suspended particles, creating differences between pore structures generated from the same solvents. Additionally, processing of solution-based samples were found to be the more facile technique. Compressive strength and water permeability of dendritic and lamellar structures were analyzed to determine functional differences between the pore structures. Results show that dendritic structures were up to 30 times stronger, while lamellar structures provided higher permeability constants. A change in freezing front velocity was shown to significantly affect permeability but not compressive strength. Finally, improved pore alignment along the freezing direction was achieved by controlling the nucleation and growth of solvent crystals through the use of a grain-selection template. Dendritic samples freeze cast with a template showed substantial increase in pore alignment, as determined by image analysis and permeability tests, with the permeability constant increasing by up to 6-fold when compared to a control sample.

Modification of physical properties of freeze-dried rice

NASA Technical Reports Server (NTRS)

Huber, C. S.

1971-01-01

Freeze cycling process consists of alternately freezing and thawing precooked rice for two cycles, rice is then frozen and freeze-dehydrated in vacuum sufficient to remove water from rice by sublimitation. Process modifies rice grain structure and porosity, enabling complete rehydration in one minute in hot water.

9 CFR 590.534 - Freezing facilities.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Freezing facilities. 590.534 Section 590.534 Animals and Animal Products FOOD SAFETY AND INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE EGG..., and Facility Requirements § 590.534 Freezing facilities. (a) Freezing rooms, either on or off the...

9 CFR 590.536 - Freezing operations.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Freezing operations. 590.536 Section 590.536 Animals and Animal Products FOOD SAFETY AND INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE EGG..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and...

The role of calcium and calmodulin in freezing-induced freezing resistance of Populus tomentosa cuttings.

PubMed

Lin, Shan-Zhi; Zhang, Zhi-Yi; Lin, Yuan-Zhen; Zhang, Qian; Guo, Huan

2004-02-01

To explore the role of calcium-calmodulin messenger system in the transduction of low temperature signal in woody plants, Populus tomentosa cuttings after being treated with CaCl(2) (10 mmol/L), Ca(2+) chelator EGTA (3 mmol/L), Ca(2+) channel inhibitor LaCl(3) (100 mmol/L) or CaM antagonist CPZ (50 mmol/L) were used for freezing acclimation at -3 degrees C. The changes in the calmodulin (CaM) and malonaldehyde (MDA) contents, the activities of superoxide dismutase (SOD), peroxidase (POD) and Ca(2+)-dependent adenosinetriphosphatase (Ca(2+)-ATPase) of mitochondrial membrane as well as freezing resistance (expressed as LT(50)) of cuttings were investigated to elucidate the physiological mechanisms by which trees adapt to freezing. The results showed that freezing acclimation increased the CaM content, the activities of SOD, POD and Ca(2+)-ATPase of mitochondrial membrane as well as freezing resistance of cuttings, and decreased the MDA content as compared with control cuttings. Treatment with CaCl(2) at the time of freezing acclimation enhanced the effect of freezing acclimation on the above-mentioned indexes, but this enhancement was abolished by Ca(2+)chelator EGTA, Ca(2+) channel inhibitor LaCl(3) or CaM antagonist CPZ, indicating that the calcium-calmodulin messenger system was involved in the course of freezing resistance development. The presence of CaCl(2) at the same time of freezing acclimation also reduced the degree of decline in CaM content, and in SOD, POD and Ca(2+)-ATPase activities caused by freezing stress at -14 degrees C, and enhanced the level of increase in CaM content, and in SOD, POD and Ca(2+)-ATPase activity in the recovery periods at 25 degrees C . The change in CaM content was found to be closely correlated to the levels of SOD, POD and Ca(2+)-ATPase, and to the degree of freezing resistance of cuttings during freezing acclimation either with or without CaCl(2) treatment. It was suggested that the increase of CaM content induced by CaCl(2) treatment promote the formation of Ca(2+)-CaM complexes, which effectively activates the activities of SOD, POD and mitochondrial Ca(2+)-ATPase and then further result in the adaptive changes associated with the development and enhancement of freezing resistance. Thus, It could be concluded that Ca(2+)-calmodulin may be involved in the regulation of the increase in SOD, POD and Ca(2+)-ATPase activities, and the induction of freezing resistance of cuttings.

Intact preservation of environmental samples by freezing under an alternating magnetic field.

PubMed

Morono, Yuki; Terada, Takeshi; Yamamoto, Yuhji; Xiao, Nan; Hirose, Takehiro; Sugeno, Masaya; Ohwada, Norio; Inagaki, Fumio

2015-04-01

The study of environmental samples requires a preservation system that stabilizes the sample structure, including cells and biomolecules. To address this fundamental issue, we tested the cell alive system (CAS)-freezing technique for subseafloor sediment core samples. In the CAS-freezing technique, an alternating magnetic field is applied during the freezing process to produce vibration of water molecules and achieve a stable, super-cooled liquid phase. Upon further cooling, the temperature decreases further, achieving a uniform freezing of sample with minimal ice crystal formation. In this study, samples were preserved using the CAS and conventional freezing techniques at 4, -20, -80 and -196 (liquid nitrogen) °C. After 6 months of storage, microbial cell counts by conventional freezing significantly decreased (down to 10.7% of initial), whereas that by CAS-freezing resulted in minimal. When Escherichia coli cells were tested under the same freezing conditions and storage for 2.5 months, CAS-frozen E. coli cells showed higher viability than the other conditions. In addition, an alternating magnetic field does not impact on the direction of remanent magnetization in sediment core samples, although slight partial demagnetization in intensity due to freezing was observed. Consequently, our data indicate that the CAS technique is highly useful for the preservation of environmental samples. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

Freeze for action: neurobiological mechanisms in animal and human freezing

PubMed Central

2017-01-01

Upon increasing levels of threat, animals activate qualitatively different defensive modes, including freezing and active fight-or-flight reactions. Whereas freezing is a form of behavioural inhibition accompanied by parasympathetically dominated heart rate deceleration, fight-or-flight reactions are associated with sympathetically driven heart rate acceleration. Despite the potential relevance of freezing for human stress-coping, its phenomenology and neurobiological underpinnings remain largely unexplored in humans. Studies in rodents have shown that freezing depends on amygdala projections to the brainstem (periaqueductal grey). Recent neuroimaging studies in humans have indicated that similar brain regions may be involved in human freezing. In addition, flexibly shifting between freezing and active defensive modes is critical for adequate stress-coping and relies on fronto-amygdala connections. This review paper presents a model detailing these neural mechanisms involved in freezing and the shift to fight-or-flight action. Freezing is not a passive state but rather a parasympathetic brake on the motor system, relevant to perception and action preparation. Study of these defensive responses in humans may advance insights into human stress-related psychopathologies characterized by rigidity in behavioural stress reactions. The paper therefore concludes with a research agenda to stimulate translational animal–human research in this emerging field of human defensive stress responses. This article is part of the themed issue ‘Movement suppression: brain mechanisms for stopping and stillness’. PMID:28242739

Structurally Caused Freezing Point Depression of Biological Tissues

PubMed Central

Bloch, Rene; Walters, D. H.; Kuhn, Werner

1963-01-01

When investigating the freezing behaviour (by thermal analysis) of the glycerol-extracted adductor muscle of Mytilus edulis it was observed that the temperature of ice formation in the muscular tissue was up to 1.5°C lower than the freezing point of the embedding liquid, a 0.25 N KCl solution with pH = 4.9 with which the tissue had been equilibrated prior to the freezing experiment. A smaller freezing point depression was observed if the pH values of the embedding 0.25 N KCl solution were above or below pH = 4.9. Reasoning from results obtained previously in analogous experiments with artificial gels, the anomalous freezing depression is explained by the impossibility of growing at the normal freezing temperature regular macroscopic crystals inside the gel, due to the presence of the gel network. The freezing temperature is here determined by the size of the microprisms penetrating the meshes of the network at the lowered freezing temperature. This process leads finally to an ice block of more or less regular structure in which the filaments are embedded. Prerequisite for this hindrance of ideal ice growth is a sufficient tensile strength of the filamental network. The existence of structurally caused freezing point depression in biological tissue is likely to invalidate many conclusions reported in the literature, in which hypertonicity was deduced from cryoscopic data. PMID:13971682

Effects of buffer composition and processing conditions on aggregation of bovine IgG during freeze-drying.

PubMed

Sarciaux, J M; Mansour, S; Hageman, M J; Nail, S L

1999-12-01

The objective of this study was to identify critical formulation and processing variables affecting aggregation of bovine IgG during freeze-drying when no lyoprotective solute is used. Parameters examined were phosphate buffer concentration and counterion (Na versus K phosphate), added salts, cooling rate, IgG concentration, residual moisture level, and presence of a surfactant. No soluble aggregates were detected in any formulation after either freezing/thawing or freeze-drying. No insoluble aggregates were detected in any formulation after freezing, but insoluble aggregate levels were always detectable after freeze-drying. The data are consistent with a mechanism of aggregate formation involving denaturation of IgG at the ice/freeze-concentrate interface which is reversible upon freeze-thawing, but becomes irreversible after freeze-drying and reconstitution. Rapid cooling (by quenching in liquid nitrogen) results in more and larger aggregates than slow cooling on the shelf of the freeze-dryer. This observation is consistent with surface area measurements and environmental electron microscopic data showing a higher surface area of freeze-dried solids after fast cooling. Annealing of rapidly cooled solutions results in significantly less aggregation in reconstituted freeze-dried solids than in nonannealed controls, with a corresponding decrease in specific surface area of the freeze-dried, annealed system. Increasing the concentration of IgG significantly improves the stability of IgG against freeze-drying-induced aggregation, which may be explained by a smaller percentage of the protein residing at the ice/freeze-concentrate interface as IgG concentration is increased. A sodium phosphate buffer system consistently results in more turbid reconstituted solids than a potassium phosphate buffer system at the same concentration, but this effect is not attributable to a pH shift during freezing. Added salts such as NaCl or KCl contribute markedly to insoluble aggregate formation. Both sodium and potassium chloride contribute more to turbidity of the reconstituted solid than either sodium or potassium phosphate buffers at similar ionic strength, with sodium chloride resulting in a substantially higher level of aggregates than potassium chloride. At a given cooling rate, the specific surface area of dried solids is approximately a factor of 2 higher for the formulation containing sodium chloride than the formulation containing potassium chloride. Turbidity is also influenced by the extent of secondary drying, which underscores the importance of minimizing secondary drying of this system. Including a surfactant such as polysorbate 80, either in the formulation or in the water used for reconstitution, decreased, but did not eliminate, insoluble aggregates. There was no correlation between pharmaceutically acceptability of the freeze-dried cake and insoluble aggregate levels in the reconstituted product.

Wheeled and standard walkers in Parkinson's disease patients with gait freezing.

PubMed

Cubo, Esther; Moore, Charity G; Leurgans, Sue; Goetz, Christopher G

2003-10-01

Compare the efficacy of two walking assistance devices (wheeled walker and standard walker) to unassisted walking for patients with PD and gait freezing. Although numerous walking devices are used clinically, their relative effects on freezing and walking speed have never been systematically tested. Nineteen PD patients (14 non-demented) walked under three conditions in randomized order: unassisted walking, standard walker, and wheeled walker. Patients walked up to three times in each condition through a standard course that included rising from a chair, walking through a doorway, straightway walking, pivoting, and return. Total walking time, freezing time and number of freezes were compared for the three conditions using mixed models (walking time) and Friedman's test (freezing). The wheeled walker was further studied by comparing the effect of an attached laser that projected a bar of light on the floor as a visual walking cue. Use of either type of device significantly slowed walking compared to unassisted walking. Neither walker reduced any index of freezing, nor the laser attachment offered any advantage to the wheeled walker. The standard walker increased freezing, and the wheeled walker had no effect on freezing. Among the non-demented subjects (n=14), the same patterns occurred, although the walking speed was less impaired by the wheeled walker than the standard walker in this group. Though walkers may stabilize patients and increase confidence, PD patients walk more slowly when using them, without reducing freezing. Because the wheeled walker was intermediate for walking time and does not aggravate freezing, if walkers are used for these subjects, this type of walker should be favored.

Tracheid diameter is the key trait determining the extent of freezing-induced embolism in conifers.

PubMed

Pittermann, Jarmila; Sperry, John

2003-09-01

We tested the hypotheses that freezing-induced embolism is related to conduit diameter, and that conifers and angiosperms with conduits of equivalent diameter will exhibit similar losses of hydraulic conductivity in response to freezing. We surveyed the freeze-thaw response of conifers with a broad range of tracheid diameters by subjecting wood segments (root, stem and trunk wood) to a freeze-thaw cycle at -0.5 MPa in a centrifuge. Embolism increased as mean tracheid diameter exceeded 30 microm. Tracheids with a critical diameter greater than 43 microm were calculated to embolize in response to freezing and thawing at a xylem pressure of -0.5 MPa. To confirm that freezing-induced embolism is a function of conduit air content, we air-saturated stems of Abies lasiocarpa (Hook.) Nutt. (mean conduit diameter 13.7 +/- 0.7 microm) by pressurizing them 1 to 60 times above atmospheric pressure, prior to freezing and thawing. The air saturation method simulated the effect of increased tracheid size because the degree of super-saturation is proportional to a tracheid volume holding an equivalent amount of dissolved air at ambient pressure. Embolism increased when the dissolved air content was equivalent to a mean tracheid diameter of 30 microm at ambient air pressure. Our centrifuge and air-saturation data show that conifers are as vulnerable to freeze-thaw embolism as angiosperms with equal conduit diameter. We suggest that the hydraulic conductivity of conifer wood is maximized by increasing tracheid diameters in locations where freezing is rare. Conversely, the narrowing of tracheid diameters protects against freezing-induced embolism in cold climates.

Evaluation and Validation of the Messinger Freezing Fraction

NASA Technical Reports Server (NTRS)

Anderson, David N.; Tsao, Jen-Ching

2005-01-01

One of the most important non-dimensional parameters used in ice-accretion modeling and scaling studies is the freezing fraction defined by the heat-balance analysis of Messinger. For fifty years this parameter has been used to indicate how rapidly freezing takes place when super-cooled water strikes a solid body. The value ranges from 0 (no freezing) to 1 (water freezes immediately on impact), and the magnitude has been shown to play a major role in determining the physical appearance of the accreted ice. Because of its importance to ice shape, this parameter and the physics underlying the expressions used to calculate it have been questioned from time to time. Until now, there has been no strong evidence either validating or casting doubt on the current expressions. This paper presents experimental measurements of the leading-edge thickness of a number of ice shapes for a variety of test conditions with nominal freezing fractions from 0.3 to 1.0. From these thickness measurements, experimental freezing fractions were calculated and compared with values found from the Messinger analysis as applied by Ruff. Within the experimental uncertainty of measuring the leading-edge thickness, agreement of the experimental and analytical freezing fraction was very good. It is also shown that values of analytical freezing fraction were entirely consistent with observed ice shapes at and near rime conditions: At an analytical freezing fraction of unity, experimental ice shapes displayed the classic rime shape, while for conditions producing analytical freezing fractions slightly lower than unity, glaze features started to appear.

Multiple Glass Transitions and Freezing Events of Aqueous Citric Acid

PubMed Central

2014-01-01

Calorimetric and optical cryo-microscope measurements of 10–64 wt % citric acid (CA) solutions subjected to moderate (3 K/min) and slow (0.5 and 0.1 K/min) cooling/warming rates and also to quenching/moderate warming between 320 and 133 K are presented. Depending on solution concentration and cooling rate, the obtained thermograms show one freezing event and from one to three liquid–glass transitions upon cooling and from one to six liquid–glass and reverse glass–liquid transitions, one or two freezing events, and one melting event upon warming of frozen/glassy CA/H2O. The multiple freezing events and glass transitions pertain to the mother CA/H2O solution itself and two freeze-concentrated solution regions, FCS1 and FCS2, of different concentrations. The FCS1 and FCS2 (or FCS22) are formed during the freezing of CA/H2O upon cooling and/or during the freezing upon warming of partly glassy or entirely glassy mother CA/H2O. The formation of two FCS1 and FCS22 regions during the freezing upon warming to our best knowledge has never been reported before. Using an optical cryo-microscope, we are able to observe the formation of a continuous ice framework (IF) and its morphology and reciprocal distribution of IF/(FCS1 + FCS2). Our results provide a new look at the freezing and glass transition behavior of aqueous solutions and can be used for the optimization of lyophilization and freezing of foods and biopharmaceutical formulations, among many other applications where freezing plays a crucial role. PMID:25482069

Freeze Tolerance of Nine Zoysiagrass Cultivars Using Natural Cold Acclimation and Freeze Chambers

USDA-ARS?s Scientific Manuscript database

Winter hardiness of zoysiagrass (Zoysia spp.) cultivars is an important attribute throughout the biogeographical transition zone, thus the inability to withstand freezing temperatures may limit the use of these cultivars. The objective of this research was to determine the freeze tolerance (LT50) of...

77 FR 12240 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-29

... Institute, 5353 Parkside Dr MC 19-RE, Jupiter, FL 33458. Instrument: Freeze Fracture/Freeze Etch device... localization of membrane proteins using freeze fracture replica immuno- gold labeling, including all kinds of receptors and channels. Because freeze-fracture replica immuno-gold labeling has a high sensitivity for the...

Surface freezing of water.

PubMed

Pérez-Díaz, J L; Álvarez-Valenzuela, M A; Rodríguez-Celis, F

2016-01-01

Freezing, melting, evaporation and condensation of water are essential ingredients for climate and eventually life on Earth. In the present work, we show how surface freezing of supercooled water in an open container is conditioned and triggered-exclusively-by humidity in air. Additionally, a change of phase is demonstrated to be triggered on the water surface forming surface ice crystals prior to freezing of bulk. The symmetry of the surface crystal, as well as the freezing point, depend on humidity, presenting at least three different types of surface crystals. Humidity triggers surface freezing as soon as it overpasses a defined value for a given temperature, generating a plurality of nucleation nodes. An evidence of simultaneous nucleation of surface ice crystals is also provided.

An Investigation of the Cryogenic Freezing of Water in Non-Metallic Pipelines

NASA Astrophysics Data System (ADS)

Martin, C. I.; Richardson, R. N.; Bowen, R. J.

2004-06-01

Pipe freezing is increasingly used in a range of industries to solve otherwise intractable pipe line maintenance and servicing problems. This paper presents the interim results from an experimental study on deliberate freezing of polymeric pipelines. Previous and contemporary works are reviewed. The object of the current research is to confirm the feasibility of ice plug formation within a polymeric pipe as a method of isolation. Tests have been conducted on a range of polymeric pipes of various sizes. The results reported here all relate to freezing of horizontal pipelines. In each case the process of plug formation was photographed, the frozen plug pressure tested and the pipe inspected for signs of damage resulting from the freeze procedure. The time to freeze was recorded and various temperatures logged. These tests have demonstrated that despite the poor thermal and mechanical properties of the polymers, freezing offers a viable alternative method of isolation in polymeric pipelines.

Frost heave susceptibility of saturated soil under constant rate of freezing

NASA Astrophysics Data System (ADS)

Ryokai, K.; Iguro, M.; Yoneyama, K.

Introduced are the results of experiments carried out to quantitatively obtain the frost heave pressure and displacement of soil subjected to artificial freezing or freezing around in-ground liquefied natural gas storage tanks. This experiment is conducted to evaluate the frost heave susceptibility of saturated soil under overconsolidation. In other words, this experiment was carried out to obtain the relation of the over-burden pressure and freezing rate to the frost heave ratio by observing the frost heave displacement and freezing time of specimens by freezing the specimens at a constant freezing rate under a constant overburden pressure, while letting water freely flow in and out of the system. Introduced are the procedures for frost heave test required to quantitatively obtain the frost heave displacement and pressure of soil. Furthermore, the relation between the frost heave susceptibility and physical properties of soil obtained by this test is reported.

Contact Freezing of Water by Salts.

PubMed

Niehaus, Joseph; Cantrell, Will

2015-09-03

Water is unlikely to crystallize homogeneously at temperatures greater than -34 °C. Freezing at higher temperatures is heterogeneous-catalyzed by the presence of a second substance. If that substance is at an air-water interface, then the mode is called contact freezing, and it typically will trigger nucleation at a higher temperature than if the substance were wholly immersed within the liquid. We find that the impact of salt particles initiates freezing in experiments using water droplets at supercoolings of 9 to 16 °C. These results show that contact freezing nuclei need not be effective as immersion mode nuclei. We discuss our results in the context of proposed mechanisms of contact freezing. Finally, we use the time scales for diffusion of heat and of ions and the propagation of a sound wave through the droplet to estimate that contact freezing occurs within 10 ns of impact.

Cold hardiness in molluscs

NASA Astrophysics Data System (ADS)

Ansart, Armelle; Vernon, Philippe

2003-05-01

Molluscs inhabit all types of environments: seawater, intertidal zone, freshwater and land, and of course may have to deal with subzero temperatures. Ectotherm animals survive cold conditions by avoiding it by extensive supercooling (freezing avoidant species) or by bearing the freezing of their extracellular body fluids (freezing tolerant species). Although some studies on cold hardiness are available for intertidal molluscs, they are scarce for freshwater and terrestrial ones. Molluscs often exhibit intermediary levels of cold hardiness, with a moderate or low ability to supercool and a limited survival to the freezing of their tissues. Several factors could be involved: their dependence on water, their ability to enter dormancy, the probability of inoculative freezing in their environment, etc. Size is an important parameter in the development of cold hardiness abilities: it influences supercooling ability in land snails, which are rather freezing avoidant and survival to ice formation in intertidal organisms, which generally tolerate freezing.

Effects of industrial pre-freezing processing and freezing handling on glucosinolates and antioxidant attributes in broccoli florets.

PubMed

Cai, Congxi; Miao, Huiying; Qian, Hongmei; Yao, Leishuan; Wang, Bingliang; Wang, Qiaomei

2016-11-01

The effects of industrial pre-freezing processing and freezing handling on the contents of glucosinolates and antioxidants (vitamin C, polyphenols, carotenoid and chlorophyll), as well as the antioxidant capacity in broccoli (Brassica oleracea L. var. italica) florets were investigated in the present study. Our results showed that the glucosinolate accumulations were significantly decreased after pre-freezing processing, whereas elevated levels of phenols, carotenoids, chlorophyll, and also antioxidant capacity were observed in frozen broccoli florets. The contents of vitamin C remained constant during above mentioned processing. In conclusion, the current industrial freezing processing method is a good practice for the preservation of main antioxidant nutrients in broccoli florets, although some improvements in pre-freezing processing, such as steam blanching and ice-water cooling, are needed to attenuate the decrease in glucosinolate content. Copyright © 2016 Elsevier Ltd. All rights reserved.

Two-dimensional freezing criteria for crystallizing colloidal monolayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Ziren; Han Yilong; Alsayed, Ahmed M.

Video microscopy was employed to explore crystallization of colloidal monolayers composed of diameter-tunable microgel spheres. Two-dimensional (2D) colloidal liquids were frozen homogenously into polycrystalline solids, and four 2D criteria for freezing were experimentally tested in thermal systems for the first time: the Hansen-Verlet freezing rule, the Loewen-Palberg-Simon dynamical freezing criterion, and two other rules based, respectively, on the split shoulder of the radial distribution function and on the distribution of the shape factor of Voronoi polygons. Importantly, these freezing criteria, usually applied in the context of single crystals, were demonstrated to apply to the formation of polycrystalline solids. At themore » freezing point, we also observed a peak in the fluctuations of the orientational order parameter and a percolation transition associated with caged particles. Speculation about these percolated clusters of caged particles casts light on solidification mechanisms and dynamic heterogeneity in freezing.« less

Effect of pasteurisation and freezing method on bioactive compounds and antioxidant activity of strawberry pulp.

PubMed

Gonçalves, Gilma Auxiliadora Santos; Resende, Nathane Silva; Carvalho, Elisângela Elena Nunes; Resende, Jaime Vilela de; Vilas Boas, Eduardo Valério de Barros

2017-09-01

This study evaluated the stability of strawberry pulp subjected to three factors, pasteurisation (pasteurised and unpasteurised), freezing method (static air and forced air) and storage time (0, 2, 4 and 6 months). Pasteurisation favoured vitamin C retention during storage but enhanced the total loss of phenolics without affecting anthocyanin levels. Freezing by forced air was more effective in retaining phenolics during the first 4 months of storage, although the freezing method did not affect the anthocyanin levels. Processing and storage reduced the levels of individual phenolics. Freezing by forced air was more effective than static air in retaining antioxidant activity of the pulp. Polyphenol oxidase and peroxidase enzyme levels were relatively stable and independent of pasteurisation, freezing and storage time. Even after 6 months of frozen storage, strawberry pulp is a significant source of nutrients and bioactive compounds and retains high antioxidant capacity independent of pasteurisation and freezing method.

Freezing and thawing or freezing, thawing, and aging effects on beef tenderness

USDA-ARS?s Scientific Manuscript database

The objective of this study was to determine the effect of freezing and thawing or freezing and thawing with an additional aging period after frozen storage on the tenderness of longissimus lumborum (LL) and semitendinosus (ST) steaks relative to aged, fresh steaks. Left-side LL and ST (n=35 each) ...

7 CFR 929.11 - To can, freeze, or dehydrate.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 8 2010-01-01 2010-01-01 false To can, freeze, or dehydrate. 929.11 Section 929.11... LONG ISLAND IN THE STATE OF NEW YORK Order Regulating Handling Definitions § 929.11 To can, freeze, or dehydrate. To can, freeze, or dehydrate means to convert cranberries into canned, frozen, or dehydrated...

Applications of Simulator Freeze to Carrier Glideslope Tracking Instruction.

DTIC Science & Technology

1982-07-01

Showing Datum Bars and Meatball . .. .. .. ... .. ... .... 19 4 Freezes Per Trial Averaged Across Freeze Conditions and Across 4-Trial Blocks of Training...algorithm linearly increased the criterion in meatball units from 1.0 at 6000 feet from the ramp to 1.5 at the ramp. "Freezes" did not occur beyond 6000

7 CFR 305.18 - Quick freeze treatment schedule.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 5 2010-01-01 2010-01-01 false Quick freeze treatment schedule. 305.18 Section 305.18... SERVICE, DEPARTMENT OF AGRICULTURE PHYTOSANITARY TREATMENTS Quick Freeze Treatments § 305.18 Quick freeze treatment schedule. (a) T110. (1) Initially, lower the commodity's temperature to 0 °F or below. (2) Hold...

The equilibrated state of freezing as a basis for distinguishing lethal stresses of freezing in plants

USDA-ARS?s Scientific Manuscript database

A model for coordination of stresses that limit winterhardiness in plants based on the thermodynamic equilibrated state of freezing and melting provides a rational basis for distinction of freeze-induced energies which can stress and injure living organisms in various ways. The departure from equili...

7 CFR 58.620 - Freezing and packaging rooms.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 3 2013-01-01 2013-01-01 false Freezing and packaging rooms. 58.620 Section 58.620... Specifications for Dairy Plants Approved for USDA Inspection and Grading Service 1 Rooms and Compartments § 58.620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts shall be...

7 CFR 58.620 - Freezing and packaging rooms.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 3 2014-01-01 2014-01-01 false Freezing and packaging rooms. 58.620 Section 58.620... Specifications for Dairy Plants Approved for USDA Inspection and Grading Service 1 Rooms and Compartments § 58.620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts shall be...

7 CFR 58.620 - Freezing and packaging rooms.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 3 2012-01-01 2012-01-01 false Freezing and packaging rooms. 58.620 Section 58.620... Specifications for Dairy Plants Approved for USDA Inspection and Grading Service 1 Rooms and Compartments § 58.620 Freezing and packaging rooms. The rooms used for freezing and packaging frozen desserts shall be...

Freezing temperature of finger skin.

PubMed

Wilson, O; Goldman, R F; Molnar, G W

1976-10-01

In 45 subjects, 154 frostnips of the finger were induced by cooling in air at -15 degrees C with various wind speeds. The mean supercooled skin temperature at which frostnip appeared was -9.4 degrees C. The mean skin temperature rise due to heat of fusion at ice crystallization was 5.3 degrees C. The skin temperature rose to what was termed the apparent freezing point. The relation of this point to the supercooled skin temperature was analyzed for the three wind speeds used. An apparent freezing point for a condition of no supercooling was calculated, estimating the highest temperature at which skin freezes at a given wind speed. The validity of the obtained differences in apparent freezing point was tested by an analysis of covariance. Although not statistically significant, the data suggest that the apparent freezing point with no supercooling decreases with increasing wind velocity. The highest calculated apparent freezing point at -15 degrees C and 6.8 m/s was 1.2 degrees C lower than the true freezing point for skin previously determined in brine, which is a statistically significant difference.

A Vivens Ex Vivo Study on the Synergistic Effect of Electrolysis and Freezing on the Cell Nucleus.

PubMed

Lugnani, Franco; Zanconati, Fabrizio; Marcuzzo, Thomas; Bottin, Cristina; Mikus, Paul; Guenther, Enric; Klein, Nina; Rubinsky, Liel; Stehling, Michael K; Rubinsky, Boris

2015-01-01

Freezing-cryosurgery, and electrolysis-electrochemical therapy (EChT), are two important minimally invasive surgery tissue ablation technologies. Despite major advantages they also have some disadvantages. Cryosurgery cannot induce cell death at high subzero freezing temperatures and requires multiple freeze thaw cycles, while EChT requires high concentrations of electrolytic products-which makes it a lengthy procedure. Based on the observation that freezing increases the concentration of solutes (including products of electrolysis) in the frozen region and permeabilizes the cell membrane to these products, this study examines the hypothesis that there could be a synergistic effect between freezing and electrolysis in their use together for tissue ablation. Using an animal model we refer to as vivens ex vivo, which may be of value in reducing the use of animals for experiments, combined with a Hematoxylin stain of the nucleus, we show that there are clinically relevant protocols in which the cell nucleus appears intact when electrolysis and freezing are used separately but is affected by certain combinations of electrolysis and freezing.

Inner ear tissue preservation by rapid freezing: Improving fixation by high-pressure freezing and hybrid methods

PubMed Central

Bullen, A.; Taylor, R.R.; Kachar, B.; Moores, C.; Fleck, R.A.; Forge, A.

2014-01-01

In the preservation of tissues in as ‘close to life’ state as possible, rapid freeze fixation has many benefits over conventional chemical fixation. One technique by which rapid freeze-fixation can be achieved, high pressure freezing (HPF), has been shown to enable ice crystal artefact-free freezing and tissue preservation to greater depths (more than 40 μm) than other quick-freezing methods. Despite increasingly becoming routine in electron microscopy, the use of HPF for the fixation of inner ear tissue has been limited. Assessment of the quality of preservation showed routine HPF techniques were suitable for preparation of inner ear tissues in a variety of species. Good preservation throughout the depth of sensory epithelia was achievable. Comparison to chemically fixed tissue indicated that fresh frozen preparations exhibited overall superior structural preservation of cells. However, HPF fixation caused characteristic artefacts in stereocilia that suggested poor quality freezing of the actin bundles. The hybrid technique of pre-fixation and high pressure freezing was shown to produce cellular preservation throughout the tissue, similar to that seen in HPF alone. Pre-fixation HPF produced consistent high quality preservation of stereociliary actin bundles. Optimising the preparation of samples with minimal artefact formation allows analysis of the links between ultrastructure and function in inner ear tissues. PMID:25016142

Identification and classification of genes required for tolerance to freeze-thaw stress revealed by genome-wide screening of Saccharomyces cerevisiae deletion strains.

PubMed

Ando, Akira; Nakamura, Toshihide; Murata, Yoshinori; Takagi, Hiroshi; Shima, Jun

2007-03-01

Yeasts used in bread making are exposed to freeze-thaw stress during frozen-dough baking. To clarify the genes required for freeze-thaw tolerance, genome-wide screening was performed using the complete deletion strain collection of diploid Saccharomyces cerevisiae. The screening identified 58 gene deletions that conferred freeze-thaw sensitivity. These genes were then classified based on their cellular function and on the localization of their products. The results showed that the genes required for freeze-thaw tolerance were frequently involved in vacuole functions and cell wall biogenesis. The highest numbers of gene products were components of vacuolar H(+)-ATPase. Next, the cross-sensitivity of the freeze-thaw-sensitive mutants to oxidative stress and to cell wall stress was studied; both of these are environmental stresses closely related to freeze-thaw stress. The results showed that defects in the functions of vacuolar H(+)-ATPase conferred sensitivity to oxidative stress and to cell wall stress. In contrast, defects in gene products involved in cell wall assembly conferred sensitivity to cell wall stress but not to oxidative stress. Our results suggest the presence of at least two different mechanisms of freeze-thaw injury: oxidative stress generated during the freeze-thaw process, and defects in cell wall assembly.

Application of freeze-drying technology in manufacturing orally disintegrating films.

PubMed

Liew, Kai Bin; Odeniyi, Michael Ayodele; Peh, Kok-Khiang

2016-01-01

Freeze drying technology has not been maximized and reported in manufacturing orally disintegrating films. The aim of this study was to explore the freeze drying technology in the formulation of sildenafil orally disintegrating films and compare the physical properties with heat-dried orally disintegrating film. Central composite design was used to investigate the effects of three factors, namely concentration of carbopol, wheat starch and polyethylene glycol 400 on the tensile strength and disintegration time of the film. Heat-dried films had higher tensile strength than films prepared using freeze-dried method. For folding endurance, freeze-dried films showed improved endurance than heat-dried films. Moreover, films prepared using freeze-dried methods were thicker and had faster disintegration time. Formulations with higher amount of carbopol and starch showed higher tensile strength and thickness whereas formulations with higher PEG 400 content showed better flexibility. Scanning electron microscopy showed that the freeze-dried films had more porous structure compared to the heat-dried film as a result of the release of water molecule from the frozen structure when it was subjected to freeze drying process. The sildenafil film was palatable. The dissolution profiles of freeze-dried and heat-dried films were similar to Viagra® with f2 of 51.04 and 65.98, respectively.

Freezing: an underutilized food safety technology?

PubMed

Archer, Douglas L

2004-01-15

Freezing is an ancient technology for preserving foods. Freezing halts the activities of spoilage microorganisms in and on foods and can preserve some microorganisms for long periods of time. Frozen foods have an excellent overall safety record. The few outbreaks of food-borne illness associated with frozen foods indicate that some, but not all human pathogens are killed by commercial freezing processes. Freezing kills microorganisms by physical and chemical effects and possibly through induced genetic changes. Research is needed to better understand the physical and chemical interactions of various food matrices with the microbial cell during freezing and holding at frozen temperatures. The literature suggests that many pathogenic microorganisms may be sublethally injured by freezing, so research should be done to determine how to prevent injured cells from resuscitating and becoming infectious. Studies on the genetics of microbial stress suggest that the induction of resistance to specific stresses may be counteracted by, for example, simple chemicals. Research is needed to better understand how resistance to the lethal effect of freezing is induced in human pathogens and means by which it can be counteracted in specific foods. Through research, it seems possible that freezing may in the future be used to reliably reduce populations of food-borne pathogens as well as to preserve foods.

The Use of High-resolution Infrared Thermography (HRIT) for the Study of Ice Nucleation and Ice Propagation in Plants

PubMed Central

Wisniewski, Michael; Neuner, Gilbert; Gusta, Lawrence V.

2015-01-01

Freezing events that occur when plants are actively growing can be a lethal event, particularly if the plant has no freezing tolerance. Such frost events often have devastating effects on agricultural production and can also play an important role in shaping community structure in natural populations of plants, especially in alpine, sub-arctic, and arctic ecosystems. Therefore, a better understanding of the freezing process in plants can play an important role in the development of methods of frost protection and understanding mechanisms of freeze avoidance. Here, we describe a protocol to visualize the freezing process in plants using high-resolution infrared thermography (HRIT). The use of this technology allows one to determine the primary sites of ice formation in plants, how ice propagates, and the presence of ice barriers. Furthermore, it allows one to examine the role of extrinsic and intrinsic nucleators in determining the temperature at which plants freeze and evaluate the ability of various compounds to either affect the freezing process or increase freezing tolerance. The use of HRIT allows one to visualize the many adaptations that have evolved in plants, which directly or indirectly impact the freezing process and ultimately enables plants to survive frost events. PMID:25992743

The use of high-resolution infrared thermography (HRIT) for the study of ice nucleation and ice propagation in plants.

PubMed

Wisniewski, Michael; Neuner, Gilbert; Gusta, Lawrence V

2015-05-08

Freezing events that occur when plants are actively growing can be a lethal event, particularly if the plant has no freezing tolerance. Such frost events often have devastating effects on agricultural production and can also play an important role in shaping community structure in natural populations of plants, especially in alpine, sub-arctic, and arctic ecosystems. Therefore, a better understanding of the freezing process in plants can play an important role in the development of methods of frost protection and understanding mechanisms of freeze avoidance. Here, we describe a protocol to visualize the freezing process in plants using high-resolution infrared thermography (HRIT). The use of this technology allows one to determine the primary sites of ice formation in plants, how ice propagates, and the presence of ice barriers. Furthermore, it allows one to examine the role of extrinsic and intrinsic nucleators in determining the temperature at which plants freeze and evaluate the ability of various compounds to either affect the freezing process or increase freezing tolerance. The use of HRIT allows one to visualize the many adaptations that have evolved in plants, which directly or indirectly impact the freezing process and ultimately enables plants to survive frost events.

Water-cooled probe technique for the study of freeze lining formation

NASA Astrophysics Data System (ADS)

Verscheure, Karel; Campforts, Mieke; Verhaeghe, Frederik; Boydens, Eddy; Blanpain, Bart; Wollants, Patrick; van Camp, Maurits

2006-12-01

Furnace protection by water-cooled freeze linings becomes increasingly important as the metal producing industry attempts to achieve higher process intensities. Systematic investigations of the growth and the resulting microstructure and compositional profile of freeze linings are necessary to understand the behavior of freeze linings, their relation with the industrial process, and their interaction with the wall cooling system. We have developed a technique based on the submergence of a water-cooled probe into a liquid slag bath. Freeze linings of two industrial nonferrous slags have been produced using this technique and their growth, microstructural, and compositional profiles as a function of submergence time were determined. Thermodynamic equilibrium for the investigated slag systems was calculated and compared with the observed microstructures. The freeze linings form in approximately 15 minutes. Close to the water cooling, the freeze linings are predominantly amorphous in structure. With increasing distance from the water cooling, the proportion of crystalline phases increases and bath material is entrapped in the microstructure. Cellular crystals are observed close to the bath. The freeze linings exhibit an approximate homogeneous composition. The results demonstrate that the technique is a successful tool in obtaining information on the growth, microstructure, and composition of freeze linings in industrial water-cooled furnaces.

Freeze-dried spermatozoa: A future tool?

PubMed

Olaciregui, M; Gil, L

2017-04-01

Cryopreservation has been routinely used to preserve sperm of human and different animal species. However, frozen sperm storage for a long time brings many inconveniences because of liquid nitrogen. Many attempts have been made to overcome the disadvantages of the current cryopreservation method. Freeze-drying has been proposed as alternative method for sperm preservation to achieve the ability to store sperm doses indefinitely at ambient temperature or in ordinary refrigerators. At present, it has been reported successfully sperm freeze-drying on many animal species including canine and feline. It is well known that during freeze-drying process, sperm DNA could be damaged, but if suitable protection is provided, the sperm nucleus could preserve the ability to activate the oocyte and embryos could be generated by intracytoplasmic sperm injection (ICSI). Many factors influence the freeze-drying efficacy, so current researches have been conducted to find strategies to control these factors to maintain the sperm DNA integrity. This review describes the latest method of sperm freeze-drying for practical application in preserving and transporting genetic resources. In addition, the approaches to improve the efficiency of the technique were studied. We demonstrated that the DNA integrity of freeze-dried dog sperm is affected by the composition of the freeze-drying solution as well as the temperature and period of storage. Further studies are necessary to refine freeze-drying protocol in order to protect the DNA and maintain the sperm functionality and obtain offspring from freeze-dried sperm. © 2016 Blackwell Verlag GmbH.

Role of cells in freezing-induced cell-fluid-matrix interactions within engineered tissues.

PubMed

Seawright, Angela; Ozcelikkale, Altug; Dutton, Craig; Han, Bumsoo

2013-09-01

During cryopreservation, ice forms in the extracellular space resulting in freezing-induced deformation of the tissue, which can be detrimental to the extracellular matrix (ECM) microstructure. Meanwhile, cells dehydrate through an osmotically driven process as the intracellular water is transported to the extracellular space, increasing the volume of fluid for freezing. Therefore, this study examines the effects of cellular presence on tissue deformation and investigates the significance of intracellular water transport and cell-ECM interactions in freezing-induced cell-fluid-matrix interactions. Freezing-induced deformation characteristics were examined through cell image deformetry (CID) measurements of collagenous engineered tissues embedded with different concentrations of MCF7 breast cancer cells versus microspheres as their osmotically inactive counterparts. Additionally, the development of a biophysical model relates the freezing-induced expansion of the tissue due to the cellular water transport and the extracellular freezing thermodynamics for further verification. The magnitude of the freezing-induced dilatation was found to be not affected by the cellular water transport for the cell concentrations considered; however, the deformation patterns for different cell concentrations were different suggesting that cell-matrix interactions may have an effect. It was, therefore, determined that intracellular water transport during freezing was insignificant at the current experimental cell concentrations; however, it may be significant at concentrations similar to native tissue. Finally, the cell-matrix interactions provided mechanical support on the ECM to minimize the expansion regions in the tissues during freezing.

Alcohol Brine Freezing of Japanese Horse Mackerel (Trachurus japonicus) for Raw Consumption

NASA Astrophysics Data System (ADS)

Maeda, Toshimichi; Yuki, Atsuhiko; Sakurai, Hiroshi; Watanabe, Koichiro; Itoh, Nobuo; Inui, Etsuro; Seike, Kazunori; Mizukami, Yoichi; Fukuda, Yutaka; Harada, Kazuki

In order to test the possible application of alcohol brine freezing to Japanese horse mackerel (Trachurus japonicus) for raw consumption, the quality and taste of fish frozen by direct immersion in 60% ethanol brine at -20, -25 and -30°C was compared with those by air freezing and fresh fish without freezing. Cracks were not found during the freezing. Smell of ethanol did not remain. K value, an indicator of freshness, of fish frozen in alcohol brine was less than 8.3%, which was at the same level as those by air freezing and fresh fish. Oxidation of lipid was at the same level as air freezing does, and lower than that of fresh fish. The pH of fish frozen in alcohol brine at -25 and -30°C was 6.5 and 6.6, respectively, which were higher than that by air freezing and that of fresh fish. Fish frozen in alcohol brine was better than that by air and at the same level as fresh fish in total evaluation of sensory tests. These results show that the alcohol brine freezing is superior to air freezing, and fish frozen in alcohol brine can be a material for raw consumption. The methods of thawing in tap water, cold water, refrigerator, and at room temperature were compared. Thawing in tap water is considered to be convenient due to the short thaw time and the quality of thawed fish that was best among the methods.

Contribution of extracellular ice formation and the solution effects to the freezing injury of PC-3 cells suspended in NaCl solutions.

PubMed

Takamatsu, Hiroshi; Zawlodzka, Sylwia

2006-08-01

The mechanism of cell injury during slow freezing was examined using PC-3 human prostate adenocarcinoma cells suspended in NaCl solutions. The objective was to evaluate contribution of extracellular ice and the 'solution effects' to freezing injury separately. The solution effects that designate the influence of elevated concentration were evaluated from a pseudo-freezing experiment, where cells were subjected to the milieu that simulated a freeze-thaw process by changing the NaCl concentration and the temperature at the same time. The effect of extracellular ice formation on cell injury was then estimated from the difference in cell survival between the pseudo-freezing experiment and a corresponding freezing experiment. When cells were frozen to a relatively higher freezing temperature at -10 degrees C, about 30% of cells were damaged mostly due to extracellular ice formation, because the concentration increase without ice formation to 2.5-M NaCl, i.e., the equilibrium concentration at -10 degrees C, had no effect on cell survival. In contrast, in the case of the lower freezing temperature at -20 degrees C, about 90% of cells were injured by both effects, particularly 60-80% by the solution effects among them. The present results suggested that the solution effects become more crucial to cell damage during slow freezing at lower temperatures, while the effect of ice is limited to some extent.

Effects of freezing conditions on quality changes in blueberries.

PubMed

Cao, Xuehui; Zhang, Fangfang; Zhao, Dongyu; Zhu, Danshi; Li, Jianrong

2018-03-12

Freezing preservation is one of the most effective methods used to maintain the flavour and nutritional value of fruit. This research studied the effects of different freezing conditions, -20 °C, -40 °C, -80 °C, and immersion in liquid nitrogen, on quality changes of freeze-thawed blueberries. The water distribution estimates of blueberries were measured based on low-field nuclear magnetic resonance (LF-NMR) analysis. The pectin content, drip loss, and fruit texture were also detected to evaluate quality changes in samples. The freezing curves of blueberry showed super-cooling points at -20 °C and - 40 °C, whereas super-cooling points were not observed at -80 °C or in liquid nitrogen. After freeze-thaw treatment, the relaxation time of the cell wall water (T 21 ), cytoplasm water and extracellular space (T 22 ), and vacuole water (T 23 ) were significantly shortened compared to fresh samples, which suggested a lower liquidity. Although the freezing speed for samples immersed in liquid nitrogen was faster than other treatments, samples treated at -80 °C showed better quality regarding vacuole water holding, drip loss, and original pectin content retention. This study contributed to understanding how freezing temperature affects the qualities of blueberries. The super-fast freezing rate might injure fruit, and an appropriate freezing rate could better preserve blueberries. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

Involvement of Multiple Types of Dehydrins in the Freezing Response in Loquat (Eriobotrya japonica)

PubMed Central

Xu, Hongxia; Yang, Yong; Xie, Li; Li, Xiaoying; Feng, Chao; Chen, Junwei; Xu, Changjie

2014-01-01

Dehydrins (DHNs) are a family of plant proteins typically induced in response to stress conditions that cause cellular dehydration, such as low temperatures, high salinity, and drought. Loquat (Eriobotrya japonica) is a perennial fruit crop that blossoms during winter. Loquat fruitlets are frequently injured by freezing. To evaluate the role of the EjDHNs in freezing resistance in loquat fruitlets, two cultivars of loquat, the freezing-sensitive ‘Ninghaibai’ (FS-NHB) and the freezing-tolerant ‘Jiajiao’ (FT-JJ), were analyzed under induced freezing stress. Freezing stress led to obvious accumulation of reactive oxygen species and considerable lipid peroxidation in membranes during the treatment period. Both these phenomena were more pronounced in ‘FS-NHB’ than in ‘FS-JJ.’ Immunogold labeling of dehydrin protein was performed. DHN proteins were found to be concentrated mainly in the vicinity of the plasma membrane, and the density of the immunogold labeling was significantly higher after freezing treatment, especially in the more freezing-tolerant cultivar ‘FT-JJ.’ Seven DHNs, showing four different structure types, were obtained from loquat fruitlets and used to study the characteristics of different EjDHN proteins. These DHN proteins are all highly hydrophilic, but they differ significantly in size, ranging from 188 to 475 amino acids, and in biochemical properties, such as theoretical pI, aliphatic index, and instability index. Freezing treatment resulted in up-regulation of the expression levels of all seven EjDHNs, regardless of structure type. The accumulation of the transcripts of these EjDHN genes was much more pronounced in ‘FT-JJ’ than in ‘FS-NHB.’ Altogether, this study provides evidence that EjDHNs are involved in the cryoprotection of the plasma membrane during freeze-induced dehydration in loquat fruitlets. PMID:24498141

Antimicrobial efficiency of essential oil and freeze-thaw treatments against Escherichia coli O157:H7 and Salmonella enterica Ser. Enteritidis in strawberry juice.

PubMed

Duan, J; Zhao, Y

2009-04-01

This study investigated the antimicrobial efficiency of 3 essential oils (EOs), lemongrass, cinnamon leaf, and basil, and freeze-thaw treatment, alone or in combination, against Escherichia coli O157:H7 and Salmonella enterica Ser. Enteritidis inoculated in strawberry juice stored at 7 degrees C. EO of lemongrass or cinnamon leaf at 0.1 to 2 microL/mL and freezing at -23 degrees C for 24 or 48 h followed by thawing at 7 degrees C for 4 h all showed significant antimicrobial activities (P < 0.05) against E. coli O157:H7 and S. Enteritidis in strawberry juice. The antimicrobial activity increased with increasing EO concentration and storage time, but extending freezing time from 24 to 48 h did not enhance the antimicrobial activity of freeze-thaw treatment (P > 0.05). EO of lemongrass or cinnamon leaf at 0.1 microL/mL and freeze-thaw treatment alone obtained a 5 log(10) reduction in the population of S. Enteritidis, while EOs at 0.1 to 0.3 microL/mL or freeze-thaw alone could not achieve a satisfactory protection against E. coli O157:H7 in strawberry juice. Combined EO and freeze-thaw treatment enhanced the overall antimicrobial effect against E. coli O157:H7, with adding EO before the freeze-thaw treatment showed a faster decontamination rate than when added EO after the freeze-thaw. EOs of lemongrass and cinnamon leaf at 0.1 or 0.3 microL/mL followed by the freeze-thawing resulted in a 5 log(10) reduction in E. coli O157:H7 on the 5th and 2nd day of storage, respectively. This study suggested that combined EO and freeze-thaw treatment may be a suitable and inexpensive method to eliminate microorganisms that can be a hazard for the consumers of unpasteurized berry juices.

"On" freezing in Parkinson's disease: resistance to visual cue walking devices.

PubMed

Kompoliti, K; Goetz, C G; Leurgans, S; Morrissey, M; Siegel, I M

2000-03-01

To measure "on" freezing during unassisted walking (UW) and test if two devices, a modified inverted stick (MIS) and a visual laser beam stick (LBS) improved walking speed and number of "on" freezing episodes in patients with Parkinson's disease (PD). Multiple visual cues can overcome "off' freezing episodes and can be useful in improving gait function in parkinsonian patients. These devices have not been specifically tested in "on" freezing, which is unresponsive to pharmacologic manipulations. Patients with PD, motor fluctuations and freezing while "on," attempted walking on a 60-ft track with each of three walking conditions in a randomized order: UW, MIS, and LBS. Total time to complete a trial, number of freezes, and the ratio of walking time to the number of freezes were compared using Friedman's test. Twenty-eight patients with PD, mean age 67.81 years (standard deviation [SD] 7.54), mean disease duration 13.04 years (SD 7.49), and mean motor Unified Parkinson's Disease Rating Scale score "on" 32.59 (SD 10.93), participated in the study. There was a statistically significant correlation of time needed to complete a trial and number of freezes for all three conditions (Spearman correlations: UW 0.973, LBS 0.0.930, and MIS 0.842). The median number of freezes, median time to walk in each condition, and median walking time per freeze were not significantly different in pairwise comparisons of the three conditions (Friedman's test). Of the 28 subjects, six showed improvement with the MIS and six with the LBS in at least one outcome measure. Assisting devices, specifically based on visual cues, are not consistently beneficial in overcoming "on" freezing in most patients with PD. Because this is an otherwise untreatable clinical problem and because occasional subjects do respond, cautious trials of such devices under the supervision of a health professional should be conducted to identify those patients who might benefit from their long-term use.

Freezing of gait in PD: prospective assessment in the DATATOP cohort.

PubMed

Giladi, N; McDermott, M P; Fahn, S; Przedborski, S; Jankovic, J; Stern, M; Tanner, C

2001-06-26

To study the development of freezing of gait in PD. Freezing of gait is a common, disabling, and poorly understood symptom in PD. The authors analyzed data from 800 patients with early PD from the Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) clinical trial who were assigned either placebo, deprenyl, tocopherol, or the combination of deprenyl and tocopherol. The primary outcome measure was the time from randomization until the freezing of gait score on the Unified Parkinson's Disease Rating Scale (UPDRS) became positive. Fifty-seven patients (7.1%) had freezing of gait at study entry and 193 (26%) of the remaining patients experienced the symptom by the end of the follow-up period. Those with freezing of gait at baseline had significantly more advanced disease than those without the symptom, as measured by total UPDRS and Hoehn and Yahr stage. High baseline risk factors for developing freezing of gait during the follow-up period were the onset of PD with a gait disorder; higher scores of rigidity, postural instability, bradykinesia and speech; and longer disease duration. In contrast, tremor was strongly associated with a decreased risk for freezing of gait. At the end of follow-up, the signs most strongly associated with the freezing phenomenon were gait, balance, and speech disorders, not rigidity or bradykinesia. Deprenyl treatment was strongly associated with a decreased risk for developing freezing of gait; tocopherol had no effect. Freezing of gait is directly related to duration of PD. Risk factors at onset of disease are the absence of tremor and PD beginning as a gait disorder. The development of freezing of gait in the course of the illness is strongly associated with the development of balance and speech problems, less so with the worsening of bradykinesia, and is not associated with the progression of rigidity. These results support the concept that the freezing phenomenon is distinct from bradykinesia. Deprenyl, in the absence of L-dopa, was found to be an effective prophylactic treatment and should be considered for patients with PD who have an onset of gait difficulty.

Gelatin-Filtered Consomme: A Practical Demonstration of the Freezing and Thawing Processes

ERIC Educational Resources Information Center

Lahne, Jacob B.; Schmidt, Shelly J.

2010-01-01

Freezing is a key food processing and preservation technique widely used in the food industry. Application of best freezing and storage practices extends the shelf-life of foods for several months, while retaining much of the original quality of the fresh food. During freezing, as well as its counterpart process, thawing, a number of critical…

The 2007 California Citrus Freeze: Vulnerability, Poverty, and Unemployment Issues of Farmworkers

ERIC Educational Resources Information Center

Orozco, Graciela Leon

2010-01-01

In January of 2007, freezing temperatures destroyed citrus and vegetable crops in California. By May 2007, more than 9,000 freeze-related unemployment applications had been fled. Through face-to-face interviews, this study documents the experience of 63 farmworkers to find out how they survived the freeze and accessed services. Findings revealed…

Method of freezing living cells and tissues with improved subsequent survival

DOEpatents

Senkan, Selim M.; Hirsch, Gerald P.

1980-01-01

This invention relates to an improved method for freezing red blood cells, ther living cells, or tissues with improved subsequent survival, wherein constant-volume freezing is utilized that results in significantly improved survival compared with constant-pressure freezing; optimization is attainable through the use of different vessel geometries, cooling baths and warming baths, and sample concentrations.

21 CFR 864.9225 - Cell-freezing apparatus and reagents for in vitro diagnostic use.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cell-freezing apparatus and reagents for in vitro... Establishments That Manufacture Blood and Blood Products § 864.9225 Cell-freezing apparatus and reagents for in vitro diagnostic use. (a) Identification. Cell-freezing apparatus and reagents for in vitro diagnostic...

21 CFR 864.9225 - Cell-freezing apparatus and reagents for in vitro diagnostic use.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cell-freezing apparatus and reagents for in vitro... Establishments That Manufacture Blood and Blood Products § 864.9225 Cell-freezing apparatus and reagents for in vitro diagnostic use. (a) Identification. Cell-freezing apparatus and reagents for in vitro diagnostic...

Plant moisture stress: a portable freezing-point meter compared with the psychrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cary, J.W.; Fisher, H.D.

A small portable instrument for measuring the freezing-point depression of plant tissue has been developed for field use. The instrument is easy to operate and can be constructed from materials costing less than $100. Moisture stress measurements made with the freezing-point meter on a variety of plants were compared with vapor pressure psychrometer measurements. Variation between duplicates in the freezing point averaged 1.2 bars, but differences between stress measurements made with the psychrometer and freezing-point instrument averaged 2.6 bars. 11 references, 5 figures, 2 tables.

Freeze drying apparatus

DOEpatents

Coppa, Nicholas V.; Stewart, Paul; Renzi, Ernesto

2001-01-01

The present invention provides methods and apparatus for freeze drying in which a solution, which can be a radioactive salt dissolved within an acid, is frozen into a solid on vertical plates provided within a freeze drying chamber. The solid is sublimated into vapor and condensed in a cold condenser positioned above the freeze drying chamber and connected thereto by a conduit. The vertical positioning of the cold condenser relative to the freeze dryer helps to help prevent substances such as radioactive materials separated from the solution from contaminating the cold condenser. Additionally, the system can be charged with an inert gas to produce a down rush of gas into the freeze drying chamber to also help prevent such substances from contaminating the cold condenser.

Freeze drying method

DOEpatents

Coppa, Nicholas V.; Stewart, Paul; Renzi, Ernesto

1999-01-01

The present invention provides methods and apparatus for freeze drying in which a solution, which can be a radioactive salt dissolved within an acid, is frozen into a solid on vertical plates provided within a freeze drying chamber. The solid is sublimated into vapor and condensed in a cold condenser positioned above the freeze drying chamber and connected thereto by a conduit. The vertical positioning of the cold condenser relative to the freeze dryer helps to help prevent substances such as radioactive materials separated from the solution from contaminating the cold condenser. Additionally, the system can be charged with an inert gas to produce a down rush of gas into the freeze drying chamber to also help prevent such substances from contaminating the cold condenser.

[Preparation of freeze-dried powder of recombinate hirudin-2 nanoparticle for nasal delivery and permeability through nasal membrane in vitro].

PubMed

Chen, Ming-Xia; Zhang, Jian-Bao; Yu, Ji-Ping; Ye, Jing; Wei, Bao-Hong; Zhang, Yu-Jie

2013-06-01

To optimize the freeze-dried powder preparation technology of recombinate hirudin-2 (rHV2) nanoparticle which has bio-adhesive characteristic for nasal delivery, also to investigate its stability and permeability through nasal membrane in vitro. Taking the appearance, rediffusion of nanoparticle and rHV2 encapsulation efficiency as the evaluation indexes. Cryoprotector, the preparative technique and the effect of illumination and high temperature factors on its stability for rHV2 freeze-dried powder were investigated. Using Fraze diffusion cell technique, the permeability of rHV2 across rabbit nasal mucous membrane in chitosan solution, chitosan nanoparticle, and nanoparticle frozen-dried powder were compared with that in normal saline solution. The optimized preparation of rHV2 nanoparticle freeze-dried powder was as follows: 5% trehalose and glucose (1:1) was used as cryoprotector, nanoparticle solution was freezed for 24 h in vacuum frozen-dryer after being pre-freezed for 24 h. The content of rHV2 in the freeze-dried powder was 1.1 ug/mg. Illumination had little effect on the appearance, rediffusion and encapsulation efficiency of the rHV2 freeze-dried powder. High temperature could obviously influence the appearance of nanoparticle freeze-dried powder. The permeability coefficient (P) of nanoparticle was 5 times more than that in chictonson solution. It was indicated that chitosan nanoparticle has effect on increasing the permeability of rHV2. The freeze-dried powder of chitosan nanoparticle can be a good nasal preparation of rHV2.

Effect of freeze-drying on viability and in vitro probiotic properties of a mixture of lactic acid bacteria and yeasts isolated from kefir.

PubMed

Bolla, Patricia A; Serradell, María de los Angeles; de Urraza, Patricio J; De Antoni, Graciela L

2011-02-01

The effect of freeze-drying on viability and probiotic properties of a microbial mixture containing selected bacterial and yeast strains isolated from kefir grains (Lactobacillus kefir, Lactobacillus plantarum, Lactococcus lactis, Saccharomyces cerevisiae and Kluyveromyces marxianus) was studied. The microorganisms were selected according to their potentially probiotic properties in vitro already reported. Two types of formulations were performed, a microbial mixture (MM) suspended in milk and a milk product fermented with MM (FMM). To test the effect of storage on viability of microorganisms, MM and FMM were freeze-dried and maintained at 4°C for six months. After 180 days of storage at 4°C, freeze-dried MM showed better survival rates for each strain than freeze-dried FMM. The addition of sugars (trehalose or sucrose) did not improve the survival rates of any of the microorganisms after freeze-drying. Freeze-drying did not affect the capacity of MM to inhibit growth of Shigella sonnei in vitro, since the co-incubation of this pathogen with freeze-dried MM produced a decrease of 2 log in Shigella viability. The safety of freeze-dried MM was tested in mice and non-translocation of microorganisms to liver or spleen was observed in BALB/c mice feed ad libitum during 7 or 20 days. To our knowledge, this is the first report about the effect of freeze-drying on viability, in vitro probiotic properties and microbial translocation of a mixture containing different strains of both bacteria and yeasts isolated from kefir.

Additional freeze hardiness in wheat acquired by exposure to -3 degreesC is associated with extensive physiological, morphological, and molecular changes.

PubMed

Herman, Eliot M; Rotter, Kelsi; Premakumar, Ramaswamy; Elwinger, G; Bae, Hanhong; Bae, Rino; Ehler-King, Linda; Chen, Sixue; Livingston, David P

2006-01-01

Cold-acclimated plants acquire an additional 3-5 degrees C increase in freezing tolerance when exposed to -3 degrees C for 12-18 h before a freezing test (LT50) is applied. The -3 degrees C treatment replicates soil freezing that can occur in the days or weeks leading to overwintering by freezing-tolerant plants. This additional freezing tolerance is called subzero acclimation (SZA) to differentiate it from cold acclimation (CA) that is acquired at above-freezing temperatures. Using wheat as a model, results have been obtained indicating that SZA is accompanied by changes in physiology, cellular structure, the transcriptome, and the proteome. Using a variety of assays, including DNA arrays, reverse transcription-polymerase chain reaction (RT-PCR), 2D gels with mass spectroscopic identification of proteins, and electron microscopy, changes were observed to occur as a consequence of SZA and the acquisition of added freezing tolerance. In contrast to CA, SZA induced the movement of intracellular water to the extracellular space. Many unknown and stress-related genes were upregulated by SZA including some with obvious roles in SZA. Many genes related to photosynthesis and plastids were downregulated. Changes resulting from SZA often appeared to be a loss of rather than an appearance of new proteins. From a cytological perspective, SZA resulted in alterations of organelle structure including the Golgi. The results indicate that the enhanced freezing tolerance of SZA is correlated with a wide diversity of changes, indicating that the additional freezing tolerance is the result of complex biological processes.

Soil Moisture Controls the Thermal Habitat of Active Layer Soils in the McMurdo Dry Valleys, Antarctica

NASA Astrophysics Data System (ADS)

Wlostowski, A. N.; Gooseff, M. N.; Adams, B. J.

2018-01-01

Antarctic soil ecosystems are strongly controlled by abiotic habitat variables. Regional climate change in the McMurdo Dry Valleys is expected to cause warming over the next century, leading to an increase in frequency of freeze-thaw cycling in the soil habitat. Previous studies show that physiological stress associated with freeze-thaw cycling adversely affects invertebrate populations by decreasing abundance and positively selecting for larger body sizes. However, it remains unclear whether or not climate warming will indeed enhance the frequency of annual freeze-thaw cycling and associated physiological stresses. This research quantifies the frequency, rate, and spatial heterogeneity of active layer freezing to better understand how regional climate change may affect active layer soil thermodynamics, and, in turn, affect soil macroinvertebrate communities. Shallow active layer temperature, specific conductance, and soil moisture were observed along natural wetness gradients. Field observations show that the frequency and rate of freeze events are nonlinearly related to freezable soil moisture (θf). Over a 2 year period, soils at θf < 0.080 m3/m3 experienced between 15 and 35 freeze events and froze rapidly compared to soils with θf > 0.080 m3/m3, which experienced between 2 and 6 freeze events and froze more gradually. A numerical soil thermodynamic model is able to simulate observed freezing rates across a range of θf, reinforcing a well-known causal relationship between soil moisture and active layer freezing dynamics. Findings show that slight increases in soil moisture can potentially offset the effect of climate warming on exacerbating soil freeze-thaw cycling.

Detailed spectral profile analysis of electrocorticograms during freezing against penicillin-induced epileptiform discharges in the anesthetized rat.

PubMed

Tokiwa, Tatsuji; Zimin, Lev; Inoue, Takao; Nomura, Sadahiro; Suzuki, Michiyasu; Yamakawa, Takeshi

2018-07-01

Cryosurgery is an alternative technique for minimally invasive treatment of lesions. We have recently examined cryosurgery for epilepsy in animal models, and found that penicillin G (PG)-induced epileptiform discharges (EDs) mostly vanished after freezing. However, EDs were provoked again after insufficient freezing. Inadequate freezing is not visually detectable during and just after freezing and is not predictable beforehand. To manage this problem, we examined whether intraoperative monitoring of electrocorticograms (ECoGs) can predict recurrence of EDs after cryosurgery. A palm-sized cryoprobe system was applied to focal seizures in a Wistar rat model in which EDs were induced in advance by intracerebral injection of PG. During stable induction of EDs, the cryoprobe was carefully inserted into the epileptic region and this region was immediately frozen. After the series of prefreezing, freezing, and postfreezing, rats in which PG-induced EDs relapsed within 3 h were defined as the ED-relapsed (EDR) group, and other rats were defined as the ED-vanished (EDV) group. Time-frequency analysis was conducted on the ECoGs in each group through each freezing series. Relapse of PG-induced EDs on ECoG after the freezing series was associated with the remaining power of the delta band in the freezing period more strongly in the EDR group than in the EDV group. Success or failure of the freezing procedure can be predicted by the specificity of the delta band of the ECoG obtained intraoperatively. Copyright © 2018 Elsevier B.V. All rights reserved.

Thermomechanical analysis of freezing-induced cell-fluid-matrix interactions in engineered tissues

PubMed Central

Han, Bumsoo; Teo, Ka Yaw; Ghosh, Soham; Dutton, J. Craig; Grinnell, Frederick

2012-01-01

Successful cryopreservation of functional engineered tissues (ETs) is significant to tissue engineering and regenerative medicine, but it is extremely challenging to develop a successful protocol because the effects of cryopreservation parameters on the post-thaw functionality of ETs are not well understood. Particularly, the effects on the microstructure of their extracellular matrix (ECM) have not been well studied, which determines many functional properties of the ETs. In this study, we investigated the effects of two key cryopreservation parameters – i) freezing temperature and corresponding cooling rate; and ii) the concentration of cryoprotective agent (CPA) on the ECM microstructure as well as the cellular viability. Using dermal equivalent as a model ET and DMSO as a model CPA, freezing-induced spatiotemporal deformation and post-thaw ECM microstructure of ETs was characterized while varying the freezing temperature and DMSO concentrations. The spatial distribution of cellular viability and the cellular actin cytoskeleton was also examined. The results showed that the tissue dilatation increased significantly with reduced freezing temperature (i.e., rapid freezing). A maximum limit of tissue deformation was observed for preservation of ECM microstructure, cell viability and cell-matrix adhesion. The dilatation decreased with the use of DMSO, and a freezing temperature dependent threshold concentration of DMSO was observed. The threshold DMSO concentration increased with lowering freezing temperature. In addition, an analysis was performed to delineate thermodynamic and mechanical components of freezing-induced tissue deformation. The results are discussed to establish a mechanistic understanding of freezing-induced cell-fluid-matrix interaction and phase change behavior within ETs in order to improve cryopreservation of ETs. PMID:23246556

Hatchling turtles survive freezing during winter hibernation.

PubMed Central

Storey, K B; Storey, J M; Brooks, S P; Churchill, T A; Brooks, R J

1988-01-01

Hatchlings of the painted turtle (Chrysemys picta marginata) are unique as the only reptile and highest vertebrate life form known to tolerate the natural freezing of extracellular body fluids during winter hibernation. Turtles survived frequent exposures to temperatures as low as -6 degrees C to -8 degrees C in their shallow terrestrial nests over the 1987-1988 winter. Hatchlings collected in April 1988 had a mean supercooling point of -3.28 +/- 0.24 degrees C and survived 24 hr of freezing at -4 degrees C with 53.4% +/- 1.98% of total body water as ice. Recovery appeared complete after 20 hr of thawing at 3 degrees C. However, freezing at -10.9 degrees C, resulting in 67% ice, was lethal. A survey of possible cryoprotectants revealed a 2- to 3-fold increase in glucose content of liver and blood and a 3-fold increase in blood glycerol in response to freezing. Although quantitatively low, these responses by spring turtles strongly indicate that these may be the winter-active cryoprotectants. The total amino acid pool of blood also increased 2.25-fold in freezing-exposed turtles, and taurine accounted for 52% of the increase. Most organs accumulated high concentrations of lactate during freezing, a response to the ischemic state imposed by extracellular freezing. Changes in glycogen phosphorylase activity and levels of glucose 6-phosphate and fructose 2,6-bisphosphate were also consistent with a dependence on anaerobic glycolysis during freezing. Studies of the molecular mechanisms of natural freeze tolerance in these turtles may identify protective strategies that can be used in mammalian organ cryopreservation technology. PMID:3186730

Animal ice-binding (antifreeze) proteins and glycolipids: an overview with emphasis on physiological function.

PubMed

Duman, John G

2015-06-01

Ice-binding proteins (IBPs) assist in subzero tolerance of multiple cold-tolerant organisms: animals, plants, fungi, bacteria etc. IBPs include: (1) antifreeze proteins (AFPs) with high thermal hysteresis antifreeze activity; (2) low thermal hysteresis IBPs; and (3) ice-nucleating proteins (INPs). Several structurally different IBPs have evolved, even within related taxa. Proteins that produce thermal hysteresis inhibit freezing by a non-colligative mechanism, whereby they adsorb onto ice crystals or ice-nucleating surfaces and prevent further growth. This lowers the so-called hysteretic freezing point below the normal equilibrium freezing/melting point, producing a difference between the two, termed thermal hysteresis. True AFPs with high thermal hysteresis are found in freeze-avoiding animals (those that must prevent freezing, as they die if frozen) especially marine fish, insects and other terrestrial arthropods where they function to prevent freezing at temperatures below those commonly experienced by the organism. Low thermal hysteresis IBPs are found in freeze-tolerant organisms (those able to survive extracellular freezing), and function to inhibit recrystallization - a potentially damaging process whereby larger ice crystals grow at the expense of smaller ones - and in some cases, prevent lethal propagation of extracellular ice into the cytoplasm. Ice-nucleator proteins inhibit supercooling and induce freezing in the extracellular fluid at high subzero temperatures in many freeze-tolerant species, thereby allowing them to control the location and temperature of ice nucleation, and the rate of ice growth. Numerous nuances to these functions have evolved. Antifreeze glycolipids with significant thermal hysteresis activity were recently identified in insects, frogs and plants. © 2015. Published by The Company of Biologists Ltd.

Freeze-drying in novel container system: Characterization of heat and mass transfer in glass syringes.

PubMed

Patel, Sajal M; Pikal, Michael J

2010-07-01

This study is aimed at characterizing and understanding different modes of heat and mass transfer in glass syringes to develop a robust freeze-drying process. Two different holder systems were used to freeze-dry in syringes: an aluminum (Al) block and a plexiglass holder. The syringe heat transfer coefficient was characterized by a sublimation test using pure water. Mannitol and sucrose (5% w/v) were also freeze-dried, as model systems, in both the assemblies. Dry layer resistance was determined from manometric temperature measurement (MTM) and product temperature was measured using thermocouples, and was also determined from MTM. Further, freeze-drying process was also designed using Smart freeze-dryer to assess its application for freeze-drying in novel container systems. Heat and mass transfer in syringes were compared against the traditional container system (i.e., glass tubing vial). In the Al block, the heat transfer was via three modes: contact conduction, gas conduction, and radiation with gas conduction being the dominant mode of heat transfer. In the plexiglass holder, the heat transfer was mostly via radiation; convection was not involved. Also, MTM/Smart freeze-drying did work reasonably well for freeze-drying in syringes. When compared to tubing vials, product temperature decreases and hence drying time increases in syringes. (c) 2010 Wiley-Liss, Inc. and the American Pharmacists Association

Freeze-drying process monitoring using a cold plasma ionization device.

PubMed

Mayeresse, Y; Veillon, R; Sibille, P H; Nomine, C

2007-01-01

A cold plasma ionization device has been designed to monitor freeze-drying processes in situ by monitoring lyophilization chamber moisture content. This plasma device, which consists of a probe that can be mounted directly on the lyophilization chamber, depends upon the ionization of nitrogen and water molecules using a radiofrequency generator and spectrometric signal collection. The study performed on this probe shows that it is steam sterilizable, simple to integrate, reproducible, and sensitive. The limitations include suitable positioning in the lyophilization chamber, calibration, and signal integration. Sensitivity was evaluated in relation to the quantity of vials and the probe positioning, and correlation with existing methods, such as microbalance, was established. These tests verified signal reproducibility through three freeze-drying cycles. Scaling-up studies demonstrated a similar product signature for the same product using pilot-scale and larger-scale equipment. On an industrial scale, the method efficiently monitored the freeze-drying cycle, but in a larger industrial freeze-dryer the signal was slightly modified. This was mainly due to the positioning of the plasma device, in relation to the vapor flow pathway, which is not necessarily homogeneous within the freeze-drying chamber. The plasma tool is a relevant method for monitoring freeze-drying processes and may in the future allow the verification of current thermodynamic freeze-drying models. This plasma technique may ultimately represent a process analytical technology (PAT) approach for the freeze-drying process.

Detection of Collapse and Crystallization of Saccharide, Protein, and Mannitol Formulations by Optical Fibers in Lyophilization

PubMed Central

Horn, Jacqueline; Friess, Wolfgang

2018-01-01

The collapse temperature (Tc) and the glass transition temperature of freeze-concentrated solutions (Tg') as well as the crystallization behavior of excipients are important physicochemical characteristics which guide the cycle development in freeze-drying. The most frequently used methods to determine these values are differential scanning calorimetry (DSC) and freeze-drying microscopy (FDM). The objective of this study was to evaluate the optical fiber system (OFS) unit as alternative tool for the analysis of Tc, Tg' and crystallization events. The OFS unit was also tested as a potential online monitoring tool during freeze-drying. Freeze/thawing and freeze-drying experiments of sucrose, trehalose, stachyose, mannitol, and highly concentrated IgG1 and lysozyme solutions were carried out and monitored by the OFS. Comparative analyses were performed by DSC and FDM. OFS and FDM results correlated well. The crystallization behavior of mannitol could be monitored by the OFS during freeze/thawing as it can be done by DSC. Online monitoring of freeze-drying runs detected collapse of amorphous saccharide matrices. The OFS unit enabled the analysis of both Tc and crystallization processes, which is usually carried out by FDM and DSC. The OFS can hence be used as novel measuring device. Additionally, detection of these events during lyophilization facilitates online-monitoring. Thus the OFS is a new beneficial tool for the development and monitoring of freeze-drying processes. PMID:29435445

Evaluation of spin freezing versus conventional freezing as part of a continuous pharmaceutical freeze-drying concept for unit doses.

PubMed

De Meyer, L; Van Bockstal, P-J; Corver, J; Vervaet, C; Remon, J P; De Beer, T

2015-12-30

Spin-freezing as alternative freezing approach was evaluated as part of an innovative continuous pharmaceutical freeze-drying concept for unit doses. The aim of this paper was to compare the sublimation rate of spin-frozen vials versus traditionally frozen vials in a batch freeze-dryer, and its impact on total drying time. Five different formulations, each having a different dry cake resistance, were tested. After freezing, the traditionally frozen vials were placed on the shelves while the spin-frozen vials were placed in aluminum vial holders providing radial energy supply during drying. Different primary drying conditions and chamber pressures were evaluated. After 2h of primary drying, the amount of sublimed ice was determined in each vial. Each formulation was monitored in-line using NIR spectroscopy during drying to determine the sublimation endpoint and the influence of drying conditions upon total drying time. For all tested formulations and applied freeze-drying conditions, there was a significant higher sublimation rate in the spin-frozen vials. This can be explained by the larger product surface and the lower importance of product resistance because of the much thinner product layers in the spin frozen vials. The in-line NIR measurements allowed evaluating the influence of applied drying conditions on the drying trajectories. Copyright © 2015 Elsevier B.V. All rights reserved.

Inner ear tissue preservation by rapid freezing: improving fixation by high-pressure freezing and hybrid methods.

PubMed

Bullen, A; Taylor, R R; Kachar, B; Moores, C; Fleck, R A; Forge, A

2014-09-01

In the preservation of tissues in as 'close to life' state as possible, rapid freeze fixation has many benefits over conventional chemical fixation. One technique by which rapid freeze-fixation can be achieved, high pressure freezing (HPF), has been shown to enable ice crystal artefact-free freezing and tissue preservation to greater depths (more than 40 μm) than other quick-freezing methods. Despite increasingly becoming routine in electron microscopy, the use of HPF for the fixation of inner ear tissue has been limited. Assessment of the quality of preservation showed routine HPF techniques were suitable for preparation of inner ear tissues in a variety of species. Good preservation throughout the depth of sensory epithelia was achievable. Comparison to chemically fixed tissue indicated that fresh frozen preparations exhibited overall superior structural preservation of cells. However, HPF fixation caused characteristic artefacts in stereocilia that suggested poor quality freezing of the actin bundles. The hybrid technique of pre-fixation and high pressure freezing was shown to produce cellular preservation throughout the tissue, similar to that seen in HPF alone. Pre-fixation HPF produced consistent high quality preservation of stereociliary actin bundles. Optimising the preparation of samples with minimal artefact formation allows analysis of the links between ultrastructure and function in inner ear tissues. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Detection of Collapse and Crystallization of Saccharide, Protein and Mannitol Formulations by Optical Fibers in Lyophilization

NASA Astrophysics Data System (ADS)

Horn, Jacqueline; Friess, Wolfgang

2018-01-01

The collapse temperature (Tc) and the glass transition temperature of freeze-concentrated solutions (Tg’) as well as the crystallization behavior of excipients are important physicochemical characteristics which guide the cycle development in freeze-drying. The most frequently used methods to determine these values are differential scanning calorimetry (DSC) and freeze-drying microscopy (FDM). The objective of this study was to evaluate the optical fiber system (OFS) unit as alternative tool for the analysis of Tc, Tg’ and crystallization events. The OFS unit was also tested as a potential online monitoring tool during freeze-drying. Freeze/thawing and freeze-drying experiments of sucrose, trehalose, stachyose, mannitol and highly concentrated IgG1 and lysozyme solutions were carried out and monitored by the OFS. Comparative analyses were performed by DSC and FDM. OFS and FDM results correlated well. The crystallization behavior of mannitol could be monitored by the OFS during freeze/thawing as it can be done by DSC. Online monitoring of freeze-drying runs detected collapse of amorphous saccharide matrices. The OFS unit enabled the analysis of both Tc and crystallization processes, which is usually carried out by FDM and DSC. The OFS can hence be used as novel measuring device. Additionally, detection of these events during lyophilization facilitate online-monitoring. Thus the OFS is a new beneficial tool for the development and monitoring of freeze-drying processes.

Development of a freeze-tolerant solar water heater using crosslinked polyethylene as a material of construction. Final report, June 18, 1976--October 1, 1977

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bradley, J.M.

The feasibility of building a freeze-tolerant absorber for a solar water heater out of carbon-black-reinforced crosslinked polyethylene has been explored. Ten-foot tube specimens made from various crosslinked polyethylene formulations were filled with water at various pressures, and then placed into a deep freeze, then thawed and frozen again for 100 freeze-thaw cycles, or until the tube specimen failed. Tube diameters were measured before and after each freezing to determine how much distention the freezing caused, and how much permanent distention was caused by the strains of repeated freezings. Five tube specimens containing water at as high as 80 psi survivedmore » 100 freeze-thaw cycles. Also, a flat plate collector was fabricated using as absorber surface a single 400 ft tube of carbon-black-reinforced crosslinked polyethylene in the form of a flat spiral coil and this collector was tested for performance at the Los Alamos Scientific Laboratory. The performance test indicates that the absorbancy of such a flat spiral coil to solar radiation is similar to typical black surfaces used on solar absorbers. Thus, it does seem very feasible that domestic water can be directly heated in a solar collector having an absorber made from crosslinked polyethylene, and that this collector can safely withstand at least 100 freeze-thaw cycles.« less

Repeated freezing induces a trade-off between cryoprotection and egg production in the goldenrod gall fly, Eurosta solidaginis.

PubMed

Marshall, Katie E; Sinclair, Brent J

2018-06-12

Internal ice formation leads to wholesale changes in ionic, osmotic and pH homeostasis, energy metabolism, and mechanical damage, across a small range of temperatures, and is thus an abiotic stressor that acts at a distinct, physiologically-relevant, threshold. Insects that experience repeated freeze-thaw cycles over winter will cross this stressor threshold many times over their lifespan. Here we examine the effect of repeatedly crossing the freezing threshold on short-term physiological parameters (metabolic reserves and cryoprotectant concentration) as well as long-term fitness-related performance (survival and egg production) in the freeze-tolerant goldenrod gall fly Eurosta solidaginis We exposed overwintering prepupae to a series of low temperatures (-10, -15, or -20 °C) with increasing numbers of freezing events (3, 6, or 10) with differing recovery periods between events (1, 5, or 10 days). Repeated freezing increased sorbitol concentration by about 50% relative to a single freezing episode, and prompted prepupae to modify long chain triacylglycerols to acetylated triacylglycerols. Long-term, repeated freezing did not significantly reduce survival, but did reduce egg production by 9.8% relative to a single freezing event. Exposure temperature did not affect any of these measures, suggesting that threshold crossing events may be more important to fitness than the intensity of stress in E. solidaginis overwintering. © 2018. Published by The Company of Biologists Ltd.

Freezing Bubbles

NASA Astrophysics Data System (ADS)

Kingett, Christian; Ahmadi, Farzad; Nath, Saurabh; Boreyko, Jonathan

2017-11-01

The two-stage freezing process of a liquid droplet on a substrate is well known; however, how bubbles freeze has not yet been studied. We first deposited bubbles on a silicon substrate that was chilled at temperatures ranging from -10 °C to -40 °C, while the air was at room temperature. We observed that the freeze front moved very slowly up the bubble, and in some cases, even came to a complete halt at a critical height. This slow freezing front propagation can be explained by the low thermal conductivity of the thin soap film, and can be observed more clearly when the bubble size or the surface temperature is increased. This delayed freezing allows the frozen portion of the bubble to cool the air within the bubble while the top part is still liquid, which induces a vapor pressure mismatch that either collapses the top or causes the top to pop. In cases where the freeze front reaches the top of the bubble, a portion of the top may melt and slowly refreeze; this can happen more than just once for a single bubble. We also investigated freezing bubbles inside of a freezer where the air was held at -20 °C. In this case, the bubbles freeze quickly and the ice grows radially from nucleation sites instead of perpendicular to the surface, which provides a clear contrast with the conduction limited room temperature bubbles.

Female Fertility Issues

Cancer.gov

Fertility issues are common in women getting cancer treatment. Fertility preservation options include egg freezing, embryo freezing, ovarian tissue freezing, ovarian shielding and ovarian transposition. Resources, support, and clinical trials are listed.

Non-Toxic, Low-Freezing, Drop-In Replacement Heat Transfer Fluids

NASA Technical Reports Server (NTRS)

Cutbirth, J. Michael

2012-01-01

A non-toxic, non-flammable, low-freezing heat transfer fluid is being developed for drop-in replacement within current and future heat transfer loops currently using water or alcohol-based coolants. Numerous water-soluble compounds were down-selected and screened for toxicological, physical, chemical, compatibility, thermodynamic, and heat transfer properties. Two fluids were developed, one with a freezing point near 0 C, and one with a suppressed freezing point. Both fluids contain an additive package to improve material compatibility and microbial resistance. The optimized sub-zero solution had a freezing point of 30 C, and a freezing volume expansion of 10-percent of water. The toxicity of the solutions was experimentally determined as LD(50) greater than 5g/kg. The solutions were found to produce minimal corrosion with materials identified by NASA as potentially existing in secondary cooling loops. Thermal/hydrodynamic performance exceeded that of glycol-based fluids with comparable freezing points for temperatures Tf greater than 20 C. The additive package was demonstrated as a buffering agent to compensate for CO2 absorption, and to prevent microbial growth. The optimized solutions were determined to have physically/chemically stable shelf lives for freeze/thaw cycles and longterm test loop tests.

The Structural Properties and Stability of Monoclonal Antibodies at Freezing Conditions

NASA Astrophysics Data System (ADS)

Perevozchikova, Tatiana; Zarraga, Isidro; Scherer, Thomas; Wagner, Norman; Liu, Yun

2013-03-01

Monoclonal Antibodies (MAb) have become a crucial therapeutic agent in a number of anti-cancer treatments. Due to the inherent unstable nature of proteins in an aqueous formulation, a freeze-drying method has been developed to maintain long-term stability of biotherapeutics. The microstructural changes in Mabs during freezing, however, remain not fully described, and it was proposed that the formed morphology of freeze drying samples could affect the final product quality after reconstitution. Furthermore, it is well known that proteins tend to aggregate during the freezing process if a careful processing procedure is not formulated. Small Angle Neutron Scattering (SANS) is a powerful tool to investigate the structural properties and interactions of Mabs during various stages of lyophilization in situ. Here we present the SANS results of freeze-thaw studies on two MAbs at several different freezing temperatures. While the chosen proteins share a significant sequence homology, their freezing properties are found to be strikingly distinctive. We also show the effect of excipients, concentration and quenching speed on the final morphology of the frozen samples. These findings provide critical information for more effective lyophilization schemes for therapeutic proteins, as well as increase our understanding on structural properties of proteins under cryogenic conditions.

Key composition optimization of meat processed protein source by vacuum freeze-drying technology.

PubMed

Ma, Yan; Wu, Xingzhuang; Zhang, Qi; Giovanni, Vigna; Meng, Xianjun

2018-05-01

Vacuum freeze-drying technology is a high technology content, a wide range of knowledge of technology in the field of drying technology is involved, it is also a method of the most complex drying equipment, the largest energy consumption, the highest cost of drying method, but due to the particularity of its dry goods: the freeze-drying food has the advantages of complex water performance is good, cooler and luster of freezing and drying food to maintain good products, less nutrient loss, light weight, easy to carry transportation, easy to long-term preservation, and on the quality is far superior to the obvious advantages of other dried food, making it become the forefront of drying technology research and development. The freeze-drying process of Chinese style ham and western Germany fruit tree tenderloin is studied in this paper, their eutectic point, melting point and collapse temperature, freeze-drying curve and its heat and mass transfer characteristics are got, then the precool temperature and the highest limiting temperature of sublimation interface are determined. The effect of system pressure on freeze-dried rate in freeze-drying process is discussed, and the method of regulating pressure circularly is determined.

Vernal freeze damage and genetic variation alter tree growth, chemistry, and insect interactions.

PubMed

Rubert-Nason, Kennedy F; Couture, John J; Gryzmala, Elizabeth A; Townsend, Philip A; Lindroth, Richard L

2017-11-01

Anticipated consequences of climate change in temperate regions include early spring warmup punctuated by intermittent hard freezes. Warm weather accelerates leaf flush in perennial woody species, potentially exposing vulnerable young tissues to damaging frosts. We employed a 2 × 6 randomized factorial design to examine how the interplay of vernal (springtime) freeze damage and genetic variation in a hardwood species (Populus tremuloides) influences tree growth, phytochemistry, and interactions with an insect herbivore (Chaitophorus stevensis). Acute effects of freezing included defoliation and mortality. Surviving trees exhibited reduced growth and altered biomass distribution. Reflushed leaves on these trees had lower mass per area, lower lignin concentrations, and higher nitrogen concentrations, altered chemical defence profiles, and supported faster aphid population growth. Many effects varied among plant genotypes and were related with herbivore performance. This study suggests that a single damaging vernal freeze event can alter tree-insect interactions through effects on plant growth and chemistry. Differential responses of various genotypes to freeze damage suggest that more frequent vernal freeze events could also influence natural selection, favouring trees with greater freeze hardiness, and more resistance or tolerance to herbivores following damage. © 2017 John Wiley & Sons Ltd.

Freeze-Thaw Durability of Air-Entrained Concrete

PubMed Central

Shang, Huai-Shuai; Yi, Ting-Hua

2013-01-01

One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to “the test method of long-term and durability on ordinary concrete” GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results. PMID:23576906

Freeze-thaw durability of air-entrained concrete.

PubMed

Shang, Huai-Shuai; Yi, Ting-Hua

2013-01-01

One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles). The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss) and internal crack growth (characterized by the loss of dynamic modulus of elasticity). The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to "the test method of long-term and durability on ordinary concrete" GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results.

Mutual Influence of Mannitol and Trehalose on Crystallization Behavior in Frozen Solutions.

PubMed

Jena, Sampreeti; Suryanarayanan, Raj; Aksan, Alptekin

2016-06-01

Phase separation of trehalose during freeze-drying could render it ineffective as a lyoprotectant. The bulking agent, mannitol, on the other hand, should crystallize readily upon freezing. It is therefore imperative to understand the mutual interaction of these sugars during freezing to ensure preservation of the API during freeze-drying. We investigated the effect of mannitol to trehalose ratio (R) on the crystallization behavior of both solutes using Differential Scanning Calorimetry, X-Ray Crystallography and FTIR Spectrosopy during controlled freezing and annealing. When R = 1, crystallization of both mannitol (as hemihydrate) and trehalose (as α-anhydrate) were observed. When R ≥ 1, extent of mannitol crystallization was directly proportional to the value of R. When R < 1, trehalose completely suppressed mannitol crystallization. At R > 1, the freeze concentrate was heterogeneous and characterized by two glass transitions - the lower temperature transition (Tg") attributed to systems containing "extra" unfrozen water. When heated above Tg", crystallization of mannitol and the associated unfrozen water resulted in Tg' (glass transition temperature of the freeze-concentrate). R and not the total solute concentration, dictates the composition of the freeze concentrate as well as the physical stability of the excipients.

Freezing as an intervention to reduce the numbers of campylobacters isolated from chicken livers.

PubMed

Harrison, D; Corry, J E L; Tchórzewska, M A; Morris, V K; Hutchison, M L

2013-09-01

The aims of this study were (i) to determine the prevalence and numbers of campylobacters in 63 samples of raw livers purchased at retail across the UK and (ii) to investigate whether the freezing of chicken livers contaminated with Campylobacter was a reliable method for decontamination. Chicken livers naturally contaminated with campylobacters were subjected to freezing at -15 and -25°C for one day and 7 days. Numbers of campylobacters on the livers were determined immediately before and after a 24-h or 7-days freeze treatment and daily during 3 days post-thaw refrigerated storage. Freezing for 24 h at -25°C can reduce numbers of Campylobacter by up to 2 log10 CFU g(-1). Freezing the livers for 24 h at -25°C, thawing overnight in a fridge set to 4°C and refreezing for another 24 h at -25°C reduced the numbers of campylobacters by up to three logs. Reduction in the numbers of campylobacters was significantly greater following a second freeze treatment compared with a single freeze treatment. © 2013 Crown copyright. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.

Gap-freezing approach for shortening the lyophilization cycle time of pharmaceutical formulations-demonstration of the concept.

PubMed

Kuu, Wei Y; Doty, Mark J; Rebbeck, Christine L; Hurst, William S; Cho, Yong K

2013-08-01

During gap freezing, vials are placed on a metal tray, which is separated from the shelf surface with a small air gap that eliminates significant conductive heat transfer from the shelf to the bottom of the vial. The purpose of this freezing approach is to reduce the lyophilization cycle time of various amorphous formulations by nearly isothermal freezing. Such isothermal freezing promotes the formation of large ice crystals, and thus large pores throughout the cake, which subsequently accelerates the primary drying rate. The nucleation temperature using gap freezing, for the experimental conditions tested, was in the range of -1°C to -6°C, much higher than the range of -10°C to -14°C found using conventional shelf freezing. Isothermal freezing becomes effective when the gap is greater than 3 mm. The pore sizes and cake resistance during primary drying for various formulations were determined using the pore diffusion model developed by Kuu et al. (Pharm Dev Technol, 2011, 16(4): 343-357). Reductions in primary drying time were 42% (for 10% sucrose), 45% (for 10% trehalose), and 33% (for 5% sucrose). Copyright © 2013 Wiley Periodicals, Inc.

Intracellular Freezing in the Infective Juveniles of Steinernema feltiae: An Entomopathogenic Nematode

PubMed Central

Ali, Farman; Wharton, David A.

2014-01-01

Taking advantage of their optical transparency, we clearly observed the third stage infective juveniles (IJs) of Steinernema feltiae freezing under a cryo-stage microscope. The IJs froze when the water surrounding them froze at −2°C and below. However, they avoid inoculative freezing at −1°C, suggesting cryoprotective dehydration. Freezing was evident as a sudden darkening and cessation of IJs' movement. Freeze substitution and transmission electron microscopy confirmed that the IJs of S. feltiae freeze intracellularly. Ice crystals were found in every compartment of the body. IJs frozen at high sub-zero temperatures (−1 and −3°C) survived and had small ice crystals. Those frozen at −10°C had large ice crystals and did not survive. However, the pattern of ice formation was not well-controlled and individual nematodes frozen at −3°C had both small and large ice crystals. IJs frozen by plunging directly into liquid nitrogen had small ice crystals, but did not survive. This study thus presents the evidence that S. feltiae is only the second freeze tolerant animal, after the Antarctic nematode Panagrolaimus davidi, shown to withstand extensive intracellular freezing. PMID:24769523

Freeze-cast alumina pore networks: Effects of freezing conditions and dispersion medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, S. M.; Xiao, X.; Faber, K. T.

Alumina ceramics were freeze-cast from water- and camphene-based slurries under varying freezing conditions and examined using X-ray computed tomography (XCT). Pore network characteristics, i.e., porosity, pore size, geometric surface area, and tortuosity, were measured from XCT reconstructions and the data were used to develop a model to predict feature size from processing conditions. Classical solidification theory was used to examine relationships between pore size, temperature gradients, and freezing front velocity. Freezing front velocity was subsequently predicted from casting conditions via the two-phase Stefan problem. Resulting models for water-based samples agreed with solidification-based theories predicting lamellar spacing of binary eutectic alloys,more » and models for camphene-based samples concurred with those for dendritic growth. Relationships between freezing conditions and geometric surface area were also modeled by considering the inverse relationship between pore size and surface area. Tortuosity was determined to be dependent primarily on the type of dispersion medium. (C) 2015 Elsevier Ltd. All rights reserved.« less

Effects of egg yolk, glycerol and the freezing rate on the viability and acrosomal structures of frozen ram spermatozoa.

PubMed

Watson, P F; Martin, I C

1975-04-01

The influence of egg yolk, glycerol and the freezing rate on the survival of ram spermatozoa and on the structure of their acrosomes after freezing was investigated. Egg yolk was shown to be beneficial not only during chilling but also during freezing; of the levels examined, 1-5% gave the greatest protection. Although the presence of glycerol in the diluent improved the survival of spermatozoa, increasing concentrations produced significant deterioration of the acrosomes. With closely controlled linear cooling rates, no overall difference was detected in the survival of spermatozoa frozen at rates between 6 and 24 degrees C per min. However, a significant interaction between freezing rate and the inclusion of glycerol in the diluent showed that glycerol was less important at the highest freezing rate. A sudden cooling phase near to the freezing point following the release of the latent heat of fusion was not detrimental to spermatozoa.

Pharmaceutical patent applications in freeze-drying.

PubMed

Ekenlebie, Edmond; Einfalt, Tomaž; Karytinos, Arianna Irò; Ingham, Andrew

2016-09-01

Injectable products are often the formulation of choice for new therapeutics; however, formulation in liquids often enhances degradation through hydrolysis. Thus, freeze-drying (lyophilization) is regularly used in pharmaceutical manufacture to reduce water activity. Here we examine its contribution to 'state of the art' and look at its future potential uses. A comprehensive search of patent databases was conducted to characterize the international patent landscape and trends in the use of freeze-drying. A total of 914 disclosures related to freeze-drying, lyophilization or drying of solid systems in pressures and temperatures equivalent to those of freeze-drying were considered over the period of 1992-2014. Current applications of sublimation technology were contrasted across two periods those with patents due to expire (1992-1993) and those currently filed. The number of freeze-drying technology patents has stabilized after initial activity across the biotechnology sector in 2011 and 2012. Alongside an increasing trend for patent submissions, freeze-drying submissions have slowed since 2002 and is indicative of a level of maturity.

Giant panda (Ailuropoda melanoleuca) sperm morphometry and function after repeated freezing and thawing.

PubMed

Santiago-Moreno, J; Esteso, M C; Pradiee, J; Castaño, C; Toledano-Díaz, A; O'Brien, E; Lopez-Sebastián, A; Martínez-Nevado, E; Delclaux, M; Fernández-Morán, J; Zhihe, Z

2016-05-01

This work examines the effects of subsequent cycles of freezing-thawing on giant panda (Ailuropoda melanoleuca) sperm morphometry and function, and assesses whether density-gradient centrifugation (DGC) can increase the number of freezing-thawing cycles this sperm can withstand. A sperm sample was collected by electroejaculation from a mature giant panda and subjected to five freezing-thawing cycles. Although repeated freezing-thawing negatively affected (P < 0.05) sperm motility and membrane integrity, in both nonselected and DCG-selected sperm samples, >60% of the sperm cells in both treatments showed acrosome integrity even after the fifth freezing cycle. In fresh semen, the sperm head length was 4.7 μm, the head width 3.6 μm, area 14.3 μm(2) and perimeter length 14.1 μm. The present results suggest that giant panda sperm trends to be resistant to repeated freezing-thawing, even without DGC selection. © 2015 Blackwell Verlag GmbH.

Ultrasound assisted immersion freezing of broccoli (Brassica oleracea L. var. botrytis L.).

PubMed

Xin, Ying; Zhang, Min; Adhikari, Benu

2014-09-01

The aim of this study was to research the ultrasound-assisted freezing (UAF) of broccoli. CaCl2 solution was used as freezing medium. The comparative advantage of using UAF over normal freezing on the freezing time, cell-wall bound calcium to total calcium ratio, textural properties, color, drip loss and L-ascorbic acid contents was evaluated. The application of UAF at selected acoustic intensity with a range of 0.250-0.412 W/cm(2) decreased the freezing time and the loss of cell-wall bound calcium content. Compared to normal freezing, the values of textural properties, color, L-ascorbic acid content were better preserved and the drip loss was significantly minimized by the application of UAF. However, when outside that range of acoustic intensity, the quality of the ultrasound-assisted frozen broccoli was inferior compared to that of the normally frozen samples. Selected the appropriate acoustic intensity was very important for the application of UAF. Copyright © 2014 Elsevier B.V. All rights reserved.

Recent developments in novel freezing and thawing technologies applied to foods.

PubMed

Wu, Xiao-Fei; Zhang, Min; Adhikari, Benu; Sun, Jincai

2017-11-22

This article reviews the recent developments in novel freezing and thawing technologies applied to foods. These novel technologies improve the quality of frozen and thawed foods and are energy efficient. The novel technologies applied to freezing include pulsed electric field pre-treatment, ultra-low temperature, ultra-rapid freezing, ultra-high pressure and ultrasound. The novel technologies applied to thawing include ultra-high pressure, ultrasound, high voltage electrostatic field (HVEF), and radio frequency. Ultra-low temperature and ultra-rapid freezing promote the formation and uniform distribution of small ice crystals throughout frozen foods. Ultra-high pressure and ultrasound assisted freezing are non-thermal methods and shorten the freezing time and improve product quality. Ultra-high pressure and HVEF thawing generate high heat transfer rates and accelerate the thawing process. Ultrasound and radio frequency thawing can facilitate thawing process by volumetrically generating heat within frozen foods. It is anticipated that these novel technologies will be increasingly used in food industries in the future.

A molecular dynamics study of freezing in a confined geometry

NASA Technical Reports Server (NTRS)

Ma, Wen-Jong; Banavar, Jayanth R.; Koplik, Joel

1992-01-01

The dynamics of freezing of a Lennard-Jones liquid in narrow channels bounded by molecular walls is studied by computer simulation. The time development of ordering is quantified and a novel freezing mechanism is observed. The liquid forms layers and subsequent in-plane ordering within a layer is accompanied by a sharpening of the layer in the transverse direction. The effects of channel size, the methods of quench, the liquid-wall interaction and the roughness of walls on the freezing mechanism are elucidated. Comparison with recent experiments on freezing in confined geometries is presented.

Hidden transition in multiferroic and magnetodielectric CuCrO2 evidenced by ac-susceptibility

NASA Astrophysics Data System (ADS)

Shukla, Kaushak K.; Pal, Arkadeb; Singh, Abhishek; Singh, Rahul; Saha, J.; Sinha, A. K.; Ghosh, A. K.; Patnaik, S.; Awasthi, A. M.; Chatterjee, Sandip

2017-04-01

Ferroelectric polarization, magnetic-field dependence of the dielectric constant and ac and dc magnetizations of frustrated CuCrO2 have been measured. A new spin freezing transition below 32 K is observed which is thermally driven. The nature of the spin freezing is to be a single-ion process. Dilution by the replacements of Cr ions by magnetic Mn ions showed suppression of the spin freezing transition suggesting it to be fundamentally a single-ion freezing process. The observed freezing, which is seemingly associated to geometrical spin frustration, represents a novel form of magnetic glassy behavior.

Design of a blood-freezing system for leukemia research

NASA Technical Reports Server (NTRS)

Williams, T. E.; Cygnarowicz, T. A.

1978-01-01

Leukemia research involves the use of cryogenic freezing and storage equipment. In a program being carried out at the National Cancer Institute (NCI), bone marrow (white blood cells) was frozen using a standard cryogenic biological freezer. With this system, it is difficult to maintain the desired rate of freezing and repeatability from sample to sample. A freezing system was developed that satisfies the requirements for a repeatable, constant freezing rate. The system was delivered to NIC and is now operational. This report describes the design of the major subsystems, the analyses, the operating procedure, and final system test results.

Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra

NASA Astrophysics Data System (ADS)

Beydoun, Hassan; Polen, Michael; Sullivan, Ryan C.

2016-10-01

Heterogeneous ice nucleation remains one of the outstanding problems in cloud physics and atmospheric science. Experimental challenges in properly simulating particle-induced freezing processes under atmospherically relevant conditions have largely contributed to the absence of a well-established parameterization of immersion freezing properties. Here, we formulate an ice active, surface-site-based stochastic model of heterogeneous freezing with the unique feature of invoking a continuum assumption on the ice nucleating activity (contact angle) of an aerosol particle's surface that requires no assumptions about the size or number of active sites. The result is a particle-specific property g that defines a distribution of local ice nucleation rates. Upon integration, this yields a full freezing probability function for an ice nucleating particle. Current cold plate droplet freezing measurements provide a valuable and inexpensive resource for studying the freezing properties of many atmospheric aerosol systems. We apply our g framework to explain the observed dependence of the freezing temperature of droplets in a cold plate on the concentration of the particle species investigated. Normalizing to the total particle mass or surface area present to derive the commonly used ice nuclei active surface (INAS) density (ns) often cannot account for the effects of particle concentration, yet concentration is typically varied to span a wider measurable freezing temperature range. A method based on determining what is denoted an ice nucleating species' specific critical surface area is presented and explains the concentration dependence as a result of increasing the variability in ice nucleating active sites between droplets. By applying this method to experimental droplet freezing data from four different systems, we demonstrate its ability to interpret immersion freezing temperature spectra of droplets containing variable particle concentrations. It is shown that general active site density functions, such as the popular ns parameterization, cannot be reliably extrapolated below this critical surface area threshold to describe freezing curves for lower particle surface area concentrations. Freezing curves obtained below this threshold translate to higher ns values, while the ns values are essentially the same from curves obtained above the critical area threshold; ns should remain the same for a system as concentration is varied. However, we can successfully predict the lower concentration freezing curves, which are more atmospherically relevant, through a process of random sampling from g distributions obtained from high particle concentration data. Our analysis is applied to cold plate freezing measurements of droplets containing variable concentrations of particles from NX illite minerals, MCC cellulose, and commercial Snomax bacterial particles. Parameterizations that can predict the temporal evolution of the frozen fraction of cloud droplets in larger atmospheric models are also derived from this new framework.

Freeze injury to southern pine seedlings

Treesearch

David B. South

2006-01-01

Freeze injury to roots and shoots of pines is affected by genotype and nursery practices. Local sources of shortleaf pine and Virginia pine that are grown in nurseries in USDA hardiness Zones 6 and 7a are relatively freeze tolerant. However, loblolly pine, slash pine, and longleaf pine seedlings have been injured by a number of freeze events (0 to 24 °F) in hardiness...

Asymmetric pedunculopontine network connectivity in parkinsonian patients with freezing of gait

PubMed Central

Fling, Brett W.; Cohen, Rajal G.; Mancini, Martina; Nutt, John G.; Fair, Damian A.

2013-01-01

Freezing of gait is one of the most debilitating symptoms in Parkinson’s disease as it causes falls and reduces mobility and quality of life. The pedunculopontine nucleus is one of the major nuclei of the mesencephalic locomotor region and has neurons related to anticipatory postural adjustments preceding step initiation as well as to the step itself, thus it may be critical for coupling posture and gait to avoid freezing. Because freezing of gait and postural impairments have been related to frontal lesions and frontal dysfunction such as executive function, we hypothesized that freezing is associated with disrupted connectivity between midbrain locomotor regions and medial frontal cortex. We used diffusion tensor imaging to quantify structural connectivity of the pedunculopontine nucleus in patients with Parkinson’s disease with freezing of gait, without freezing, and healthy age-matched controls. We also included behavioural tasks to gauge severity of freezing of gait, quantify gait metrics, and assess executive cognitive functions to determine whether between-group differences in executive dysfunction were related to pedunculopontine nucleus structural network connectivity. Using seed regions from the pedunculopontine nucleus, we were able to delineate white matter connections between the spinal cord, cerebellum, pedunculopontine nucleus, subcortical and frontal/prefrontal cortical regions. The current study is the first to demonstrate differences in structural connectivity of the identified locomotor pathway in patients with freezing of gait. We report reduced connectivity of the pedunculopontine nucleus with the cerebellum, thalamus and multiple regions of the frontal cortex. Moreover, these structural differences were observed solely in the right hemisphere of patients with freezing of gait. Finally, we show that the more left hemisphere-lateralized the pedunculopontine nucleus tract volume, the poorer the performance on cognitive tasks requiring the initiation of appropriate actions and/or the inhibition of inappropriate actions, specifically within patients with freezing. These results support the notion that freezing of gait is strongly related to structural deficits in the right hemisphere’s locomotor network involving prefrontal cortical areas involved in executive inhibition function. PMID:23824487

Heave, settlement and fracture of chalk during physical modelling experiments with temperature cycling above and below 0 °C

NASA Astrophysics Data System (ADS)

Murton, Julian B.; Ozouf, Jean-Claude; Peterson, Rorik

2016-10-01

To elucidate the early stages of heave, settlement and fracture of intact frost-susceptible rock by temperature cycling above and below 0 °C, two physical modelling experiments were performed on 10 rectangular blocks 450 mm high of fine-grained, soft limestone. One experiment simulated 21 cycles of bidirectional freezing (upward and downward) of an active layer above permafrost, and the other simulated 26 cycles of unidirectional freezing (downward) of a seasonally frozen bedrock in a non-permafrost region. Heave and settlement of the top of the blocks were monitored in relation to rock temperature and unfrozen water content, which ranged from almost dry to almost saturated. In the bidirectional freezing experiment, heave of the wettest block initially occurred abruptly at the onset of freezing periods and gradually during thawing periods (summer heave). After the crossing of a threshold marked by the appearance of a macrocrack in the upper layer of permafrost, summer heave increased by an order of magnitude as segregated ice accumulated incrementally in macrocracks, interrupted episodically by abrupt settlement that coincided with unusually high air temperatures. In the unidirectional freezing experiment, the wet blocks heaved during freezing periods and settled during thawing periods, whereas the driest blocks showed the opposite behaviour. The two wettest blocks settled progressively during the first 15 freeze-thaw cycles, before starting to heave progressively as macrocracks developed. Four processes, operating singly or in combination in the blocks account for their heave and settlement: (1) thermal expansion and contraction caused heave and settlement when little or no water-ice phase change was involved; (2) volumetric expansion of water freezing in situ caused short bursts of heave of the outer millimetres of wet rock; (3) ice segregation deeper in the blocks caused sustained heave during thawing and freezing periods; and (4) freeze-thaw cycling caused consolidation and settlement of wet blocks prior to macrocracking in the unidirectional freezing experiment. Rock fracture developed by growth of segregated ice in microcracks and macrocracks at depths determined by the freezing regime. Overall, the heave, settlement and fracture behaviour of the limestone is similar to that of frost-susceptible soil.

Freezing and fractionation: effects of preservation on carbon and nitrogen stable isotope ratios of some limnetic organisms.

PubMed

Wolf, J Marshall; Johnson, Brett; Silver, Douglas; Pate, William; Christianson, Kyle

2016-03-15

Stable isotopes of carbon and nitrogen have become important natural tracers for studying food-web structure and function. Considerable research has demonstrated that chemical preservatives and fixatives shift the isotopic ratios of aquatic organisms. Much less is known about the effects of freezing as a preservation method although this technique is commonly used. We conducted a controlled experiment to test the effects of freezing (-10 °C) and flash freezing (–79 °C) on the carbon and nitrogen isotope ratios of zooplankton (Cladocera), Mysis diluviana and Rainbow Trout (Oncorhynchus mykiss). Subsamples (~0.5 mg) of dried material were analyzed for percentage carbon, percentage nitrogen, and the relative abundance of stable carbon and nitrogen isotopes (δ13C and δ15N values) using a Carlo Erba NC2500 elemental analyzer interfaced to a ThermoFinnigan MAT Delta Plus isotope ratio mass spectrometer. The effects of freezing were taxon-dependent. Freezing had no effect on the isotopic or elemental values of Rainbow Trout muscle. Effects on the δ13C and δ15N values of zooplankton and Mysis were statistically significant but small relative to typical values of trophic fractionation. The treatment-control offsets had larger absolute values for Mysis (δ13C: ≤0.76 ± 0.41‰, δ15N: ≤0.37 ± 0.16‰) than for zooplankton (δ13C: ≤0.12 ± 0.06‰, δ15N: ≤0.30 ± 0.27‰). The effects of freezing were more variable for the δ13C values of Mysis, and more variable for the δ15N values of zooplankton. Generally, both freezing methods reduced the carbon content of zooplankton and Mysis, but freezing had a negative effect on the %N of zooplankton and a positive effect on the %N of Mysis. The species-dependencies and variability of freezing effects on aquatic organisms suggest that more research is needed to understand the mechanisms responsible for freezing-related fractionation before standardized protocols for freezing as a preservation method can be adopted.

Implementation of a process analytical technology system in a freeze-drying process using Raman spectroscopy for in-line process monitoring.

PubMed

De Beer, T R M; Allesø, M; Goethals, F; Coppens, A; Heyden, Y Vander; De Diego, H Lopez; Rantanen, J; Verpoort, F; Vervaet, C; Remon, J P; Baeyens, W R G

2007-11-01

The aim of the present study was to propose a strategy for the implementation of a Process Analytical Technology system in freeze-drying processes. Mannitol solutions, some of them supplied with NaCl, were used as models to freeze-dry. Noninvasive and in-line Raman measurements were continuously performed during lyophilization of the solutions to monitor real time the mannitol solid state, the end points of the different process steps (freezing, primary drying, secondary drying), and physical phenomena occurring during the process. At-line near-infrared (NIR) and X-ray powder diffractometry (XRPD) measurements were done to confirm the Raman conclusions and to find out additional information. The collected spectra during the processes were analyzed using principal component analysis and multivariate curve resolution. A two-level full factorial design was used to study the significant influence of process (freezing rate) and formulation variables (concentration of mannitol, concentration of NaCl, volume of freeze-dried sample) upon freeze-drying. Raman spectroscopy was able to monitor (i) the mannitol solid state (amorphous, alpha, beta, delta, and hemihydrate), (ii) several process step end points (end of mannitol crystallization during freezing, primary drying), and (iii) physical phenomena occurring during freeze-drying (onset of ice nucleation, onset of mannitol crystallization during the freezing step, onset of ice sublimation). NIR proved to be a more sensitive tool to monitor sublimation than Raman spectroscopy, while XRPD helped to unravel the mannitol hemihydrate in the samples. The experimental design results showed that several process and formulation variables significantly influence different aspects of lyophilization and that both are interrelated. Raman spectroscopy (in-line) and NIR spectroscopy and XRPD (at-line) not only allowed the real-time monitoring of mannitol freeze-drying processes but also helped (in combination with experimental design) us to understand the process.

Anhydrobiosis and freezing-tolerance: adaptations that facilitate the establishment of Panagrolaimus nematodes in polar habitats.

PubMed

McGill, Lorraine M; Shannon, Adam J; Pisani, Davide; Félix, Marie-Anne; Ramløv, Hans; Dix, Ilona; Wharton, David A; Burnell, Ann M

2015-01-01

Anhydrobiotic animals can survive the loss of both free and bound water from their cells. While in this state they are also resistant to freezing. This physiology adapts anhydrobiotes to harsh environments and it aids their dispersal. Panagrolaimus davidi, a bacterial feeding anhydrobiotic nematode isolated from Ross Island Antarctica, can survive intracellular ice formation when fully hydrated. A capacity to survive freezing while fully hydrated has also been observed in some other Antarctic nematodes. We experimentally determined the anhydrobiotic and freezing-tolerance phenotypes of 24 Panagrolaimus strains from tropical, temperate, continental and polar habitats and we analysed their phylogenetic relationships. We found that several other Panagrolaimus isolates can also survive freezing when fully hydrated and that tissue extracts from these freezing-tolerant nematodes can inhibit the growth of ice crystals. We show that P. davidi belongs to a clade of anhydrobiotic and freezing-tolerant panagrolaimids containing strains from temperate and continental regions and that P. superbus, an early colonizer at Surtsey island, Iceland after its volcanic formation, is closely related to a species from Pennsylvania, USA. Ancestral state reconstructions show that anhydrobiosis evolved deep in the phylogeny of Panagrolaimus. The early-diverging Panagrolaimus lineages are strongly anhydrobiotic but weakly freezing-tolerant, suggesting that freezing tolerance is most likely a derived trait. The common ancestors of the davidi and the superbus clades were anhydrobiotic and also possessed robust freezing tolerance, along with a capacity to inhibit the growth and recrystallization of ice crystals. Unlike other endemic Antarctic nematodes, the life history traits of P. davidi do not show evidence of an evolved response to polar conditions. Thus we suggest that the colonization of Antarctica by P. davidi and of Surtsey by P. superbus may be examples of recent "ecological fitting" of freezing-tolerant anhydrobiotic propagules to the respective abiotic conditions in Ross Island and Surtsey.

Bursts of CO2 released during freezing offer a new perspective on avoidance of winter embolism in trees.

PubMed

Lintunen, A; Lindfors, L; Kolari, P; Juurola, E; Nikinmaa, E; Hölttä, T

2014-12-01

Woody plants can suffer from winter embolism as gas bubbles are formed in the water-conducting conduits when freezing occurs: gases are not soluble in ice, and the bubbles may expand and fill the conduits with air during thawing. A major assumption usually made in studies of winter embolism formation is that all of the gas dissolved in the xylem sap is trapped within the conduits and forms bubbles during freezing. The current study tested whether this assumption is actually valid, or whether efflux of gases from the stem during freezing reduces the occurrence of embolism. CO2 efflux measurements were conducted during freezing experiments for saplings of three Scots pine (Pinus sylvestris) and three Norway spruce (Picea abies) trees under laboratory conditions, and the magnitudes of the freezing-related bursts of CO2 released from the stems were analysed using a previously published mechanistic model of CO2 production, storage, diffusion and efflux from a tree stem. The freezing-related bursts of CO2 released from a mature Scots pine tree growing in field conditions were also measured and analysed. Substantial freezing-related bursts of CO2 released from the stem were found to occur during both the laboratory experiments and under field conditions. In the laboratory, the fraction of CO2 released from the stem ranged between 27 and 96 % of the total CO2 content within the stem. All gases dissolved in the xylem sap are not trapped within the ice in the stem during freezing, as has previously been assumed, thus adding a new dimension to the understanding of winter embolism formation. The conduit water volume not only determines the volume of bubbles formed during freezing, but also the efficiency of gas efflux out of the conduit during the freezing process. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company.

The Role of Hydrogen Peroxide in Mediating the Mechanical Wounding-Induced Freezing Tolerance in Wheat

PubMed Central

Si, Tong; Wang, Xiao; Zhao, Chunzhao; Huang, Mei; Cai, Jian; Zhou, Qin; Dai, Tingbo; Jiang, Dong

2018-01-01

Systemic wound response (SWR), a well-characterized systemic signaling response, plays crucial roles in plant defense responses. Progress in understanding of the SWR in abiotic stress has also been aided by the researchers. However, the function of SWR in freezing stress remains elusive. In this study, we showed that local mild mechanical wounding enhanced freezing tolerance in newly occurred systemic leaves of wheat plants (Triticum aestivum L.). Wounding significantly increased the maximal photochemical efficiency of photosystem II, net photosynthetic rate, and the activities of the antioxidant enzymes under freezing stress. Wounding also alleviated freezing-induced chlorophyll decomposition, electrolyte leakage, water lose, and membrane peroxidation. In addition, wounding-induced freezing stress mitigation was closely associated with the ratio between reduced glutathione (GSH) and oxidized glutathione (GSSG), and the ratio between ascorbate (AsA) and dehydroascorbate (DHA), as well as the contents of total soluble sugars and free amino acids. Importantly, pharmacological study showed that wounding-induced freezing tolerance was substantially arrested by pretreatment of wheat leaves with the scavenger of hydrogen peroxide (H2O2) or the inhibitor of NADPH oxidase (RBOH). These results support the hypothesis that local mechanical wounding-induced SWR in newly occurred leaves is largely attributed to RBOH-dependent H2O2 production, which may subsequently induce freezing tolerance in wheat plants. This mechanism may have a potential application to reduce the yield losses of wheat under late spring freezing conditions. Highlights: In our previous research, we found that local mechanical wounding could induce freezing tolerance in the upper systemic leaves of wheat plants. Surprisingly, in this paper, we further demonstrated that local mechanical wounding could also increase freezing resistance in newly occurred leaves of wheat plants. RBOH mediated H2O2 and ascorbate–glutathione cycle participate in this systemic wound response. PMID:29593774

Anhydrobiosis and Freezing-Tolerance: Adaptations That Facilitate the Establishment of Panagrolaimus Nematodes in Polar Habitats

PubMed Central

McGill, Lorraine M.; Shannon, Adam J.; Pisani, Davide; Félix, Marie-Anne; Ramløv, Hans; Dix, Ilona; Wharton, David A.; Burnell, Ann M.

2015-01-01

Anhydrobiotic animals can survive the loss of both free and bound water from their cells. While in this state they are also resistant to freezing. This physiology adapts anhydrobiotes to harsh environments and it aids their dispersal. Panagrolaimus davidi, a bacterial feeding anhydrobiotic nematode isolated from Ross Island Antarctica, can survive intracellular ice formation when fully hydrated. A capacity to survive freezing while fully hydrated has also been observed in some other Antarctic nematodes. We experimentally determined the anhydrobiotic and freezing-tolerance phenotypes of 24 Panagrolaimus strains from tropical, temperate, continental and polar habitats and we analysed their phylogenetic relationships. We found that several other Panagrolaimus isolates can also survive freezing when fully hydrated and that tissue extracts from these freezing-tolerant nematodes can inhibit the growth of ice crystals. We show that P. davidi belongs to a clade of anhydrobiotic and freezing-tolerant panagrolaimids containing strains from temperate and continental regions and that P. superbus, an early colonizer at Surtsey island, Iceland after its volcanic formation, is closely related to a species from Pennsylvania, USA. Ancestral state reconstructions show that anhydrobiosis evolved deep in the phylogeny of Panagrolaimus. The early-diverging Panagrolaimus lineages are strongly anhydrobiotic but weakly freezing-tolerant, suggesting that freezing tolerance is most likely a derived trait. The common ancestors of the davidi and the superbus clades were anhydrobiotic and also possessed robust freezing tolerance, along with a capacity to inhibit the growth and recrystallization of ice crystals. Unlike other endemic Antarctic nematodes, the life history traits of P. davidi do not show evidence of an evolved response to polar conditions. Thus we suggest that the colonization of Antarctica by P. davidi and of Surtsey by P. superbus may be examples of recent “ecological fitting” of freezing-tolerant anhydrobiotic propagules to the respective abiotic conditions in Ross Island and Surtsey. PMID:25747673

A low membrane lipid phase transition temperature is associated with a high cryotolerance of Lactobacillus delbrueckii subspecies bulgaricus CFL1.

PubMed

Gautier, J; Passot, S; Pénicaud, C; Guillemin, H; Cenard, S; Lieben, P; Fonseca, F

2013-09-01

The mechanisms of cellular damage that lactic acid bacteria incur during freeze-thaw processes have not been elucidated to date. Fourier transform infrared spectroscopy was used to investigate in situ the lipid phase transition behavior of the membrane of Lactobacillus delbrueckii ssp. bulgaricus CFL1 cells during the freeze-thaw process. Our objective was to relate the lipid membrane behavior to membrane integrity losses during freezing and to cell-freezing resistance. Cells were produced by using 2 different culture media: de Man, Rogosa, and Sharpe (MRS) broth (complex medium) or mild whey-based medium (minimal medium commonly used in the dairy industry), to obtain different membrane lipid compositions corresponding to different recovery rates of cell viability and functionality after freezing. The lipid membrane behavior studied by Fourier transform infrared spectroscopy was found to be different according to the cell lipid composition and cryotolerance. Freeze-resistant cells, exhibiting a higher content of unsaturated and cyclic fatty acids, presented a lower lipid phase transition temperature (Ts) during freezing (Ts=-8°C), occurring within the same temperature range as the ice nucleation, than freeze-sensitive cells (Ts=+22°C). A subzero value of lipid phase transition allowed the maintenance of the cell membrane in a relatively fluid state during freezing, thus facilitating water flux from the cell and the concomitant volume reduction following ice formation in the extracellular medium. In addition, the lipid phase transition of freeze-resistant cells occurred within a short temperature range, which could be ascribed to a reduced number of fatty acids, representing more than 80% of the total. This short lipid phase transition could be associated with a limited phenomenon of lateral phase separation and membrane permeabilization. This work highlights that membrane phase transitions occurring during freeze-thawing play a fundamental role in the cryotolerance of Lb. delbrueckii ssp. bulgaricus CFL1 cells. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Air-Cooled Stack Freeze Tolerance Freeze Failure Modes and Freeze Tolerance Strategies for GenDriveTM Material Handling Application Systems and Stacks Final Scientific Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hancock, David, W.

2012-02-14

Air-cooled stack technology offers the potential for a simpler system architecture (versus liquid-cooled) for applications below 4 kilowatts. The combined cooling and cathode air allows for a reduction in part count and hence a lower cost solution. However, efficient heat rejection challenges escalate as power and ambient temperature increase. For applications in ambient temperatures below freezing, the air-cooled approach has additional challenges associated with not overcooling the fuel cell stack. The focus of this project was freeze tolerance while maintaining all other stack and system requirements. Through this project, Plug Power advanced the state of the art in technology formore » air-cooled PEM fuel cell stacks and related GenDrive material handling application fuel cell systems. This was accomplished through a collaborative work plan to improve freeze tolerance and mitigate freeze-thaw effect failure modes within innovative material handling equipment fuel cell systems designed for use in freezer forklift applications. Freeze tolerance remains an area where additional research and understanding can help fuel cells to become commercially viable. This project evaluated both stack level and system level solutions to improve fuel cell stack freeze tolerance. At this time, the most cost effective solutions are at the system level. The freeze mitigation strategies developed over the course of this project could be used to drive fuel cell commercialization. The fuel cell system studied in this project was Plug Power's commercially available GenDrive platform providing battery replacement for equipment in the material handling industry. The fuel cell stacks were Ballard's commercially available FCvelocity 9SSL (9SSL) liquid-cooled PEM fuel cell stack and FCvelocity 1020ACS (Mk1020) air-cooled PEM fuel cell stack.« less

Bulk water freezing dynamics on superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Chavan, S.; Carpenter, J.; Nallapaneni, M.; Chen, J. Y.; Miljkovic, N.

2017-01-01

In this study, we elucidate the mechanisms governing the heat-transfer mediated, non-thermodynamic limited, freezing delay on non-wetting surfaces for a variety of characteristic length scales, Lc (volume/surface area, 3 mm < Lc < 6 mm) using carefully designed freezing experiments in a temperature-controlled, zero-humidity environment on thin water slabs. To probe the effect of surface wettability, we investigated the total time for room temperature water to completely freeze into ice on superhydrophilic ( θaapp→ 0°), hydrophilic (0° < θa < 90°), hydrophobic (90° < θa < 125°), and superhydrophobic ( θaapp→ 180°) surfaces. Our results show that at macroscopic length scales, heat conduction through the bulk water/ice layer dominates the freezing process when compared to heat conduction through the functional coatings or nanoscale gaps at the superhydrophobic substrate-water/ice interface. In order to verify our findings, and to determine when the surface structure thermal resistance approaches the water/ice resistance, we fabricated and tested the additional substrates coated with commercial superhydrophobic spray coatings, showing a monotonic increase in freezing time with coating thickness. The added thermal resistance of thicker coatings was much larger than that of the nanoscale superhydrophobic features, which reduced the droplet heat transfer and increased the total freezing time. Transient finite element method heat transfer simulations of the water slab freezing process were performed to calculate the overall heat transfer coefficient at the substrate-water/ice interface during freezing, and shown to be in the range of 1-2.5 kW/m2K for these experiments. The results shown here suggest that in order to exploit the heat-transfer mediated freezing delay, thicker superhydrophobic coatings must be deposited on the surface, where the coating resistance is comparable to the bulk water/ice conduction resistance.

Porous and strong bioactive glass (13–93) scaffolds prepared by unidirectional freezing of camphene-based suspensions

PubMed Central

Liu, Xin; Rahaman, Mohamed N.; Fu, Qiang; Tomsia, Antoni P.

2011-01-01

Scaffolds of 13–93 bioactive glass (6Na2O, 12K2O, 5MgO, 20CaO, 4P2O5, 53SiO2; wt %) with an oriented pore architecture were formed by unidirectional freezing of camphene-based suspensions, followed by thermal annealing of the frozen constructs to grow the camphene crystals. After sublimation of the camphene, the constructs were sintered (1 h at 700 °C) to produce a dense glass phase with oriented macropores. The objective of this work was to study how constant freezing rates (1–7 °C/min) during the freezing step influenced the pore orientation and mechanical response of the scaffolds. When compared to scaffolds prepared by freezing the suspensions on a substrate kept at a constant temperature of 3 °C (time-dependent freezing rate), higher freezing rates resulted in better pore orientation, a more homogeneous microstructure, and a marked improvement in the mechanical response of the scaffolds in compression. Scaffolds fabricated using a constant freezing rate of 7 °C/min (porosity = 50 ± 4%; average pore diameter = 100 μm), had a compressive strength of 47 ± 5 MPa and an elastic modulus of 11 ± 3 GPa (in the orientation direction). In comparison, scaffolds prepared by freezing on the constant-temperature substrate had strength and modulus values of 35 ± 11 MPa and 8 ± 3 GPa, respectively. These oriented bioactive glass scaffolds prepared by the constant freezing rate route could potentially be used for the repair of defects in load-bearing bones, such as segmental defects in the long bones. PMID:21855661

Mutagenic effect of freezing on nuclear DNA of Saccharomyces cerevisiae.

PubMed

Todorova, T; Pesheva, M; Stamenova, R; Dimitrov, M; Venkov, P

2012-05-01

Although fragmentation of DNA has been observed in cells undergoing freezing procedures, a mutagenic effect of sub-zero temperature treatment has not been proved by induction and isolation of mutants in nuclear DNA (nDNA). In this communication we supply evidence for mutagenicity of freezing on nDNA of Saccharomyces cerevisiae cells. In the absence of cryoprotectors, cooling for 2 h at +4°C and freezing for 1 h at -10°C and 16 h at -20°C, with a cooling rate of 3°C/min, resulted in induction of frame-shift and reverse mutations in microsatellite and coding regions of nDNA. The sub-zero temperature exposure also has a strong recombinogenic effect, evidenced by induction of gene-conversion and crossing-over events. Freezing induces mutations and enhances recombination with a frequency equal to or higher than that of methylmethanesulphonate at comparable survival rates. The signals for the appearance of nDNA lesions induced by freezing are detected and transduced by the DNA damage pathway. Extracellular cryoprotectors did not prevent the mutagenic effect of freezing, while accumulation of trehalose inside cells reduced nDNA cryodamage. Freezing of cells is accompanied by generation of high ROS levels, and the oxidative stress raised during the freeze-thaw process is the most likely reason for the DNA damaging effect. Experiments with mitochondrial rho⁻ mutants or scavengers of ROS indicated that mutagenic and recombinogenic effects of sub-zero temperatures can be decreased but not eliminated by reduction of ROS level. The complete protection against cryodamage in nDNA required simultaneous usage of intracellular cryoprotector and ROS scavenger during the freeze-thaw process. Copyright © 2012 John Wiley & Sons, Ltd.

Effects of a controlled freeze-thaw event on dissolved and colloidal soil organic matter.

PubMed

Kim, Eun-Ah; Lee, Ha Kyung; Choi, Jung Hyun

2017-01-01

This study investigated the effects of the freezing and thawing that accompany the warming process on the composition of the soil organic matter in the dissolved and colloidal fractions. Temperate soil samples were incubated in a refrigerator at 2 °C for 4 weeks and compared with those frozen at -20 °C in the second week followed by thawing at 2 °C to study a freeze-thaw effect with minimal effect from the thawing temperature. The freeze-thaw group was compared with those incubated at 25 °C in the last week to investigate a warming effect after thawing. Thawing at 2 °C after freezing at -20 °C increased the dissolved organic carbon (DOC), but decreased colloidal Ca. The subsequent warming condition greatly increased both DOC and colloidal Ca. The colloidal organic carbon (COC) and dissolved Ca showed rather subtle changes in response to the freeze-thaw and warming treatments compared to the changes in DOC and colloidal Ca. The fluorescence excitation-emission matrix (EEM) and Fourier transformation-infrared spectrometry (FT-IR) results showed that the freeze-thaw and warming treatments gave the opposite effects on the compositions of dissolved humic-like substances, polysaccharides or silicates, and aliphatic alcohols. A principal component analysis (PCA) with the DOC, fluorescence EEM, and FT-IR spectra produced two principal components that successfully distinguished the effects of the freeze-thaw and warming treatments. Due to the contrasting effects of the freeze-thaw and warming treatments, the overall effects of freeze-thaw events in nature on the dissolved and colloidal soil organic matter could vary depending on the thawing temperature.

Colloid-facilitated mobilization of metals by freeze-thaw cycles.

PubMed

Mohanty, Sanjay K; Saiers, James E; Ryan, Joseph N

2014-01-21

The potential of freeze-thaw cycles to release colloids and colloid-associated contaminants into water is unknown. We examined the effect of freeze-thaw cycles on the mobilization of cesium and strontium in association with colloids in intact cores of a fractured soil, where preferential flow paths are prevalent. Two intact cores were contaminated with cesium and strontium. To mobilize colloids and metal cations sequestered in the soil cores, each core was subjected to 10 intermittent wetting events separated by 66 h pauses. During the first five pauses, the cores were dried at room temperature, and during last five pauses, the cores were subjected to 42 h of freezing followed by 24 h of thawing. In comparison to drying, freeze-thaw cycles created additional preferential flow paths through which colloids, cesium, and strontium were mobilized. The wetting events following freeze-thaw intervals mobilized about twice as many colloids as wetting events following drying at room temperature. Successive wetting events following 66 h of drying mobilized similar amounts of colloids; in contrast, successive wetting events after 66 h of freeze-thaw intervals mobilized greater amounts of colloids than the previous one. Drying and freeze-thaw treatments, respectively, increased and decreased the dissolved cesium and strontium, but both treatments increased the colloidal cesium and strontium. Overall, the freeze-thaw cycles increased the mobilization of metal contaminants primarily in association with colloids through preferential flow paths. These findings suggest that the mobilization of colloid and colloid-associated contaminants could increase when temperature variations occur around the freezing point of water. Thus, climate extremes have the potential to mobilize contaminants that have been sequestered in the vadose zone for decades.

Monitoring Freeze Injury and Evaluating Losingto Sugar-Cane Using RS and GPS

NASA Astrophysics Data System (ADS)

Tan, Zongkun; Ding, Meihua; Wang, Longhe; Yang, Xin; Ou, Zhaorong

From Jan 12th to Feb 12th 2008, the most severity cold chilling and freeze injury weather took place during the last 50 years in the southern of China.Sugar-cane was suffered injury severity. However, the losing of sugar-cane which it was aroused by thisweather disaster had not been exactitude evaluated till on Apr 1st, 2008. It was not only affected the sugar-cane ordinary harvesting and crushing, but also affected reserving sugar-cane seed for planting. Freeze injury is common disaster for sugar-cane in southern of China and monitoring freeze injury using RS and GIS are of great economic significance but little research work about it has been done in China Freeze injuring is not only related to crop growth stage and the cold air intension from northern to southern and weather types, but also consanguineous related to land form and physiognomy and geographical latitude and height above sea level etc and crop planting spatial distribution. The case study of Guangxi province which is the biggest region of sugar-cane planting in China in this paper, the values of sugar-cane NDVI among the freeze injury occur former and after in early 2008 and without freeze injury occur in the same term 2007 were analyzed and compared based on the sugar-cane planting spatial distribution information which were carried out by using multi-phase EOS/MODIS data. The result showed that it was not only commendably reflected the spatial distribution of freeze injury but also reflected the sugarcane suffered from degree using the values of sugar-cane NDVIof freeze injury occur former and after. The field sample investigation data of using GPS was integrated with the NDVI, the evaluation of region sugar-cane suffer from freeze injury losing could quickly and exactly realize.

Comparative transcriptome profiling of freezing stress responses in loquat (Eriobotrya japonica) fruitlets.

PubMed

Xu, Hong-Xia; Li, Xiao-Ying; Chen, Jun-Wei

2017-09-01

Loquat (Eriobotrya japonica Lindl.) is an important subtropical, commercial fruit in China. It blossoms during autumn and winter in most areas of China and its fruitlets usually suffer from freezing stress. However, studies about the mechanisms underlying freezing stress in loquat are very limited. The gene expression profiles of loquat fruitlets subjected to freezing (G2 library) versus non-treated ones (G1 library) were investigated using Illumina sequencing technology to elucidate the molecular mechanisms and identify the genes that play vital roles in the freezing stress response. The results showed that approximately 157.63 million reads in total were obtained from freeze-treated and non-treated loquat fruitlets. These reads were assembled into 87,379 unigenes with an average length of 710 bp and an N50 of 1,200 bp. After comparing the profiles obtained from the G1 and G2 libraries, 2,892 differentially expressed genes were identified, of which 1,883 were up-regulated and 1,009 were down-regulated in the treated samples compared to non-treated ones. These unigenes showed significant differences in expression for carbohydrate transport and metabolism, amino acid metabolism, energy metabolism, and lipid metabolism, which are involved in defense against freezing stress. Glycolysis/gluconeogenesis was one of the most significantly regulated pathways. Freezing also significantly damaged the membrane system of loquat fruitlets, and several defense mechanisms were induced. Some selected genes related to low temperature resistance were validated by quantitative real-time PCR (qRT-PCR). The results revealed many genes and pathways that are part of freezing resistance processes and expand our understanding of the complex molecular events involved in freezing stress.

Infective Juveniles of the Entomopathogenic Nematode, Steinernema feltiae Produce Cryoprotectants in Response to Freezing and Cold Acclimation

PubMed Central

Ali, Farman; Wharton, David A.

2015-01-01

Steinernema feltiae is a moderately freeze-tolerant entomopathogenic nematode which survives intracellular freezing. We have detected by gas chromatography that infective juveniles of S. feltiae produce cryoprotectants in response to cold acclimation and to freezing. Since the survival of this nematode varies with temperature, we analyzed their cryoprotectant profiles under different acclimation and freezing regimes. The principal cryoprotectants detected were trehalose and glycerol with glucose being the minor component. The amount of cryoprotectants varied with the temperature and duration of exposure. Trehalose was accumulated in higher concentrations when nematodes were acclimated at 5°C for two weeks whereas glycerol level decreased from that of the non-acclimated controls. Nematodes were seeded with a small ice crystal and held at -1°C, a regime that does not produce freezing of the nematodes but their bodies lose water to the surrounding ice (cryoprotective dehydration). This increased the levels of both trehalose and glycerol, with glycerol reaching a higher concentration than trehalose. Nematodes frozen at -3°C, a regime that produces freezing of the nematodes and results in intracellular ice formation, had elevated glycerol levels while trehalose levels did not change. Steinernema feltiae thus has two strategies of cryoprotectant accumulation: one is an acclimation response to low temperature when the body fluids are in a cooled or supercooled state and the infective juveniles produce trehalose before freezing. During this process a portion of the glycerol is converted to trehalose. The second strategy is a rapid response to freezing which induces the production of glycerol but trehalose levels do not change. These low molecular weight compounds are surmised to act as cryoprotectants for this species and to play an important role in its freezing tolerance. PMID:26509788

Enzymatic Regulation of Glycogenolysis in a Subarctic Population of the Wood Frog: Implications for Extreme Freeze Tolerance

PubMed Central

do Amaral, M. Clara F.; Lee, Richard E.; Costanzo, Jon P.

2013-01-01

The wood frog, Rana sylvatica, from Interior Alaska survives freezing at –16°C, a temperature 10–13°C below that tolerated by its southern conspecifics. We investigated the hepatic freezing response in this northern phenotype to determine if its profound freeze tolerance is associated with an enhanced glucosic cryoprotectant system. Alaskan frogs had a larger liver glycogen reserve that was mobilized faster during early freezing as compared to conspecifics from a cool-temperate region (southern Ohio, USA). In Alaskan frogs the rapid glucose production in the first hours of freezing was associated with a 7-fold increase in glycogen phosphorylase activity above unfrozen frog levels, and the activity of this enzyme was higher than that of frozen Ohioan frogs. Freezing of Ohioan frogs induced a more modest (4-fold) increase in glycogen phosphorylase activity above unfrozen frog values. Relative to the Ohioan frogs, Alaskan frogs maintained a higher total protein kinase A activity throughout an experimental freezing/thawing time course, and this may have potentiated glycogenolysis during early freezing. We found populational variation in the activity and protein level of protein kinase A which suggested that the Alaskan population had a more efficient form of this enzyme. Alaskan frogs modulated their glycogenolytic response by decreasing the activity of glycogen phosphorylase after cryoprotectant mobilization was well under way, thereby conserving their hepatic glycogen reserve. Ohioan frogs, however, sustained high glycogen phosphorylase activity until early thawing and consumed nearly all their liver glycogen. These unique hepatic responses of Alaskan R. sylvatica likely contribute to this phenotype’s exceptional freeze tolerance, which is necessary for their survival in a subarctic climate. PMID:24236105

Preservation of flavor in freeze dried green beans

NASA Technical Reports Server (NTRS)

Huber, C. S.; Heidelbaugh, N. D.; Davis, D.

1973-01-01

Before freeze drying, green beans are heated to point at which their cell structure is altered. Beans freeze dried with altered cell structure have improved rehydration properties and retain color, flavor, and texture.

9 CFR 590.536 - Freezing operations.

Code of Federal Regulations, 2012 CFR

2012-01-01

..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and... outside of liquid egg containers shall be clean and free from evidence of liquid egg. (e) Frozen egg...

9 CFR 590.536 - Freezing operations.

Code of Federal Regulations, 2014 CFR

2014-01-01

..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and... outside of liquid egg containers shall be clean and free from evidence of liquid egg. (e) Frozen egg...

9 CFR 590.536 - Freezing operations.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and... outside of liquid egg containers shall be clean and free from evidence of liquid egg. (e) Frozen egg...

9 CFR 590.536 - Freezing operations.

Code of Federal Regulations, 2013 CFR

2013-01-01

..., and Facility Requirements § 590.536 Freezing operations. (a) Freezing rooms shall be kept clean and... outside of liquid egg containers shall be clean and free from evidence of liquid egg. (e) Frozen egg...

Freeze-In dark matter with displaced signatures at colliders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Co, Raymond T.; D’Eramo, Francesco; Hall, Lawrence J.

2015-12-11

Dark matter, X, may be generated by new physics at the TeV scale during an early matter-dominated (MD) era that ends at temperature T{sub R}≪ TeV. Compared to the conventional radiation-dominated (RD) results, yields from both Freeze-Out and Freeze-In processes are greatly suppressed by dilution from entropy production, making Freeze-Out less plausible while allowing successful Freeze-In with a much larger coupling strength. Freeze-In is typically dominated by the decay of a particle B of the thermal bath, B→X. For a large fraction of the relevant cosmological parameter space, the decay rate required to produce the observed dark matter abundance leadsmore » to displaced signals at LHC and future colliders, for any m{sub X} in the range keV« less

Effect of ultrasonic waves on the freezing rates of potatoes in degassed coolant and untreated coolant.

PubMed

Yu, D Y; Liu, B L

2014-01-01

Ultrasonic waves are shown to enhance the rate of freezing. To elucidate the mechanism of immersion freezing of potatos with ultrasonic waves. Ultrasound is applied to potato samples immersed in degassed coolant and untreated coolant. Sonic waves were intermittently applied at temperature below -1 degree C. The freezing rates were measured under different experimental conditions. The use of ultrasonic waves increased the freezing rates of potatoes immersed in both degassed coolant and untreated coolant. However, the freezing rate in the degassed coolant was less than that in the untreated coolant. Heat transfer on the interface between the potato sample and sonicated degassed coolant appears to be less than that within the sample in the absence of cavitation. The interface heat transfer between the potato sample and untreated coolant is likely improved due to ultrasonic cavitation.

Photomicrographic Investigation of Spontaneous Freezing Temperatures of Supercooled Water Droplets

NASA Technical Reports Server (NTRS)

Dorsch, R. G.; Hacker, P. T.

1950-01-01

A photomicrographic technique for investigating eupercooled. water droplets has been devised and. used. to determine the spontaneous freezing temperatures of eupercooled. water droplets of the size ordinarily found. in the atmosphere. The freezing temperatures of 4527 droplets ranging from 8.75 to 1000 microns in diameter supported on a platinum surface and 571 droplets supported on copper were obtained. The average spontaneous freezing temperature decreased with decrease in the size of the droplets. The effect of size on the spontaneous freezing temperature was particularly marked below 60 microns. Frequency-distribution curves of the spontaneous freezing temperatures observed for droplets of a given size were obtained. Although no droplet froze at a temperature above 20 0 F, all droplets melted at 32 F. Results obtained with a copper support did not differ essentially from those obtained with a platinum surface.

Design of freeze-drying processes for pharmaceuticals: practical advice.

PubMed

Tang, Xiaolin; Pikal, Michael J

2004-02-01

Design of freeze-drying processes is often approached with a "trial and error" experimental plan or, worse yet, the protocol used in the first laboratory run is adopted without further attempts at optimization. Consequently, commercial freeze-drying processes are often neither robust nor efficient. It is our thesis that design of an "optimized" freeze-drying process is not particularly difficult for most products, as long as some simple rules based on well-accepted scientific principles are followed. It is the purpose of this review to discuss the scientific foundations of the freeze-drying process design and then to consolidate these principles into a set of guidelines for rational process design and optimization. General advice is given concerning common stability issues with proteins, but unusual and difficult stability issues are beyond the scope of this review. Control of ice nucleation and crystallization during the freezing step is discussed, and the impact of freezing on the rest of the process and final product quality is reviewed. Representative freezing protocols are presented. The significance of the collapse temperature and the thermal transition, denoted Tg', are discussed, and procedures for the selection of the "target product temperature" for primary drying are presented. Furthermore, guidelines are given for selection of the optimal shelf temperature and chamber pressure settings required to achieve the target product temperature without thermal and/or mass transfer overload of the freeze dryer. Finally, guidelines and "rules" for optimization of secondary drying and representative secondary drying protocols are presented.

Optimum Parameters for Freeze-Drying Decellularized Arterial Scaffolds

PubMed Central

Sheridan, William S.; Duffy, Garry P.

2013-01-01

Decellularized arterial scaffolds have achieved success in advancing toward clinical use as vascular grafts. However, concerns remain regarding long-term preservation and sterilization of these scaffolds. Freeze drying offers a means of overcoming these concerns. In this study, we investigated the effects of various freeze-drying protocols on decellularized porcine carotid arteries and consequently, determined the optimum parameters to fabricate a stable, preserved scaffold with unaltered mechanical properties. Freeze drying by constant slow cooling to two final temperatures ((Tf), −10°C and −40°C) versus instant freezing was investigated by histological examination and mechanical testing. Slow cooling to Tf= −10°C produced a stiffer and less distensible response than the non freeze-dried scaffolds and resulted in disruption to the collagen fibers. The mechanical response of Tf= −40°C scaffolds demonstrated disruption to the elastin network, which was confirmed with histology. Snap freezing scaffolds in liquid nitrogen and freeze drying to Tf= −40°C with a precooled shelf at −60°C produced scaffolds with unaltered mechanical properties and a histology resembling non-freeze-dried scaffolds. The results of this study demonstrate the importance of optimizing the nucleation and ice crystal growth/size to ensure homogenous drying, preventing extracellular matrix disruption and subsequent inferior mechanical properties. This new manufacturing protocol creates the means for the preservation and sterilization of decellularized arterial scaffolds while simultaneously maintaining the mechanical properties of the tissue. PMID:23614758

Validation of the shake test for detecting freeze damage to adsorbed vaccines.

PubMed

Kartoglu, Umit; Ozgüler, Nejat Kenan; Wolfson, Lara J; Kurzatkowski, Wiesław

2010-08-01

To determine the validity of the shake test for detecting freeze damage in aluminium-based, adsorbed, freeze-sensitive vaccines. A double-blind crossover design was used to compare the performance of the shake test conducted by trained health-care workers (HCWs) with that of phase contrast microscopy as a "gold standard". A total of 475 vials of 8 different types of World Health Organization prequalified freeze-sensitive vaccines from 10 different manufacturers were used. Vaccines were kept at 5 degrees C. Selected numbers of vials from each type were then exposed to -25 degrees C and -2 degrees C for 24-hour periods. There was complete concordance between HCWs and phase-contrast microscopy in identifying freeze-damaged vials and non-frozen samples. Non-frozen samples showed a fine-grain structure under phase contrast microscopy, but freeze-damaged samples showed large conglomerates of massed precipitates with amorphous, crystalline, solid and needle-like structures. Particles in the non-frozen samples measured from 1 microm (vaccines against diphtheria-tetanus-pertussis; Haemophilus influenzae type b; hepatitis B; diphtheria-tetanus-pertussis-hepatitis B) to 20 microm (diphtheria and tetanus vaccines, alone or in combination). By contrast, aggregates in the freeze-damaged samples measured up to 700 microm (diphtheria-tetanus-pertussis) and 350 microm on average. The shake test had 100% sensitivity, 100% specificity and 100% positive predictive value in this study, which confirms its validity for detecting freeze damage to aluminium-based freeze-sensitive vaccines.

Model for heat and mass transfer in freeze-drying of pellets.

PubMed

Trelea, Ioan Cristian; Passot, Stéphanie; Marin, Michèle; Fonseca, Fernanda

2009-07-01

Lyophilizing frozen pellets, and especially spray freeze-drying, have been receiving growing interest. To design efficient and safe freeze-drying cycles, local temperature and moisture content in the product bed have to be known, but both are difficult to measure in the industry. Mathematical modeling of heat and mass transfer helps to determine local freeze-drying conditions and predict effects of operation policy, and equipment and recipe changes on drying time and product quality. Representative pellets situated at different positions in the product slab were considered. One-dimensional transfer in the slab and radial transfer in the pellets were assumed. Coupled heat and vapor transfer equations between the temperature-controlled shelf, the product bulk, the sublimation front inside the pellets, and the chamber were established and solved numerically. The model was validated based on bulk temperature measurement performed at two different locations in the product slab and on partial vapor pressure measurement in the freeze-drying chamber. Fair agreement between measured and calculated values was found. In contrast, a previously developed model for compact product layer was found inadequate in describing freeze-drying of pellets. The developed model represents a good starting basis for studying freeze-drying of pellets. It has to be further improved and validated for a variety of product types and freeze-drying conditions (shelf temperature, total chamber pressure, pellet size, slab thickness, etc.). It could be used to develop freeze-drying cycles based on product quality criteria such as local moisture content and glass transition temperature.

Freezing Nitrogen Ethanol Composite May be a Viable Approach for Cryotherapy of Human Giant Cell Tumor of Bone.

PubMed

Wu, Po-Kuei; Chen, Cheng-Fong; Wang, Jir-You; Chen, Paul Chih-Hsueh; Chang, Ming-Chau; Hung, Shih-Chieh; Chen, Wei-Ming

2017-06-01

Liquid nitrogen has been used as adjuvant cryotherapy for treating giant cell tumor (GCT) of bone. However, the liquid phase and ultrafreezing (-196° C) properties increase the risk of damage to the adjacent tissues and may lead to perioperative complications. A novel semisolid cryogen, freezing nitrogen ethanol composite, might mitigate these shortcomings because of less-extreme freezing. We therefore wished to evaluate freezing nitrogen ethanol composite as a coolant to determine its properties in tumor cryoablation. (1) Is freezing nitrogen ethanol composite-mediated freezing effective for tumor cryoablation in an ex vivo model, and if yes, is apoptosis involved in the tumor-killing mechanism? (2) Does freezing nitrogen ethanol composite treatment block neovascularization and neoplastic progression of the grafted GCTs and is it comparable to that of liquid nitrogen in an in vivo chicken model? (3) Can use of freezing nitrogen ethanol composite as an adjuvant to curettage result in successful short-term treatment, defined as absence of GCT recurrence at a minimum of 1 year in a small proof-of-concept clinical series? The cryogenic effect on bone tissue mediated by freezing nitrogen ethanol composite and liquid nitrogen was verified by thermal measurement in a time-course manner. Cryoablation on human GCT tissue was examined ex vivo for effect on morphologic features (cell shrinkage) and DNA fragmentation (apoptosis). The presumed mechanism was investigated by molecular analysis of apoptosis regulatory proteins including caspases 3, 8, and 9 and Bax/Bcl-2. Chicken chorioallantoic membrane was used as an in vivo model to evaluate the effects of freezing nitrogen ethanol composite and liquid nitrogen treatment on GCT-derived neovascularization and tumor neoplasm. A small group of patients with GCT of bone was treated by curettage and adjuvant freezing nitrogen ethanol composite cryotherapy in a proof-of-concept study. Tumor recurrence and perioperative complications were evaluated at a minimum of 19 months followup (mean, 24 months; range, 19-30 months). Freshly prepared freezing nitrogen ethanol composite froze to -136° C and achieved -122° C isotherm across a piece of 10 ± 0.50-mm-thick bone with a freezing rate of -34° C per minute, a temperature expected to meet clinical tumor-killing requirements. Human GCT tissues revealed histologic changes including shrinkage in morphologic features of multinucleated giant cells in the liquid nitrogen (202 ± 45 μm; p = 0.006) and freezing nitrogen ethanol composite groups (169 ± 27.4 μm; p < 0.001), and a decreased nucleated area of neoplastic stromal cells for the 30-second treatment. Enhanced counts of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells verified the involvement of DNA fragmentation in cryoablated GCT tissues. Western blotting analysis on the expression of apoptosis regulatory proteins showed enhancement of proteocleavage-activated caspases 3, 8, and 9 and higher ratios of Bax/Bcl2 in the liquid nitrogen- and freezing nitrogen ethanol composite-treated samples. Numbers of blood vessels and human origin tumor cells also were decreased by freezing nitrogen ethanol composite and liquid nitrogen treatment in the GCT-grafted chicken chorioallantoic membrane model. Seven patients with GCT treated by curettage and adjuvant cryotherapy by use of freezing nitrogen ethanol composite preparation had no intra- or postoperative complications related to the freezing, and no recurrences during the study surveillance period. These preliminary in vitro and clinical findings suggest that freezing nitrogen ethanol composite may be an effective cryogen showing ex vivo and in vivo tumor cryoablation comparable to liquid nitrogen. The semisolid phase and proper thermal conduction might avoid some of the disadvantages of liquid nitrogen in cryotherapy, but a larger clinical study is needed to confirm these findings. Level IV, therapeutic study.

Freeze-thaw-induced embolism in Pinus contorta: centrifuge experiments validate the 'thaw-expansion hypothesis' but conflict with ultrasonic emission data.

PubMed

Mayr, Stefan; Sperry, John S

2010-03-01

*The 'thaw-expansion hypothesis' postulates that xylem embolism is caused by the formation of gas bubbles on freezing and their expansion on thawing. We evaluated the hypothesis using centrifuge experiments and ultrasonic emission monitoring in Pinus contorta. *Stem samples were exposed to freeze-thaw cycles at varying xylem pressure (P) in a centrifuge before the percentage loss of hydraulic conductivity (PLC) was measured. Ultrasonic acoustic emissions were registered on samples exposed to freeze-thaw cycles in a temperature chamber. *Freeze-thaw exposure of samples spun at -3 MPa induced a PLC of 32% (one frost cycle) and 50% (two cycles). An increase in P to -0.5 MPa during freezing had no PLC effect, whereas increased P during thaw lowered PLC to 7%. Ultrasonic acoustic emissions were observed during freezing and thawing at -3 MPa, but not in air-dried or water-saturated samples. A decrease in minimum temperature caused additional ultrasonic acoustic emissions, but had no effect on PLC. *The centrifuge experiments indicate that the 'thaw-expansion hypothesis' correctly describes the embolization process. Possible explanations for the increase in PLC on repeated frost cycles and for the ultrasonic acoustic emissions observed during freezing and with decreasing ice temperature are discussed.

Apoptosis-like death was involved in freeze-drying-preserved fungus Mucor rouxii and can be inhibited by L-proline.

PubMed

Wang, Xiaoyun; Wang, Youzhi

2016-02-01

Freeze-drying is one of the most effective methods to preserve fungi for an extended period. However, it is associated with a loss of viability and shortened storage time in some fungi. This study evaluated the stresses that led to the death of freeze-dried Mucor rouxii by using cell apoptotic methods. The results showed there were apoptosis-inducing stresses, such as the generation of obvious intracellular reactive oxygen species (ROS) and metacaspase activation. Moreover, nuclear condensation and a delayed cell death peak were determined after rehydration and 24 h incubation in freeze-dried M. rouxii via a propidium iodide (PI) assay, which is similar to the phenomenon of cryopreservation-induced delayed-onset cell death (CIDOCD). Then, several protective agents were tested to decrease the apoptosis-inducing stresses and to improve the viability. Finally, it was found that 1.6 mM L-proline can effectively decrease the nuclear condensation rate and increase the survival rate in freeze-dried M. rouxii. (1) apoptosis-inducing factors occur in freeze-dried M. rouxii. (2) ROS and activated metacaspases lead to death in freeze-dried M. rouxii. (3)L-proline increases the survival rate of freeze-dried M. rouxii. Copyright © 2015 Elsevier Inc. All rights reserved.

Effects of annealing on the physical properties of therapeutic proteins during freeze drying process.

PubMed

Lim, Jun Yeul; Lim, Dae Gon; Kim, Ki Hyun; Park, Sang-Koo; Jeong, Seong Hoon

2018-02-01

Effects of annealing steps during the freeze drying process on etanercept, model protein, were evaluated using various analytical methods. The annealing was introduced in three different ways depending on time and temperature. Residual water contents of dried cakes varied from 2.91% to 6.39% and decreased when the annealing step was adopted, suggesting that they are directly affected by the freeze drying methods Moreover, the samples were more homogenous when annealing was adopted. Transition temperatures of the excipients (sucrose, mannitol, and glycine) were dependent on the freeze drying steps. Size exclusion chromatography showed that monomer contents were high when annealing was adopted and also they decreased less after thermal storage at 60°C. Dynamic light scattering results exhibited that annealing can be helpful in inhibiting aggregation and that thermal storage of freeze-dried samples preferably induced fragmentation over aggregation. Shift of circular dichroism spectrum and of the contents of etanercept secondary structure was observed with different freeze drying steps and thermal storage conditions. All analytical results suggest that the physicochemical properties of etanercept formulation can differ in response to different freeze drying steps and that annealing is beneficial for maintaining stability of protein and reducing the time of freeze drying process. Copyright © 2017 Elsevier B.V. All rights reserved.

Hatchling painted turtles (Chrysemys picta) survive only brief freezing of their bodily fluids.

PubMed

Attaway, M B; Packard, G C; Packard, M J

1998-07-01

Neonatal painted turtles (Chrysemys picta) spend their first winter inside the shallow, subterranean nest cavity where they completed embryogenesis. Consequently, hatchlings at high latitudes may be exposed to ice and cold during the winter. This study was undertaken to determine how long hatchlings withstand freezing at temperatures slightly below 0 degree C because tolerance for freezing has been proposed to be the key to survival by overwintering animals. A thermocouple was glued to the carapace of each hatchling. The animal was dipped in water to provide a site of nucleation of ice and was then placed into a glass jar that was partially immersed in a circulating bath at -2 degrees C. Carapace temperature was monitored throughout the procedure. When a freezing exotherm was detected, timing of the freezing event began. Animals were maintained in a frozen state for 12-48 h prior to being warmed to room temperature. Of the 39 hatchlings, 22 did not survive, and mortality increased as the duration of freezing increased. Logistic regression indicates that no turtle would have survived in a frozen state for more than 54 h. These results indicate that hatchlings can survive only brief exposure to freezing of the body fluids. Thus, hatchlings cannot tolerate freezing during prolonged periods of cold.

Metabolic Changes in Avena sativa Crowns Recovering from Freezing

PubMed Central

Henson, Cynthia A.; Duke, Stanley H.; Livingston, David P.

2014-01-01

Extensive research has been conducted on cold acclimation and freezing tolerance of fall-sown cereal plants due to their economic importance; however, little has been reported on the biochemical changes occurring over time after the freezing conditions are replaced by conditions favorable for recovery and growth such as would occur during spring. In this study, GC-MS was used to detect metabolic changes in the overwintering crown tissue of oat (Avena sativa L.) during a fourteen day time-course after freezing. Metabolomic analysis revealed increases in most amino acids, particularly proline, 5-oxoproline and arginine, which increased greatly in crowns that were frozen compared to controls and correlated very significantly with days after freezing. In contrast, sugar and sugar related metabolites were little changed by freezing, except sucrose and fructose which decreased dramatically. In frozen tissue all TCA cycle metabolites, especially citrate and malate, decreased in relation to unfrozen tissue. Alterations in some amino acid pools after freezing were similar to those observed in cold acclimation whereas most changes in sugar pools after freezing were not. These similarities and differences suggest that there are common as well as unique genetic mechanisms between these two environmental conditions that are crucial to the winter survival of plants. PMID:24675792

Simulation of the process kinetics and analysis of physicochemical properties in the freeze drying of kale

NASA Astrophysics Data System (ADS)

Dziki, Dariusz; Polak, Renata; Rudy, Stanisław; Krzykowski, Andrzej; Gawlik-Dziki, Urszula; Różyło, Renata; Miś, Antoni; Combrzyński, Maciej

2018-01-01

Investigations were performed to study the freeze-drying process of kale (Brassica oleracea L. var acephala). The process of freeze-drying was performed at temperatures of 20, 40, and 60°C for whole pieces of leaves and for pulped leaves. The kinetics of the freeze-drying of both kale leaves and kale pulp were best described by the Page model. The increasing freeze-drying temperature from 20 to 60°C induced an approximately two-fold decrease in the drying time. Freeze-drying significantly increased the value of the lightness, delta Chroma, and browning index of kale, and had little influence on the hue angle. The highest increase in the lightness and delta Chroma was observed for whole leaves freeze-dried at 20°C. An increase in the drying temperature brought about a slight decrease in the lightness, delta Chroma and the total colour difference. Pulping decreased the lightness and hue angle, and increased browning index. Freeze-drying engendered a slight decrease in the total phenolics content and antioxidant activity, in comparison to fresh leaves. The temperature of the process and pulping had little influence on the total phenolics content and antioxidant activity of dried kale, but significantly decreased the contents of chlorophyll a and chlorophyll b.

Characterization of Propylene Glycol-Mitigated Freeze/Thaw Agglomeration of a Frozen Liquid nOMV Vaccine Formulation by Static Light Scattering and Micro-Flow Imaging.

PubMed

Mensch, Christopher D; Davis, Harrison B; Blue, Jeffrey T

2015-01-01

The purpose of this work was to investigate the susceptibility of an aluminum adjuvant and an aluminum-adjuvanted native outer membrane vesicle (nOMV) vaccine formulation to freeze/thaw-induced agglomeration using static light scattering and micro-flow Imaging analysis; and to evaluate the use of propylene glycol as a vaccine formulation excipient by which freeze/thaw-induced agglomeration of a nOMV vaccine formulation could be mitigated. Our results indicate that including 7% v/v propylene glycol in an nOMV containing aluminum adjuvanted vaccine formulation, mitigates freeze/thaw-induced agglomeration. We evaluated the effect of freeze-thawing on an aluminum adjuvant and an aluminum adjuvanted native outer membrane vesicle (nOMV) vaccine formulation. Specifically, we characterized the freeze/thaw-induced agglomeration through the use of static light scattering, micro-flow imaging, and cryo-electron microscopy analysis. Further, we evaluated the use of 0-9% v/v propylene glycol as an excipient which could be included in the formulation for the purpose of mitigating the agglomeration induced by freeze/thaw. The results indicate that using 7% v/v propylene glycol as a formulation excipient is effective at mitigating agglomeration of the nOMV vaccine formulation, otherwise induced by freeze-thawing. © PDA, Inc. 2015.

Effect of Novel Quick Freezing Techniques Combined with Different Thawing Processes on Beef Quality

PubMed Central

Yoo, Seon-Mi; Han, Gui-Jung

2014-01-01

This study investigated the effect of various freezing and thawing techniques on the quality of beef. Meat samples were frozen using natural convection freezing (NF), individual quick freezing (IQF), or cryogenic freezing (CF) techniques, followed by natural convection thawing (NCT) or running water thawing (RT). The meat was frozen until the core temperature reached -12℃ and then stored at -24℃, followed by thawing until the temperature reached 5℃. Quality parameters, such as the pH, water binding properties, CIE color, shear force, and microstructure of the beef were elucidated. Although the freezing and thawing combinations did not cause remarkable changes in the quality parameters, rapid freezing, in the order of CF, IQF, and NF, was found to minimize the quality deterioration. In the case of thawing methods, NCT was better than RT and the meat quality was influence on the thawing temperature rather than the thawing rate. Although the microstructure of the frozen beef exhibited an excessive loss of integrity after the freezing and thawing, it did not cause any remarkable change in the beef quality. Taken together, these results demonstrate that CF and NCT form the best combination for beef processing; however, IQF and NCT may have practical applications in the frozen food industry. PMID:26761674

Monitoring of Freezing Dynamics in Trees: A Simple Phase Shift Causes Complexity1[OPEN

PubMed Central

Charra-Vaskou, Katline

2017-01-01

During winter, trees have to cope with harsh conditions, including extreme freeze-thaw stress. This study focused on ice nucleation and propagation, related water shifts and xylem cavitation, as well as cell damage and was based on in situ monitoring of xylem (thermocouples) and surface temperatures (infrared imaging), ultrasonic emissions, and dendrometer analysis. Field experiments during late winter on Picea abies growing at the alpine timberline revealed three distinct freezing patterns: (1) from the top of the tree toward the base, (2) from thin branches toward the main stem’s top and base, and (3) from the base toward the top. Infrared imaging showed freezing within branches from their base toward distal parts. Such complex freezing causes dynamic and heterogenous patterns in water potential and probably in cavitation. This study highlights the interaction between environmental conditions upon freezing and thawing and demonstrates the enormous complexity of freezing processes in trees. Diameter shrinkage, which indicated water fluxes within the stem, and acoustic emission analysis, which indicated cavitation events near the ice front upon freezing, were both related to minimum temperature and, upon thawing, related to vapor pressure deficit and soil temperature. These complex patterns, emphasizing the common mechanisms between frost and drought stress, shed new light on winter tree physiology. PMID:28242655

Folic acid content in thermostabilized and freeze-dried space shuttle foods

NASA Technical Reports Server (NTRS)

Lane, H. W.; Nillen, J. L.; Kloeris, V. L.

1995-01-01

This study was designed to determine whether freeze-dried and thermostabilized foods on a space shuttle contain adequate folate and to investigate any effects of freeze-drying on folacin. Frozen vegetables were analyzed after three states of processing: thawed; cooked; and rehydrated. Thermostabilized items were analyzed as supplied with no further processing. Measurable folate decreased in some freeze-dried vegetables and increased in others. Folacin content of thermostabilized food items was comparable with published values. We concluded that although the folacin content of some freeze-dried foods was low, adequate folate is available from the shuttle menu to meet RDA guidelines.

Survival differences among freeze-dried genetically engineered and wild-type bacteria.

PubMed Central

Israeli, E; Shaffer, B T; Hoyt, J A; Lighthart, B; Ganio, L M

1993-01-01

Because the death mechanisms of freeze-dried and air-dried bacteria are thought to be similar, freeze-drying was used to investigate the survival differences between potentially airborne genetically engineered microorganisms and their wild types. To this end, engineered strains of Escherichia coli and Pseudomonas syringae were freeze-dried and exposed to air, visible light, or both. The death rates of all engineered strains were significantly higher than those of their parental strains. Light and air exposure were found to increase the death rates of all strains. Application of death rate models to freeze-dried engineered bacteria to be released into the environment is discussed. PMID:8434925

The effect of variety and maturity on the quality of freeze-dried carrots. The effect of microwave blanching on the nutritional and textural quality of freeze-dried spinach

NASA Technical Reports Server (NTRS)

1979-01-01

Using carrots, the quality of freeze-dried products was studied to determine the optimum varieties and maturation stages for quality attributes such as appearance, flavor, texture, and nutritive value. The quality of freeze-dried carrots is discussed in terms of Gardner color, alcohol insoluble solids, viscosity, and core/cortex ratio. Also, microwave blanching of freeze-dried spinach was studied to determine vitamin interrelationships, anatomical changes, and oxidative deteriorations in terms of preprocessing microwave treatments. Statistical methods were employed in the gathering of data and interpretation of results in both studies.

Topological Spin Glass in Diluted Spin Ice

NASA Astrophysics Data System (ADS)

Sen, Arnab; Moessner, R.

2015-06-01

It is a salient experimental fact that a large fraction of candidate spin liquid materials freeze as the temperature is lowered. The question naturally arises whether such freezing is intrinsic to the spin liquid ("disorder-free glassiness") or extrinsic, in the sense that a topological phase simply coexists with standard freezing of impurities. Here, we demonstrate a surprising third alternative, namely, that freezing and topological liquidity are inseparably linked. The topological phase reacts to the introduction of disorder by generating degrees of freedom of a new type (along with interactions between them), which in turn undergo a freezing transition while the topological phase supporting them remains intact.

Topological Spin Glass in Diluted Spin Ice.

PubMed

Sen, Arnab; Moessner, R

2015-06-19

It is a salient experimental fact that a large fraction of candidate spin liquid materials freeze as the temperature is lowered. The question naturally arises whether such freezing is intrinsic to the spin liquid ("disorder-free glassiness") or extrinsic, in the sense that a topological phase simply coexists with standard freezing of impurities. Here, we demonstrate a surprising third alternative, namely, that freezing and topological liquidity are inseparably linked. The topological phase reacts to the introduction of disorder by generating degrees of freedom of a new type (along with interactions between them), which in turn undergo a freezing transition while the topological phase supporting them remains intact.

A whole-plant screening test to identify genotypes with superior freezing tolerance.

PubMed

Bertrand, Annick; Castonguay, Yves; Bourassa, Josée

2014-01-01

Freezing tolerance is a determinant factor of persistence of perennials grown in northern climate. Selection for winterhardiness in field nurseries is difficult because of the unpredictability of occurrence of test winters allowing the identification of hardy genotypes. Here we describe a whole-plant assay entirely performed indoor in growth chambers and walk-in freezers to identify genotypes with superior tolerance to freezing within populations of open pollinated species. Three successive freezing stresses are applied to progressively eliminate 90 % of the population and to retain only the 10 % best performing genotypes. This approach can be used to generate recurrently selected populations more tolerant to freezing in different species.

Breeding of Freeze-tolerant Yeast and the Mechanisms of Stress-tolerance

NASA Astrophysics Data System (ADS)

Hino, Akihiro

Frozen dough method have been adopted in the baking industry to reduce labor and to produce fresh breads in stores. New freeze-tolerant yeasts for frozen dough preparations were isolated from banana peel and identified. To obtain strains that have fermentative ability even after several months of frozen storage in fermented dough, we attempted to breed new freeze-tolerantstrain. The hybrid between S.cerevisiae, which is a isolated freeze-tolerant strain, and a strain isolated from bakers' yeast with sexual conjugation gave a good quality bread made from frozen dough method. Freeze-tolerant strains showed higher surviving and trehalose accumulating abilities than freeze-sensitive strains. The freeze tolerance of the yeasts was associated with the basal amount of intracellular trehalose after rapid degradation at the onset of the prefermentation period. The complicated metabolic pathway and the regulation system of trehalose in yeast cells are introduced. The trehalose synthesis may act as a metabolic buffer system which contribute to maintain the intracellular inorganic phosphate and as a feedback regulation system in the glycolysis. However, it is not known enough how the trehalose protects yeast cells from stress.

Freezing Directed Construction of Bio/Nano Interfaces: Reagentless Conjugation, Denser Spherical Nucleic Acids, and Better Nanoflares.

PubMed

Liu, Biwu; Liu, Juewen

2017-07-19

While nanoparticle solutions cannot freeze in general, they may remain stable in the presence of polymer stabilizers. We herein communicate that gold nanoparticles (AuNPs) are stable in the presence of thiolated DNA after a freeze-thaw cycle. The DNA is conjugated to AuNPs during freezing without additional reagents and the conjugation can be completed in a few minutes. More importantly, the DNA density is 20-30% higher than that prepared by the typical salt-aging method. By lowering temperature, DNA hybridization is also promoted, allowing the construction of better nanoflares with doubled probe density and signaling sensitivity. This freezing method works for AuNPs from 5 to 100 nm and all tested DNA sequences. The mechanism was studied by separating the effect of temperature, freezing and thawing, where the exclusion of salt and AuNPs by the growing ice crystals is deemed critical. In addition to developing a simple method, this study articulates unique physical processes during freezing with important fundamental surface science implications, and it could be extended to other systems.

Experimental realization of self-guided quantum coherence freezing

NASA Astrophysics Data System (ADS)

Yu, Shang; Wang, Yi-Tao; Ke, Zhi-Jin; Liu, Wei; Zhang, Wen-Hao; Chen, Geng; Tang, Jian-Shun; Li, Chuan-Feng; Guo, Guang-Can

2017-12-01

Quantum coherence is the most essential characteristic of quantum physics, specifcially, when it is subject to the resource-theoretical framework, it is considered as the most fundamental resource for quantum techniques. Other quantum resources, e.g., entanglement, are all based on coherence. Therefore, it becomes urgently important to learn how to preserve coherence in quantum channels. The best preservation is coherence freezing, which has been studied recently. However, in these studies, the freezing condition is theoretically calculated, and there still lacks a practical way to achieve this freezing; in addition the channels are usually fixed, but actually, there are also degrees of freedom that can be used to adapt the channels to quantum states. Here we develop a self-guided quantum coherence freezing method, which can guide either the quantum channels (tunable-channel scheme with upgraded channels) or the initial state (fixed-channel scheme) to the coherence-freezing zone from any starting estimate. Specifically, in the fixed-channel scheme, the final-iterative quantum states all satisfy the previously calculated freezing condition. This coincidence demonstrates the validity of our method. Our work will be helpful for the better protection of quantum coherence.

Effects of high pressure freezing (HPF) on denaturation of natural actomyosin extracted from prawn (Metapenaeus ensis).

PubMed

Cheng, Lina; Sun, Da-Wen; Zhu, Zhiwei; Zhang, Zhihang

2017-08-15

Effects of protein denaturation caused by high pressure freezing, involving Pressure-Factors (pressure, time) and Freezing-Factors (temperature, phase transition, recrystallization, ice crystal types), are complicated. In the current study, the conformation and functional changes of natural actomyosin (NAM) under pressure assisted freezing (PAF, 100,150,300,400,500MPa P -20°C/25min ), pressure shift freezing (PSF, 200MPa P -20°C/25min ), and immersion freezing ( 0.1MPa P -20°C/5min ) after pressure was released to 0.1MPa, as compared to normal immersion freezing process (IF, 0.1MPa P -20°C/30min ). Results indicated that PSF ( 200MPa P -20°C/30min ) could reduce the denaturation of frozen NAM and a pressure of 300MPa was the critical point to induce such a denaturation. During the periods of B→D in PSF or B→C→D in PAF, the generation and growth of ice crystals played an important role on changing the secondary and tertiary structure of the treated NAM. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of ultrasound-assisted freezing on the physico-chemical properties and volatile compounds of red radish.

PubMed

Xu, Bao-Guo; Zhang, Min; Bhandari, Bhesh; Cheng, Xin-Feng; Islam, Md Nahidul

2015-11-01

Power ultrasound, which can enhance nucleation rate and crystal growth rate, can also affect the physico-chemical properties of immersion frozen products. In this study, the influence of slow freezing (SF), immersion freezing (IF) and ultrasound-assisted freezing (UAF) on physico-chemical properties and volatile compounds of red radish was investigated. Results showed that ultrasound application significantly improved the freezing rate; the freezing time of ultrasound application at 0.26 W/cm(2) was shorten by 14% and 90%, compared to IF and SF, respectively. UAF products showed significant (p<0.05) reduction in drip loss and phytonutrients (anthocyanins, vitamin C and phenolics) loss. Compared to SF products, IF and UAF products showed better textural preservation and higher calcium content. The radish tissues exhibited better cellular structures under ultrasonic power intensities of 0.17 and 0.26 W/cm(2) with less cell separation and disruption. Volatile compound data revealed that radish aromatic profile was also affected in the freezing process. Copyright © 2015 Elsevier B.V. All rights reserved.

A comparative study of sodium dodecyl sulfate and freezing/thawing treatment on wheat starch: The role of water absorption.

PubMed

Tao, Han; Wang, Pei; Zhang, Bao; Wu, Fengfeng; Jin, Zhengyu; Xu, Xueming

2016-06-05

The effect of freezing on functionality of native and sodium dodecyl sulfate (SDS)-treated wheat starches was investigated, with the aim of understanding the role of water absorption during freezing process. SDS is one of most efficient detergents to remove non-starch components (such as proteins and lipids) for starches but does not cause any apparent damage on granular structure. Slow swelling could be converted to rapid swelling by SDS washing, indicating higher water absorption. Freezing process induced slight roughness on starch granules but the non-starch components content was little affected. Combined SDS+freezing treatment significantly decreased both amylose and proteins non-starch components contents, which was accompanied with high gelatinization temperatures, melting enthalpy, and pasting viscosities. A smaller bread specific volume was obtained from SDS+freezing-treated starches while the crumb firmness significantly increased (p<0.05). SDS mainly extracted the surface components from starch granules, leading to high water absorption and making granules sensitive to the freezing treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

A Vivens Ex Vivo Study on the Synergistic Effect of Electrolysis and Freezing on the Cell Nucleus

PubMed Central

Lugnani, Franco; Zanconati, Fabrizio; Marcuzzo, Thomas; Bottin, Cristina; Mikus, Paul; Guenther, Enric; Klein, Nina; Rubinsky, Liel; Stehling, Michael K.; Rubinsky, Boris

2015-01-01

Freezing—cryosurgery, and electrolysis—electrochemical therapy (EChT), are two important minimally invasive surgery tissue ablation technologies. Despite major advantages they also have some disadvantages. Cryosurgery cannot induce cell death at high subzero freezing temperatures and requires multiple freeze thaw cycles, while EChT requires high concentrations of electrolytic products—which makes it a lengthy procedure. Based on the observation that freezing increases the concentration of solutes (including products of electrolysis) in the frozen region and permeabilizes the cell membrane to these products, this study examines the hypothesis that there could be a synergistic effect between freezing and electrolysis in their use together for tissue ablation. Using an animal model we refer to as vivens ex vivo, which may be of value in reducing the use of animals for experiments, combined with a Hematoxylin stain of the nucleus, we show that there are clinically relevant protocols in which the cell nucleus appears intact when electrolysis and freezing are used separately but is affected by certain combinations of electrolysis and freezing. PMID:26695185

Fundamental technical elements of freeze-fracture/freeze-etch in biological electron microscopy.

PubMed

Carson, Johnny L

2014-09-11

Freeze-fracture/freeze-etch describes a process whereby specimens, typically biological or nanomaterial in nature, are frozen, fractured, and replicated to generate a carbon/platinum "cast" intended for examination by transmission electron microscopy. Specimens are subjected to ultrarapid freezing rates, often in the presence of cryoprotective agents to limit ice crystal formation, with subsequent fracturing of the specimen at liquid nitrogen cooled temperatures under high vacuum. The resultant fractured surface is replicated and stabilized by evaporation of carbon and platinum from an angle that confers surface three-dimensional detail to the cast. This technique has proved particularly enlightening for the investigation of cell membranes and their specializations and has contributed considerably to the understanding of cellular form to related cell function. In this report, we survey the instrument requirements and technical protocol for performing freeze-fracture, the associated nomenclature and characteristics of fracture planes, variations on the conventional procedure, and criteria for interpretation of freeze-fracture images. This technique has been widely used for ultrastructural investigation in many areas of cell biology and holds promise as an emerging imaging technique for molecular, nanotechnology, and materials science studies.

Potential weathering by freeze-thaw action in alpine rocks in the European Alps during a nine year monitoring period

NASA Astrophysics Data System (ADS)

Kellerer-Pirklbauer, Andreas

2017-11-01

A quantification of rock weathering by freeze-thaw processes in alpine rocks requires at least rock temperature data in high temporal resolution, in high quality, and over a sufficient period of time. In this study up to nine years of rock temperature data (2006-2015) from eleven rock monitoring sites in two of the highest mountain ranges of Austria were analyzed. Data were recorded at a half-hourly or hourly logging interval and at rock depths of 3, 10, and 30-40 cm. These data have been used to quantify mean conditions, ranges, and relationships of the potential near-surface weathering by freeze-thaw action considering volumetric-expansion of ice and ice segregation. For the former, freeze-thaw cycles and effective freeze-thaw cycles for frost shattering have been considered. For the latter, the intensity and duration of freezing events as well as time within the 'frost cracking window' have been analyzed. Results show that the eleven sites are in rather extreme topoclimatic positions and hence represent some of the highest and coolest parts of Austria and therefore the Eastern Alps. Only four sites are presumably affected by permafrost. Most sites are influenced by a long-lasting seasonal snow cover. Freeze-thaw cycles and effective freeze-thaw cycles for frost shattering are mainly affecting the near-surface and are unimportant at few tens of centimeters below the rock surface. The lowest temperatures during freezing events and the shortest freezing events have been quantified at all eleven monitoring sites very close to the surface. The time within the frost cracking window decreases in most cases from the rock surface inwards apart from very cold years/sites with very low temperatures close to the surface. As shown by this study and predicted climate change scenarios, assumed warmer rock temperature conditions in the future at alpine rock walls in Austria will lead to less severe freezing events and to shorter time periods within the frost-cracking window. Statistical correlation analyses showed furthermore that the longer the duration of the seasonal snow cover, the fewer are freeze-thaw cycles, the fewer are effective freeze-thaw cycles, the longer is the mean and the maximum duration of freezing events, and the lower is the mean annual ground temperature. The interaction of the winter snow cover history and the winter thermal regime has a complex effect on the duration of the frost cracking window but also on the number of freeze-thaw cycles as shown by a conceptual model. Predicted future warmer and snow-depleted winters in the European Alps will therefore have a complex impact on the potential weathering of alpine rocks by frost action which makes potential weathering predictions difficult. Neglecting rock moisture and rock properties in determining rock weathering limits the usefulness of solely rock temperature data. However, rock temperature data allow getting an estimate about potential weathering by freeze-thaw action which is often substantially more than previously known.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, M.F.

A freeze-thaw power cycle is described that includes a piston driven by the expansion power of a fluid such as water in a cyclinder on freezing and the thawing thereof with alternate, rapid freezing and thawing of the fluid by low and high temperature means with heat transfer rates facilitated by the use of heat pipes or tubes or other conductor means to produce a continuous single or multi cyclinder quick, polution free and noiseless freeze/thaw power cycle.

References on Compression of Freeze-Dried Foods

DTIC Science & Technology

1978-08-01

ready-to-eat, freeze-dried scrambled egg . Swift and Co., Contract No. DA 19- 129-AMC-121. 67-49-FD (FD-54). January 1967 (AD 650637). In the design...significantly poorer in organoleptic properties than from grades A and B eggs. Freeze- dried scrambled egg packed in cans kept better in storage than when...scrambled, cooked, freeze-dried whole egg product was developed which possessed the appearance, aroma, flavor and texture similar to pan- fried scrambled

Method of quantifying the loss of acidification activity of lactic acid starters during freezing and frozen storage.

PubMed

Fonseca, F; Béal, C; Corrieu, G

2000-02-01

We have developed a method to quantify the resistance to freezing and frozen storage of lactic acid starters, based on measuring the time necessary to reach the maximum acidification rate in milk (tm) using the Cinac system. Depending on the operating conditions, tm increased during the freezing step and storage. The loss of acidification activity during freezing was quantified by the difference (delta tm) between the tm values of the concentrated cell suspension before and after freezing. During storage at -20 degrees C, linear relationships between tm and the storage time were established. Their slope, k, allowed the quantitation of the decrease in acidification activity during 9-14 weeks of frozen storage. The method was applied to determine the resistance to freezing and frozen storage of four strains of lactic acid bacteria and to quantify the cryoprotective effect of glycerol.

Influence of freezing down to 77.15 K on structure and antioxidant power of some proteins

NASA Astrophysics Data System (ADS)

Rozanova, S. L.; Narozhnyi, S. V.; Nardid, O. A.

2017-06-01

The purpose of the present work was to investigate influence of different freeze-thawing protocols on structure and antioxidant properties of isolated proteins. In our experiments we have studied human serum albumin, human hemoglobin and cytochrome C derived from equine heart frozen down to 77.15 K with 1-2 deg/min and 300 deg/min rate with following thawing on a water bath at 293.15 K. Native proteins were assumed as a control. Influence of freeze-thawing protocols on protein structure was investigated using spectrophotometric and fluorescent assays. Antioxidant activities of isolated proteins were estimated by their ability to reduce ABTS+ radical. It has been established that unfolding derived from freeze-thawing exposure leads to protein antioxidant activity increasing while decreasing of such an activity may be connected with macromolecule aggregation. Character of freeze-thawing influence on antioxidant activity of proteins depends on molecule structure peculiarities and freezing protocols.

Morphology of supercooled droplets freezing on solid surfaces

NASA Astrophysics Data System (ADS)

La, Shiren; Huang, Zhiting; Liu, Cong; Zhang, Xingyi

2018-05-01

Supercooled droplets freezing on solid surfaces are ubiquitous in nature. This letter investigates the influences of droplet viscosity on freezing velocity and frosting formation. Several experiments were conducted for three kinds of sessile droplets (water, silicone oil and oil) on two types of substrates (copper and iron) with different surface roughness at various temperatures. The results show that the water droplets exhibit obvious phase transition lines and their freezing speeds increase when the temperature of substrates decreases. It is found that the freezing speed is independent of the thermal conductivities of the substrates. Notably, the water droplets develop prominent bulges after freezing and subsequently nucleate to frost. In contrast, the high viscosity oil and silicone oil do not manifest an obvious phase transition line. Besides, no bulges are observed in these two kinds of droplets, suggesting that these frosting forms are of different mechanisms compared with water droplets.

Natural genetic variation of freezing tolerance in Arabidopsis.

PubMed

Hannah, Matthew A; Wiese, Dana; Freund, Susanne; Fiehn, Oliver; Heyer, Arnd G; Hincha, Dirk K

2006-09-01

Low temperature is a primary determinant of plant growth and survival. Using accessions of Arabidopsis (Arabidopsis thaliana) originating from Scandinavia to the Cape Verde Islands, we show that freezing tolerance of natural accessions correlates with habitat winter temperatures, identifying low temperature as an important selective pressure for Arabidopsis. Combined metabolite and transcript profiling show that during cold exposure, global changes of transcripts, but not of metabolites, correlate with the ability of Arabidopsis to cold acclimate. There are, however, metabolites and transcripts, including several transcription factors, that correlate with freezing tolerance, indicating regulatory pathways that may be of primary importance for this trait. These data identify that enhanced freezing tolerance is associated with the down-regulation of photosynthesis and hormonal responses and the induction of flavonoid metabolism, provide evidence for naturally increased nonacclimated freezing tolerance due to the constitutive activation of the C-repeat binding factors pathway, and identify candidate transcriptional regulators that correlate with freezing tolerance.

The effect of freeze-thawing on magnetic resonance imaging T2* of freshly harvested bovine patellar tendon

PubMed Central

Pownder, Sarah L.; Shah, Parina H.; Potter, Hollis G.

2015-01-01

Background Analysis of fresh specimens in research studies is ideal; however, it is often necessary to freeze samples for evaluation at a later time. Limited evaluation of the effect of freeze-thawing of tendon tissue samples on inherent magnetic resonance imaging (MRI) parameters, such as ultrashort echo time (UTE) T2* values, have been performed to date. Methods This study performed UTE MRI on 14 bovine patellar tendons at harvest and after four consecutive freeze-thaw cycles. Results Results demonstrated a small but significant reduction (12%) in tendon T2* values after the first freeze thaw cycle, but not after successive cycles. Tendons from juvenile animals with open physis had a significant reduction of T2* following a single freeze thaw cycle, P<0.0001. Conclusions The results of this study emphasize the importance of using uniform tendon storage protocols when using UTE MRI in preclinical models. PMID:26029639

Limited Impact of Subglacial Supercooling Freeze-on for Greenland Ice Sheet Stratigraphy

NASA Astrophysics Data System (ADS)

Dow, Christine F.; Karlsson, Nanna B.; Werder, Mauro A.

2018-02-01

Large units of disrupted radiostratigraphy (UDR) are visible in many radio-echo sounding data sets from the Greenland Ice Sheet. This study investigates whether supercooling freeze-on rates at the bed can cause the observed UDR. We use a subglacial hydrology model to calculate both freezing and melting rates at the base of the ice sheet in a distributed sheet and within basal channels. We find that while supercooling freeze-on is a phenomenon that occurs in many areas of the ice sheet, there is no discernible correlation with the occurrence of UDR. The supercooling freeze-on rates are so low that it would require tens of thousands of years with minimal downstream ice motion to form the hundreds of meters of disrupted radiostratigraphy. Overall, the melt rates at the base of the ice sheet greatly overwhelm the freeze-on rates, which has implications for mass balance calculations of Greenland ice.

Realization of the Temperature Scale in the Range from 234.3 K (Hg Triple Point) to 1084.62°C (Cu Freezing Point) in Croatia

NASA Astrophysics Data System (ADS)

Zvizdic, Davor; Veliki, Tomislav; Grgec Bermanec, Lovorka

2008-06-01

This article describes the realization of the International Temperature Scale in the range from 234.3 K (mercury triple point) to 1084.62°C (copper freezing point) at the Laboratory for Process Measurement (LPM), Faculty of Mechanical Engineering and Naval Architecture (FSB), University of Zagreb. The system for the realization of the ITS-90 consists of the sealed fixed-point cells (mercury triple point, water triple point and gallium melting point) and the apparatus designed for the optimal realization of open fixed-point cells which include the gallium melting point, tin freezing point, zinc freezing point, aluminum freezing point, and copper freezing point. The maintenance of the open fixed-point cells is described, including the system for filling the cells with pure argon and for maintaining the pressure during the realization.

The principles of ultrasound and its application in freezing related processes of food materials: A review.

PubMed

Cheng, Xinfeng; Zhang, Min; Xu, Baoguo; Adhikari, Benu; Sun, Jincai

2015-11-01

Ultrasonic processing is a novel and promising technology in food industry. The propagation of ultrasound in a medium generates various physical and chemical effects and these effects have been harnessed to improve the efficiency of various food processing operations. Ultrasound has also been used in food quality control as diagnostic technology. This article provides an overview of recent developments related to the application of ultrasound in low temperature and closely related processes such as freezing, thawing, freeze concentration and freeze drying. The applications of high intensity ultrasound to improve the efficiency of freezing process, to control the size and size distribution of ice crystals and to improve the quality of frozen foods have been discussed in considerable detail. The use of low intensity ultrasound in monitoring the ice content and to monitor the progress of freezing process has also been highlighted. Copyright © 2015 Elsevier B.V. All rights reserved.

Freeze-drying process design by manometric temperature measurement: design of a smart freeze-dryer.

PubMed

Tang, Xiaolin Charlie; Nail, Steven L; Pikal, Michael J

2005-04-01

To develop a procedure based on manometric temperature measurement (MTM) and an expert system for good practices in freeze drying that will allow development of an optimized freeze-drying process during a single laboratory freeze-drying experiment. Freeze drying was performed with a FTS Dura-Stop/Dura-Top freeze dryer with the manometric temperature measurement software installed. Five percent solutions of glycine, sucrose, or mannitol with 2 ml to 4 ml fill in 5 ml vials were used, with all vials loaded on one shelf. Details of freezing, optimization of chamber pressure, target product temperature, and some aspects of secondary drying are determined by the expert system algorithms. MTM measurements were used to select the optimum shelf temperature, to determine drying end points, and to evaluate residual moisture content in real-time. MTM measurements were made at 1 hour or half-hour intervals during primary drying and secondary drying, with a data collection frequency of 4 points per second. The improved MTM equations were fit to pressure-time data generated by the MTM procedure using Microcal Origin software to obtain product temperature and dry layer resistance. Using heat and mass transfer theory, the MTM results were used to evaluate mass and heat transfer rates and to estimate the shelf temperature required to maintain the target product temperature. MTM product dry layer resistance is accurate until about two-thirds of total primary drying time is over, and the MTM product temperature is normally accurate almost to the end of primary drying provided that effective thermal shielding is used in the freeze-drying process. The primary drying times can be accurately estimated from mass transfer rates calculated very early in the run, and we find the target product temperature can be achieved and maintained with only a few adjustments of shelf temperature. The freeze-dryer overload conditions can be estimated by calculation of heat/mass flow at the target product temperature. It was found that the MTM results serve as an excellent indicator of the end point of primary drying. Further, we find that the rate of water desorption during secondary drying may be accurately measured by a variation of the basic MTM procedure. Thus, both the end point of secondary drying and real-time residual moisture may be obtained during secondary drying. Manometric temperature measurement and the expert system for good practices in freeze drying does allow development of an optimized freeze-drying process during a single laboratory freeze-drying experiment.

Freezing-induced deformation of biomaterials in cryomedicine

NASA Astrophysics Data System (ADS)

Ozcelikkale, Altug

Cryomedicine utilizes low temperature treatments of biological proteins, cells and tissues for cryopreservation, materials processing and cryotherapy. Lack of proper understanding of cryodamage that occurs during these applications remains to be the primary bottleneck for development of successful tissue cryopreservation and cryosurgery procedures. An engineering approach based on a view of biological systems as functional biomaterials can help identify, predict and control the primary cryodamage mechanisms by developing an understanding of underlying freezing-induced biophysical processes. In particular, freezing constitutes the main structural/mechanical origin of cryodamage and results in significant deformation of biomaterials at multiple length scales. Understanding of these freezing-induced deformation processes and their effects on post-thaw biomaterial functionality is currently lacking but will be critical to engineer improved cryomedicine procedures. This dissertation addresses this problem by presenting three separate but related studies of freezing-induced deformation at multiple length scales including nanometer-scale protein fibrils, single cells and whole tissues. A combination of rigorous experimentation and computational modeling is used to characterize post-thaw biomaterial structure and properties, predict biomaterial behavior and assess its post-thaw biological functionality. Firstly, freezing-induced damage on hierarchical extracellular matrix structure of collagen is investigated at molecular, fibril and matrix levels. Results indicate to a specific kind of fibril damage due to freezing-induced expansion of intrafibrillar fluid. This is followed by a study of freezing-induced cell and tissue deformation coupled to osmotically driven cellular water transport. Computational and semi empirical modeling of these processes indicate that intracellular deformation of the cell during freezing is heterogeneous and can interfere with cellular water transport, thereby leading to previously unconsidered mechanisms of cell freezing response. In addition, cellular water transport is identified as the critical limiting factor on the amount of freezing-induced tissue deformation, particularly in native tissues with high cell densities. Finally, effects of cryopreservation on post-thaw biological functionality of collagen engineered tissue constructs is investigated where cell-matrix interactions during fibroblast migration are considered as the functional response. Simultaneous cell migration and extracellular matrix deformation are characterized. Results show diminished cell-matrix coupling by freeze/thaw accompanied by a subtle decrease in cell migration. A connection between these results and freezing-induced collagen fibril damage is also suggested. Overall, this dissertation provides new fundamental knowledge on cryodamage mechanisms and a collection of novel multi-purpose engineering tools that will open the way for rational design of cryomedicine technologies.

An Equipment to Measure the Freezing Point of Soils under Higher Pressure

NASA Astrophysics Data System (ADS)

Wang, Dayan; Guan, Hui; Wen, Zhi; Ma, Wei

2014-05-01

Soil freezing point is the highest temperature at which ice can be presented in the system and soil can be referred to as frozen. The freezing temperature of soil is an important parameter for solving many practical problems in civil engineering, such as evaluation of soil freezing depth, prediction of soil heaving, force of soil suction, etc. However, as the freezing temperature is always affected by many factors like soil particle size, mineral composition, water content and the external pressure endured by soils, to measure soil freezing point is a rather difficult task until now, not to mention the soil suffering higher pressure. But recently, with the artificial freezing technology widely used in the excavation of deep underground space, the frozen wall thickness is a key factor to impact the security and stability of deep frozen wall. To determine the freeze wall thickness, the location of the freezing front must be determined firstly, which will deal with the determination of the soil freezing temperature. So how to measure the freezing temperature of soil suffering higher pressure is an important problem to be solved. This paper will introduce an equipment which was developed lately by State Key Laboratory of Frozen Soil Engineering to measure the freezing-point of soils under higher pressure. The equipment is consisted of cooling and keeping temperature system, temperature sensor and data collection system. By cooling and keeping temperature system, not only can we make the higher pressure soil sample's temperature drop to a discretionary minus temperature, but also keep it and reduce the heat exchange of soil sample with the outside. The temperature sensor is the key part to our measurement, which is featured by high precision and high sensitivity, what is more important is that the temperature sensor can work in a higher pressure condition. Moreover, the major benefit of this equipment is that the soil specimen's loads can be loaded by any microcomputer control electron universal testing machines. All of above mentioned advantages of this equipment ensures one to catch up the moment soil turns from the thawed state into ice and enable one to determine the freezing point experimentally by recording the temperature-time history (cooling curve) at particular points within the sample used for analysis. Therefore, this equipment has excellent characteristics such as compact construction, convenient operation, high reliability and the measuring accuracy. The authors would like to thank the following agents for their financial supports: the National Natural Science Foundation (No.41071048),Hundred Talent Young Scientists program of the Chinese Academy of Sciences granted to Dr. Zhi Wen.

Evaluation of a New Motion-correction Algorithm Using On-rigid Registration in Respiratory-gated PET/CT Images of Liver Tumors.

PubMed

Wagatsuma, Kei; Osawa, Tatsufumi; Yokokawa, Naoki; Miwa, Kenta; Oda, Keiichi; Kudo, Yoshiro; Unno, Yasushi; Ito, Kimiteru; Ishii, Kenji

2016-01-01

The present study aimed to determine the qualitative and quantitative accuracy of the Q.Freeze algorithm in PET/CT images of liver tumors. A body phantom and hot spheres representing liver tumors contained 5.3 and 21.2 kBq/mL of a solution containing 18 F radioactivity, respectively. The phantoms were moved in the superior-inferior direction at a motion displacement of 20 mm. Conventional respiratory-gated (RG) and Q.Freeze images were sorted into 6, 10, and 13 phase-groups. The SUV ave was calculated from the background of the body phantom, and the SUV max was determined from the hot spheres of the liver tumors. Three patients with four liver tumors were also clinically assessed by whole-body and RG PET. The RG and Q.Freeze images derived from the clinical study were also sorted into 6, 10 and 13 phase-groups. Liver signal-to-noise ratio (SNR) and SUV max were determined from the RG and Q.Freeze clinical images. The SUV ave of Q.Freeze images was the same as those derived from the body phantom using RG. The liver SNR improved with Q.Freeze, and the SUVs max was not overestimated when Q.Freeze was applied in both the phantom and clinical studies. Q.Freeze did not degrade the liver SNR and SUV max even though the phase number was larger. Q.Freeze delivered qualitative and quantitative motion correction than conventional RG imaging even in 10-phase groups.

A numerical model for water and heat transport in freezing soils with nonequilibrium ice-water interfaces

NASA Astrophysics Data System (ADS)

Peng, Zhenyang; Tian, Fuqiang; Wu, Jingwei; Huang, Jiesheng; Hu, Hongchang; Darnault, Christophe J. G.

2016-09-01

A one-dimensional numerical model of heat and water transport in freezing soils is developed by assuming that ice-water interfaces are not necessarily in equilibrium. The Clapeyron equation, which is derived from a static ice-water interface using the thermal equilibrium theory, cannot be readily applied to a dynamic system, such as freezing soils. Therefore, we handled the redistribution of liquid water with the Richard's equation. In this application, the sink term is replaced by the freezing rate of pore water, which is proportional to the extent of supercooling and available water content for freezing by a coefficient, β. Three short-term laboratory column simulations show reasonable agreement with observations, with standard error of simulation on water content ranging between 0.007 and 0.011 cm3 cm-3, showing improved accuracy over other models that assume equilibrium ice-water interfaces. Simulation results suggest that when the freezing front is fixed at a specific depth, deviation of the ice-water interface from equilibrium, at this location, will increase with time. However, this deviation tends to weaken when the freezing front slowly penetrates to a greater depth, accompanied with thinner soils of significant deviation. The coefficient, β, plays an important role in the simulation of heat and water transport. A smaller β results in a larger deviation in the ice-water interface from equilibrium, and backward estimation of the freezing front. It also leads to an underestimation of water content in soils that were previously frozen by a rapid freezing rate, and an overestimation of water content in the rest of the soils.

Genome-Wide Investigation of MicroRNAs and Their Targets in Response to Freezing Stress in Medicago sativa L., Based on High-Throughput Sequencing

PubMed Central

Shu, Yongjun; Liu, Ying; Li, Wei; Song, Lili; Zhang, Jun; Guo, Changhong

2016-01-01

Winter damage, especially in northern climates, is a major limitation of the utilization of perennial forages such as alfalfa. Therefore, improving freezing tolerance is imperative in alfalfa genetic breeding. However, freezing tolerance is a complex trait that is determined by many genes. To understand the complex regulation mechanisms of freezing tolerance in alfalfa, we performed small RNA sequencing analysis under cold (4°) and freezing (−8°) stress. The sequencing results revealed that 173 known, and 24 novel miRNAs were expressed, and that the expression of 35 miRNAs was affected by cold and/or freezing stress. Meanwhile, 105 target genes cleaved by these miRNAs were characterized by degradome sequencing. These targets were associated with biological regulation, cellular processes, metabolic processes, and response to stress. Interestingly, most of them were characterized as transcription factors (TFs), including auxin response factors, SBP, NAC, AP2/ERF, and GRF, which play important roles in plant abiotic responses. In addition, important miRNAs and mRNAs involved in nodulation were also identified, for example, the relationship between miR169 and the TF CCAAT (also named as NF-YA/HAP2), which suggested that nodulation has an important function in freezing tolerance in alfalfa. Our results provide valuable information to help determine the molecular mechanisms of freezing tolerance in alfalfa, which will aid the application of these miRNAs and their targets in the improvement of freezing tolerance in alfalfa and related plants. PMID:26801649

Heat and mass transfer scale-up issues during freeze-drying, III: control and characterization of dryer differences via operational qualification tests.

PubMed

Rambhatla, S; Tchessalov, S; Pikal, Michael J

2006-04-21

The objective of this research was to estimate differences in heat and mass transfer between freeze dryers due to inherent design characteristics using data obtained from sublimation tests. This study also aimed to provide guidelines for convenient scale-up of the freeze-drying process. Data obtained from sublimation tests performed on laboratory-scale, pilot, and production freeze dryers were used to evaluate various heat and mass transfer parameters: nonuniformity in shelf surface temperatures, resistance of pipe, refrigeration system, and condenser. Emissivity measurements of relevant surfaces such as the chamber wall and the freeze dryer door were taken to evaluate the impact of atypical radiation heat transfer during scale-up. "Hot" and "cold" spots were identified on the shelf surface of different freeze dryers, and the impact of variation in shelf surface temperatures on the primary drying time and the product temperature during primary drying was studied. Calculations performed using emissivity measurements on different freeze dryers suggest that a front vial in the laboratory lyophilizer received 1.8 times more heat than a front vial in a manufacturing freeze dryer operating at a shelf temperature of -25 degrees C and a chamber pressure of 150 mTorr during primary drying. Therefore, front vials in the laboratory are much more atypical than front vials in manufacturing. Steady-state heat and mass transfer equations were used to study a combination of different scale-up issues pertinent during lyophilization cycles commonly used for the freeze-drying of pharmaceuticals.

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

PubMed

Sinclair, Brent J; Marshall, David J; Singh, Sarika; Chown, Steven L

2004-11-01

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.

Effects of rasagiline on freezing of gait in Parkinson's disease - an open-label, multicenter study.

PubMed

Cibulcik, Frantisek; Benetin, Jan; Kurca, Egon; Grofik, Milan; Dvorak, Miloslav; Richter, Denis; Donath, Vladimir; Kothaj, Jan; Minar, Michal; Valkovic, Peter

2016-12-01

Freezing of gait is a disabling symptom in advanced Parkinson's disease. Positive effects have been suggested with MAO-B inhibitors. We report on an open label clinical study on the efficacy of rasagiline as add-on therapy on freezing of gait and quality of life in patients with Parkinson's disease. Forty two patients with freezing of gait were treated with 1 mg rasagiline daily as an add-on therapy. Patients were assessed at baseline and after 1, 2 and 3 months of treatment. Freezing of gait severity was assessed using the Freezing of Gait Questionnaire, motor impairment by the modified MDS UPDRS part III, and quality of life using the PDQ-39 questionnaire. Patients treated with rasagiline had a statistically significant decrease in FoG-Q score and modified MDS UPDRS score after 1, 2 and 3 months of therapy. A moderately strong (r = 0.686, P = 0.002) correlation between the effects on mobility and freezing of gait was found. We also observed a statistically significant improvement in global QoL and in the subscales mobility, ADL, stigma and bodily discomfort in patients after 3 months of rasagiline therapy. A significant correlation (r = 0.570, P = 0.02) between baseline FoG-Q score and the baseline score for the PDQ Mobility subscale was found. In our study rasagiline as add-on antiparkinsonian therapy significantly improved mobility, freezing of gait and quality of life. The positive effect on freezing of gait appears to be related to improvement of mobility.

The Impact of Repeated Freeze-Thaw Cycles on the Quality of Biomolecules in Four Different Tissues.

PubMed

Ji, Xiaoli; Wang, Min; Li, Lingling; Chen, Fang; Zhang, Yanyang; Li, Qian; Zhou, Junmei

2017-10-01

High-quality biosamples are valuable resources for biomedical research. However, some tissues are stored without being sectioned into small aliquots and have to undergo repeated freeze-thaw cycles throughout prolonged experimentation. Little is known regarding the effects of repeated freeze-thaw cycles on the quality of biomolecules in tissues. The aim of this study was to evaluate the impact of repeated freeze-thaw (at room temperature or on ice) cycles on biomolecules and gene expression in four different types of tissues. Each fresh tissue was sectioned into seven aliquots and snap-frozen before undergoing repeated freeze-thaw cycles at room temperature or on ice. Biomolecules were extracted and analyzed. Both relative and absolute quantification were used to detect the changes in gene expression. The results indicated that the impact of repeated freeze-thaw cycles on RNA integrity varied by tissue type. Gene expression, including the housekeeping gene, was affected in RNA-degraded samples according to absolute quantification rather than relative quantification. Furthermore, our results suggest that thawing on ice could protect RNA integrity compared with thawing at room temperature. No obvious degradation of protein or DNA was observed with repeated freeze-thaw cycles either at room temperature or on ice. This research provides ample evidence for the necessity of sectioning fresh tissues into small aliquots before snap-freezing, thus avoiding degradation of RNA and alteration of gene expression resulting from repeated freeze-thaw cycles. For frozen tissue samples that were already in storage and had to be used repeatedly during their lifecycle, thawing on ice or sectioned at ultralow temperature is recommended.

The human milk oligosaccharides are not affected by pasteurization and freeze-drying.

PubMed

Hahn, Won-Ho; Kim, Jaehan; Song, Seunghyun; Park, Suyeon; Kang, Nam Mi

2017-11-06

Human milk oligosaccharides (HMOs) are known as important factors in neurologic and immunologic development of neonates. Moreover, freeze-drying seems to be a promising storage method to improve the processes of human milk banks. However, the effects of pasteurization and freeze-drying on HMOs were not evaluated yet. The purpose of this study is to analyze and compare the HMOs profiles of human milk collected before and after the pasteurization and freeze-drying. Totally nine fresh human milk samples were collected from three healthy mothers at the first, second, and third week after delivery. The samples were treated with Holder pasteurization and freeze-drying. HMOs profiles were analyzed by matrix-assisted laser desorption/ionization (MALDI) time-of-flight/time-of-flight (TOF/TOF) mass spectrometry and compared between samples collected before and after the treatments. Human milk samples showed significantly different HMO patterns between mothers. However, HMOs were not affected by lactation periods within 3 weeks after delivery (r 2  = 0.972-0.999, p < .001). Moreover, both of pasteurization and freeze-drying were found not to affect HMO patterns in a correlation analysis (r 2  = 0.989-0.999, p < .001). HMO patterns were found not to be affected by pasteurization and freeze-drying of donor milks. We hope that introducing freeze-drying to the human milk banks would be encouraged by the present study. However, the storage length without composition changes of HMOs after freeze-drying needs to be evaluated in the further studies.

The importance of heat flow direction for reproducible and homogeneous freezing of bulk protein solutions.

PubMed

Rodrigues, Miguel A; Balzan, Gustavo; Rosa, Mónica; Gomes, Diana; de Azevedo, Edmundo G; Singh, Satish K; Matos, Henrique A; Geraldes, Vítor

2013-01-01

Freezing is an important operation in biotherapeutics industry. However, water crystallization in solution, containing electrolytes, sugars and proteins, is difficult to control and usually leads to substantial spatial solute heterogeneity. Herein, we address the influence of the geometry of freezing direction (axial or radial) on the heterogeneity of the frozen matrix, in terms of local concentration of solutes and thermal history. Solutions of hemoglobin were frozen radially and axially using small-scale and pilot-scale freezing systems. Concentration of hemoglobin, sucrose and pH values were measured by ice-core sampling and temperature profiles were measured at several locations. The results showed that natural convection is the major source for the cryoconcentration heterogeneity of solutes over the geometry of the container. A significant improvement in this spatial heterogeneity was observed when the freezing geometry was nonconvective, i.e., the freezing front progression was unidirectional from bottom to top. Using this geometry, less than 10% variation in solutes concentration was obtained throughout the frozen solutions. This result was reproducible, even when the volume was increased by two orders of magnitude (from 30 mL to 3 L). The temperature profiles obtained for the nonconvective freezing geometry were predicted using a relatively simple computational fluid dynamics model. The reproducible solutes distribution, predictable temperature profiles, and scalability demonstrate that the bottom to top freezing geometry enables an extended control over the freezing process. This geometry has therefore shown the potential to contribute to a better understanding and control of the risks inherent to frozen storage. © 2013 American Institute of Chemical Engineers.

Water vapor movement in freezing aggregate base materials.

DOT National Transportation Integrated Search

2014-06-01

The objectives of this research were to 1) measure the extent to which water vapor movement results in : water accumulation in freezing base materials; 2) evaluate the effect of soil stabilization on water vapor movement : in freezing base materials;...

Freezing temperature protection admixture for Portland cement concrete

DOT National Transportation Integrated Search

1996-10-01

A number of experimental admixtures were compared to Pozzutec 20 admixture for their ability to protect fresh concrete from freezing and for increasing the rate of cement hydration at below-freezing temperatures. The commercial accelerator and low-te...

Freezing tolerance of conifer seeds and germinants.

PubMed

Hawkins, B J; Guest, H J; Kolotelo, D

2003-12-01

Survival after freezing was measured for seeds and germinants of four seedlots each of interior spruce (Picea glauca x engelmannii complex), lodgepole pine (Pinus contorta Dougl. ex Loud.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western red cedar (Thuja plicata Donn ex D. Donn). Effects of eight seed treatments on post-freezing survival of seeds and germinants were tested: dry, imbibed and stratified seed, and seed placed in a growth chamber for 2, 5, 10, 15, 20 or 30 days in a 16-h photoperiod and a 22/17 degrees C thermoperiod. Survival was related to the water content of seeds and germinants, germination rate and seedlot origin. After freezing for 3 h at -196 degrees C, dry seed of most seedlots of interior spruce, Douglas-fir and western red cedar had 84-96% germination, whereas lodgepole pine seedlots had 53-82% germination. Freezing tolerance declined significantly after imbibition in lodgepole pine, Douglas-fir and interior spruce seed (western red cedar was not tested), and mean LT50 of imbibed seed of these species was -30, -24.5 and -20 degrees C, respectively. Freezing tolerance continued to decline to a minimum LT50 of -4 to -7 degrees C after 10 days in a growth chamber for interior spruce, Douglas-fir and lodgepole pine, or after 15 days for western red cedar. Minimum freezing tolerance was reached at the stage of rapid hypocotyl elongation. In all species, a slight increase in freezing tolerance of germinants was observed once cotyledons emerged from the seed coat. The decrease in freezing tolerance during the transition from dry to germinating seed correlated with increases in seed water content. Changes in freezing tolerance between 10 and 30 days in the growth chamber were not correlated with seedling water content. Within a species, seedlots differed significantly in freezing tolerance after 2 or 5 days in the growth chamber. Because all seedlots of interior spruce and lodgepole pine germinated quickly, there was no correlation between seedlot hardiness and rate of germination. Germination rate and freezing tolerance of Douglas-fir and western red cedar seedlots was negatively correlated. There was a significant correlation between LT50 after 10 days in the growth chamber and minimum spring temperature at the location of seedlot origin for interior spruce and three seedlots of western red cedar, but no relationship was apparent for lodgepole pine and Douglas-fir.

A comparative study of K-rich and Na/Ca-rich feldspar ice-nucleating particles in a nanoliter droplet freezing assay

NASA Astrophysics Data System (ADS)

Peckhaus, Andreas; Kiselev, Alexei; Hiron, Thibault; Ebert, Martin; Leisner, Thomas

2016-09-01

A recently designed droplet freezing assay was used to study the freezing of up to 1500 identical 0.2 nL water droplets containing suspensions of one Na/Ca-rich feldspar and three K-rich and one Na/Ca-rich feldspar particles. Three types of experiments have been conducted: cooling ramp, isothermal freezing at a constant temperature, and freeze-thaw cycles. The observed freezing behavior has been interpreted with the help of a model based on the classical nucleation theory (soccer ball model (SBM); Niedermeier et al., 2015). By applying the model to the different freezing experiments conducted with the same ice-nucleating material, the unique sets of model parameters for specific feldspar suspensions could be derived. The SBM was shown to adequately describe the observed cooling rate dependence, the ice-nucleating active sites (INAS) surface density ns(T) in a wide temperature range, and the shift of the freezing curves towards lower temperature with dilution. Moreover, the SBM was capable of reproducing the variation of INAS surface density ns(T) with concentration of ice-nucleating particles in the suspension droplets and correctly predicting the leveling-off of ns(T) at low temperature. The freeze-thaw experiments have clearly shown that the heterogeneous freezing induced even by very active ice-nucleating species still possesses a stochastic nature, with the degree of randomness increasing towards homogeneous nucleation. A population of the high-temperature INAS has been identified in one of the K-rich feldspar samples. The freezing of 0.8 wt % suspension droplets of this particular feldspar was observed already at -5 °C. These high-temperature active sites could be deactivated by treating the sample with hydrogen peroxide but survived heating up to 90 °C. Given a high mass concentration of these high-temperature active sites (2.9 × 108 g-1) and a very low value of contact angle (0.56 rad) the possibility of biological contamination of the sample was concluded to be unlikely but could not be completely ruled out. The freezing efficacy of all feldspar samples has been shown to reduce only slightly after suspension in water for over 5 months.

Storing Blood Cells

NASA Technical Reports Server (NTRS)

1976-01-01

The National Cancer Institute worked with Goddard Space Flight Center to propose a solution to the blood-cell freezing problem. White blood cells and bone marrow are stored for future use by leukemia patients as a result of Goddard and Jet Propulsion Laboratory expertise in electronics and cryogenics. White blood cell and bone marrow bank established using freezing unit. Freezing unit monitors temperature of cells themselves. Thermocouple placed against polyethylene container relays temperature signals to an electronic system which controls small heaters located outside container. Heaters allow liquid nitrogen to circulate at constant temperature and maintain consistent freezing rate. Ability to freeze, store, and thaw white cells and bone marrow without damage is important in leukemia treatment.

Effect of demedullation on freezing injury in hind limbs of rats

NASA Astrophysics Data System (ADS)

Dhingra, Shashi; Bhatia, B.; Chhina, G. S.; Singh, Baldev

1987-09-01

Freezing incidence and tissue loss on exposure of hind limbs of female Wistar rats to freezing mixture was reduced by demedullation 6 days prior to cold exposure (p<0.01 and p<0.001 respectively); demedullation 1 h after freezing injury had no effect on tissue loss. Noradrenaline (1 mg/kg i.p.) 5 min before exposure increased the freezing incidence in intact (p<0.05) as well as in demedullated rats (p<0.01), with no effect on tissue loss. Adrenaline (500 mg/kg i.p.) had no effect on either. A sustained fall in plasma adrenaline after demedullation leading to reduced reactivity of the blood vessels to some vasoactive agents is postulated.

Extending the Season for Concrete Construction and Repair. Phase II - Defining Engineering Parameters

DTIC Science & Technology

2006-04-01

dosages, seemed to improve the freeze –thaw durability of concrete. Phase II found what appears to be a maximum dosage after which freeze –thaw...durability becomes a concern. That is because cement hydration can only create a finite amount of space to absorb these chemicals. Thus, for freeze ...protection, admixture dosages should be designed according to water content as specified in Phase I, while, for freeze –thaw durability, admixture dosages

Freeze-Drying of Plant Tissue Containing HBV Surface Antigen for the Oral Vaccine against Hepatitis B

PubMed Central

Milczarek, Magdalena; Pajtasz-Piasecka, Elżbieta; Wietrzyk, Joanna

2014-01-01

The aim of this study was to develop a freeze-drying protocol facilitating successful processing of plant material containing the small surface antigen of hepatitis B virus (S-HBsAg) while preserving its VLP structure and immunogenicity. Freeze-drying of the antigen in lettuce leaf tissue, without any isolation or purification step, was investigated. Each process step was consecutively evaluated and the best parameters were applied. Several drying profiles and excipients were tested. The profile of 20°C for 20 h for primary and 22°C for 2 h for secondary drying as well as sucrose expressed efficient stabilisation of S-HBsAg during freeze-drying. Freezing rate and postprocess residual moisture were also analysed as important factors affecting S-HBsAg preservation. The process was reproducible and provided a product with VLP content up to 200 µg/g DW. Assays for VLPs and total antigen together with animal immunisation trials confirmed preservation of antigenicity and immunogenicity of S-HBsAg in freeze-dried powder. Long-term stability tests revealed that the stored freeze-dried product was stable at 4°C for one year, but degraded at elevated temperatures. As a result, a basis for an efficient freeze-drying process has been established and a suitable semiproduct for oral plant-derived vaccine against HBV was obtained. PMID:25371900

SLAPex Freeze/Thaw 2015: The First Dedicated Soil Freeze/Thaw Airborne Campaign

NASA Technical Reports Server (NTRS)

Kim, Edward; Wu, Albert; DeMarco, Eugenia; Powers, Jarrett; Berg, Aaron; Rowlandson, Tracy; Freeman, Jacqueline; Gottfried, Kurt; Toose, Peter; Roy, Alexandre;

Effect of photoperiod prior to cold acclimation on freezing tolerance and carbohydrate metabolism in alfalfa (Medicago sativa L.).

PubMed

Bertrand, Annick; Bipfubusa, Marie; Claessens, Annie; Rocher, Solen; Castonguay, Yves

2017-11-01

Cold acclimation proceeds sequentially in response to decreases in photoperiod and temperature. This study aimed at assessing the impact of photoperiod prior to cold acclimation on freezing tolerance and related biochemical and molecular responses in two alfalfa cultivars. The fall dormant cultivar Evolution and semi-dormant cultivar 6010 were grown in growth chambers under different photoperiods (8, 10, 12, 14 or 16h) prior to cold acclimation. Freezing tolerance was evaluated as well as carbohydrate concentrations, levels of transcripts encoding enzymes of carbohydrate metabolism as well as a K-3dehydrin, before and after cold acclimation. The fall dormant cultivar Evolution had a better freezing tolerance than the semi-dormant cultivar 6010. The effect of photoperiod prior to cold acclimation on the level of freezing tolerance differed between the two cultivars: an 8h-photoperiod induced the highest level of freezing tolerance in Evolution and the lowest in 6010. In Evolution, the 8h-induced superior freezing tolerance was associated with higher concentration of raffinose-family oligosaccharides (RFO). The transcript levels of sucrose synthase (SuSy) decreased whereas those of sucrose phosphatase synthase (SPS) and galactinol synthase (GaS) increased in response to cold acclimation in both cultivars. Our results indicate that RFO metabolism could be involved in short photoperiod-induced freezing tolerance in dormant alfalfa cultivars. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

Kinetic freeze-out conditions for the production of resonances, hadronic molecules, and light nuclei

NASA Astrophysics Data System (ADS)

Cho, Sungtae; Song, Taesoo; Lee, Su Houng

2018-02-01

We investigate the freeze-out conditions of a particle in an expanding system of interacting particles in order to understand the productions of resonances, hadronic molecules, and light nuclei in heavy-ion collisions. Applying the kinetic freeze-out condition with explicit hydrodynamic calculations for the expanding hadronic phase to the daughter particles of K* mesons, we find that the larger suppression of the yield ratio of K*/K at the Large Hadron Collider (LHC) than at the Relativisitic Heavy Ion Collider (RHIC) compared to the expectations from the statistical hadronization model based on chemical freeze-out parameters reflects the lower kinetic freeze-out temperature at LHC than at RHIC. Furthermore, we point out that for the light nuclei or hadronic molecules that are bound, the freeze-out condition should be applied to the respective particle in the hadronic matter. It is then shown through the rate equation that when the nucleon and pion numbers are kept constant at the chemical freeze-out value during the hadronic phase, the deuteron number quickly approaches an asymptotic value that is close to the statistical model prediction at the chemical freeze-out point. We argue that the reduction seen in K* numbers is a typical result for a particle that has a large natural decay width decaying into daughter particles, while that for deuteron is typical for a stable hadronic bound state.

Stem water transport and freeze-thaw xylem embolism in conifers and angiosperms in a Tasmanian treeline heath.

PubMed

Feild, Taylor S; Brodribb, Tim

2001-05-01

The effect of freezing on stem xylem hydraulic conductivity and leaf chlorophyll a fluorescence was measured in 12 tree and shrub species from a treeline heath in Tasmania, Australia. Reduction in stem hydraulic conductivity after a single freeze-thaw cycle was minimal in conifers and the vessel-less angiosperm species Tasmannia lanceolata (Winteraceae), whereas mean loss of conductivity in vessel-forming angiosperms fell in the range 17-83%. A positive linear relationship was observed between percentage loss of hydraulic conductivity by freeze-thaw and the average conduit diameter across all 12 species. This supports the hypothesis that large-diameter vascular conduits have a greater likelihood of freeze-thaw cavitation because larger bubbles are produced, which are more likely to expand under tension. Leaf frost tolerances, as measured by a 50% loss of maximum PSII quantum yield, varied from -6 to -13°C, indicating that these species were more frost-sensitive than plants from northern hemisphere temperate forest and treeline communities. There was no evidence of a relationship between frost tolerance of leaves and the resilience of stem water transport to freezing, suggesting that low temperature survival and the resistance of stem water transport to freezing are independently evolving traits. The results of this study bear on the ecological importance of stem freezing in the southern hemisphere treeline zones.

Slow-freezing-induced changes of birefringent structures in human oocytes are related to responsiveness to ovulation induction.

PubMed

Molinari, Emanuela; Revelli, Alberto; Racca, Cinzia; Delle Piane, Luisa; Massobrio, Marco

2010-05-01

The slow-freezing method is widely used to freeze human oocytes, both for fertility preservation and in routine IVF programmes. Slow freezing damages some of the cell's structures, including the meiotic spindle (MS) and the zona pellucida (ZP). Polarized light microscopy was used to study the variations induced by slow freezing on the MS and the ZP of human oocytes and to analyse the relationship between slow-freezing effects on the gamete and some clinical characteristics, such as age, body mass index and ovarian responsiveness to ovulation induction (expressed as total follicle-stimulating hormone dose/retrieved oocyte). Both the MS and the ZP (particularly its inner layer) underwent significant changes during slow-freezing procedure. The MS became thinner and structurally less organized (lower retardance) (P<0.001 and P<0.05, respectively), whereas the ZP became thicker and its inner layer lost structural organization (both P<0.05). These morphological changes were unrelated to the patient's age or body mass index, but ZP variations in thickness and retardance were significantly related to ovarian responsiveness (P=0.033 and P=0.026, respectively), suggesting that patients with a higher response to gonadotrophins produce oocytes better able to preserve their characteristics after freezing-thawing. Copyright (c) 2010 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

Genes Upregulated in Winter Wheat (Triticum aestivum L.) during Mild Freezing and Subsequent Thawing Suggest Sequential Activation of Multiple Response Mechanisms.

PubMed

Skinner, Daniel Z

2015-01-01

Exposing fully cold-acclimated wheat plants to a mild freeze-thaw cycle of -3 °C for 24h followed by +3 °C for 24 or 48 h results in dramatically improved tolerance of subsequent exposure to sub-freezing temperatures. Gene enrichment analysis of crown tissue from plants collected before or after the -3 °C freeze or after thawing at +3 °C for 24 or 48 h revealed that many biological processes and molecular functions were activated during the freeze-thaw cycle in an increasing cascade of responses such that over 150 processes or functions were significantly enhanced by the end of the 48 h, post-freeze thaw. Nearly 2,000 individual genes were upregulated more than 2-fold over the 72 h course of freezing and thawing, but more than 70% of these genes were upregulated during only one of the time periods examined, suggesting a series of genes and gene functions were involved in activation of the processes that led to enhanced freezing tolerance. This series of functions appeared to include extensive cell signaling, activation of stress response mechanisms and the phenylpropanoid biosynthetic pathway, extensive modification of secondary metabolites, and physical restructuring of cell membranes. By identifying plant lines that are especially able to activate these multiple mechanisms it may be possible to develop lines with enhanced winterhardiness.

Effect of mixing time, freeze-drying and baking on phenolics, anthocyanins and antioxidant capacity of raspberry juice during processing of muffins.

PubMed

Rosales-Soto, Maria U; Powers, Joseph R; Alldredge, J Richard

2012-05-01

Consumption of baked products constitutes an important part of a daily breakfast considering that people are continually grabbing meals on the go. Among baked products, muffins rank third in breakfast products and attract a broad range of consumers. Incorporation of red raspberry juice into muffins can add value to the product while preserving health benefits to the consumer. The purpose of this study was to evaluate the effect of mixing time, freeze-drying and baking on the phenolic and anthocyanin contents and antioxidant capacity of raspberry juice during the preparation of muffins. Freeze-drying of raspberry batters reduced their phenolic content and antioxidant capacity regardless of mixing time. Non-freeze-dried raspberry batter mixed for 5 min had the highest phenolic content (0.88 mg gallic acid equivalent g(-1) dry matter (DM)). Non-freeze-dried raspberry muffins had the highest antioxidant capacity (0.041 µmol Trolox equivalent g(-1) DM). Freeze-dried raspberry batters mixed for 5 and 10 min had the highest anthocyanin content (0.065 mg cyanidin-3-glucoside g(-1) DM). Baking reduced the anthocyanin content of both non-freeze-dried and freeze-dried raspberry muffins. Despite the reduction in valuable compounds, muffin is a vehicle for the delivery of these compounds. Copyright © 2012 Society of Chemical Industry.

Development of freeze-dried miyeokguk, Korean seaweed soup, as space food sterilized by irradiation

NASA Astrophysics Data System (ADS)

Song, Beom-Seok; Park, Jin-Gyu; Kim, Jae-Hun; Choi, Jong-Il; Ahn, Dong-Hyun; Hao, Chen; Lee, Ju-Woon

2012-08-01

The purpose of this study was to evaluate microbial populations, Hunter's color values (L*, a*, b*) and the sensory quality of freeze-dried miyeokguk, Korean seaweed soup, in order to use it as space food. Microorganisms were not detected in non-irradiated freeze-dried miyeokguk within the detection limit of 1.00 log CFU/g. However, the microbial population in rehydrated miyeokguk was 7.01 log CFU/g after incubation at 35 °C for 48 h, indicating that freeze-dried miyeokguk was not sterilized by heat treatment during the preparation process. Bacteria in the freeze-dried miyeokguk were tentatively identified as Bacillus cereus, B. subtilis, Enterobacter hormaechei, and Ancinetobacter genomosp. using the 16S rDNA sequencing. In samples that were gamma-irradiated above 10 kGy, it was confirmed that all microorganisms were inactivated. Hunter's color values of the samples irradiated at doses less than 10 kGy were not significantly altered from their baseline appearance (p>0.05). Sensory evaluation showed that preference scores in all sensory properties decreased when freeze-dried miyeokguk was irradiated at doses greater than 10 kGy. Therefore, the results of this study suggest that gamma irradiation at 10 kGy is sufficient to sterilize freeze-dried miyeokguk without significant deterioration in the sensory quality, and thus, the freeze-dried and irradiated miyeokguk at 10 kGy fulfills the microbiological requirements as space food.

Effect of freezing on the rheological, chemical and colour properties of Serpa cheese.

PubMed

Alvarenga, Nuno; Canada, João; Sousa, Isabel

2011-02-01

The effect of freezing on the properties of a raw ewes'-milk semi-soft cheese (Serpa cheese) was studied using small amplitude oscillatory (SAOS) and texture measurements, colour and chemical parameters. The freezing was introduced at three different stages of the ripening process (28, 35 and 42 days), and the cheeses were maintained frozen for 12 months. Cheeses were submitted to a slow or fast freezing method, and to different storage temperatures: -10 and -20°C (three replicates for each set conditions). Chemical data showed that only the proteolysis indicators exhibited differences between frozen and non-frozen samples; frozen samples showed higher values of NPN than the non-frozen samples, indicating that the freezing process did not prevent the secondary proteolysis of cheese. Frozen samples showed a significantly (P<0·05) stronger structure than the non-frozen, as indicated by hardness. However, the differences between the frozen and non-frozen samples were not significantly for storage modulus (G' 1Hz) and loss tangent (tan δ 1Hz) (P>0·05). Freezing affected mainly colour parameters: frozen samples were more luminous, and more yellow-green. The results allowed us to conclude that the damages caused by freezing to cheese properties could be minimized if this type of storage is introduced at the end of ripening (42 d) using a freezing temperature of -20°C.

Dynamics and characteristics of soil temperature and moisture of active layer in central Tibetan Plateau

NASA Astrophysics Data System (ADS)

Zhao, L.; Hu, G.; Wu, X.; Tian, L.

2017-12-01

Research on the hydrothermal properties of active layer during the thawing and freezing processes was considered as a key question to revealing the heat and moisture exchanges between permafrost and atmosphere. The characteristics of freezing and thawing processes at Tanggula (TGL) site in permafrost regions on the Tibetan Plateau, the results revealed that the depth of daily soil temperature transmission was about 40 cm shallower during thawing period than that during the freezing period. Soil warming process at the depth above 140 cm was slower than the cooling process, whereas they were close below 140 cm depth. Moreover, the hydro-thermal properties differed significantly among different stages. Precipitation caused an obviously increase in soil moisture at 0-20 cm depth. The vertical distribution of soil moisture could be divided into two main zones: less than 12% in the freeze state and greater than 12% in the thaw state. In addition, coupling of moisture and heat during the freezing and thawing processes also showed that soil temperature decreased faster than soil moisture during the freezing process. At the freezing stage, soil moisture exhibited an exponential relationship with the absolute soil temperature. Energy consumed for water-ice conversion during the freezing process was 149.83 MJ/m2 and 141.22 MJ/m2 in 2011 and 2012, respectively, which was estimated by the soil moisture variation.

Freezing/Thawing without Cryoprotectant Damages Native but not Decellularized Porcine Renal Tissue

PubMed Central

Poornejad, Nafiseh; Frost, Timothy S; Scott, Daniel R; Elton, Brinden B; Reynolds, Paul R; Roeder, Beverly L; Cook, Alonzo D

2015-01-01

abstract Whole organ decellularization of porcine renal tissue and recellularization with a patient's own cells would potentially overcome immunorejection, which is one of the most significant problems with allogeneic kidney transplantation. However, there are obstacles to achieving this goal, including preservation of the decellularized extracellular matrix (ECM), identifying the proper cell types, and repopulating the ECM before transplantation. Freezing biological tissue is the best option to avoid spoilage; however, it may damage the structure of the tissue or disrupt cellular membranes through ice crystal formation. Cryoprotectants have been used to repress ice formation during freezing, although cell toxicity can still occur. The effect of freezing/thawing on native (n = 10) and decellularized (n = 10) whole porcine kidneys was studied without using cryoprotectants. Results showed that the elastic modulus of native kidneys was reduced by a factor of 22 (P < 0.0001) by freezing/thawing or decellularization, while the elastic modulus for decellularized ECM was essentially unchanged by the freezing/thawing process (p = 0.0636). Arterial pressure, representative of structural integrity, was also reduced by a factor of 52 (P < 0.0001) after freezing/thawing for native kidneys, compared to a factor of 43 (P < 0.0001) for decellularization and a factor of 4 (P < 0.0001) for freezing/thawing decellularized structures. Both freezing/thawing and decellularization reduced stiffness, but the reductions were not additive. Investigation of the microstructure of frozen/thawed native and decellularized renal tissues showed increased porosity due to cell removal and ice crystal formation. Orcein and Sirius staining showed partial damage to elastic and collagen fibers after freezing/thawing. It was concluded that cellular damage and removal was more responsible for reducing stiffness than fibril destruction. Cell viability and growth were demonstrated on decellularized frozen/thawed and non-frozen samples using human renal cortical tubular epithelial (RCTE) cells over 12 d. No adverse effect on the ability to recellularize after freezing/thawing was observed. It is recommended that porcine kidneys be frozen prior to decellularization to prevent contamination, and after decellularization to prevent protein denaturation. Cryoprotectants may still be necessary, however, during storage and transportation after recellularization. PMID:25730294

Isolation of a Soluble Component of Plasmodium berghei Which Induces Immunity in Rats

PubMed Central

Grothaus, G. D.; Kreier, J. P.

1980-01-01

Soluble material was obtained from sonically freed plasmodiae by three procedures. Two procedures, cryo-impacting and freeze-thawing, were evaluated for their ability to disrupt the parasites and release soluble material. The soluble materials obtained by these procedures were compared to materials washed from the surfaces of sonically freed parasites. Between 35 and 40% of the total parasite protein was solubilized by freeze-thawing or cryo-impacting. One cycle of freeze-thawing released nearly as much protein as could be released by this method, and additional cycles of freeze-thawing had little additional effect. Cryo-impacting solubilized only a small amount of protein in addition to that which was released by the cycle of freeze-thawing inherent in the procedure. Reductions in the packed cell volume of the material remaining after freeze-thawing or cryo-impacting indicate that the insoluble fragments are broken into smaller pieces as treatment is extended. Electron microscopy of 30-s cryo-impacted and three-times freeze-thawed parasites revealed membrane fragments similar in appearance. Patterns obtained by polyacrylamide gel electrophoresis of the soluble material from freeze-thawed and cryo-impacted parasites were also similar, and approximately 13 protein bands were demonstrated. The material washed from the surfaces of the free parasites, on the other hand, resolved into only two to four major bands on the gel columns. In immunization studies, the soluble and insoluble fractions obtained by freeze-thawing or cryo-impacting and the material washed from the surfaces of the parasites all stimulated a protective immune response. On the basis of the amount of protein required to stimulate roughly comparable immunity, the soluble fraction obtained by freeze-thawing or cryo-impacting free parasites was about twice as potent an immunogen as was the insoluble fraction. The material obtained by gentle washing of the freed parasites was approximately 20 times as potent an immunogen as were the freed parasites and about 7 times as potent as the soluble material obtained by freeze-thawing or cryo-impacting. Images Fig. 1 Fig. 2 PMID:6991439

Model simulations with COSMO-SPECS: impact of heterogeneous freezing modes and ice nucleating particle types on ice formation and precipitation in a deep convective cloud

NASA Astrophysics Data System (ADS)

Diehl, Karoline; Grützun, Verena

2018-03-01

In deep convective clouds, heavy rain is often formed involving the ice phase. Simulations were performed using the 3-D cloud resolving model COSMO-SPECS with detailed spectral microphysics including parameterizations of homogeneous and three heterogeneous freezing modes. The initial conditions were selected to result in a deep convective cloud reaching 14 km of altitude with strong updrafts up to 40 m s-1. At such altitudes with corresponding temperatures below -40 °C the major fraction of liquid drops freezes homogeneously. The goal of the present model simulations was to investigate how additional heterogeneous freezing will affect ice formation and precipitation although its contribution to total ice formation may be rather low. In such a situation small perturbations that do not show significant effects at first sight may trigger cloud microphysical responses. Effects of the following small perturbations were studied: (1) additional ice formation via immersion, contact, and deposition modes in comparison to solely homogeneous freezing, (2) contact and deposition freezing in comparison to immersion freezing, and (3) small fractions of biological ice nucleating particles (INPs) in comparison to higher fractions of mineral dust INP. The results indicate that the modification of precipitation proceeds via the formation of larger ice particles, which may be supported by direct freezing of larger drops, the growth of pristine ice particles by riming, and by nucleation of larger drops by collisions with pristine ice particles. In comparison to the reference case with homogeneous freezing only, such small perturbations due to additional heterogeneous freezing rather affect the total precipitation amount. It is more likely that the temporal development and the local distribution of precipitation are affected by such perturbations. This results in a gradual increase in precipitation at early cloud stages instead of a strong increase at later cloud stages coupled with approximately 50 % more precipitation in the cloud center. The modifications depend on the active freezing modes, the fractions of active INP, and the composition of the internal mixtures in the drops.

Effects of whole body (56)Fe radiation on contextual freezing and Arc-positive cells in the dentate gyrus.

PubMed

Raber, Jacob; Allen, Antiño R; Rosi, Susanna; Sharma, Sourabh; Dayger, Catherine; Davis, Matthew J; Fike, John R

2013-06-01

The space radiation environment contains high-energy charged particles such as (56)Fe, which could pose a significant hazard to hippocampal function in astronauts during and after the mission(s). The mechanisms underlying impairments in cognition are not clear but might involve alterations in the percentage of neurons in the dentate gyrus expressing the plasticity-related immediate early gene Arc. Previously, we showed effects of cranial (56)Fe irradiation on hippocampus-dependent contextual freezing and on the percentage of Arc-positive cells in the enclosed, but not free, blade. Because it is unclear whether whole body (56)Fe irradiation causes similar effects on these markers of hippocampal function, in the present study we quantified the effects of whole body (56)Fe irradiation (600MeV, 0.5 or 1Gy) on hippocampus-dependent and hippocampus-independent cognitive performance and determined whether these effects were associated with changes in Arc expression in the enclosed and free blades of the dentate gyrus. Whole body (56)Fe irradiation impacted contextual but not cued fear freezing and the percentage of Arc-positive cells in the enclosed and free blades. In mice tested for contextual freezing, there was a correlation between Arc-positive cells in the enclosed and free blades. In addition, in mice irradiated with 0.5Gy, contextual freezing in the absence of aversive stimuli correlated with the percentage of Arc-positive cells in the enclosed blade. In mice tested for cued freezing, there was no correlation between Arc-positive cells in the enclosed and free blades. In contrast, cued freezing in the presence or absence of aversive stimuli correlated with Arc-positive cells in the free blade. In addition, in mice irradiated with 1Gy cued freezing in the absence of aversive stimuli correlated with the percentage of Arc-positive neurons in the free blade. These data indicate that while whole body (56)Fe radiation affects contextual freezing and Arc-positive cells in the dentate gyrus, the enclosed blade might be more important for contextual freezing while the free blade might be more important for cued freezing. Copyright © 2013 Elsevier B.V. All rights reserved.

Freeze-thaw performance testing of whole concrete railroad ties.

DOT National Transportation Integrated Search

2013-10-01

Freezing and thawing durability tests of prestressed concrete ties are normally performed according to ASTM C666 specifications. Small specimens are cut from the shoulders of concrete ties and tested through 300 cycles of freezing and thawing. Saw-cu...

Effect of the Winter Wheat Cheyenne 5A Substituted Chromosome on Dynamics of Abscisic Acid and Cytokinins in Freezing-Sensitive Chinese Spring Genetic Background

PubMed Central

Kalapos, Balázs; Novák, Aliz; Dobrev, Petre; Vítámvás, Pavel; Marincs, Ferenc; Galiba, Gábor; Vanková, Radomira

2017-01-01

The effect of short- and long-term cold treatment on the abscisic acid (ABA) and cytokinin (CK) metabolism, and their main biosynthesis- and signaling-related genes were investigated in freezing-sensitive and freezing-tolerant wheat genotypes. Varieties Cheyenne and Chinese Spring substituted with the 5A Cheyenne chromosome, which represented freezing-tolerant genotypes, were compared with the freezing-sensitive Chinese Spring. Hormone levels and gene expression data indicated that the short- and long-term cold treatments are associated with specific regulation of the accumulation of cold-protective proteins and phytohormone levels, as well as the expression profiles of the hormone-related genes. The significant differences were observed between the genotypes, and between their leaf and crown tissues, too. The level of dehydrins, including WCS120 protein, and expression of WCS120 gene were considerably higher in the freezing-tolerant genotypes after 21 days of cold treatment. Expression of Cor14b and CBF14, cold-responsive regulator genes, was increased by cold treatment in all genotypes, to higher extent in freezing-tolerant genotypes. Cluster analysis revealed that the tolerant genotypes had a similar response to cold treatment, regarding expression of the ABA and CK metabolic genes, as well as hormone levels in leaves. As far as hormone levels in crowns are concerned, however, the strongly freezing-tolerant Cheyenne variety clustered separately from the Chinese Spring and the substitution line, which were more similar to each other after both 1 and 21 days of cold treatment than to Cheyenne. Based on these results we concluded that the 5A chromosome of wheat might have both a direct and an indirect impact on the phytohormone-dependent cold-induced freezing tolerance. Based on the gene expression data, novel genetic markers could be developed, which may be used to determine the freezing tolerance level in a wide range of wheat varieties. PMID:29238355

Effect of controlled ice nucleation on primary drying stage and protein recovery in vials cooled in a modified freeze-dryer.

PubMed

Passot, Stéphanie; Tréléa, Ioan Cristian; Marin, Michèle; Galan, Miquel; Morris, G John; Fonseca, Fernanda

2009-07-01

The freezing step influences lyophilization efficiency and protein stability. The main objective of this work was to investigate the impact on the primary drying stage of an ultrasound controlled ice nucleation technology, compared with usual freezing protocols. Lyophilization cycles involving different freezing protocols (applying a constant shelf cooling rate of 1 degrees C/min or 0.2 degrees C/min, putting vials on a precooled shelf, and controlling nucleation by ultrasounds or by addition of a nucleating agent) were performed in a prototype freeze-dryer. Three protective media including sucrose or maltodextrin and differing by their thermal properties and their ability to preserve a model protein (catalase) were used. The visual aspect of the lyophilized cake, residual water content, and enzymatic activity recovery of catalase were assessed after each lyophilization cycle and after 1 month of storage of the lyophilized product at 4 degrees C and 25 degrees C. The freezing protocols allowing increasing nucleation temperature (precooled shelf and controlled nucleation by using ultrasounds or a nucleating agent) induced a faster sublimation step and higher sublimation rate homogeneity. Whatever the composition of the protective medium, applying the ultrasound technology made it possible to decrease the sublimation time by 14%, compared with the freezing method involving a constant shelf cooling rate of 1 degrees C/min. Concerning the enzyme activity recovery, the impact of the freezing protocol was observed only for the protective medium involving maltodextrin, a less effective protective agent than sucrose. Higher activity recovery results were obtained after storage when the ultrasound technology or the precooled shelf method was applied. Controlling ice nucleation during the freezing step of the lyophilization process improved the homogeneity of the sublimation rates, which will, in turn, reduce the intervial heterogeneity. The freeze-dryer prototype including the system of controlled nucleation by ultrasounds appears to be a promising tool in accelerating sublimation and improving intrabatch homogeneity.

Freeze-Thaw Cycles and Soil Biogeochemistry: Implications for Greenhouse Gas emission

NASA Astrophysics Data System (ADS)

Rezanezhad, F.; Milojevic, T.; Oh, D. H.; Parsons, C. T.; Smeaton, C. M.; Van Cappellen, P.

2016-12-01

Freeze-thaw cycles represent a major natural climate forcing acting on soils at middle and high latitudes. Repeated freezing and thawing of soils changes their physical properties, geochemistry, and microbial community structure, which together govern the biogeochemical cycling of carbon and nutrients. In this presentation, we focus on how freeze-thaw cycles regulate carbon and nitrogen cycling and how these transformations influence greenhouse gas (GHG) fluxes. We present a novel approach, which combines the acquisition of physical and chemical data in a newly developed experimental soil column system. This system simulates realistic soil temperature profiles during freeze-thaw cycles. A high-resolution, Multi-Fiber Optode (MuFO) microsensor technique was used to detect oxygen (O2) continuously in the column at multiple depths. Surface and subsurface changes to gas and aqueous phase chemistry were measured to delineate the pathways and quantify soil respiration rates during freeze-thaw cycles. The results indicate that the time-dependent release of GHG from the soil surface is influenced by a combination of two key factors. Firstly, fluctuations in temperature and O2 availability affect soil biogeochemical activity and GHG production. Secondly, the recurrent development of a physical ice barrier prevents exchange of gaseous compounds between the soil and atmosphere during freezing conditions; removal of this barrier during thaw conditions increases GHG fluxes. During freezing, O2 levels in the unsaturated zone decreased due to restricted gas exchange with the atmosphere. As the soil thawed, O2 penetrated deeper into the soil enhancing the aerobic mineralization of organic carbon and nitrogen. Additionally, with the onset of thawing a pulse of gas flux occurred, which is attributed to the build-up of respiratory gases in the pore space during freezing. The latter implies enhanced anaerobic respiration as O2 supply ceases when the upper soil layer freezes.

Remote sensing of freeze-thaw transitions in Arctic soils using the complex resistivity method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Yuxin; Hubbard, Susan S; Ulrich, Craig

2013-01-01

Our ability to monitor freeze - thaw transitions is critical to developing a predictive understanding of biogeochemical transitions and carbon dynamics in high latitude environments. In this study, we conducted laboratory column experiments to explore the potential of the complex resistivity method for monitoring the freeze - thaw transitions of the arctic permafrost soils. Samples for the experiment were collected from the upper active layer of Gelisol soils at the Barrow Environmental Observatory, Barrow Alaska. Freeze - thaw transitions were induced through exposing the soil column to controlled temperature environments at 4 C and -20 C. Complex resistivity and temperaturemore » measurements were collected regularly during the freeze - thaw transitions using electrodes and temperature sensors installed along the column. During the experiments, over two orders of magnitude of resistivity variations were observed when the temperature was increased or decreased between -20 C and 0 C. Smaller resistivity variations were also observed during the isothermal thawing or freezing processes that occurred near 0 C. Single frequency electrical phase response and imaginary conductivity at 1 Hz were found to be exclusively related to the unfrozen water in the soil matrix, suggesting that these geophysical 24 attributes can be used as a proxy for the monitoring of the onset and progression of the freeze - thaw transitions. Spectral electrical responses and fitted Cole Cole parameters contained additional information about the freeze - thaw transition affected by the soil grain size distribution. Specifically, a shift of the observed spectral response to lower frequency was observed during isothermal thawing process, which we interpret to be due to sequential thawing, first from fine then to coarse particles within the soil matrix. Our study demonstrates the potential of the complex resistivity method for remote monitoring of freeze - thaw transitions in arctic soils. Although conducted at the laboratory scale, this study provides the foundation for exploring the potential of the complex resistivity signals for monitoring spatiotemporal variations of freeze - thaw transitions over field-relevant scales.« less

Tandem High-pressure Freezing and Quick Freeze Substitution of Plant Tissues for Transmission Electron Microscopy

PubMed Central

Bobik, Krzysztof; Dunlap, John R.; Burch-Smith, Tessa M.

2014-01-01

Since the 1940s transmission electron microscopy (TEM) has been providing biologists with ultra-high resolution images of biological materials. Yet, because of laborious and time-consuming protocols that also demand experience in preparation of artifact-free samples, TEM is not considered a user-friendly technique. Traditional sample preparation for TEM used chemical fixatives to preserve cellular structures. High-pressure freezing is the cryofixation of biological samples under high pressures to produce very fast cooling rates, thereby restricting ice formation, which is detrimental to the integrity of cellular ultrastructure. High-pressure freezing and freeze substitution are currently the methods of choice for producing the highest quality morphology in resin sections for TEM. These methods minimize the artifacts normally associated with conventional processing for TEM of thin sections. After cryofixation the frozen water in the sample is replaced with liquid organic solvent at low temperatures, a process called freeze substitution. Freeze substitution is typically carried out over several days in dedicated, costly equipment. A recent innovation allows the process to be completed in three hours, instead of the usual two days. This is typically followed by several more days of sample preparation that includes infiltration and embedding in epoxy resins before sectioning. Here we present a protocol combining high-pressure freezing and quick freeze substitution that enables plant sample fixation to be accomplished within hours. The protocol can readily be adapted for working with other tissues or organisms. Plant tissues are of special concern because of the presence of aerated spaces and water-filled vacuoles that impede ice-free freezing of water. In addition, the process of chemical fixation is especially long in plants due to cell walls impeding the penetration of the chemicals to deep within the tissues. Plant tissues are therefore particularly challenging, but this protocol is reliable and produces samples of the highest quality. PMID:25350384

Roles of testosterone and amygdaloid LTP induction in determining sex differences in fear memory magnitude.

PubMed

Chen, Li-Shen; Tzeng, Wen-Yu; Chuang, Jia-Ying; Cherng, Chianfang G; Gean, Po-Wu; Yu, Lung

2014-08-01

Women are thought to form fear memory more robust than men do and testosterone is suspected to play a role in determining such a sex difference. Mouse cued fear freezing was used to study the sex-related susceptibility and the role of testosterone in fear memory in humans. A 75-dB tone was found to provoke weak freezing, while 0.15-mA and 0.20-mA footshock caused strong freezing responses. No sex differences were noticed in the tone- or footshock-induced (naïve fear) freezing. Following the conditionings, female mice exhibited greater tone (cued fear)-induced freezing than did male mice. Nonetheless, female mice demonstrated indistinctive cued fear freezing across the estrous phases and ovariectomy did not affect such freezing in female mice. Orchidectomy enhanced the cued fear freezing in male mice. Systemic testosterone administrations and an intra-lateral nucleus of amygdala (LA) testosterone infusion diminished the cued fear freezing in orchidectomized male mice, while pretreatment with flutamide (Flu) eradicated these effects. Long-term potentiation (LTP) magnitude in LA has been known to correlate with the strength of the cued fear conditioning. We found that LA LTP magnitude was indeed greater in female than male mice. Orchidectomy enhanced LTP magnitude in males' LA, while ovariectomy decreased LTP magnitude in females' LA. Testosterone decreased LTP magnitude in orchidectomized males' LA and estradiol enhanced LTP magnitude in ovariectomized females' LA. Finally, male mice had lower LA GluR1 expression than female mice and orchidectomy enhanced the GluR1 expression in male mice. These findings, taken together, suggest that testosterone plays a critical role in rendering the sex differences in the cued fear freezing and LA LTP. Testosterone is negatively associated with LA LTP and the cued fear memory in male mice. However, ovarian hormones and LA LTP are loosely associated with the cued fear memory in female mice. Copyright © 2014 Elsevier Inc. All rights reserved.

Reducing the loss of vaccines from accidental freezing in the cold chain: the experience of continuous temperature monitoring in Tunisia.

PubMed

Lloyd, John; Lydon, Patrick; Ouhichi, Ramzi; Zaffran, Michel

2015-02-11

Accidental freezing of vaccines is a growing threat and a real risk for national immunization programs when the potency of many vaccines can be compromised if these are exposed to sub-zero temperatures in the cold chain. In Tunisia, this issue is compounded by using sub-standard domestic cold chain equipment instead of equipping the program with medical refrigerators designed specifically for storing vaccines and temperature sensitive pharmaceuticals. Against this backdrop, this paper presents the findings of a demonstration project conducted in Tunisia in 2012 that tested the impact of introducing several freeze prevention solutions to mitigate the risk of accidental freezing of vaccines. The main finding is that, despite the continued use of underperforming domestic refrigerators, continuous temperature monitoring using new technologies combined with other technological interventions significantly reduced the prevalence of accidental exposure to freezing temperatures. These improvements were noticed for cold chain storage at regional, district and health center levels, and during the transport legs that were part of the demonstration conducted in the regions of Kasserine in the South-Eastern part of Tunisia. Subsequent to introducing these freeze prevention solutions, the incidence of freeze alarms was reduced and the percent of time the temperatures dropped below the 2 °C recommended threshold. The incidence of freeze alarms at health center level was reduced by 40%. Lastly, the solutions implemented reduced risk of freezing during transport from 13.8% to 1.7%. Although the solution implemented is not optimal in the longer term because domestic refrigerators are used extensively in district stores and health centers, the risk of accidental freezing is significantly reduced by introducing the practice of continuous temperature monitoring as a standard. The management of the cold chain equipment was strengthened as a result which helps protect the potency of vaccines to the areas of most difficult access. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Optimization of the freezing process for hematopoietic progenitor cells: effect of precooling, initial dimethyl sulfoxide concentration, freezing program, and storage in vapor-phase or liquid nitrogen on in vitro white blood cell quality.

PubMed

Dijkstra-Tiekstra, Margriet J; Setroikromo, Airies C; Kraan, Marcha; Gkoumassi, Effimia; de Wildt-Eggen, Janny

2014-12-01

Adding dimethyl sulfoxide (DMSO) to hematopoietic progenitor cells (HPCs) causes an exothermic reaction, potentially affecting their viability. The freezing method might also influence this. The aim was to investigate the effect of 1) precooling of DMSO and plasma (D/P) and white blood cell (WBC)-enriched product, 2) DMSO concentration of D/P, 3) freezing program, and 4) storage method on WBC quality. WBC-enriched product without CD34+ cells was used instead of HPCs. This was divided into six or eight portions. D/P (20 or 50%; precooled or room temperature [RT]) was added to the WBC-enriched product (precooled or RT), resulting in 10% DMSO, while monitoring temperature. The product was frozen using controlled-rate freezing ("fast-rate" or "slow-rate") and placed in vapor-phase or liquid nitrogen. After thawing, WBC recovery and viability were determined. Temperature increased most for precooled D/P to precooled WBC-enriched product, without influence of 20 or 50% D/P, but remained for all variations below 30°C. WBC recovery for both freezing programs was more than 95%. Recovery of WBC viability was higher for slow-rate freezing compared to fast-rate freezing (74% vs. 61%; p < 0.05) and also for 50% compared to 20% D/P (two test variations). Effect of precooling D/P or WBC-enriched product and of storage in vapor-phase or liquid nitrogen was marginal. Based on these results, precooling is not necessary. Fifty percent D/P is preferred over 20% D/P. Slow-rate freezing is preferred over fast-rate freezing. For safety reasons storage in vapor-phase nitrogen is preferred over storage in liquid nitrogen. Additional testing using real HPCs might be necessary. © 2014 AABB.

Saccharomyces cerevisiae glycerol/H+ symporter Stl1p is essential for cold/near-freeze and freeze stress adaptation. A simple recipe with high biotechnological potential is given

PubMed Central

2010-01-01

Background Freezing is an increasingly important means of preservation and storage of microbial strains used for many types of industrial applications including food processing. However, the yeast mechanisms of tolerance and sensitivity to freeze or near-freeze stress are still poorly understood. More knowledge on this regard would improve their biotechnological potential. Glycerol, in particular intracellular glycerol, has been assigned as a cryoprotectant, also important for cold/near-freeze stress adaptation. The S. cerevisiae glycerol active transporter Stl1p plays an important role on the fast accumulation of glycerol. This gene is expressed under gluconeogenic conditions, under osmotic shock and stress, as well as under high temperatures. Results We found that cells grown on STL1 induction medium (YPGE) and subjected to cold/near-freeze stress, displayed an extremely high expression of this gene, also visible at glycerol/H+ symporter activity level. Under the same conditions, the strains harbouring this transporter accumulated more than 400 mM glycerol, whereas the glycerol/H+ symporter mutant presented less than 1 mM. Consistently, the strains able to accumulate glycerol survive 25-50% more than the stl1Δ mutant. Conclusions In this work, we report the contribution of the glycerol/H+ symporter Stl1p for the accumulation and maintenance of glycerol intracellular levels, and consequently cell survival at cold/near-freeze and freeze temperatures. These findings have a high biotechnological impact, as they show that any S. cerevisiae strain already in use can become more resistant to cold/freeze-thaw stress just by simply adding glycerol to the broth. The combination of low temperatures with extracellular glycerol will induce the transporter Stl1p. This solution avoids the use of transgenic strains, in particular in food industry. PMID:21047428

Effect of freezing temperature on the color of frozen salmon.

PubMed

Ottestad, Silje; Enersen, Grethe; Wold, Jens Petter

2011-09-01

New freezing methods developed with the purpose of improved product quality after thawing can sometimes be difficult to get accepted in the market. The reason for this is the formation of ice crystals that can give the product a temporary color loss and make it less appealing. We have here used microscopy to study ice crystal size as a function of freezing temperature by investigating the voids in the cell tissue left by the ice crystals. We have also investigated how freezing temperature affects the color and the visible absorption spectra of frozen salmon. Freezing temperatures previously determined to be the best for quality after thawing (-40 to -60 °C) were found to cause a substantial loss in perceived color intensity during frozen state. This illustrated the conflict between optimal freezing temperatures with respect to quality after thawing against visual appearance during frozen state. Low freezing temperatures gave many small ice crystals, increased light scattering and an increased absorption level for all wavelengths in the visible region. Increased astaxanthin concentration on the other hand would give higher absorption at 490 nm. The results showed a clear potential of using visible interactance spectroscopy to differentiate between poor product coloration due to lack of pigmentation and temporary color loss due to light scattering by ice crystal. This type of measurements could be a useful tool in the development of new freezing methods and to monitor ice crystal growth during frozen storage. It could also potentially be used by the industry to prove good product quality. In this article we have shown that freezing food products at intermediate to low temperatures (-40 to -80 °C) can result in paler color during frozen state, which could affect consumer acceptance. We have also presented a spectroscopic method that can separate between poor product color and temporary color loss due to freezing. © 2011 Institute of Food Technologists®

Proteomic analysis of spring freeze-stress responsive proteins in leaves of bread wheat (Triticum aestivum L.).

PubMed

Han, Qiaoxia; Kang, Guozhang; Guo, Tiancai

2013-02-01

Following three-day exposure to -5 °C simulated spring freeze stress, wheat plants at the anther connective tissue formation phase of spike development displayed the drooping and wilting of leaves and markedly increased rates of relative electrolyte leakage. We analysed freeze-stress responsive proteins in wheat leaves at one and three days following freeze-stress exposure, using two-dimensional electrophoresis and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Our results indicate that out of 75 protein spots successfully identified under freeze-stress conditions 52 spots were upregulated and 18 were downregulated. These spring freeze-stress responsive proteins were involved in signal transduction, stress/defence/detoxification, protein metabolism (i.e. translation, processing, and degradation), photosynthesis, amino acid metabolism, carbohydrate metabolism, and energy pathways, and may therefore be functionally relevant for many biological processes. The enhanced accumulation of signal transduction proteins such as a C2H2 zinc finger protein, stress/defence/detoxification proteins including LEA-related COR protein, disease resistance protein, Cu/Zn superoxide dismutase, and two ascorbate peroxidases may play crucial roles in the mechanisms of response to spring freeze stress in wheat plants. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Reproductive technology and the life course: current debates and research in social egg freezing.

PubMed

Baldwin, Kylie; Culley, Lorraine; Hudson, Nicky; Mitchell, Helene

2014-09-01

While there are currently few confirmed births from previously frozen eggs in the UK, the improved outcomes of new technologies of vitrification and intra-cytoplasmic sperm injection (ICSI) have led to the marketing of egg freezing for non-medical reasons, whereby women are offered the possibility of preserving their eggs until such time as they wish to have a child. Non-academic commentary on this phenomenon has commonly constructed it within a neo-liberal discourse of 'choice', whereby women are positioned as choosing to 'delay motherhood,' often for reasons relating to their careers. However, there have been relatively few research studies which explore either women's awareness and understandings of social egg freezing or the reasons why women consider or undertake egg freezing. This paper summarises the current academic discussion surrounding social egg freezing and outlines the limited body of empirical literature identified from a systematic search of relevant databases. The potential benefits and harms of social egg freezing and the ethical issues it raises are well rehearsed in existing literature, but there is limited empirical evidence about who is accessing social egg freezing, why they are taking this option and what their experiences and future intentions are.

Extracellular ice phase transitions in insects.

PubMed

Hawes, T C

2014-01-01

At temperatures below their temperature of crystallization (Tc), the extracellular body fluids of insects undergo a phase transition from liquid to solid. Insects that survive the transition to equilibrium (complete freezing of the body fluids) are designated as freeze tolerant. Although this phenomenon has been reported and described in many Insecta, current nomenclature and theory does not clearly delineate between the process of transition (freezing) and the final solid phase itself (the frozen state). Thus freeze tolerant insects are currently, by convention, described in terms of the temperature at which the crystallization of their body fluids is initiated, Tc. In fact, the correct descriptor for insects that tolerate freezing is the temperature of equilibrium freezing, Tef. The process of freezing is itself a separate physical event with unique physiological stresses that are associated with ice growth. Correspondingly there are a number of insects whose physiological cryo-limits are very specifically delineated by this transitional envelope. The distinction also has considerable significance for our understanding of insect cryobiology: firstly, because the ability to manage endogenous ice growth is a fundamental segregator of cryotype; and secondly, because our understanding of internal ice management is still largely nascent.

Cryopreservation of human sperm: efficacy and use of a new nitrogen-free controlled rate freezer versus liquid nitrogen vapour freezing.

PubMed

Creemers, E; Nijs, M; Vanheusden, E; Ombelet, W

2011-12-01

Preservation of spermatozoa is an important aspect of assisted reproductive medicine. The aim of this study was to investigate the efficacy and use of a recently developed liquid nitrogen and cryogen-free controlled rate freezer and this compared with the classical liquid nitrogen vapour freezing method for the cryopreservation of human spermatozoa. Ten patients entering the IVF programme donated semen samples for the study. Samples were analysed according to the World Health Organization guidelines. No significant difference in total sperm motility after freeze-thawing between the new technique and classical technique was demonstrated. The advantage of the new freezing technique is that it uses no liquid nitrogen during the freezing process, hence being safer to use and clean room compatible. Investment costs are higher for the apparatus but running costs are only 1% in comparison with classical liquid nitrogen freezing. In conclusion, post-thaw motility of samples frozen with the classical liquid nitrogen vapour technique was comparable with samples frozen with the new nitrogen-free freezing technique. This latter technique can thus be a very useful asset to the sperm cryopreservation laboratory. © 2011 Blackwell Verlag GmbH.

Freezing behavior of adherent neuron-like cells and morphological change and viability of post-thaw cells.

PubMed

Uemura, Makoto; Ishiguro, Hiroshi

2015-04-01

Freezing of nerve cells forming a neuronal network has largely been neglected, despite the fact that the cryopreservation of nerve cells benefits the study of cells in the areas of medicine and poison screening. Freezing of nerve cells is also attractive for studying cell morphology because of the characteristic long, thread-like neurites extending from the cell body. In the present study, freezing of neuron-like cells adhering to the substrate (differentiated PC12 cells), in physiological saline, was investigated in order to understand the fundamental freezing and thawing characteristics of nerve cells with neurites. The microscopic freezing behavior of cells under different cooling rates was observed. Next, the post-thaw morphological changes in the cells, including the cytoskeleton, were investigated and post-thaw cell viability was evaluated by dye exclusion using propidium iodide. Two categories of morphological changes, beading and shortening of the neurites, were found and quantified. Also, the morphological changes of neurites due to osmotic stress from sodium chloride were studied to gain a better understanding of causation. The results showed that morphological changes and cell death were promoted with a decrease in end temperature during freezing. Copyright © 2015 Elsevier Inc. All rights reserved.

Role of ice structuring proteins on freezing-thawing cycles of pasta sauces.

PubMed

Calderara, Marianna; Deorsola, Fabio A; Bensaid, Samir; Fino, Debora; Russo, Nunzio; Geobaldo, Francesco

2016-12-01

The freezing of the food is one of the most important technological developments for the storage of food in terms of quality and safety. The aim of this work was to study the role of an ice structuring protein (ISP) on freezing-thawing cycles of different solutions and commercial Italian pasta sauces. Ice structuring proteins were related to the modification of the structure of ice. The results showed that the freezing time of an aqueous solution containing the protein was reduced to about 20% with respect to a pure water solution. The same effect was demonstrated in sugar-containing solutions and in lipid-containing sauces. The study proved a specific role of ISP during thawing, inducing a time decrease similar to that of freezing and even more important in the case of tomato-based sauces. This work demonstrated the role of ISP in the freezing-thawing process, showing a significant reduction of processing in the freezing and thawing phase by adding the protein to pure water and different sugar-, salt- and lipid-containing solutions and commercial sauces, with considerable benefits for the food industry in terms of costs and food quality.

Identification of Arabidopsis mutants with altered freezing tolerance.

PubMed

Perea-Resa, Carlos; Salinas, Julio

2014-01-01

Low temperature is an important determinant in the configuration of natural plant communities and defines the range of distribution and growth of important crops. Some plants, including Arabidopsis, have evolved sophisticated adaptive mechanisms to tolerate low and freezing temperatures. Central to this adaptation is the process of cold acclimation. By means of this process, many plants from temperate regions are able to develop or increase their freezing tolerance in response to low, nonfreezing temperatures. The identification and characterization of factors involved in freezing tolerance are crucial to understand the molecular mechanisms underlying the cold acclimation response and have a potential interest to improve crop tolerance to freezing temperatures. Many genes implicated in cold acclimation have been identified in numerous plant species by using molecular approaches followed by reverse genetic analysis. Remarkably, however, direct genetic analyses have not been conveniently exploited in their capacity for identifying genes with pivotal roles in that adaptive response. In this chapter, we describe a protocol for evaluating the freezing tolerance of both non-acclimated and cold-acclimated Arabidopsis plants. This protocol allows the accurate and simple screening of mutant collections for the identification of novel factors involved in freezing tolerance and cold acclimation.

A New Freezing Method Using Pre-Dehydration by Microwave-Vacuum Drying

NASA Astrophysics Data System (ADS)

Tsuruta, Takaharu; Hamidi, Nurkholis

Partial dehydration by microwave-vacuum drying has been applied to tuna and strawberry in order to reduce cell-damages caused by the formation of large ice-crystals during freezing. The samples were subjected to microwave vacuum drying at pressure of 5 kPa and temperature less than 27°C to remove small amount of water prior to freezing. The tuna were cooled by using the freezing chamber at temperature -50°C or -150°C, while the strawberries were frozen at temperature -30°C or -80°C, respectively. The temperature transients in tuna showed that removing some water before freezing made the freezing time shorter. The observations of ice crystal clearly indicated that rapid cooling and pre-dehydration prior to freezing were effective in minimizing the size of ice crystal. It is also understood that the formation of large ice crystals has a close relation to the cell damages. After thawing, the observation of microstructure was done on the tuna and strawberry halves. The pre-dehydrated samples showed a better structure than the un-dehydrated one. It is concluded that the pre-dehydration by microwave-vacuum drying is one promising method for the cryo-preservation of foods.

Simulations of Polar Stratospheric Clouds and Denitrification Using Laboratory Freezing Rates

NASA Technical Reports Server (NTRS)

Drdla, Katja; Tabazadeh, Azadeh; Gore, Warren J. (Technical Monitor)

2001-01-01

During the 1999-2000 Arctic winter, the SAGE (Stratospheric Aerosol and Gas Experiment) III Ozone Loss and Validation Experiment (SOLVE) provided evidence of widespread solid-phase polar stratospheric clouds (PSCs) accompanied by severe nitrification. Previous simulations have shown that a freezing process occurring at temperatures above the ice frost point is necessary to explain these observations. In this work, the nitric acid freezing rates measured by Salcedo et al. and discussed by Tabazadeh et al. have been examined. These freezing rates have been tested in winter-long microphysical simulations of the 1999-2000 Arctic vortex evolution in order to determine whether they can explain the observations. A range of cases have been explored, including whether the PSC particles are composed of nitric acid dihydrate or trihydrate, whether the freezing process is a bulk process or occurs only on the particle surfaces, and uncertainties in the derived freezing rates. Finally, the possibility that meteoritic debris enhances the freezing rate has also been examined. The results of these simulations have been compared with key PSC and denitrification measurements made by the SOLVE campaign. The cases that best reproduce the measurements will he highlighted, with a discussion of the implications for our understanding of PSCs.

Beneficial effect of directional freezing on in vitro viability of cryopreserved sheep whole ovaries and ovarian cortical slices.

PubMed

Maffei, S; Pennarossa, G; Brevini, T A L; Arav, A; Gandolfi, F

2014-01-01

Does directional freezing improve the structural and functional integrity of ovarian fragments compared with conventional slow freezing and to whole ovary cryopreservation? Compared with slow freezing, the use of directional freezing significantly improves all structural and functional parameters of ovarian fragments assessed in vitro and, overall, whole ovaries were better preserved than ovarian fragments. Directional freezing has been developed to provide an alternative way to cryopreserve large biological samples and it is known to improve the structural and functional integrity of whole ovaries. Conventional slow freezing of ovarian fragments is the procedure more widely used in clinical settings but it causes substantial structural damage that limits the functional period after transfer back into the patient. We performed a 2 × 2 factorial design experiment on a total of 40 sheep ovaries, divided into four groups (n = 10 ovaries per group): (i) directional freezing of whole ovary (DFwo); (ii) directional freezing of ovarian fragments (DFof); (iii) conventional freezing of whole ovary (CFwo); (iv) conventional freezing of ovarian fragments (CFof). An additional eight ovaries were used as fresh controls. Ewe ovaries were randomly assigned to one of the experimental groups and frozen accordingly. Upon thawing, ovarian tissue was examined morphologically and cultured in vitro for 7 days. Samples were analyzed for cell proliferation and apoptosis, for DNA damage and repair activity, and for the presence of a panel of heat shock proteins (HSPs) by immunohistochemistry. Most studied parameters were significantly improved (P < 0.05) in all samples cryopreserved with directional compared with slow freezing. The proportion of primordial follicles, which developed to the primary stage in whole ovaries (53 ± 1.7%) and in ovarian fragments (44 ± 1.8%) cryopreserved with directional freezing, was greater than with slow frozen whole ovaries (6 ± 0.5%, P = 0.001) or fragments (32 ± 1.5%, P = 0.004). After 7 days of culture, cell proliferation in DFwo (28 ± 0.73%) was the highest of all groups (P < 0.05) followed by DFof (23 ± 0.81%), CFof (20 ± 0.79%) and CFwo (9 ± 0.85%). Directional freezing also resulted in a better preservation of the cell capacity to repair DNA damage compared with slow freezing both in whole ovaries and ovarian fragments. Apoptosis and HSP protein levels were significantly increased only in the CFwo group. Direct comparison demonstrated that, overall, DFwo had better parameters than DFof and was no different from the fresh controls. The study is limited to an in vitro evaluation and uses sheep ovaries, which are smaller than human ovaries and therefore may withstand the procedures better. Improved integrity of ovarian morphology may translate to improved outcomes after transplantation. Alternatively, the particularly good preservation of whole ovaries suggests they could provide a source of ovarian follicles for in vitro culture in those cases when the presence of malignant cells poses a substantial risk for the patient. Supported by: Associazione Italiana per la Ricerca sul Cancro (AIRC) IG 10376, Carraresi Foundation and by Legge 7 Regione Autonoma Sardegna (R.A.S). There are no conflicts of interest.

49 CFR 1039.10 - Exemption of agricultural commodities except grain, soybeans, and sunflower seeds.

Code of Federal Regulations, 2010 CFR

2010-10-01

... other marine products. 20-11 Fresh meat. 20-15 Fresh dressed poultry. 20-17 Processed poultry. 20-21.... 20-999-76 Freeze-dried poultry. 20-999-77 Freeze-dried meat. 20-999-78 Freeze-dried salad ingredients...

Effect of Freezing on the Level of Contaminants in Uncontrolled Hazardous Waste Sites. Part 1. Literature Review.

DTIC Science & Technology

1986-07-01

pure water. Dissolved ions in the soil solution lower the freezing point; this is called freezing point depression. Many of the early studies of...them in the remaining soil solution . The temperature and concentration of this solution affect the chemical reactions and the forms of ions in...in the soil solution freezes, more concentrated "% solutes will be present in soil solution . 3. Water will travel even in frozen soils and sediments

Preparation of freezing quantum state for quantum coherence

NASA Astrophysics Data System (ADS)

Yang, Lian-Wu; Man, Zhong-Xiao; Zhang, Ying-Jie; Han, Feng; Du, Shao-jiang; Xia, Yun-Jie

2018-06-01

We provide a method to prepare the freezing quantum state for quantum coherence via unitary operations. The initial product state consists of the control qubit and target qubit; when it satisfies certain conditions, the initial product state converts into the particular Bell diagonal state under the unitary operations, which have the property of freezing of quantum coherence under quantum channels. We calculate the frozen quantum coherence and corresponding quantum correlations, and find that the quantities are determined by the control qubit only when the freezing phenomena occur.

New High-Performance Droplet Freezing Assay (HP-DFA) for the Analysis of Ice Nuclei with Complex Composition

NASA Astrophysics Data System (ADS)

Kunert, Anna Theresa; Scheel, Jan Frederik; Helleis, Frank; Klimach, Thomas; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine

2016-04-01

Freezing of water above homogeneous freezing is catalyzed by ice nucleation active (INA) particles called ice nuclei (IN), which can be of various inorganic or biological origin. The freezing temperatures reach up to -1 °C for some biological samples and are dependent on the chemical composition of the IN. The standard method to analyze IN in solution is the droplet freezing assay (DFA) established by Gabor Vali in 1970. Several modifications and improvements were already made within the last decades, but they are still limited by either small droplet numbers, large droplet volumes or inadequate separation of the single droplets resulting in mutual interferences and therefore improper measurements. The probability that miscellaneous IN are concentrated together in one droplet increases with the volume of the droplet, which can be described by the Poisson distribution. At a given concentration, the partition of a droplet into several smaller droplets leads to finely dispersed IN resulting in better statistics and therefore in a better resolution of the nucleation spectrum. We designed a new customized high-performance droplet freezing assay (HP-DFA), which represents an upgrade of the previously existing DFAs in terms of temperature range and statistics. The necessity of observing freezing events at temperatures lower than homogeneous freezing due to freezing point depression, requires high-performance thermostats combined with an optimal insulation. Furthermore, we developed a cooling setup, which allows both huge and tiny temperature changes within a very short period of time. Besides that, the new DFA provides the analysis of more than 750 droplets per run with a small droplet volume of 5 μL. This enables a fast and more precise analysis of biological samples with complex IN composition as well as better statistics for every sample at the same time.

The impact of freeze-drying infant fecal samples on measures of their bacterial community profiles and milk-derived oligosaccharide content.

PubMed

Lewis, Zachery T; Davis, Jasmine C C; Smilowitz, Jennifer T; German, J Bruce; Lebrilla, Carlito B; Mills, David A

2016-01-01

Infant fecal samples are commonly studied to investigate the impacts of breastfeeding on the development of the microbiota and subsequent health effects. Comparisons of infants living in different geographic regions and environmental contexts are needed to aid our understanding of evolutionarily-selected milk adaptations. However, the preservation of fecal samples from individuals in remote locales until they can be processed can be a challenge. Freeze-drying (lyophilization) offers a cost-effective way to preserve some biological samples for transport and analysis at a later date. Currently, it is unknown what, if any, biases are introduced into various analyses by the freeze-drying process. Here, we investigated how freeze-drying affected analysis of two relevant and intertwined aspects of infant fecal samples, marker gene amplicon sequencing of the bacterial community and the fecal oligosaccharide profile (undigested human milk oligosaccharides). No differences were discovered between the fecal oligosaccharide profiles of wet and freeze-dried samples. The marker gene sequencing data showed an increase in proportional representation of Bacteriodes and a decrease in detection of bifidobacteria and members of class Bacilli after freeze-drying. This sample treatment bias may possibly be related to the cell morphology of these different taxa (Gram status). However, these effects did not overwhelm the natural variation among individuals, as the community data still strongly grouped by subject and not by freeze-drying status. We also found that compensating for sample concentration during freeze-drying, while not necessary, was also not detrimental. Freeze-drying may therefore be an acceptable method of sample preservation and mass reduction for some studies of microbial ecology and milk glycan analysis.

Transcriptional and metabolomic analysis of Ascophyllum nodosum mediated freezing tolerance in Arabidopsis thaliana

PubMed Central

2012-01-01

Background We have previously shown that lipophilic components (LPC) of the brown seaweed Ascophyllum nodosum (ANE) improved freezing tolerance in Arabidopsis thaliana. However, the mechanism(s) of this induced freezing stress tolerance is largely unknown. Here, we investigated LPC induced changes in the transcriptome and metabolome of A. thaliana undergoing freezing stress. Results Gene expression studies revealed that the accumulation of proline was mediated by an increase in the expression of the proline synthesis genes P5CS1 and P5CS2 and a marginal reduction in the expression of the proline dehydrogenase (ProDH) gene. Moreover, LPC application significantly increased the concentration of total soluble sugars in the cytosol in response to freezing stress. Arabidopsis sfr4 mutant plants, defective in the accumulation of free sugars, treated with LPC, exhibited freezing sensitivity similar to that of untreated controls. The 1H NMR metabolite profile of LPC-treated Arabidopsis plants exposed to freezing stress revealed a spectrum dominated by chemical shifts (δ) representing soluble sugars, sugar alcohols, organic acids and lipophilic components like fatty acids, as compared to control plants. Additionally, 2D NMR spectra suggested an increase in the degree of unsaturation of fatty acids in LPC treated plants under freezing stress. These results were supported by global transcriptome analysis. Transcriptome analysis revealed that LPC treatment altered the expression of 1113 genes (5%) in comparison with untreated plants. A total of 463 genes (2%) were up regulated while 650 genes (3%) were down regulated. Conclusion Taken together, the results of the experiments presented in this paper provide evidence to support LPC mediated freezing tolerance enhancement through a combination of the priming of plants for the increased accumulation of osmoprotectants and alteration of cellular fatty acid composition. PMID:23171218

Experimental and numerical study on frost heave of saturated rock under uniform freezing conditions

NASA Astrophysics Data System (ADS)

Lv, Zhitao; Xia, Caichu; Li, Qiang

2018-04-01

A series of freezing experiments are conducted on saturated sandstone and mortar specimens to investigate the frost heave of saturated rock under uniform freezing conditions. The experimental results show that the frost heave of saturated rock is isotropic under uniform freezing conditions. During the freezing process, three stages are observed in the curves of variation of total frost heaving strain versus time: the thermal contraction stage, the frost heaving stage and the steady stage. Moreover, the amount of final stable frost heave first increases and then decreases with decrease in freezing temperature, and the maximum final stable frost heave occurs at different freezing temperature in saturated sandstone and mortar. Furthermore, a coupled thermal-mechanical (TM) model of frost heave of saturated rock is proposed in which a constraint coefficient \\zeta is used to consider the susceptibility of the internal rock grain structure to the expansion of pore ice. Then, numerical simulations are implemented with COMSOL to solve the governing equations of the TM model. Comparisons of the numerical results with the experimental results are performed to demonstrate the reliability of the model. The influences of elastic modulus and porosity on frost heave are also investigated, and the results show that the total frost heaving strain decreases non-linearly with increasing elastic modulus, and the decrease is significant when the elastic modulus is less than 3000 MPa, or approximately five times the elastic modulus of ice. In addition, the total frost heaving strain increases linearly with increasing porosity. Finally, an empirical equation between total frost heaving strain and freezing temperature is proposed and the equation well describes the variation of total frost heaving strain with freezing temperature.

Overexpression of the calcineurin target CRZ1 provides freeze tolerance and enhances the fermentative capacity of baker's yeast.

PubMed

Panadero, Joaquín; Hernández-López, Maria José; Prieto, José Antonio; Randez-Gil, Francisca

2007-08-01

Recent years have shown a huge growth in the market of industrial baker's yeasts (Saccharomyces cerevisiae), with the need for strains affording better performance in prefrozen dough. Evidence suggests that during the freezing process, cells can suffer biochemical damage caused by osmotic stress. Nevertheless, the involvement of ion-responsive transcriptional factors and pathways in conferring freeze resistance has not yet been examined. Here, we have investigated the role of the salt-responsive calcineurin-Crz1p pathway in mediating tolerance to freezing by industrial baker's yeast. Overexpression of CRZ1 in the industrial HS13 strain increased both salt and freeze tolerance and improved the leavening ability of baker's yeast in high-sugar dough. Moreover, engineered cells were able to produce more gas during fermentation of prefrozen dough than the parental strain. Similar effects were observed for overexpression of TdCRZ1, the homologue to CRZ1 in Torulaspora delbrueckii, suggesting that expression of calcineurin-Crz1p target genes can alleviate the harmful effects of ionic stress during freezing. However, overexpression of STZ and FTZ, two unrelated Arabidopsis thaliana genes encoding Cys(2)/His(2)-type zinc finger proteins, also conferred freeze resistance in yeast. Furthermore, experiments with Deltacnb1 and Deltacrz1 mutants failed to show a freeze-sensitive phenotype, even in cells pretreated with NaCl. Overall, our results demonstrate that overexpression of CRZ1 has the potential to be a useful tool for increasing freeze tolerance and fermentative capacity in industrial strains. However, these effects do not appear to be mediated through activation of known salt-responding pathways.

Effect of Repeated Freeze-Thaw Cycles on Beef Quality and Safety

PubMed Central

Rahman, Mohammad Hafizur; Hossain, Mohammad Mujaffar; Rahman, Syed Mohammad Ehsanur; Hashem, Mohammad Abul

2014-01-01

The objectives of this study were to know the effect of repeated freeze-thaw cycles of beef on the sensory, physicochemical quality and microbiological assessment. The effects of three successive freeze-thaw cycles on beef forelimb were investigated comparing with unfrozen fresh beef for 75 d by keeping at −20±1℃. The freeze-thaw cycles were subjected to three thawing methods and carried out to know the best one. As the number of freeze-thaw cycles increased color and odor declined significantly before cook within the cycles and tenderness, overall acceptability also declined among the cycles after cook by thawing methods. The thawing loss increased and dripping loss decreased significantly (p<0.05). Water holding capacity (WHC) increased (p<0.05) until two cycles and then decreased. Cooking loss increased in cycle 1 and 3, but decreased in cycle 2. pH decreased significantly (p<0.05) among the cycles. Moreover, drip loss, cooking loss and WHC were affected (p<0.05) by thawing methods within the cycles. 2-Thiobarbituric acid (TBARS) value increased (p<0.05) gradually within the cycles and among the cycles by thawing methods. Total viable bacteria, total coliform and total yeast-mould count decreased significantly (p<0.05) within and among the cycles in comparison to the initial count in repeated freeze-thaw cycles. As a result, repeated freeze-thaw cycles affected the sensory, physicochemical and microbiological qua- lity of beef, causing the deterioration of beef quality, but improved the microbiological quality. Although repeated freeze-thaw cycles did not affect much on beef quality and safety but it may be concluded that repeated freeze and thaw should be minimized in terms of beef color for commercial value and WHC and tenderness/juiciness for eating quality. PMID:26761286

Cryoprotectants and Extreme Freeze Tolerance in a Subarctic Population of the Wood Frog

PubMed Central

Costanzo, Jon P.; Reynolds, Alice M.; do Amaral, M. Clara F.; Rosendale, Andrew J.; Lee, Richard E.

2015-01-01

Wood frogs (Rana sylvatica) exhibit marked geographic variation in freeze tolerance, with subarctic populations tolerating experimental freezing to temperatures at least 10-13 degrees Celsius below the lethal limits for conspecifics from more temperate locales. We determined how seasonal responses enhance the cryoprotectant system in these northern frogs, and also investigated their physiological responses to somatic freezing at extreme temperatures. Alaskan frogs collected in late summer had plasma urea levels near 10 μmol ml-1, but this level rose during preparation for winter to 85.5 ± 2.9 μmol ml-1 (mean ± SEM) in frogs that remained fully hydrated, and to 186.9 ± 12.4 μmol ml-1 in frogs held under a restricted moisture regime. An osmolality gap indicated that the plasma of winter-conditioned frogs contained an as yet unidentified osmolyte(s) that contributed about 75 mOsmol kg-1 to total osmotic pressure. Experimental freezing to –8°C, either directly or following three cycles of freezing/thawing between –4 and 0°C, or –16°C increased the liver’s synthesis of glucose and, to a lesser extent, urea. Concomitantly, organs shed up to one-half (skeletal muscle) or two-thirds (liver) of their water, with cryoprotectant in the remaining fluid reaching concentrations as high as 0.2 and 2.1 M, respectively. Freeze/thaw cycling, which was readily survived by winter-conditioned frogs, greatly increased hepatic glycogenolysis and delivery of glucose (but not urea) to skeletal muscle. We conclude that cryoprotectant accrual in anticipation of and in response to freezing have been greatly enhanced and contribute to extreme freeze tolerance in northern R. sylvatica. PMID:25688861

Inactivation kinetics of Vibrio vulnificus in phosphate-buffered saline at different freezing and storage temperatures and times.

PubMed

Seminario, Diana M; Balaban, Murat O; Rodrick, Gary

2011-03-01

Vibrio vulnificus (Vv) is a pathogen that can be found in raw oysters. Freezing can reduce Vv and increase the shelf life of oysters. The objective of this study was to develop predictive inactivation kinetic models for pure cultures of Vv at different frozen storage temperatures and times. Vv was diluted in phosphate-buffered saline (PBS) to obtain about 10(7) CFU/mL. Samples were frozen at -10, -35, and -80 °C (different freezing rates), and stored at different temperatures. Survival of Vv was followed after freezing and storage at -10 °C (0, 3, 6, and 9 d) and at -35 and -80 °C (every week for 6 wk). For every treatment, time-temperature data was obtained using thermocouples in blank vials. Predictive models were developed using first-order, Weibull and Peleg inactivation kinetics. Different freezing temperatures did not significantly (α = 0.05) affect survival of Vv immediately after freezing. The combined effect of freezing and 1 wk frozen storage resulted in 1.5, 2.6, and 4.9 log10 reductions for samples stored at -80, -35, and -10 °C, respectively. Storage temperature was the critical parameter in survival of Vv. A modified Weibull model successfully predicted Vv survival during frozen storage: log10 Nt = log 10No - 1.22 - ([t/10{-1.163-0.0466T}][0.00025T(2) + 0.049325]). N(o) and N(t) are initial and time t (d) survival counts, T is frozen storage temperature, Celsius degree. Vibrio vulnificus can be inactivated by freezing. Models to predict survival of V. vulnificus at different freezing temperatures and times were developed. This is the first step towards the prediction of V. vulnificus related safety of frozen oysters.

Three keys to the radiation of angiosperms into freezing environments.

PubMed

Zanne, Amy E; Tank, David C; Cornwell, William K; Eastman, Jonathan M; Smith, Stephen A; FitzJohn, Richard G; McGlinn, Daniel J; O'Meara, Brian C; Moles, Angela T; Reich, Peter B; Royer, Dana L; Soltis, Douglas E; Stevens, Peter F; Westoby, Mark; Wright, Ian J; Aarssen, Lonnie; Bertin, Robert I; Calaminus, Andre; Govaerts, Rafaël; Hemmings, Frank; Leishman, Michelle R; Oleksyn, Jacek; Soltis, Pamela S; Swenson, Nathan G; Warman, Laura; Beaulieu, Jeremy M

2014-02-06

Early flowering plants are thought to have been woody species restricted to warm habitats. This lineage has since radiated into almost every climate, with manifold growth forms. As angiosperms spread and climate changed, they evolved mechanisms to cope with episodic freezing. To explore the evolution of traits underpinning the ability to persist in freezing conditions, we assembled a large species-level database of growth habit (woody or herbaceous; 49,064 species), as well as leaf phenology (evergreen or deciduous), diameter of hydraulic conduits (that is, xylem vessels and tracheids) and climate occupancies (exposure to freezing). To model the evolution of species' traits and climate occupancies, we combined these data with an unparalleled dated molecular phylogeny (32,223 species) for land plants. Here we show that woody clades successfully moved into freezing-prone environments by either possessing transport networks of small safe conduits and/or shutting down hydraulic function by dropping leaves during freezing. Herbaceous species largely avoided freezing periods by senescing cheaply constructed aboveground tissue. Growth habit has long been considered labile, but we find that growth habit was less labile than climate occupancy. Additionally, freezing environments were largely filled by lineages that had already become herbs or, when remaining woody, already had small conduits (that is, the trait evolved before the climate occupancy). By contrast, most deciduous woody lineages had an evolutionary shift to seasonally shedding their leaves only after exposure to freezing (that is, the climate occupancy evolved before the trait). For angiosperms to inhabit novel cold environments they had to gain new structural and functional trait solutions; our results suggest that many of these solutions were probably acquired before their foray into the cold.

Freezing and drying effects on potential plant contributions to phosphorus in runoff.

PubMed

Roberson, Tiffany; Bundy, Larry G; Andraski, Todd W

2007-01-01

Phosphorus (P) in runoff from landscapes can promote eutrophication of natural waters. Soluble P released from plant material can contribute significant amounts of P to runoff particularly after plant freezing or drying. This study was conducted to evaluate P losses from alfalfa or grass after freezing or drying as potential contributors to runoff P. Alfalfa (Medicago sativa L.) and grass (principally, Agropyron repens L.) plant samples were subjected to freezing and drying treatments to determine P release. Simulated rainfall runoff and natural runoff from established alfalfa fields and a grass waterway were collected to study P contributions from plant tissue to runoff. The effects of freezing and drying on P released from plant tissue were simulated by a herbicide treatment in selected experiments. Soluble reactive P (SP) extracted from alfalfa and grass samples was markedly increased by freezing or drying. In general, SP extracted from plant samples increased in the order fresh < frozen < frozen/thawed < dried, and averaged 1, 8, 14, and 26% of total P in alfalfa, respectively. Soluble reactive P extracted from alfalfa after freezing or drying increased with increasing soil test P (r(2) = 0.64 to 0.68), suggesting that excessive soil P levels increased the risk of plant P contributions to runoff losses. In simulated rainfall studies, paraquat (1,1'-dimethyl-4, 4''-bipyridinium ion) treatment of alfalfa increased P losses in runoff, and results suggested that this treatment simulated the effects of drying on plant P loss. In contrast to the simulated rainfall results, natural runoff studies over 2 yr did not show higher runoff P losses that could be attributed to P from alfalfa. Actual P losses likely depend on the timing and extent of plant freezing and drying and of precipitation events after freezing.

Identification, analysis and monitoring of risks of freezing affecting aircraft flying over the Guadarrama Mountains (Spain)

NASA Astrophysics Data System (ADS)

Fernández-González, Sergio; Sánchez, José Luis; Gascón, Estíbaliz; Merino, Andrés; Hermida, Lucía; López, Laura; Marcos, José Luis; García-Ortega, Eduardo

2014-05-01

Freezing is one of the main causes of aircraft accidents registered over the last few decades. This means it is very important to be able to predict this situation so that aircraft can change their routes to avoid freezing risk areas. Also, by using satellites it is possible to observe changes in the horizontal and vertical extension of cloud cover likely to cause freezing in real time as well as microphysical changes in the clouds. The METEOSAT Second Generation (MSG) makes it possible to create different red-green-blue (RGB) compositions that provide a large amount of information associated with the microphysics of clouds, in order to identify super-cooled water clouds that pose a high risk of freezing to aircraft. During the winter of 2011/12 in the Guadarrama Mountains, in the centre of the Iberian Peninsula, a series of scientific flights (conducted by INTA) were organised in order to study the cloud systems that affected this region during the winter. On the flight of the 1st of February 2012, the aircraft was affected by freezing after crossing over a mountain ridge with supercooled large drops (SLD). Although freezing was not expected during that day's flight, the orography caused a series of mesoscale factors that led to the appearance of localised freezing conditions. By analysing this case, we have been able to conclude that the use of satellite images makes it possible to monitor the risk of freezing, especially under specific mesoscale circumstances. Acknowledgements S. Fernández-González acknowledges the grant supported from the FPU program (AP 2010-2093). This study was supported by the following grants: GRANIMETRO (CGL2010-15930); MICROMETEO (IPT-310000-2010-22). The authors would like to thank the INTA for its scientific flights.

Emerging freeze-drying process development and scale-up issues.

PubMed

Patel, Sajal Manubhai; Pikal, Michael J

2011-03-01

Although several guidelines do exist for freeze-drying process development and scale-up, there are still a number of issues that require additional attention. The objective of this review article is to discuss some emerging process development and scale-up issue with emphasis on effect of load condition and freeze-drying in novel container systems such as syringes, Lyoguard trays, ampoules, and 96-well plates. Understanding the heat and mass transfer under different load conditions and for freeze-drying in these novel container systems will help in developing a robust freeze-drying process which is also easier to scale-up. Further research and development needs in these emerging areas have also been addressed. © 2011 American Association of Pharmaceutical Scientists

7 CFR 305.7 - Quick freeze treatment requirements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 5 2012-01-01 2012-01-01 false Quick freeze treatment requirements. 305.7 Section 305.7 Agriculture Regulations of the Department of Agriculture (Continued) ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE PHYTOSANITARY TREATMENTS § 305.7 Quick freeze treatment...

Development and demonstration of a freezing drizzle algorithm for roadway environmental sensing Systems.

DOT National Transportation Integrated Search

2012-10-01

The primary goal of this project is to demonstrate the accuracy and utility of a freezing drizzle algorithm that can be implemented on roadway environmental sensing systems (ESSs). : The types of problems related to the occurrence of freezing precipi...

Development of a Method to Produce Freeze-Dried Cubes from 3 Pacific Salmon Species

USDA-ARS?s Scientific Manuscript database

Freeze-dried boneless skinless cubes of pink (Oncorhynchus gorbuscha), sockeye (Oncorhynchus nerka), and chum (Oncorhynchus keta) salmon were prepared and physical properties evaluated. To minimize freeze-drying time, the kinetics of dehydration and processing yields were investigated. The physical ...

Experimental research of "microcable in a microconduct" system stability to effect of freezing water

NASA Astrophysics Data System (ADS)

Andreev, Vladimir A.; Burdin, Vladimir A.; Nikulina, Tatiana G.; Alekhin, Ivan N.; Gavryushin, Sergey A.; Nikulin, Aleksey G.; Praporshchikov, Denis E.

2011-12-01

Results of experimental researches of "optical microcable in a microduct" system stability to effect of freezing water are presented. It is shown this system is steadier to water freezing in comparison to lighten optical cable in protective polymer tube.

Freeze-drying of lactic acid bacteria.

PubMed

Fonseca, Fernanda; Cenard, Stéphanie; Passot, Stéphanie

2015-01-01

Lactic acid bacteria are of great importance for the food and biotechnology industry. They are widely used as starters for manufacturing food (e.g., yogurt, cheese, fermented meats, and vegetables) and probiotic products, as well as for green chemistry applications. Freeze-drying or lyophilization is a convenient method for preservation of bacteria. By reducing water activity to values below 0.2, it allows long-term storage and low-cost distribution at suprazero temperatures, while minimizing losses in viability and functionality. Stabilization of bacteria via freeze-drying starts with the addition of a protectant solution to the bacterial suspension. Freeze-drying includes three steps, namely, (1) freezing of the concentrated and protected cell suspension, (2) primary drying to remove ice by sublimation, and (3) secondary drying to remove unfrozen water by desorption. In this chapter we describe a method for freeze-drying of lactic acid bacteria at a pilot scale, thus allowing control of the process parameters for maximal survival and functionality recovery.

'Banking time': egg freezing and the negotiation of future fertility.

PubMed

Waldby, Catherine

2015-01-01

This paper examines the relatively recent practice of non-medical egg freezing, in which women bank their eggs for later use in conceiving a child. Non-medical egg freezing has only been available for about the last five years, as new vitrification techniques have made the success rates for actual conception more reliable than the earlier method of slow freezing. I draw on interviews with both clinicians and women who have banked their eggs to consider how this novel practice articulates with broader issues about the relationship between sexuality, reproduction and the political economy of household formation. Non-medical egg-freezing provides a technical solution to a number of different problems women face with regard to the elongation of the life course, the extension of education, the cost of household establishment and the iterative nature of relationship formation, thematised by the ubiquity of internet dating among the interviewees. I focus on the ways women used egg freezing to manage and reconcile different forms of time.

Cryopreservation of day 2-3 embryos by vitrification yields better outcome than slow freezing.

PubMed

Levron, Jacob; Leibovitz, Oshrit; Brengauz, Masha; Gitman, Hila; Yerushalmi, Gil M; Katorza, Eldad; Gat, Itai; Elizur, Shai E

2014-03-01

To compare the outcome of vitrification versus slow freezing cryopreservation for cleavage stage day 2-3 embryos. A retrospective observational study. All thawed embryos assisted reproduction cycles between January 2010 and December 2012 at a single IVF laboratory of a Tertiary Medical Center. Five hundred and thirty-nine cycles of day 2-3 thawed embryos. In 327 of the thawed cycles, the embryos were vitrified and in 212 of the cycles the embryos were derived from slow freezing embryos. Embryo survival rate, blastomere surviving rate and pregnancy rate. Embryo survival rate was significantly higher after vitrification compared with slow freezing (81.6%, 647/793 versus 70.0%, 393/562 embryos, p < 0.0001). The clinical pregnancy rate per ET was significantly higher following vitrification compared to slow freezing, 20.0%, 63/314 versus 11.9%, 23/193, respectively (p = 0.02). Vitrification of day 2-3 cleavage stage embryos yields better cycle outcome in all the parameters compared to slow freezing.

Dynamical freeze-out criterion in a hydrodynamical description of Au + Au collisions at √{sNN}=200 GeV and Pb + Pb collisions at √{sNN}=2760 GeV

NASA Astrophysics Data System (ADS)

Ahmad, Saeed; Holopainen, Hannu; Huovinen, Pasi

2017-05-01

In hydrodynamical modeling of ultrarelativistic heavy-ion collisions, the freeze-out is typically assumed to take place at a surface of constant temperature or energy density. A more physical approach is to assume that freeze-out takes place at a surface of constant Knudsen number. We evaluate the Knudsen number as a ratio of the expansion rate of the system to the pion-scattering rate and apply the constant Knudsen number freeze-out criterion to the ideal hydrodynamical description of heavy-ion collisions at the Relativistic Heavy Ion Collider at BNL (√{sNN}=200 GeV) and the Large Hadron Collider (√{sNN}=2760 GeV) energies. We see that once the numerical values of freeze-out temperature and freeze-out Knudsen number are chosen to produce similar pT distributions, the elliptic and triangular anisotropies are similar too, in both event-by-event and averaged initial state calculations.

The initial freezing point temperature of beef rises with the rise in pH: a short communication.

PubMed

Farouk, M M; Kemp, R M; Cartwright, S; North, M

2013-05-01

This study tested the hypothesis that the initial freezing point temperature of meat is affected by pH. Sixty four bovine M. longissimus thoracis et lumborum were classified into two ultimate pH groups: low (<5.8) and high pH (>6.2) and their cooling and freezing point temperatures were determined. The initial freezing temperatures for beef ranged from -0.9 to -1.5°C (∆=0.6°C) with the higher and lower temperatures associated with high and low ultimate pH respectively. There was a significant correlation (r=+0.73, P<0.01) between beef pH and freezing point temperature in the present study. The outcome of this study has implications for the meat industry where evidence of freezing (ice formation) in a shipment as a result of high pH meat could result in a container load of valuable chilled product being downgraded to a lower value frozen product. Copyright © 2013 Elsevier Ltd. All rights reserved.

Freezing, thawing and aging effects on beef tenderness from Bos indicus and Bos taurus cattle.

PubMed

Aroeira, Carolina N; Torres Filho, Robledo A; Fontes, Paulo Rogério; Gomide, Lúcio Alberto M; Ramos, Alcinéia L S; Ladeira, Márcio M; Ramos, Eduardo M

2016-06-01

The objective of this study was to determine the effects of freezing prior to aging on the meat tenderness of young Nellore and Aberdeen Angus bulls. Samples of the longissimus thoracis muscle were submitted to two treatments: conventional aging and freezing (-20°C for 40 days) followed by thawing and aging periods. The meats were evaluated after 0, 7, 14 and 21 aging days (1°C). Freezing increased (P<0.05) purge, cooking loss and total exudate loss throughout aging. Nellore meats had greater total exudate loss and shorter sarcomere lengths (P<0.05). Freezing increased proteolysis during aging in the meats of both breeds, but reduced shear force was found (P<0.05) only in Aberdeen Angus meats and only at time zero. These results suggest that the meat tenderizing process by freezing prior to aging may contribute to meat tenderness in the first weeks of aging, but it is dependent on the animal breed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dispersion Stability of O/W Emulsions with Different Oil Contents Under Various Freezing and Thawing Conditions.

PubMed

Katsuki, Kazutaka; Miyagawa, Yayoi; Nakagawa, Kyuya; Adachi, Shuji

2017-07-01

Freezing and thawing of oil-in-water (O/W) emulsion-type foods bring about oil-water separation and deterioration; hence, the effects of freezing and thawing conditions on the destabilization of O/W emulsions were examined. The freezing rate and thawing temperature hardly affected the stability of the O/W emulsion. O/W emulsions having different oil fractions were stored at temperatures ranging from -30 to -20 °C and then thawed. The stability after thawing depended on the storage temperature, irrespective of the oil fraction of the emulsion. A good correlation was found between the time at which the stability began to decrease and the time taken for the oil to crystalize. These results indicated that the dominant cause for the destabilization of the O/W emulsion during freezing and thawing is the crystallization of the oil phase and that the effects of the freezing and thawing rates on the stability are insignificant. © 2017 Institute of Food Technologists®.

Effect of freezing prior to aging on myoglobin redox forms and CIE color of beef from Nellore and Aberdeen Angus cattle.

PubMed

Aroeira, Carolina Naves; de Almeida Torres Filho, Robledo; Fontes, Paulo Rogério; de Lemos Souza Ramos, Alcinéia; de Miranda Gomide, Lúcio Alberto; Ladeira, Márcio Machado; Ramos, Eduardo Mendes

2017-03-01

The objective of this study was to evaluate the effect of freezing prior to wet aging on the color of Nellore and Aberdeen Angus cattle meat. Samples of the Longissimus thoracis muscle were subjected to two treatments: conventional aging (0, 7, 14 and 21days); and freezing (-20°C for 40days) followed by thawing and aging. Freezing promoted (P<0.05) formation of metmyoglobin during aging, especially in Nellore beef. Frozen meats showed (P<0.05) lower lightness (L*) values and higher redness (a*), chroma (C*) and hue angle (h*) values at the first day of storage, deteriorating quickly with aging time. The color of the Nellore meat was less (P<0.05) stable to freezing, being lighter, yellower and less red than Angus meat. The results suggest that color stability in vacuum-packed beef is reduced by freezing prior to aging and that reduction depends on the animal breed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of waxy rice flour substitution for wheat flour on characteristics of batter and freeze-thawed cake.

PubMed

Jongsutjarittam, Nisachon; Charoenrein, Sanguansri

2013-09-12

This study aimed to improve the freeze-thawed cake properties by10-20% waxy rice flour (WRF) substitution for wheat flour (WF). Viscosity of WRF-substituted batters was lower; consequently, trapped air was less uniformly distributed than WF batter. After five freeze-thaw cycles, firmness and enthalpy of melting retrograded amylopectin of WF- and WRF-substituted cakes increased and the matrix surrounding the air pores from SEM images was denser than in fresh-baked cakes. Sensory evaluation showed an increase in firmness and a decrease in firmness acceptability of freeze-thawed cakes. However, freeze-thawed cake with WRF substitution had significantly less firmness, less dense matrix and more acceptability than WF cake. This could have been due to a low amylose content of WRF and the spread of ruptured waxy rice starch granules around swollen wheat starch granules as observed by CLSM. Thus, WRF could be used for WF substitution to improve the firmness in freeze-thawed cake. Copyright © 2013 Elsevier Ltd. All rights reserved.

Fundamentals of freeze-drying.

PubMed

Nail, Steven L; Jiang, Shan; Chongprasert, Suchart; Knopp, Shawn A

2002-01-01

Given the increasing importance of reducing development time for new pharmaceutical products, formulation and process development scientists must continually look for ways to "work smarter, not harder." Within the product development arena, this means reducing the amount of trial and error empiricism in arriving at a formulation and identification of processing conditions which will result in a quality final dosage form. Characterization of the freezing behavior of the intended formulation is necessary for developing processing conditions which will result in the shortest drying time while maintaining all critical quality attributes of the freeze-dried product. Analysis of frozen systems was discussed in detail, particularly with respect to the glass transition as the physical event underlying collapse during freeze-drying, eutectic mixture formation, and crystallization events upon warming of frozen systems. Experiments to determine how freezing and freeze-drying behavior is affected by changes in the composition of the formulation are often useful in establishing the "robustness" of a formulation. It is not uncommon for seemingly subtle changes in composition of the formulation, such as a change in formulation pH, buffer salt, drug concentration, or an additional excipient, to result in striking differences in freezing and freeze-drying behavior. With regard to selecting a formulation, it is wise to keep the formulation as simple as possible. If a buffer is needed, a minimum concentration should be used. The same principle applies to added salts: If used at all, the concentration should be kept to a minimum. For many proteins a combination of an amorphous excipient, such as a disaccharide, and a crystallizing excipient, such as glycine, will result in a suitable combination of chemical stability and physical stability of the freeze-dried solid. Concepts of heat and mass transfer are valuable in rational design of processing conditions. Heat transfer by conduction--the dominant mechanism of heat transfer in freeze-drying--is inefficient at the pressures used in freeze-drying. Steps should be taken to improve the thermal contact between the product and the shelf of the freeze dryer, such as eliminating metal trays from the drying process. Quantitation of the heat transfer coefficient for the geometry used is a useful way of assessing the impact of changes in the system such as elimination of product trays and changes in the vial. Because heat transfer by conduction through the vapor increases with increasing pressure, the commonly held point of view that "the lower the pressure, the better" is not true with respect to process efficiency. The optimum pressure for a given product is a function of the temperature at which freeze-drying is carried out, and lower pressures are needed at low product temperatures. The controlling resistance to mass transfer is almost always the resistance of the partially dried solids above the submination interface. This resistance can be minimized by avoiding fill volumes of more than about half the volume of the container. The development scientist should also recognize that very high concentrations of solute may not be appropriate for optimum freeze-drying, particularly if the resistance of the dried product layer increases sharply with concentration. Although the last 10 years has seen the publication of a significant body of literature of great value in allowing development scientists and engineers to "work smarter," there is still much work needed in both the science and the technology of freeze-drying. Scientific development is needed for improving analytical methodology for characterization of frozen systems and freeze-dried solids. A better understanding of the relationship between molecular mobility and reactivity is needed to allow accurate prediction of product stability at the intended storage temperature based on accelerated stability at higher temperatures. This requires that the temperature dependence of glass transition-associated mobility, particularly at temperatures below the glass transition, be studied in greater depth. The relevance of the concept of strong and fragile glasses to frozen systems and freeze-dried solids has only begun to be explored. The list of pharmaceutically acceptable protective solutes is very short, and more imagination--and work--is needed in order to develop pharmaceutically acceptable alternative stabilizers. There is a need for technology development in process monitoring, particularly in developing a way to measure the status of the product during freezing and freeze-drying without placing temperature measurement probes in individual vials of product. The current practice of placing thermocouples in vials is uncertain with respect to reliability of the data, inconsistent with elimination of personnel in close proximity to open vials of product in an aseptic environment, and incompatible with technology for automatic material handling in freeze-drying. In addition, a method for controlling the degree of supercooling during freezing would allow better control of freezing rate and would, in many cases, result in more consistent product quality.

Freeze-dried dog sperm: Dynamics of DNA integrity.

PubMed

Olaciregui, M; Luño, V; Gonzalez, N; De Blas, I; Gil, L

2015-10-01

Freeze-drying (FD) has been proposed as an alternative method to preserve spermatozoa. During the FD procedure, sperm DNA might become damaged by both freezing and drying stresses caused by the endonucleases, the oxidative stress and the storage conditions. We examined the DNA integrity of dog sperm freeze-dried with two kinds of chelating agents in FD buffers and storage at two different temperatures. Ejaculated sperm from four dogs were suspended in basic medium (10 mM Tris-HCl buffer+50 mM NaCl) supplemented with 50 mM EGTA or with 50 mM EDTA and then freeze-dried. Sperm samples were stored at 4°C as room temperature, and the analysis of DNA damage was performed after a month and 5 months of storage using a Sperm Chromatin Dispersion test. We found four different sperm populations according to the size of the halos around the sperm head: (1) absent halo, (2) <6 μm, (3) 6-10 μm, (4) >10 μm. All of them coexisted in each freeze-dried dog semen samples and differed significantly among different treatments. The highest percentage of spermatozoa with halo >10 μm was obtained when the semen samples were freeze-dried in EDTA medium and stored at room temperature for five months. Results suggested that both, the kind of chelating agent as well as storage temperature and period, influenced DNA integrity of freeze-dried dog sperm. Copyright © 2015 Elsevier Inc. All rights reserved.

Redistribution of ice nuclei between cloud and rain droplets: Parameterization and application to deep convective clouds

NASA Astrophysics Data System (ADS)

Paukert, M.; Hoose, C.; Simmel, M.

2017-03-01

In model studies of aerosol-dependent immersion freezing in clouds, a common assumption is that each ice nucleating aerosol particle corresponds to exactly one cloud droplet. In contrast, the immersion freezing of larger drops—"rain"—is usually represented by a liquid volume-dependent approach, making the parameterizations of rain freezing independent of specific aerosol types and concentrations. This may lead to inconsistencies when aerosol effects on clouds and precipitation shall be investigated, since raindrops consist of the cloud droplets—and corresponding aerosol particles—that have been involved in drop-drop-collisions. Here we introduce an extension to a two-moment microphysical scheme in order to account explicitly for particle accumulation in raindrops by tracking the rates of selfcollection, autoconversion, and accretion. This provides a direct link between ice nuclei and the primary formation of large precipitating ice particles. A new parameterization scheme of drop freezing is presented to consider multiple ice nuclei within one drop and effective drop cooling rates. In our test cases of deep convective clouds, we find that at altitudes which are most relevant for immersion freezing, the majority of potential ice nuclei have been converted from cloud droplets into raindrops. Compared to the standard treatment of freezing in our model, the less efficient mineral dust-based freezing results in higher rainwater contents in the convective core, affecting both rain and hail precipitation. The aerosol-dependent treatment of rain freezing can reverse the signs of simulated precipitation sensitivities to ice nuclei perturbations.

Microbial analysis and survey test of gamma-irradiated freeze-dried fruits for patient's food

NASA Astrophysics Data System (ADS)

Park, Jae-Nam; Sung, Nak-Yun; Byun, Eui-Hong; Byun, Eui-Baek; Song, Beom-Seok; Kim, Jae-Hun; Lee, Kyung-A.; Son, Eun-Joo; Lyu, Eun-Soon

2015-06-01

This study examined the microbiological and organoleptic qualities of gamma-irradiated freeze-dried apples, pears, strawberries, pineapples, and grapes, and evaluated the organoleptic acceptability of the sterilized freeze-dried fruits for hospitalized patients. The freeze-dried fruits were gamma-irradiated at 0, 1, 2, 3, 4, 5, 10, 12, and 15 kGy, and their quality was evaluated. Microorganisms were not detected in apples after 1 kGy, in strawberries and pears after 4 kGy, in pineapples after 5 kGy, and in grapes after 12 kGy of gamma irradiation. The overall acceptance score, of the irradiated freeze-dried fruits on a 7-point scale at the sterilization doses was 5.5, 4.2, 4.0, 4.1, and 5.1 points for apples, strawberries, pears, pineapples, and grapes, respectively. The sensory survey of the hospitalized cancer patients (N=102) resulted in scores of 3.8, 3.7, 3.9, 3.9, and 3.7 on a 5-point scale for the gamma-irradiated freeze-dried apples, strawberries, pears, pineapples, and grapes, respectively. The results suggest that freeze-dried fruits can be sterilized with a dose of 5 kGy, except for grapes, which require a dose of 12 kGy, and that the organoleptic quality of the fruits is acceptable to immuno-compromised patients. However, to clarify the microbiological quality and safety of freeze-dried fruits should be verified by plating for both aerobic and anaerobic microorganisms.

Effect of Freezing Rate and Microwave Thawing on Texture and Microstructural Properties of Potato (Solanum tuberosum).

PubMed

Phinney, David M; Frelka, John C; Wickramasinghe, Anita; Heldman, Dennis R

2017-04-01

Food freezing is a preservation process that works by lowering temperature while simultaneously decreasing water activity. It is accepted that although freezing preserves foods, it generally has a negative effect on textural quality. This research investigated the texture response of potatoes (Solanum tuberosum) as a function of time to freeze (defined as the time for the center temperature to reach -20 °C) and thawing process. Potatoes slices (6 mm) were blanched then frozen in an ethanol/carbon dioxide bath, a pilot scale high velocity air freezer (HVAF) and a still air freezer to achieve various times to freeze. Slices were stabilized at -20 °C and thawed by 2 methods; room temperature air and microwave. Afterwards, samples were allowed to come to room temperature prior to texture profile analysis (TPA). Results indicate a maximum texture loss of the potato was reached at a time to freeze of approximately 8 min (corresponding to the HVAF). The texture difference between room temperature and microwave thawing methods was not shown to be significant (P = 0.05). SEM images showed the cellular structure of the potato in a HVAF to be similar to that of the still air freezer, validating that the matrix was maximally damaged in both conditions. This work created a continuous quality loss model for the potato as a function of time to freeze and showed no textural benefit to high velocity over still air freezing. © 2017 Institute of Food Technologists®.

Handwriting Impairments in People With Parkinson's Disease and Freezing of Gait.

PubMed

Heremans, Elke; Nackaerts, Evelien; Broeder, Sanne; Vervoort, Griet; Swinnen, Stephan P; Nieuwboer, Alice

2016-11-01

Recent studies show that patients with Parkinson's disease (PD) and freezing of gait (FOG) experience motor problems outside their gait freezing episodes. Because handwriting is also a sequential movement, it may be affected in PD patients with FOG relative to those without. The current study aimed to assess the quality of writing in PD patients with and without FOG in comparison to healthy controls (CTs) during various writing tasks. Handwriting was assessed by the writing of cursive loops on a touch-sensitive writing tablet and by means of the Systematic Screening of Handwriting Difficulties (SOS) test in 30 PD patients with and without freezing and 15 healthy age-matched CTs. The tablet tests were performed at 2 different sizes, either continuously or alternatingly, as indicated by visual target lines. Patients with freezing showed decreased writing amplitudes and increased variability compared with CTs and patients without freezing on the writing tablet tests. Writing problems were present during both tests but were more pronounced during writing at alternating compared with writing at continuous size. Patients with freezing also had a higher total score on the SOS test than patients without freezing and CTs, reflecting more extensive handwriting problems, particularly with writing fluency. Writing is more severely affected in PD patients with FOG than in those without FOG. These results indicate that deficient movement sequencing and adaptation is a generic problem in patients with FOG. © The Author(s) 2016.

Fuel freeze-point investigations. Final report, September 1982-March 1984

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desmarais, L.A.; Tolle, F.F.

1984-07-01

The objective of this program was to conduct a detailed assessment of the low-temperature environment to which USAF aircraft are exposed for the purpose of defining a maximum acceptable fuel freeze-point and also to define any operational changes required with the use of a high freeze-point fuel. A previous study of B-52, C-141, and KC-135 operational missions indicated that the -58 C freeze point specification was too conservative. Based on recommendations resulting from the previous program, several improvements in the method of analysis were made, such as: expansion of the atmospheric temperature data base, the addition of ground temperature analysis,more » the addition of fuel-freezing analysis to the one-dimensional fuel-temperature computer program, and the examination of heat transfer in external fuel tanks, such as pylon or tip tanks. The B-52, C-141, and KC-135 mission were analyzed again, along with the operational missions of two tactical airplanes, the A-10 and F-15; -50C was determined to be the maximum allowable freeze point for a general-purpose USAF aviation turbine fuel. Higher freeze points can be tolerated if the probability of operational interference is acceptably low or if operational changes can be made. Study of atmospheric temperatures encountered for the missions of the five-study aircraft indicates that a maximum freeze point of -48 C would not likely create any operational difficulties in Northern Europe.« less

Freeze-thaw and high-voltage discharge allow macromolecule uptake into ileal brush-border vesicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donowitz, M.; Emmer, E.; McCullen, J.

1987-06-01

High-voltage discharge or one cycle of freeze-thawing are shown to transiently permeabilize rabbit ileal brush-border membrane vesicles to macromolecules. Uptake of the radiolabeled macromolecule dextran, mol wt 70,000, used as a marker for vesicle permeability, was determined by a rapid filtration technique, with uptake defined as substrate associated with the vesicle and releasable after incubation of vesicles with 0.1% saponin. Dextran added immediately after electric shock (2000 V) or at the beginning of one cycle of freeze-thawing was taken up approximately eightfold compared with control. ATP also was taken up into freeze-thawed vesicles, whereas there was no significant uptake intomore » control vesicles. The increase in vesicle permeability was reversible, based on Na-dependent D-glucose uptake being decreased when studied 5 but not 15 min after electric shock, and was not significantly decreased after completion of one cycle of freeze-thawing. In addition, adenosine 3',5'-cyclic monophosphate and Ca/sup 2 +/-calmodulin-dependent protein kinase activity were similar in control vesicles and vesicles exposed to high-voltage discharge or freeze-thawing. Also, vesicles freeze-thawed with (/sup 32/P)ATP demonstrated increased phosphorylation compared with nonfrozen vesicles, while freeze-thawing did not alter vesicle protein as judged by Coomassie blue staining. These techniques should allow intestinal membrane vesicles to be used for studies of intracellular control of transport processes, for instance, studies of protein kinase regulation of transport.« less

Physicochemical interaction mechanism between nanoparticles and tetrasaccharides (stachyose) during freeze-drying.

PubMed

Kamiya, Seitaro; Nakashima, Kenichiro

2017-12-01

Nanoparticle suspensions are thermodynamically unstable and subject to aggregation. Freeze-drying on addition of saccharides is a useful method for preventing aggregation. In the present study, tetrasaccharides (stachyose) was employed as an additive. In addition, we hypothesize the interactive mechanism between stachyose and the nanoparticles during freeze-drying for the first time. The mean particle size of the rehydrated freeze-dried stachyose-containing nanoparticles (104.7 nm) was similar to the initial particle size before freeze-drying (76.8 nm), indicating that the particle size had been maintained. The mean particle size of the rehydrated normal-dried stachyose-containing nanoparticles was 222.2 nm. The powder X-ray diffraction of the freeze-dried stachyose-containing nanoparticles revealed a halo pattern. The powder X-ray diffraction of the normally dried stachyose-containing nanoparticles produced mainly a halo pattern and a partial peak. These results suggest an interaction between the nanoparticles and stachyose, and that this relationship depends on whether the mixture is freeze-dried or dried normally. In the case of normal drying, although most molecules cannot move rapidly thereby settling irregularly, some stachyose molecules can arrange regularly leading to some degree of crystallization and potentially some aggregation. In contrast, during freeze-drying, the moisture sublimed, while the stachyose molecules and nanoparticles were immobilized in the ice. After sublimation, stachyose remained in the space occupied by water and played the role of a buffer material, thus preventing aggregation.

Influence of Rapid Freeze-Thaw Cycling on the Mechanical Properties of Sustainable Strain-Hardening Cement Composite (2SHCC)

PubMed Central

Jang, Seok-Joon; Rokugo, Keitetsu; Park, Wan-Shin; Yun, Hyun-Do

2014-01-01

This paper provides experimental results to investigate the mechanical properties of sustainable strain-hardening cement composite (2SHCC) for infrastructures after freeze-thaw actions. To improve the sustainability of SHCC materials in this study, high energy-consumptive components—silica sand, cement, and polyvinyl alcohol (PVA) fibers—in the conventional SHCC materials are partially replaced with recycled materials such as recycled sand, fly ash, and polyethylene terephthalate (PET) fibers, respectively. To investigate the mechanical properties of green SHCC that contains recycled materials, the cement, PVA fiber and silica sand were replaced with 10% fly ash, 25% PET fiber, and 10% recycled aggregate based on preliminary experimental results for the development of 2SHCC material, respectively. The dynamic modulus of elasticity and weight for 2SHCC material were measured at every 30 cycles of freeze-thaw. The effects of freeze-thaw cycles on the mechanical properties of sustainable SHCC are evaluated by conducting compressive tests, four-point flexural tests, direct tensile tests and prism splitting tests after 90, 180, and 300 cycles of rapid freeze-thaw. Freeze-thaw testing was conducted according to ASTM C 666 Procedure A. Test results show that after 300 cycles of freezing and thawing actions, the dynamic modulus of elasticity and mass loss of damaged 2SHCC were similar to those of virgin 2SHCC, while the freeze-thaw cycles influence mechanical properties of the 2SHCC material except for compressive behavior. PMID:28788522

Migration of Water in Litopenaeus Vannamei Muscle Following Freezing and Thawing.

PubMed

Deng, Qi; Wang, Yaling; Sun, Lijun; Li, Jianrong; Fang, Zhijia; Gooneratne, Ravi

2018-06-15

Water and protein are major constituents of shrimp, any changes in protein and the state of water influence the quality of shrimp. Therefore, a study to examine the law of moisture migration and protein denaturation under different freezing and thawing conditions is important. The proton density images of thawed frozen-shrimp revealed that the water loss during quick-freezing was much greater than that during slow freezing or microfreezing. At room temperature (25 °C), the water loss from brine-thawing was more than still-water thawing and still-water thawing was more than thawing spontaneously. Freezing-thawing resulted in uniform water redistribution in shrimp muscle. Nuclear magnetic resonance technology (low field magnetic imaging) was used to directly monitor the dynamic processes of fluidity state in shrimp and indirectly monitor protein denaturation and thereby determine the optimal method of freezing-thawing shrimp. Our research showed that microfreezing preservation minimized weight loss, juice leakage and protein denaturation in shrimp muscle during thawing. Water is one of the major components in most organs and is an important factor that influences the shrimp muscle quality. Water migration patterns and subsequent effects on the shrimp muscle under different freezing and thawing conditions were examined using low field nuclear magnetic resonance (NMR) technology. This research provides a theoretical foundation for shrimp processing plants to improve the freezing and thawing process to obtain optimal quality and flavor of shrimp products. © 2018 Institute of Food Technologists®.

Protective effect of sugars on storage stability of microwave freeze-dried and freeze-dried Lactobacillus paracasei F19.

PubMed

Ambros, S; Hofer, F; Kulozik, U

2018-05-31

Microwave freeze drying in comparison to conventional freeze drying allows for intensification of the preservation process of lactic acid bacteria without imposing additional processing stress. Viability as a function of storage time of microwave freeze-dried Lactobacillus paracasei ssp. paracasei F19 was investigated in comparison to conventionally lyophilized bacteria of the same strain. Further, the impact of the protectants, sorbitol, trehalose and maltodextrin, on shelf life was analyzed. The highest inactivation rates of 0.035 and 0.045 d -1 , respectively, were found for cultures without protectants. Thus, all additives were found to exhibit a protective effect during storage with inactivation rates between 0.015 and 0.040 d -1 . Although trehalose and maltodextrin samples were in the glassy state during storage, in contrast to samples containing sorbitol as protectant, the best protective effect could be found for sorbitol with the lowest inactivation rate of 0.015 d -1 . Due to its low molecular weight, it might protect cells owing to better adsorption to the cytoplasma membrane. Sorbitol additionally shows antioxidative properties. Storage behavior of microwave freeze-dried cultures follows the typical behavior of a product dried by conventional lyophilization. No significant influence of the drying technique on storage behavior was detected. General findings concerning storage behavior in freeze drying are likely to be applicable in microwave freeze drying with only slight adjustments. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

3 CFR - Pay Freeze

Code of Federal Regulations, 2010 CFR

2010-01-01

... 3 The President 1 2010-01-01 2010-01-01 false Pay Freeze Presidential Documents Other Presidential Documents Memorandum of January 21, 2009 Pay Freeze Memorandum for the Assistant to the President and Chief... the White House staff forgo pay increases until further notice. Accordingly, as a signal of our shared...

Stress, deformation and micromorphological aspects of soil freezing under laboratory conditions

NASA Astrophysics Data System (ADS)

Jetchick, Elizabeth

In this thesis, frost heave is viewed as a process resulting from the interactions between thermodynamic conditions, soil environment controls such as texture, stress/deformation conditions and soil microstructure. A series of laboratory experiments was devised to investigate the links between these aspects. Because a limited number of studies exist on the development of internal stresses and strains in freezing soil, the work focussed on obtaining rheological data using conventional soil strain gauges and prototype stress transducers. A fine-grained unstructured silt was placed in a column (30 cm diameter by 100 cm length) and subjected to freezing and freeze-thaw cycles from the top down, lasting up to three months. Heat and water flows, as well as stresses and strains were monitored. The frozen soil was sectioned at the end of four of the experiments to examine the soil fabrics that had developed. From the experimental results, schematic stress and strain curves are proposed. For a single freeze cycle, compressive normal and tensile normal stresses were recorded simultaneously by the measuring devices within the freezing soil profile. Ice lens inception took place when the stress field changed, a condition which occurred either at the frost front level or at the base of the growing ice lens. Negative and positive strains reflected the different stress states that were sustained below and above the freezing front. Negative strains or soil consolidation took place as stresses increased before the passage of the frost line. Negligible soil strains were recorded as maximum soil consolidation was attained, before soil expansion. Distinct positive strain patterns indicating secondary and continuing heave, were recorded simultaneously throughout a thickness of soil, over a range of temperatures. Ice lens growth mostly took place as secondary frost heave, but continuing heave was measured, and the temperature conditions for both types of heave were determined. During subsequent freeze-thaw cycles, the stress patterns upon freezing were more complex in the second and third cycles due to previous soil structuration. At thaw, the stress pattern was uniform although positive strains in excess of those generated at freezing were recorded over the course of a few hours. Specific soil fabrics and features were evident from a single freeze cycle and for freeze-thaw conditions. Formation mechanisms are proposed for certain fabrics and features. A zonation with depth of these fabrics can be linked to the stress strain history of the soil, revealing the links and feedbacks between rheological processes and cryogenic soil structures.

Site-directed Nanotherapeutics to Abrogate RRMS and Promote Remyelination Repair (Rev)

DTIC Science & Technology

2013-03-01

in the labs additionally delayed the onset of the practical work.  Long lasting defect in freeze / dryer prevented a more in depth investigation of...drug content and reduced functionality of the peptides. Freezing of the NP without cryoprotection leads to disassembly; freezing with a cryoprotectant

Investigation of the impact of nanotechnology on the freeze-thaw durability of concrete containing d-cracking aggregates : [technical summary].

DOT National Transportation Integrated Search

2015-05-01

Freezing and thawing damage is the most common cause of distress in : Kansas pavements. Many locally available aggregates in Kansas do not : meet current standards for use in concrete pavements because of poor : freeze-thaw durability. The use of nan...

Investigation of the impact of nanotechnology on the freeze-thaw durability of concrete containing d-cracking aggregates.

DOT National Transportation Integrated Search

2015-05-01

Freezing and thawing damage is the most common cause of distress in Kansas pavements. Many : locally available aggregates in Kansas do not meet current standards for use in concrete pavements because : of poor freeze-thaw durability. The use of nanot...

7 CFR 58.638 - Freezing the mix.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 3 2013-01-01 2013-01-01 false Freezing the mix. 58.638 Section 58.638 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Procedures § 58.638 Freezing the mix. After the mix enters the freezer, it shall be frozen as rapidly as...

7 CFR 58.638 - Freezing the mix.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 3 2012-01-01 2012-01-01 false Freezing the mix. 58.638 Section 58.638 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Procedures § 58.638 Freezing the mix. After the mix enters the freezer, it shall be frozen as rapidly as...

7 CFR 58.638 - Freezing the mix.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 3 2014-01-01 2014-01-01 false Freezing the mix. 58.638 Section 58.638 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Procedures § 58.638 Freezing the mix. After the mix enters the freezer, it shall be frozen as rapidly as...

Reagan and the Nuclear Freeze: "Stars Wars" as a Rhetorical Strategy.

ERIC Educational Resources Information Center

Bjork, Rebecca S.

1988-01-01

Analyzes the interaction between nuclear freeze activists and proponents of a Strategic Defense Initiative (SDI). Argues that SDI strengthens Reagan's rhetorical position concerning nuclear weapons policy because it reduces the argumentative ground of the freeze movement by envisioning a defensive weapons system that would nullify nuclear weapons.…

Comparison of survival rate of cleavage stage embryos produced from in vitro maturation cycles after slow freezing and after vitrification.

PubMed

Son, Weon-Young; Chung, Jin-Tae; Gidoni, Yariv; Holzer, Hananel; Levin, Dan; Chian, Ri-Cheng; Tan, Seang Lin

2009-09-01

Significantly more embryos survived the vitrification procedure compared to slow freezing (85.5% vs. 61.8%) in cleavage-stage human embryos produced from in vitro maturation cycles, suggesting that vitrification is more efficient than slow freezing for cryopreservation.

The Freezing Bomb

ERIC Educational Resources Information Center

Mills, Allan

2010-01-01

The extreme pressures that are generated when water freezes were traditionally demonstrated by sealing a small volume in a massive cast iron "bomb" and then surrounding it with a freezing mixture of ice and salt. This vessel would dramatically fail by brittle fracture, but no quantitative measurement of bursting pressure was available. Calculation…

Thermal analysis of the position of the freezing front around an LNG in-ground storage tank with a heat barrier

NASA Astrophysics Data System (ADS)

Watanabe, O.; Tanaka, M.

A technique of controlling the extent of the freezing zone created by in ground liquefied natural gas storage tanks by installing a heat barrier is described. The freezing conditions around three representative tanks after operating the system were compared.

Measurement of the pore size distribution of limestone aggregates in concrete pavement cores : phase I.

DOT National Transportation Integrated Search

2012-04-01

Freeze-thaw damage is one of the common forms of distress for concrete pavements in Kansas. D-Cracking is a form of : freeze-thaw damage caused by aggregates with poor freeze-thaw durability. It is believed that pores in the aggregates below : 10 m...

9 CFR 381.66 - Temperatures and chilling and freezing procedures.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Temperatures and chilling and freezing procedures. 381.66 Section 381.66 Animals and Animal Products FOOD SAFETY AND INSPECTION SERVICE, DEPARTMENT... Procedures § 381.66 Temperatures and chilling and freezing procedures. (a) General. Temperatures and...

Laboratory freeze-thaw durability of previous concrete with respect to curing time and addition of sand, slag, silica fume, and saltguard.

DOT National Transportation Integrated Search

2016-11-22

Concerns persist regarding pervious concrete durability in cold climates related to freeze-thaw and exposure to salt. This study was conducted as an extension to previous work regarding pervious concrete in Vermont, to further investigate freeze-thaw...

Laboratory freeze-thaw durability of pervious concrete with respect to curing time and addition of sand, slag, silica fume, and saltguard.

DOT National Transportation Integrated Search

2016-11-22

Concerns persist regarding pervious concrete durability in cold climates related to freeze-thaw : and exposure to salt. This study was conducted as an extension to previous work regarding pervious : concrete in Vermont, to further investigate freeze-...

Mathematical modeling of the growth and coarsening of ice particles in the context of high pressure shift freezing processes.

PubMed

Smith, N A S; Burlakov, V M; Ramos, Á M

2013-07-25

High pressure shift freezing (HPSF) has been proven more beneficial for ice crystal size and shape than traditional (at atmospheric pressure) freezing.1-3 A model for growth and coarsening of ice crystals inside a frozen food sample (either at atmospheric or high pressure) is developed, and some numerical experiments are given, with which the model is validated by using experimental data. To the best of our knowledge, this is the first model suited for freezing crystallization in the context of high pressure.

Immunoelectron Microscopy of Cryofixed and Freeze-Substituted Plant Tissues.

PubMed

Takeuchi, Miyuki; Takabe, Keiji; Mineyuki, Yoshinobu

2016-01-01

Cryofixation and freeze-substitution techniques provide excellent preservation of plant ultrastructure. The advantage of cryofixation is not only in structural preservation, as seen in the smooth plasma membrane, but also in the speed in arresting cell activity. Immunoelectron microscopy reveals the subcellular localization of molecules within cells. Immunolabeling in combination with cryofixation and freeze-substitution techniques provides more detailed information on the immunoelectron-microscopic localization of molecules in the plant cell than can be obtained from chemically fixed tissues. Here, we introduce methods for immunoelectron microscopy of cryofixed and freeze-substituted plant tissues.

Biomimetic Materials by Freeze Casting

NASA Astrophysics Data System (ADS)

Porter, Michael M.; Mckittrick, Joanna; Meyers, Marc A.

2013-06-01

Natural materials, such as bone and abalone nacre, exhibit exceptional mechanical properties, a product of their intricate microstructural organization. Freeze casting is a relatively simple, inexpensive, and adaptable materials processing method to form porous ceramic scaffolds with controllable microstructural features. After infiltration of a second polymeric phase, hybrid ceramic-polymer composites can be fabricated that closely resemble the architecture and mechanical performance of natural bone and nacre. Inspired by the narwhal tusk, magnetic fields applied during freeze casting can be used to further control architectural alignment, resulting in freeze-cast materials with enhanced mechanical properties.

SIMPLE MODEL OF ICE SEGREGATION USING AN ANALYTIC FUNCTION TO MODEL HEAT AND SOIL-WATER FLOW.

USGS Publications Warehouse

Hromadka, T.V.; Guymon, G.L.

1984-01-01

This paper reports on the development of a simple two-dimensional model of coupled heat and soil-water flow in freezing or thawing soil. The model also estimates ice-segregation (frost-heave) evolution. Ice segregation in soil results from water drawn into a freezing zone by hydraulic gradients created by the freezing of soil-water. Thus, with a favorable balance between the rate of heat extraction and the rate of water transport to a freezing zone, segregated ice lenses may form.

Universal pion freeze-out in heavy-ion collisions.

PubMed

Adamová, D; Agakichiev, G; Appelshäuser, H; Belaga, V; Braun-Munzinger, P; Castillo, A; Cherlin, A; Damjanović, S; Dietel, T; Dietrich, L; Drees, A; Esumi, S I; Filimonov, K; Fomenko, K; Fraenkel, Z; Garabatos, C; Glässel, P; Hering, G; Holeczek, J; Kushpil, V; Lenkeit, B; Ludolphs, W; Maas, A; Marín, A; Milosević, J; Milov, A; Miśkowiec, D; Panebrattsev, Yu; Petchenova, O; Petrácek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Rehak, P; Sako, H; Schmitz, W; Schukraft, J; Sedykh, S; Shimansky, S; Slívová, J; Specht, H J; Stachel, J; Sumbera, M; Tilsner, H; Tserruya, I; Wessels, J P; Wienold, T; Windelband, B; Wurm, J P; Xie, W; Yurevich, S; Yurevich, V

2003-01-17

Based on an evaluation of data on pion interferometry and on particle yields at midrapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda(f) reaches a value of about 1 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and beam energy from the Alternating Gradient Synchrotron to the Relativistic Heavy Ion Collider.

Rapid formation of phase-clean 110 K (Bi-2223) powders derived via freeze-drying process

DOEpatents

Balachandran, Uthamalingam

1996-01-01

A process for the preparation of amorphous precursor powders for Pb-doped Bi.sub.2 Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.x (2223) includes a freeze-drying process incorporating a splat-freezing step. The process generally includes splat freezing a nitrate solution of Bi, Pb, Sr, Ca, and Cu to form flakes of the solution without any phase separation; grinding the frozen flakes to form a powder; freeze-drying the frozen powder; heating the dried powder to form a dry green precursor powders; denitrating the green-powders; heating the denitrated powders to form phase-clean Bi-2223 powders. The grain boundaries of the 2223 grains appear to be clean, leading to good intergrain contact between 2223 grains.

Rapid formation of phase-clean 110 K (Bi-2223) powders derived via freeze-drying process

DOEpatents

Balachandran, U.

1996-06-04

A process for the preparation of amorphous precursor powders for Pb-doped Bi{sub 2}Sr{sub 2} Ca{sub 2}Cu{sub 3}O{sub x} (2223) includes a freeze-drying process incorporating a splat-freezing step. The process generally includes splat freezing a nitrate solution of Bi, Pb, Sr, Ca, and Cu to form flakes of the solution without any phase separation; grinding the frozen flakes to form a powder; freeze-drying the frozen powder; heating the dried powder to form a dry green precursor powders; denitrating the green-powders; heating the denitrated powders to form phase-clean Bi-2223 powders. The grain boundaries of the 2223 grains appear to be clean, leading to good intergrain contact between 2223 grains. 11 figs.

Prediction model for carbonation depth of concrete subjected to freezing-thawing cycles

NASA Astrophysics Data System (ADS)

Xiao, Qian Hui; Li, Qiang; Guan, Xiao; Xian Zou, Ying

2018-03-01

Through the indoor simulation test of the concrete durability under the coupling effect of freezing-thawing and carbonation, the variation regularity of concrete neutralization depth under freezing-thawing and carbonation was obtained. Based on concrete carbonation mechanism, the relationship between the air diffusion coefficient and porosity in concrete was analyzed and the calculation method of porosity in Portland cement concrete and fly ash cement concrete was investigated, considering the influence of the freezing-thawing damage on the concrete diffusion coefficient. Finally, a prediction model of carbonation depth of concrete under freezing-thawing circumstance was established. The results obtained using this prediction model agreed well with the experimental test results, and provided a theoretical reference and basis for the concrete durability analysis under multi-factor environments.

Sperm preservation by freeze-drying for the conservation of wild animals.

PubMed

Kaneko, Takehito; Ito, Hideyuki; Sakamoto, Hidefusa; Onuma, Manabu; Inoue-Murayama, Miho

2014-01-01

Sperm preservation is a useful technique for the maintenance of biological resources in experimental and domestic animals, and in wild animals. A new preservation method has been developed that enables sperm to be stored for a long time in a refrigerator at 4 °C. Sperm are freeze-dried in a solution containing 10 mM Tris and 1 mM EDTA. Using this method, liquid nitrogen is not required for the storage and transportation of sperm. We demonstrate that chimpanzee, giraffe, jaguar, weasel and the long-haired rat sperm remain viable after freeze-drying. In all species, pronuclei were formed after the injection of freeze-dried sperm into the mouse oocytes. Although preliminary, these results may be useful for the future establishment of "freeze-drying zoo" to conserve wild animals.

Scanning electron microscopy of high-pressure-frozen sea urchin embryos.

PubMed

Walther, P; Chen, Y; Malecki, M; Zoran, S L; Schatten, G P; Pawley, J B

1993-12-01

High-pressure-freezing permits direct cryo-fixation of sea urchin embryos having a defined developmental state without the formation of large ice crystals. We have investigated preparation protocols for observing high-pressure-frozen and freeze-fractured samples in the scanning electron microscope. High-pressure-freezing was superior to other freezing protocols, because the whole bulk sample was reasonably well frozen and the overall three-dimensional shape of the embryos was well preserved. The samples were either dehydrated by freeze-substitution and critical-point-drying, or imaged in the partially hydrated state, using a cold stage in the SEM. During freeze-substitution the samples were stabilized by fixatives. The disadvantage of this method was that shrinking and extraction effects, caused by the removal of the water, could not be avoided. These disadvantages were avoided when the sample was imaged in the frozen-hydrated state using a cold-stage in the SEM. This would be the method of choice for morphometric studies. Frozen-hydrated samples, however, were very beam sensitive and many structures remained covered by the ice and were not visible. Frozen-hydrated samples were partially freeze-dried to make visible additional structures that had been covered by ice. However, this method also caused drying artifacts when too much water was removed.

Role of intracellular poroelasticity on freezing-induced deformation of cells in engineered tissues

PubMed Central

Ghosh, Soham; Ozcelikkale, Altug; Dutton, J. Craig

2016-01-01

Freezing of biomaterials is important in a wide variety of biomedical applications, including cryopreservation and cryosurgeries. For the success of these applications to various biomaterials, biophysical mechanisms, which determine freezing-induced changes in cells and tissues, need to be well understood. Specifically, the significance of the intracellular mechanics during freezing is not well understood. Thus, we hypothesize that cells interact during freezing with the surroundings such as suspension media and the extracellular matrix (ECM) via two distinct but related mechanisms—water transport and cytoskeletal mechanics. The underlying rationale is that the cytoplasm of the cells has poroelastic nature, which can regulate both cellular water transport and cytoskeletal mechanics. A poroelasticity-based cell dehydration model is developed and confirmed to provide insight into the effects of the hydraulic conductivity and stiffness of the cytoplasm on the dehydration of cells in suspension during freezing. We further investigated the effect of the cytoskeletal structures on the cryoresponse of cells embedded in the ECM by measuring the spatio-temporal intracellular deformation with dermal equivalent as a model tissue. The freezing-induced change in cell, nucleus and cytoplasm volume was quantified, and the possible mechanism of the volumetric change was proposed. The results are discussed considering the hierarchical poroelasticity of biological tissues. PMID:27707905

The interaction between freezing tolerance and phenology in temperate deciduous trees

PubMed Central

Vitasse, Yann; Lenz, Armando; Körner, Christian

2014-01-01

Temperate climates are defined by distinct temperature seasonality with large and often unpredictable weather during any of the four seasons. To thrive in such climates, trees have to withstand a cold winter and the stochastic occurrence of freeze events during any time of the year. The physiological mechanisms trees adopt to escape, avoid, and tolerate freezing temperatures include a cold acclimation in autumn, a dormancy period during winter (leafless in deciduous trees), and the maintenance of a certain freezing tolerance during dehardening in early spring. The change from one phase to the next is mediated by complex interactions between temperature and photoperiod. This review aims at providing an overview of the interplay between phenology of leaves and species-specific freezing resistance. First, we address the long-term evolutionary responses that enabled temperate trees to tolerate certain low temperature extremes. We provide evidence that short term acclimation of freezing resistance plays a crucial role both in dormant and active buds, including re-acclimation to cold conditions following warm spells. This ability declines to almost zero during leaf emergence. Second, we show that the risk that native temperate trees encounter freeze injuries is low and is confined to spring and underline that this risk might be altered by climate warming depending on species-specific phenological responses to environmental cues. PMID:25346748

The Arabidopsis RCC1 Family Protein TCF1 Regulates Freezing Tolerance and Cold Acclimation through Modulating Lignin Biosynthesis

PubMed Central

Jenkins, Gareth I.; Wang, Shuangfeng; Shang, Zhonglin; Shi, Yiting; Yang, Shuhua; Li, Xia

2015-01-01

Abstract Cell water permeability and cell wall properties are critical to survival of plant cells during freezing, however the underlying molecular mechanisms remain elusive. Here, we report that a specifically cold-induced nuclear protein, Tolerant to Chilling and Freezing 1 (TCF1), interacts with histones H3 and H4 and associates with chromatin containing a target gene, BLUE-COPPER-BINDING PROTEIN (BCB), encoding a glycosylphosphatidylinositol-anchored protein that regulates lignin biosynthesis. Loss of TCF1 function leads to reduced BCB transcription through affecting H3K4me2 and H3K27me3 levels within the BCB gene, resulting in reduced lignin content and enhanced freezing tolerance. Furthermore, plants with knocked-down BCB expression (amiRNA-BCB) under cold acclimation had reduced lignin accumulation and increased freezing tolerance. The pal1pal2 double mutant (lignin content reduced by 30% compared with WT) also showed the freezing tolerant phenotype, and TCF1 and BCB act upstream of PALs to regulate lignin content. In addition, TCF1 acts independently of the CBF (C-repeat binding factor) pathway. Our findings delineate a novel molecular pathway linking the TCF1-mediated cold-specific transcriptional program to lignin biosynthesis, thus achieving cell wall remodeling with increased freezing tolerance. PMID:26393916

Toward intradermal vaccination: preparation of powder formulations by collapse freeze-drying.

PubMed

Etzl, Elsa E; Winter, Gerhard; Engert, Julia

2014-03-01

Intradermal powder immunization is an emerging technique in vaccine delivery. The purpose of this study was to generate powder particles for intradermal injection by freeze-drying and subsequent cryo-milling. Two different freeze-drying protocols were compared, a moderate freeze-drying cycle and an aggressive freeze-drying cycle, which induced a controlled collapse of the sugar matrix. Ovalbumin served as model antigen. The influence of collapse drying and cryo-milling on particle morphology and protein stability was investigated. Cryo-milling generated irregularly shaped particles of size 20-70 µm. The recovery of soluble monomer of ovalbumin was not changed during freeze-drying and after cryo-milling, or after 12 months of storage at 2-8 °C. A slight increase in higher molecular weight aggregates was found in formulations containing the polymer dextran after 12 months of storage at 50 °C. Light obscuration measurements showed an increase in cumulative particle counts after cryo-milling that did not further increase during storage at 2-8 °C for 12 months. The applicability of the cryo-milling process to other therapeutic proteins was shown using recombinant human granulocyte-colony stimulating factor. Collapse freeze-drying and subsequent cryo-milling allows the generation of particles suitable for intradermal powder injection.

Effects of six substances on the growth and freeze-drying of Lactobacillus delbrueckii subsp. bulgaricus.

PubMed

Chen, He; Huang, Jie; Shi, Xiaoyu; Li, Yichao; Liu, Yu

2017-01-01

The efficacy of Lactobacillus delbrueckii subsp. bulgaricus as starter cultures for the dairy industry depends largely on the number of viable and active cells. Freeze-drying is the most convenient and successful method to preserve the bacterial cells. However, not all strains survived during freeze-drying. The effects of six substances including NaCl, sorbitol, mannitol, mannose, sodium glutamate, betaine added to the MRS medium on the growth and freeze-drying survival rate and viable counts of Lb. delbrueckii subsp. bulgaricus were studied through a single-factor test and Plackett-Burman design. Subsequently, the optimum freeze-drying conditions of Lb. delbrueckii subsp. bulgaricus were determined. Lb. delbrueckii subsp. bulgaricus survival rates were up to the maximum of 42.7%, 45.4%, 23.6%, while the concentrations of NaCl, sorbitol, sodium glutamate were 0.6%, 0.15%, 0.09%, respectively. In the optimum concentration, the viable counts in broth is 6.1, 6.9, 5.13 (×108 CFU/mL), respectively; the viable counts in freeze-drying power are 3.09, 5.2, 2.7 (×1010 CFU/g), respectively. Three antifreeze factors including NaCl, sorbitol, sodium glutamate have a positive effect on the growth and freeze-drying of Lb. delbrueckii subsp. bulgaricus. The results are beneficial for developing Lb. delbrueckii subsp. bulgaricus.

Protein crowding in solution, frozen and freeze-dried states: small-angle neutron and X-ray scattering study of lysozyme/sorbitol/water systems

NASA Astrophysics Data System (ADS)

Krueger, Susan; Khodadadi, Sheila; Clark, Nicholas; McAuley, Arnold; Cristiglio, Viviana; Theyencheri, Narayanan; Curtis, Joseph; Shalaev, Evgenyi

2015-03-01

For effective preservation, proteins are often stored as frozen solutions or in glassy states using a freeze-drying process. However, aggregation is often observed after freeze-thaw or reconstitution of freeze-dried powder and the stability of the protein is no longer assured. In this study, small-angle neutron and X-ray scattering (SANS and SAXS) have been used to investigate changes in protein-protein interaction distances of a model protein/cryoprotectant system of lysozyme/sorbitol/water, under representative pharmaceutical processing conditions. The results demonstrate the utility of SAXS and SANS methods to monitor protein crowding at different stages of freezing and drying. The SANS measurements of solution samples showed at least one protein interaction peak corresponding to an interaction distance of ~ 90 Å. In the frozen state, two protein interaction peaks were observed by SANS with corresponding interaction distances at 40 Å as well as 90 Å. On the other hand, both SAXS and SANS data for freeze-dried samples showed three peaks, suggesting interaction distances ranging from ~ 15 Å to 170 Å. Possible interpretations of these interaction peaks will be discussed, as well as the role of sorbitol as a cryoprotectant during the freezing and drying process.

Impaired cognitive control in Parkinson's disease patients with freezing of gait in response to cognitive load.

PubMed

Walton, Courtney C; Shine, James M; Mowszowski, Loren; Gilat, Moran; Hall, Julie M; O'Callaghan, Claire; Naismith, Sharon L; Lewis, Simon J G

2015-05-01

Freezing of gait is a frequent and disabling symptom experienced by many patients with Parkinson's disease. A number of executive deficits have been shown to be associated with the phenomenon suggesting a common underlying pathophysiology, which as of yet remains unclear. Neuroimaging studies have also implicated the role of the cognitive control network in patients with freezing. To explore this concept, the current study examined error-monitoring as a measure of cognitive control. Thirty-four patients with and 38 without freezing of gait, who were otherwise well matched on disease severity, completed a colour-word interference task that allowed the specific assessment of error monitoring during conflict. Whilst both groups performed colour-naming and word-reading tasks equally well, those patients with freezing showed a pattern between conditions whereby they were better able to monitor performance and self-correct errors in the pure inhibition task but not after a switching rule was introduced. The novel results shown here provide insight into possible pathophysiological mechanisms involved in cognitive load and error monitoring in patients with freezing of gait. These results provide further evidence for the role of functional frontostriatal circuitry impairments in patients with freezing of gait and have implications for future studies and possible therapeutic interventions.

Vernalization Requirement and the Chromosomal VRN1-Region can Affect Freezing Tolerance and Expression of Cold-Regulated Genes in Festuca pratensis

PubMed Central

Ergon, Åshild; Melby, Tone I.; Höglind, Mats; Rognli, Odd A.

2016-01-01

Plants adapted to cold winters go through annual cycles of gain followed by loss of freezing tolerance (cold acclimation and deacclimation). Warm spells during winter and early spring can cause deacclimation, and if temperatures drop, freezing damage may occur. Many plants are vernalized during winter, a process making them competent to flower in the following summer. In winter cereals, a coincidence in the timing of vernalization saturation, deacclimation, downregulation of cold-induced genes, and reduced ability to reacclimate, occurs under long photoperiods and is under control of the main regulator of vernalization requirement in cereals, VRN1, and/or closely linked gene(s). Thus, the probability of freezing damage after a warm spell may depend on both vernalization saturation and photoperiod. We investigated the role of vernalization and the VRN1-region on freezing tolerance of meadow fescue (Festuca pratensis Huds.), a perennial grass species. Two F2 populations, divergently selected for high and low vernalization requirement, were studied. Each genotype was characterized for the copy number of one of the four parental haplotypes of the VRN1-region. Clonal plants were cold acclimated for 2 weeks or vernalized/cold acclimated for a total of 9 weeks, after which the F2 populations reached different levels of vernalization saturation. Vernalized and cold acclimated plants were deacclimated for 1 week and then reacclimated for 2 weeks. All treatments were given at 8 h photoperiod. Flowering response, freezing tolerance and expression of the cold-induced genes VRN1, MADS3, CBF6, COR14B, CR7 (BLT14), LOS2, and IRI1 was measured. We found that some genotypes can lose some freezing tolerance after vernalization and a deacclimation–reacclimation cycle. The relationship between vernalization and freezing tolerance was complex. We found effects of the VRN1-region on freezing tolerance in plants cold acclimated for 2 weeks, timing of heading after 9 weeks of vernalization, expression of COR14B, CBF6, and LOS2 in vernalized and/or deacclimated treatments, and restoration of freezing tolerance during reacclimation. While expression of VRN1, COR14B, CBF6, LOS2, and IRI1 was correlated, CR7 was associated with vernalization requirement by other mechanisms, and appeared to play a role in freezing tolerance in reacclimated plants. PMID:26941767

Use of freeze-casting in advanced burner reactor fuel design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lang, A. L.; Yablinsky, C. A.; Allen, T. R.

2012-07-01

This paper will detail the modeling of a fast reactor with fuel pins created using a freeze-casting process. Freeze-casting is a method of creating an inert scaffold within a fuel pin. The scaffold is created using a directional solidification process and results in open porosity for emplacement of fuel, with pores ranging in size from 300 microns to 500 microns in diameter. These pores allow multiple fuel types and enrichments to be loaded into one fuel pin. Also, each pore could be filled with varying amounts of fuel to allow for the specific volume of fission gases created by thatmore » fuel type. Currently fast reactors, including advanced burner reactors (ABR's), are not economically feasible due to the high cost of operating the reactors and of reprocessing the fuel. However, if the fuel could be very precisely placed, such as within a freeze-cast scaffold, this could increase fuel performance and result in a valid design with a much lower cost per megawatt. In addition to competitive costs, freeze-cast fuel would also allow for selective breeding or burning of actinides within specific locations in fast reactors. For example, fast flux peak locations could be utilized on a minute scale to target specific actinides for transmutation. Freeze-cast fuel is extremely flexible and has great potential in a variety of applications. This paper performs initial modeling of freeze-cast fuel, with the generic fast reactor parameters for this model based on EBR-II. The core has an assumed power of 62.5 MWt. The neutronics code used was Monte Carlo N-Particle (MCNP5) transport code. Uniform pore sizes were used in increments of 100 microns. Two different freeze-cast scaffold materials were used: ceramic (MgO-ZrO{sub 2}) and steel (SS316L). Separate models were needed for each material because the freeze-cast ceramic and metal scaffolds have different structural characteristics and overall porosities. Basic criticality results were compiled for the various models. Preliminary results show that criticality is achievable with freeze-cast fuel pins despite the significant amount of inert fuel matrix. Freeze casting is a promising method to achieve very precise fuel placement within fuel pins. (authors)« less

Simulation of Changes in the Near-Surface Soil Freeze/Thaw Cycle Using CLM4.5 With Four Atmospheric Forcing Data Sets

NASA Astrophysics Data System (ADS)

Guo, Donglin; Wang, Aihui; Li, Duo; Hua, Wei

2018-03-01

Change in the near-surface soil freeze/thaw cycle is critical for assessments of hydrological activity, ecosystems, and climate change. Previous studies investigated the near-surface soil freeze/thaw cycle change mostly based on in situ observations and satellite monitoring. Here numerical simulation method is tested to estimate the long-term change in the near-surface soil freeze/thaw cycle in response to recent climate warming for its application to predictions. Four simulations are performed at 0.5° × 0.5° resolution from 1979 to 2009 using the Community Land Model version 4.5, each driven by one of the four atmospheric forcing data sets (i.e., one default Climate Research Unit-National Centers for Environmental Prediction [CRUNCEP] and three newly developed Modern Era Retrospective-Analysis for Research and Applications, Climate Forecast System Reanalysis, and European Centre for Medium-Range Weather Forecasts Reanalysis Interim). The observations from 299 weather stations in both Russia and China are employed to validate the simulated results. The results show that all simulations reasonably reproduce the observed variations in the ground temperature, the freeze start and end dates, and the freeze duration (the correlation coefficients range from 0.47 to 0.99, and the Nash-Sutcliffe efficiencies range from 0.19 to 0.98). Part of the simulations also exactly simulate the trends of the ground temperature, the freeze start and end dates, and the freeze duration. Of the four simulations, the results from the simulation using the CRUNCEP data set show the best overall agreement with the in situ observations, indicating that the CRUNCEP data set could be preferentially considered as the basic atmospheric forcing data set for future prediction. The simulated area-averaged annual freeze duration shortened by 8.03 days on average from 1979 to 2009, with an uncertainty (one standard deviation) of 0.67 days caused by the different atmospheric forcing data sets. These results address the performance of numerical model in simulating the long-term changes in the near-surface soil freeze/thaw cycle and the role of different atmospheric forcing data sets in the simulation, which are useful for the prediction of future freeze/thaw dynamics.

Basal Freeze-on: An Active Component of Hydrology from the Ice Divide to the Margin

NASA Astrophysics Data System (ADS)

Bell, R. E.; Tinto, K. J.; Abdi, A.; Creyts, T. T.; Wolovick, M.; Das, I.; Ferraccioli, F.; Csatho, B. M.

2012-12-01

Subglacial hydrology is considered a key control of ice sheet dynamics. Here we show that basal freeze-on is a process that can terminate basal hydrologic networks both in the interior of East Antarctica and at the margins of the Greenland Ice Sheet. Basal freeze-on modifies the ice thickness, ice structure, and ice rheology and therefore must be considered in developing accurate understanding of how hydrology interacts with ice dynamics. In East Antarctica, the freeze-on process follows well-defined hydrologic networks within Gamburtsev Mountain valleys. The steep mountain topography strongly controls the routing of the subglacial water. Ice surface slope drives the water up the mountain valleys and freeze-on occurs at the valley heads. Freeze-on ice is characterized by distinct basal radar reflectors that emerge from the hydrologic network. Evidence that these spatially coherent reflectors demark accreted ice is the upward deflection of the overlying internal layers accompanied by thickening of base of the ice sheet. Individual accretion bodies can be 25 km wide across flow, 100 km along flow with average thicknesses of ~500m although the maximum thickness is 1100m. Regional accumulation rates near the accretion sites average 4cm/yr with low ice velocity (1.5 m/yr). The volume of the ice enclosed by the accretion ice reflectors is 45-1064 km3. The accretion occurs beneath 2200-3000m thick ice and has been persistent for at least 50,000yr. Other basal reflectors in northern Greenland appear in radar from NASA's Icebridge mission and CRESIS. To identify freeze-on ice, we use specific criteria: reflectors must originate from the bed, must be spatially continuous from line to line and the meteoric stratigraphy is deflected upward. The absence of coincident gravity anomalies indicates these reflectors define distinct packages of ice rather than frozen sediment or off-nadir subglacial topography. In the Petermann Glacier Catchment, one of the largest in northern Greenland, we have identified 14 distinct basal ice packages over a wide region. The accumulation rate (~17 cm/yr) and ice velocity (~5-200m/yr) are higher than East Antarctica. These accretion bodies are 10-50 km wide, up to 940m thick and can be traced up to 140 km. The volume of the ice enclosed by the accretion ice reflector units is ~70-300 km3. We estimate that the freeze-on process in Petermann has been active for at least 6,000yr. Water has been mapped beneath much of the Greenland ice sheet and adjacent to the inland freeze-on site flat bright reflectors are interpreted as basal water. The onset of fast flow in Petermann Glacier is associated with the development of the thickest unit of freeze-on ice. Other areas of Greenland also have basal freeze-on ice. North of Jakobshavn Isbrae where the ice sheet is ~1000 m thick, evidence exists for a nearly 10 km wide, 200 m thick unit of basal ice in airborne radar. Located close to the site where basal freeze-on outcrops at the ice sheet margin at Pakitsoq, this unit may be the result of freeze-on of water draining from a supraglacial lake. Basal freeze-on is a critical component of subglacial hydrology. The evidence for large scale freeze-on East Antarctica and many areas of Greenland indicates widespread modification of the base of the ice sheet by basal hydrology.

The effects of cold acclimation on photosynthetic apparatus and the expression of COR14b in four genotypes of barley (Hordeum vulgare) contrasting in their tolerance to freezing and high-light treatment in cold conditions.

PubMed

Rapacz, Marcin; Wolanin, Barbara; Hura, Katarzyna; Tyrka, Miroslaw

2008-04-01

Cold acclimation modifies the balance of the energy absorbed and metabolized in the dark processes of photosynthesis, which may affect the expression of cold-regulated (COR) genes. At the same time, a gradual acclimation to the relatively high light conditions is observed, thereby minimizing the potential for photo-oxidative damage. As a result, the resistance to photoinhibition in the cold has often been identified as a trait closely related to freezing tolerance. Using four barley genotypes that differentially express both traits, the effect of cold acclimation on freezing tolerance and high-light tolerance was studied together with the expression of COR14b, one of the best-characterized barley COR genes. Plants were cold acclimated for 2 weeks at 2 degrees C. Freezing tolerance was studied by means of electrolyte leakage. Changes in photosynthetic apparatus and high-light tolerance were monitored by means of chlorophyll fluorescence. Accumulation of COR14b and some proteins important in photosynthetic acclimation to cold were studied with western analysis. COR14b transcript accumulation during cold acclimation was assessed with real-time PCR. Cold acclimation increased both freezing tolerance and high-light tolerance, especially when plants were treated with high light after non-lethal freezing. In all plants, cold acclimation triggered the increase in photosynthetic capacity during high-light treatment. In two plants that were characterized by higher high-light tolerance but lower freezing tolerance, higher accumulation of COR14b transcript and protein was observed after 7 d and 14 d of cold acclimation, while a higher transient induction of COR14b expression was observed in freezing-tolerant plants during the first day of cold acclimation. High-light tolerant plants were also characterized with a higher level of PsbS accumulation and more efficient dissipation of excess light energy. Accumulation of COR14b in barley seems to be important for resistance to combined freezing and high-light tolerance, but not for freezing tolerance per se.

A water activity based model of heterogeneous ice nucleation kinetics for freezing of water and aqueous solution droplets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knopf, Daniel A.; Alpert, Peter A.

Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process of heterogeneous ice nucleation which occurs in many environments, especially in the atmosphere where it results in the glaciation of clouds. Here we experimentally show, using a variety of IN types suspended in various aqueous solutions, that immersion freezing temperatures and kinetics can be described solely by temperature, T, and solution water activity, aw, which is the ratio of the vapour pressure of the solution and the saturation water vapour pressure under the same conditions and, in equilibrium, equivalent to relative humiditymore » (RH). This allows the freezing point and corresponding heterogeneous ice nucleation rate coefficient, Jhet, to be uniquely expressed by T and aw, a result we term the aw based immersion freezing model (ABIFM). This method is independent of the nature of the solute and accounts for several varying parameters, including cooling rate and IN surface area, while providing a holistic description of immersion freezing and allowing prediction of freezing temperatures, Jhet, frozen fractions, ice particle production rates and numbers. Our findings are based on experimental freezing data collected for various IN surface areas, A, and cooling rates, r, of droplets variously containing marine biogenic material, two soil humic acids, four mineral dusts, and one organic monolayer acting as IN. For all investigated IN types we demonstrate that droplet freezing temperatures increase as A increases. Similarly, droplet freezing temperatures increase as the cooling rate decreases. The log 10(J het) values for the various IN types derived exclusively by T and aw, provide a complete description of the heterogeneous ice nucleation kinetics. Thus, the ABIFM can be applied over the entire range of T, RH, total particulate surface area, and cloud activation timescales typical of atmospheric conditions. Finally, we demonstrate that ABIFM can be used to derive frozen fractions of droplets and ice particle production for atmospheric models of cirrus and mixed phase cloud conditions.« less

Role of mono- and oligosaccharides from FOS as stabilizing agents during freeze-drying and storage of Lactobacillus delbrueckii subsp. bulgaricus.

PubMed

Romano, Nelson; Schebor, Carolina; Mobili, Pablo; Gómez-Zavaglia, Andrea

2016-12-01

The aim of this work was to assess the role of mono- and oligosaccharides present in fructo-oligosaccharides (FOS) mixtures as protective agents during freeze-drying and storage of Lactobacillus delbrueckii subsp. bulgaricus CIDCA 333. Different FOS mixtures were enzymatically obtained from sucrose and further purified by removing the monosaccharides produced as secondary products. Their glass transition temperatures (T g ) were determined at 11, 22 and 33% relative humidity (RH). Bacterial cultures were freeze-dried in the presence of 20% w/v solutions of the studied FOS. Their protective effect during freeze-drying was assessed by bacterial plate counting, and by determining the lag time from growth kinetics and the uptake of propidium iodide (PI). Plate counting during bacterial storage at 4°C, and 11, 22 and 33% RH for 80days completed this rational analysis of the protective effect of FOS. Purification of FOS led to an increase of T g in all the conditions assayed. Microorganisms freeze-dried in the presence of non-purified FOS were those with the shortest lag times. Bacteria freeze-dried with pure or commercial FOS (92% of total FOS) showed larger lag times (8.9-12.6h). The cultivability of microorganisms freeze-dried with non-purified FOS and with sucrose was not significantly different from that of bacteria before freeze-drying (8.74±0.14logCFU/mL). Pure or commercial FOS were less efficient in protecting bacteria during freeze-drying. All the protectants prevented membrane damage. The cultivability of bacteria freeze-dried with FOS decayed <1logarithmicunit after 80days of storage at 11% RH. When storing at 22 and 33% RH, pure and commercial FOS were those that best protected bacteria, and FOS containing monosaccharides were less efficient. The effect of FOS on bacterial protection is the result of a balance between monosaccharides, sucrose and larger FOS in the mixtures: the smallest sugars are more efficient in protecting lipid membranes, and the larger ones favor the formation of vitreous states. Copyright © 2016 Elsevier Ltd. All rights reserved.

A water activity based model of heterogeneous ice nucleation kinetics for freezing of water and aqueous solution droplets.

PubMed

Knopf, Daniel A; Alpert, Peter A

2013-01-01

Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process of heterogeneous ice nucleation which occurs in many environments, especially in the atmosphere where it results in the glaciation of clouds. Here we experimentally show, using a variety of IN types suspended in various aqueous solutions, that immersion freezing temperatures and kinetics can be described solely by temperature, T, and solution water activity, a(w), which is the ratio of the vapour pressure of the solution and the saturation water vapour pressure under the same conditions and, in equilibrium, equivalent to relative humidity (RH). This allows the freezing point and corresponding heterogeneous ice nucleation rate coefficient, J(het), to be uniquely expressed by T and a(w), a result we term the a(w) based immersion freezing model (ABIFM). This method is independent of the nature of the solute and accounts for several varying parameters, including cooling rate and IN surface area, while providing a holistic description of immersion freezing and allowing prediction of freezing temperatures, J(het), frozen fractions, ice particle production rates and numbers. Our findings are based on experimental freezing data collected for various IN surface areas, A, and cooling rates, r, of droplets variously containing marine biogenic material, two soil humic acids, four mineral dusts, and one organic monolayer acting as IN. For all investigated IN types we demonstrate that droplet freezing temperatures increase as A increases. Similarly, droplet freezing temperatures increase as the cooling rate decreases. The log10(J(het)) values for the various IN types derived exclusively by Tand a(w), provide a complete description of the heterogeneous ice nucleation kinetics. Thus, the ABIFM can be applied over the entire range of T, RH, total particulate surface area, and cloud activation timescales typical of atmospheric conditions. Lastly, we demonstrate that ABIFM can be used to derive frozen fractions of droplets and ice particle production for atmospheric models of cirrus and mixed phase cloud conditions.

Influence of freeze-thaw events on carbon dioxide emission from soils at different moisture and land use.

PubMed

Kurganova, Irina; Teepe, Robert; Loftfield, Norman

2007-02-19

The repeated freeze-thaw events during cold season, freezing of soils in autumn and thawing in spring are typical for the tundra, boreal, and temperate soils. The thawing of soils during winter-summer transitions induces the release of decomposable organic carbon and acceleration of soil respiration. The winter-spring fluxes of CO2 from permanently and seasonally frozen soils are essential part of annual carbon budget varying from 5 to 50%. The mechanisms of the freeze-thaw activation are not absolutely clear and need clarifying. We investigated the effect of repeated freezing-thawing events on CO2 emission from intact arable and forest soils (Luvisols, loamy silt; Central Germany) at different moisture (65% and 100% of WHC). Due to the measurement of the CO2 flux in two hours intervals, the dynamics of CO2 emission during freezing-thawing events was described in a detailed way. At +10 degrees C (initial level) in soils investigated, carbon dioxide emission varied between 7.4 to 43.8 mg C m-2h-1 depending on land use and moisture. CO2 flux from the totally frozen soil never reached zero and amounted to 5 to 20% of the initial level, indicating that microbial community was still active at -5 degrees C. Significant burst of CO2 emission (1.2-1.7-fold increase depending on moisture and land use) was observed during thawing. There was close linear correlation between CO2 emission and soil temperature (R2 = 0.86-0.97, P < 0.001). Our investigations showed that soil moisture and land use governed the initial rate of soil respiration, duration of freezing and thawing of soil, pattern of CO2 dynamics and extra CO2 fluxes. As a rule, the emissions of CO2 induced by freezing-thawing were more significant in dry soils and during the first freezing-thawing cycle (FTC). The acceleration of CO2 emission was caused by different processes: the liberation of nutrients upon the soil freezing, biological activity occurring in unfrozen water films, and respiration of cold-adapted microflora.

A water activity based model of heterogeneous ice nucleation kinetics for freezing of water and aqueous solution droplets

DOE PAGES

Knopf, Daniel A.; Alpert, Peter A.

2013-04-24

Immersion freezing of water and aqueous solutions by particles acting as ice nuclei (IN) is a common process of heterogeneous ice nucleation which occurs in many environments, especially in the atmosphere where it results in the glaciation of clouds. Here we experimentally show, using a variety of IN types suspended in various aqueous solutions, that immersion freezing temperatures and kinetics can be described solely by temperature, T, and solution water activity, aw, which is the ratio of the vapour pressure of the solution and the saturation water vapour pressure under the same conditions and, in equilibrium, equivalent to relative humiditymore » (RH). This allows the freezing point and corresponding heterogeneous ice nucleation rate coefficient, Jhet, to be uniquely expressed by T and aw, a result we term the aw based immersion freezing model (ABIFM). This method is independent of the nature of the solute and accounts for several varying parameters, including cooling rate and IN surface area, while providing a holistic description of immersion freezing and allowing prediction of freezing temperatures, Jhet, frozen fractions, ice particle production rates and numbers. Our findings are based on experimental freezing data collected for various IN surface areas, A, and cooling rates, r, of droplets variously containing marine biogenic material, two soil humic acids, four mineral dusts, and one organic monolayer acting as IN. For all investigated IN types we demonstrate that droplet freezing temperatures increase as A increases. Similarly, droplet freezing temperatures increase as the cooling rate decreases. The log 10(J het) values for the various IN types derived exclusively by T and aw, provide a complete description of the heterogeneous ice nucleation kinetics. Thus, the ABIFM can be applied over the entire range of T, RH, total particulate surface area, and cloud activation timescales typical of atmospheric conditions. Finally, we demonstrate that ABIFM can be used to derive frozen fractions of droplets and ice particle production for atmospheric models of cirrus and mixed phase cloud conditions.« less

Critical viewpoints on the methods of realizing the metal freezing points of the ITS-90

NASA Astrophysics Data System (ADS)

Ma, C. K.

1995-08-01

The time-honored method for realizing the freezing point tf of a metal (in practice necessarily a dilute alloy) is that of continuous, slow freezing where the plateau temperature (which is the result of solidifying material's being so pure that its phase-transition temperature is observably constant) is measured. The freezing point being an equilibrium temperature, Ancsin considers this method to be inappropriate in principle: equilibrium between the solid and liquid phases cannot be achieved while the solid is being cooled to dispose of the releasing latent heat and while it is accreting at the expense of the liquid. In place of the continuous freezing method he has employed the pulse-heating method (in which the sample is allowed to approach equilibrium after each heat pulse) in his study of Ag; his measurements suggest that freezing can produce non-negligible errors. Here we examine both methods and conclude that the freezing method, employing an inside solid-liquid interface thermally isolated by an outside interface, can provide realizations of the highest accuracy; in either method, perturbation, by inducing solid-liquid phase transition continuously or intermittently, is essential for detecting equilibrium thermally. The respective merits and disadvantages of these two methods and also of the inner-melt method are discussed. We conclude that in a freezing-point measurement what is being measured is in effect the however minutely varying phase transition, and nonconstitutional equilibrium, temperature ti at the solid-liquid interface. The objective is then to measure the ti that is the best measure of tf, which is, normally, the plateau temperature.

Redistribution of ice nuclei between cloud and rain droplets: Parameterization and application to deep convective clouds: ICE NUCLEI IN RAIN DROPLETS

DOE PAGES

Paukert, M.; Hoose, C.; Simmel, M.

2017-02-21

In model studies of aerosol-dependent immersion freezing in clouds, a common assumption is that each ice nucleating aerosol particle corresponds to exactly one cloud droplet. Conversely, the immersion freezing of larger drops—“rain”—is usually represented by a liquid volume-dependent approach, making the parameterizations of rain freezing independent of specific aerosol types and concentrations. This may lead to inconsistencies when aerosol effects on clouds and precipitation shall be investigated, since raindrops consist of the cloud droplets—and corresponding aerosol particles—that have been involved in drop-drop-collisions. We introduce an extension to a two-moment microphysical scheme in order to account explicitly for particle accumulation inmore » raindrops by tracking the rates of selfcollection, autoconversion, and accretion. This also provides a direct link between ice nuclei and the primary formation of large precipitating ice particles. A new parameterization scheme of drop freezing is presented to consider multiple ice nuclei within one drop and effective drop cooling rates. In our test cases of deep convective clouds, we find that at altitudes which are most relevant for immersion freezing, the majority of potential ice nuclei have been converted from cloud droplets into raindrops. Compared to the standard treatment of freezing in our model, the less efficient mineral dust-based freezing results in higher rainwater contents in the convective core, affecting both rain and hail precipitation. The aerosol-dependent treatment of rain freezing can reverse the signs of simulated precipitation sensitivities to ice nuclei perturbations.« less

Freezing-induced uptake of trehalose into mammalian cells facilitates cryopreservation.

PubMed

Zhang, Miao; Oldenhof, Harriëtte; Sieme, Harald; Wolkers, Willem F

2016-06-01

The aim of this study was to investigate if membrane-impermeable molecules are taken up by fibroblasts when exposing the cells to membrane phase transitions and/or freezing-induced osmotic forces. The membrane-impermeable fluorescent dye lucifer yellow (LY) was used to visualize and quantify uptake during endocytosis, and after freezing-thawing. In addition, trehalose uptake after freezing and thawing was studied. Fourier transform infrared spectroscopic studies showed that fibroblasts display a minor non-cooperative phase transition during cooling at suprazero temperatures, whereas cells display strong highly cooperative fluid-to-gel membrane phase transitions during freezing, both in the absence and presence of protectants. Cells do not show uptake of LY upon passing the suprazero membrane phase transition at 30-10°C, whereas after freezing and thawing cells show intracellular LY equally distributed within the cell. Both, LY and trehalose are taken up by fibroblasts after freezing and thawing with loading efficiencies approaching 50%. When using 250 mM extracellular trehalose during cryopreservation, intracellular concentrations greater than 100 mM were determined after thawing. A plot of cryosurvival versus the cooling rate showed a narrow inverted-'U'-shaped curve with an optimal cooling rate of 40°C min(-1). Diluting cells cryopreserved with trehalose in isotonic cell culture medium resulted in a loss of cell viability, which was attributed to intracellular trehalose causing an osmotic imbalance. Taken together, mammalian cells can be loaded with membrane-impermeable compounds, including the protective agent trehalose, by subjecting the cells to freezing-induced osmotic stress. Copyright © 2016 Elsevier B.V. All rights reserved.

Spacecraft Radiator Freeze Protection Using a Regenerative Heat Exchanger with Bypass Setpoint Temperature Control

NASA Technical Reports Server (NTRS)

Ungar, Eugene K.

2008-01-01

Spacecraft radiators are sized for their maximum heat load in their warmest thermal environment, but must operate at reduced heat loads and in colder environments. For systems where the radiator environment can be colder than the working fluid freezing temperature, radiator freezing becomes an issue. Radiator freezing has not been a major issue for the Space Shuttle and the International Space Station (ISS) active thermal control systems (ATCSs) because they operate in environments that are warm relative to the freezing point of their external coolants (Freon-21 and ammonia, respectively). For a vehicle that lands at the Lunar South Pole, the design thermal environment is 215K, but the radiator working fluid must also be kept from freezing during the 0 K sink of transit. A radiator bypass flow control design such as those used on the Space Shuttle and ISS requires more than 30% of the design heat load to avoid radiator freezing during transit - even with a very low freezing point working fluid. By changing the traditional ATCS architecture to include a regenerating heat exchanger inboard of the radiator and by using a regenerator bypass flow control valve to maintain system setpoint, the required minimum heat load can be reduced by more than half. This gives the spacecraft much more flexibility in design and operation. The present work describes the regenerator bypass ATCS setpoint control methodology. It includes analytical results comparing the performance of this system to the traditional radiator bypass system. Finally, a summary of the advantages of the regenerator bypass system are presented.

Effect of exogenous carbon addition and the freeze-thaw cycle on soil microbes and mineral nitrogen pools1

NASA Astrophysics Data System (ADS)

Hu, Xia; Yin, Peng; Nong, Xiang; Liao, Jinhua

2018-01-01

To elucidate the alpine soil process in winter, the response mechanism of soil mineral nitrogen and soil microbes to exogenous carbon (0 mg C, 1 mg C, 2 mg C, 4 mg C and 8 mg C·g-1 dry soil) and the freeze-thaw cycle (-2 °C, -2 ∼ 2 °C, -20 ∼2°C) were studied by laboratory simulation. The freeze-thaw treatment had no significant effect on microbial biomass nitrogen and the number of bacteria. The soil mineral N pool, the number of fungi, and enzyme activities were obviously affected by the freeze-thaw cycle. A mild freeze-thaw cycle (-2∼2°C) significantly increased the number of fungi and catalase activity, while severe freeze-thaw cycle (-20∼2°C) obviously decreased invertase activity. The results suggested that both the freeze-thaw rate and freeze-thaw temperature amplitudes have a strong effect on soil microbial dynamics in the alpine zone in winter. The results showed that exogenous carbon addition significantly decreased soil NO3-N and NH4 +-N contents, increased soil microbial biomass, the number of microbes, and soil enzyme activities. The results showed that microbial growth in the eastern Tibetan Plateau was somewhat limited by available C. It may represent a larger potential pulse of soil nutrient for alpine plants in the next spring, and may be instrumental for plant community shifts under future climate change predictions due to the possible increased litter addition.

Effective freezing rate for semen cryopreservation in endangered Mediterranean brown trout (Salmo trutta macrostigma) inhabiting the Biferno river (South Italy).

PubMed

Iaffaldano, Nicolaia; Di Iorio, Michele; Manchisi, Angelo; Esposito, Stefano; Gibertoni, Pier Paolo

2016-10-01

This study was designed to determine: (i) the in vitro effects of different freezing rates on post-thaw semen quality of Mediterranean brown trout (Salmo trutta macrostigma) from the Biferno river; and (ii) the in vivo fertilization and hatching percentage of freezing rate giving rise to the best post-thaw semen quality. Pooled semen samples were diluted 1:3 (v:v) in a freezing extender composed of 300 mM glucose, 10% egg yolk and 10% dimethyl sulfoxide (DMSO). The extended semen was packaged in 0.25 ml plastic straws and frozen at different heights above the liquid nitrogen surface (1, 5 or 10 cm) for 10 min to give three different freezing rates. Semen samples were thawed at 30°C for 10 s. The variables assessed after thawing were sperm motility, duration of motility and viability. Our results clearly indicate a significant effect of freezing rate on post-thaw semen quality. Semen frozen 5 cm above the liquid nitrogen surface showed the best quality after freezing/thawing. Based on these in vitro data, 2 groups of 200 eggs were fertilized with fresh semen or semen frozen 5 cm above the liquid nitrogen surface. Fertilization and hatching rates recorded for eggs fertilized with frozen semen were significantly lower (25.4% and 22.5%, respectively) than the ones obtained using fresh semen (87.8% and 75.5%, respectively). An effective freezing protocol will allow for the creation of a sperm cryobank to recover the original population of Mediterranean brown trout in the Biferno river.

Redistribution of ice nuclei between cloud and rain droplets: Parameterization and application to deep convective clouds: ICE NUCLEI IN RAIN DROPLETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paukert, M.; Hoose, C.; Simmel, M.

In model studies of aerosol-dependent immersion freezing in clouds, a common assumption is that each ice nucleating aerosol particle corresponds to exactly one cloud droplet. Conversely, the immersion freezing of larger drops—“rain”—is usually represented by a liquid volume-dependent approach, making the parameterizations of rain freezing independent of specific aerosol types and concentrations. This may lead to inconsistencies when aerosol effects on clouds and precipitation shall be investigated, since raindrops consist of the cloud droplets—and corresponding aerosol particles—that have been involved in drop-drop-collisions. We introduce an extension to a two-moment microphysical scheme in order to account explicitly for particle accumulation inmore » raindrops by tracking the rates of selfcollection, autoconversion, and accretion. This also provides a direct link between ice nuclei and the primary formation of large precipitating ice particles. A new parameterization scheme of drop freezing is presented to consider multiple ice nuclei within one drop and effective drop cooling rates. In our test cases of deep convective clouds, we find that at altitudes which are most relevant for immersion freezing, the majority of potential ice nuclei have been converted from cloud droplets into raindrops. Compared to the standard treatment of freezing in our model, the less efficient mineral dust-based freezing results in higher rainwater contents in the convective core, affecting both rain and hail precipitation. The aerosol-dependent treatment of rain freezing can reverse the signs of simulated precipitation sensitivities to ice nuclei perturbations.« less

Freezing of gait: Promising avenues for future treatment.

PubMed

Gilat, Moran; Lígia Silva de Lima, Ana; Bloem, Bastiaan R; Shine, James M; Nonnekes, Jorik; Lewis, Simon J G

2018-03-12

Freezing of gait is a devastating symptom of Parkinson's disease and other forms of parkinsonism. It poses a major burden on both patients and their families, as freezing often leads to falls, fall-related injuries and a loss of independence. Treating freezing of gait is difficult for a variety of reasons: it has a paroxysmal and unpredictable nature; a multifaceted pathophysiology, with an interplay between motor elements (disturbed stepping mechanisms) and non-motor elements (cognitive decline, anxiety); and a complex (and likely heterogeneous) underlying neural substrate, involving multiple failing neural networks. In recent years, advances in translational neuroscience have offered new insights into the pathophysiology underlying freezing. Furthermore, the mechanisms behind the effectiveness of available treatments (or lack thereof) are better understood. Driven by these concepts, researchers and clinicians have begun to improve currently available treatment options, and develop new and better treatment methods. Here, we evaluate the range of pharmacological (i.e. closed-looped approaches), surgical (i.e. multi-target and adaptive deep brain and spinal cord stimulation) and behavioural (i.e. biofeedback and cueing on demand) treatment options that are under development, and propose novel avenues that are likely to play a crucial role in the clinical management of freezing of gait in the near future. The outcomes of this review suggest that the successful future management of freezing of gait will require individualized treatments that can be implemented in an on-demand manner in response to imminent freezing. With this review we hope to guide much-needed advances in treating this devastating symptom of Parkinson's disease. Copyright © 2018 Elsevier Ltd. All rights reserved.

Freeze-all cycle for all normal responders?

PubMed

Roque, Matheus; Valle, Marcello; Guimarães, Fernando; Sampaio, Marcos; Geber, Selmo

2017-02-01

The purpose of this study is to evaluate the freeze-all strategy in subgroups of normal responders, to assess whether this strategy is beneficial regardless of ovarian response, and to evaluate the possibility of implementing an individualized embryo transfer (iET) based on ovarian response. This was an observational, cohort study performed in a private IVF center. A total of 938 IVF cycles were included in this study. The patients were submitted to controlled ovarian stimulation (COS) with a gonadotropin-releasing hormone (GnRH) antagonist protocol and a cleavage-stage day 3 embryo transfer. We performed a comparison of outcomes between the fresh embryo transfer (n = 523) and the freeze-all cycles (n = 415). The analysis was performed in two subgroups of patients based on the number of retrieved oocytes: Group 1 (4-9 oocytes) and Group 2 (10-15 oocytes). In Group 1 (4-9 retrieved oocytes), the implantation rates (IR) were 17.9 and 20.5% (P = 0.259) in the fresh and freeze-all group, respectively; the ongoing pregnancy rates (OPR) were 31 and 33% (P = 0.577) in the fresh and freeze-all group, respectively. In Group 2 (10-15 oocytes), the IR were 22.1 and 30.1% (P = 0.028) and the OPR were 34 and 47% (P = 0.021) in the fresh and freeze-all groups, respectively. Although the freeze-all policy may be related to better in vitro fertilization (IVF) outcomes in normal responders, these potential advantages decrease with worsening ovarian response. Patients with poorer ovarian response do not benefit from the freeze-all strategy.

Solid Lipid Nanoparticle assemblies (SLNas) for an anti-TB inhalation treatment-A Design of Experiments approach to investigate the influence of pre-freezing conditions on the powder respirability.

PubMed

Maretti, Eleonora; Rustichelli, Cecilia; Romagnoli, Marcello; Balducci, Anna Giulia; Buttini, Francesca; Sacchetti, Francesca; Leo, Eliana; Iannuccelli, Valentina

2016-09-10

For direct intramacrophagic antitubercular therapy, pulmonary administration through Dry Powder Inhaler (DPI) devices is a reasonable option. For the achievement of efficacious aerosolisation, rifampicin-loaded Solid Lipid Nanoparticle assemblies (SLNas) were developed using the melt emulsifying technique followed by freeze-drying. Indeed, this drying method can cause freezing or drying stresses compromising powder respirability. It is the aim of this research to offer novel information regarding pre-freezing variables. These included type and concentration of cryoprotectants, pre-freezing temperature, and nanoparticle concentration in the suspension. In particular, the effects of such variables were observed at two main levels. First of all, on SLNas characteristics - i.e., size, polydispersity index, zeta-potential, circularity, density, and drug loading. Secondly, on powder respirability, taking into account aerodynamic diameter, emitted dose, and respirable fraction. Considering the complexity of the factors involved in a successful respirable powder, a Design of Experiments (DoE) approach was adopted as a statistical tool for evaluating the effect of pre-freezing conditions. Interestingly, the most favourable impact on powder respirability was exerted by quick-freezing combined with a certain grade of sample dilution before the pre-freezing step without the use of cryoprotectants. In such conditions, a very high SLNas respirable fraction (>50%) was achieved, along with acceptable yields in the final dry powder as well as a reduction of powder mass to be introduced into DPI capsules with benefits in terms of administered drug dose feasibility. Copyright © 2016 Elsevier B.V. All rights reserved.

3 CFR - Freezing Federal Employee Pay Schedules and Rates That Are Set By Administrative Discretion

Code of Federal Regulations, 2011 CFR

2011-01-01

... 3 The President 1 2011-01-01 2011-01-01 false Freezing Federal Employee Pay Schedules and Rates That Are Set By Administrative Discretion Presidential Documents Other Presidential Documents Memorandum of December 22, 2010 Freezing Federal Employee Pay Schedules and Rates That Are Set By...

B-2 Systems Engineering Case Study

DTIC Science & Technology

2007-01-01

formal configuration freeze , an immediate refocus of the Task Teams was required. Within several days, the air vehicle task teams were conducting...39 3.3.3 Configuration Freeze ...1983 PDR 1 Oct 1982 Reconfiguration Feb 1983-Aug 1983 (LP3, LP4) Configuration Freeze July 1983 PDR 2 Mar-April 1984 CDR Dec 1986

Assessment of freeze injury of grapevine green tissues in response to cultivars and a cryoprotectant product

USDA-ARS?s Scientific Manuscript database

Spring frosts and subsequent crop losses threaten the economic sustainability of fruit crop producers all over the world. This study used a controlled-freezing technique to impose a post-budbreak freezing stress to grapevine shoots forced from one-node cuttings ['Albariño', 'Cabernet Franc', 'Cabern...

Projecting potential adoption of genetically engineered freeze-tolerant Eucalyptus in the United States

Treesearch

David N. Wear; Ernest Dixon IV; Robert C. Abt; Navinder Singh

2015-01-01

Development of commercial Eucalyptus plantations has been limited in the United States because of the species’ sensitivity to freezing temperatures. Recently developed genetically engineered clones of a Eucalyptus hybrid, which confer freeze tolerance, could expand the range of commercial plantations. This study explores how...

9 CFR 381.66 - Temperatures and chilling and freezing procedures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 9 Animals and Animal Products 2 2012-01-01 2012-01-01 false Temperatures and chilling and freezing... Procedures § 381.66 Temperatures and chilling and freezing procedures. (a) General. Temperatures and... temperature is reduced to 40 °F. or less, as provided in paragraph (b)(2) of this section unless such poultry...

9 CFR 381.66 - Temperatures and chilling and freezing procedures.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 9 Animals and Animal Products 2 2013-01-01 2013-01-01 false Temperatures and chilling and freezing... Procedures § 381.66 Temperatures and chilling and freezing procedures. (a) General. Temperatures and... temperature is reduced to 40 °F. or less, as provided in paragraph (b)(2) of this section unless such poultry...

9 CFR 381.66 - Temperatures and chilling and freezing procedures.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 9 Animals and Animal Products 2 2011-01-01 2011-01-01 false Temperatures and chilling and freezing... Procedures § 381.66 Temperatures and chilling and freezing procedures. (a) General. Temperatures and... temperature is reduced to 40 °F. or less, as provided in paragraph (b)(2) of this section unless such poultry...

23 CFR 658.23 - LCV freeze; cargo-carrying unit freeze.

Code of Federal Regulations, 2010 CFR

2010-04-01

... safety purposes and road construction, a State may make minor adjustments of a temporary and emergency... decision is reached that minor adjustments made by a State are not legitimately attributable to road or bridge construction or safety, the FHWA will inform the State, and the original conditions of the freeze...

Map showing length of freeze-free season in the Salina quadrangle, Utah

USGS Publications Warehouse

Covington, Harry R.

1972-01-01

In general, long freeze-free periods occur at low elevations, and short freeze-free periods occur at high elevations. But some valley floors have shorter freeze-free seasons than the glancing foothills because air cooled at high elevations flows downward and is trapped in the valleys. This temperature pattern occurs in the western part of the quadrangle in Rabbit Valley, Grass Valley, and the Sevier River Valley near Salina.Because year-round weather stations are sparse in Utah, a special technique for estimating length of freeze-free season was developed by Dr. Gaylen L. Ashcroft, Assistant Professor of Climatology, Utah State University, and E. Arlo Richardson, State Climatologist, U.S. Weather Bureau, based on average annual temperature, average annual temperature range, average daily temperature range, and average july maximum temperature. This technique was used in preparation of the map showing “Length of 32°F freeze-free season for Utah,” figure 23 in Hydrologic Atlas of Utah (Utah State University and Utah Division of Water Resources, 1968), from which the data for this map were taken.

Effect of Multiple Freezing/Thawing Cycles on the Structural and Functional Properties of Waxy Rice Starch

PubMed Central

Tao, Han; Yan, Juan; Zhao, Jianwei; Tian, Yaoqi; Jin, Zhengyu; Xu, Xueming

2015-01-01

The structural and functional properties of non-gelatinized waxy rice starch were investigated after 1, 3, 7, and 10 freezing/thawing cycles. Freezing caused an increasing damaged starch from 1.36% in native waxy rice starch to 5.77% in 10 freezing/thawing-treated starch (FTS), as evidenced by the cracking surface on starch granules. More dry matter concentration was leached, which was characterized by high amylopectin concentration (4.34 mg/mL). The leaching was accompanied by a decrease in relative crystallinity from 35.19% in native starch to 31.34% in 10 FTS. Freezing treatment also led to significant deviations in the functional characteristics, for instance decreased gelatinization temperature range, enthalpy, and pasting viscosities. The resistant starch content of 10FTS significantly decreased from 58.9% to 19%, whereas the slowly digested starch content greatly increased from 23.8% in native starch to 50.3%. The increase in susceptibility to enzyme hydrolysis may be attributed to porous granular surface, amylopectin leaching, and the decrease in the relative crystallinity caused by freezing water. PMID:26018506

Development of the gametophyte of the fern Schizaea pusilla

NASA Technical Reports Server (NTRS)

Kiss, J. Z.; Swatzell, L. J.

1996-01-01

Schizaea pusilla is a pteridophyte with several unique developmental characteristics. In contrast to most other fern species, S. pusilla gametophytes remain filamentous throughout their development, and the gametophytes are associated with an endophytic fungus which appears to be mycorrhizal. In terms of tropistic responses, apical filament cells of young gametophytes are negatively phototropic compared with germ filaments of other ferns which exhibit positive phototropism. Cryofixation (propane jet freezing and high-pressure freezing) in conjunction with freeze substitution electron microscopy was used to study young gametophytes. The results demonstrate that apical filament cells have a distinctive structural polarity and that rhizoids also can be successfully frozen by these methods. The cytoskeleton and endomembrane system were particularly well preserved in cryofixed cells. In addition, Schizaea gametophytes were used as a test system to evaluate potential artifacts of propane jet freezing and high pressure freezing. There was little apparent difference in ultrastructure between cells cryofixed by either freezing method. These gametophytes will be useful in determining the effectiveness of cryofixation techniques and as a model system in tip growth studies.

An Improved Model for Nucleation-Limited Ice Formation in Living Cells during Freezing

PubMed Central

Zhao, Gang; He, Xiaoming

2014-01-01

Ice formation in living cells is a lethal event during freezing and its characterization is important to the development of optimal protocols for not only cryopreservation but also cryotherapy applications. Although the model for probability of ice formation (PIF) in cells developed by Toner et al. has been widely used to predict nucleation-limited intracellular ice formation (IIF), our data of freezing Hela cells suggest that this model could give misleading prediction of PIF when the maximum PIF in cells during freezing is less than 1 (PIF ranges from 0 to 1). We introduce a new model to overcome this problem by incorporating a critical cell volume to modify the Toner's original model. We further reveal that this critical cell volume is dependent on the mechanisms of ice nucleation in cells during freezing, i.e., surface-catalyzed nucleation (SCN) and volume-catalyzed nucleation (VCN). Taken together, the improved PIF model may be valuable for better understanding of the mechanisms of ice nucleation in cells during freezing and more accurate prediction of PIF for cryopreservation and cryotherapy applications. PMID:24852166

Involvement of two specific causes of cell mortality in freeze-thaw cycles with freezing to -196 degrees C.

PubMed

Dumont, Frédéric; Marechal, Pierre-André; Gervais, Patrick

2006-02-01

The purpose of this study was to examine cell viability after freezing. Two distinct ranges of temperature were identified as corresponding to stages at which yeast cell mortality occurred during freezing to -196 degrees C. The upper temperature range was related to the temperature of crystallization of the medium, which was dependent on the solute concentration; in this range mortality was prevented by high solute concentrations, and the proportion of the medium in the vitreous state was greater than the proportion in the crystallized state. The lower temperature range was related to recrystallization that occurred during thawing. Mortality in this temperature range was increased by a high cooling rate and/or high solute concentration in the freezing medium and a low temperature (less than -70 degrees C). However, a high rate of thawing prevented yeast mortality in this lower temperature range. Overall, it was found that cell viability could be conserved better under freezing conditions by increasing the osmotic pressure of the medium and by using an increased warming rate.

Involvement of Two Specific Causes of Cell Mortality in Freeze-Thaw Cycles with Freezing to −196°C

PubMed Central

Dumont, Frédéric; Marechal, Pierre-André; Gervais, Patrick

2006-01-01

The purpose of this study was to examine cell viability after freezing. Two distinct ranges of temperature were identified as corresponding to stages at which yeast cell mortality occurred during freezing to −196°C. The upper temperature range was related to the temperature of crystallization of the medium, which was dependent on the solute concentration; in this range mortality was prevented by high solute concentrations, and the proportion of the medium in the vitreous state was greater than the proportion in the crystallized state. The lower temperature range was related to recrystallization that occurred during thawing. Mortality in this temperature range was increased by a high cooling rate and/or high solute concentration in the freezing medium and a low temperature (less than −70°C). However, a high rate of thawing prevented yeast mortality in this lower temperature range. Overall, it was found that cell viability could be conserved better under freezing conditions by increasing the osmotic pressure of the medium and by using an increased warming rate. PMID:16461684

Effect of multiple freezing/thawing cycles on the structural and functional properties of waxy rice starch.

PubMed

Tao, Han; Yan, Juan; Zhao, Jianwei; Tian, Yaoqi; Jin, Zhengyu; Xu, Xueming

2015-01-01

The structural and functional properties of non-gelatinized waxy rice starch were investigated after 1, 3, 7, and 10 freezing/thawing cycles. Freezing caused an increasing damaged starch from 1.36% in native waxy rice starch to 5.77% in 10 freezing/thawing-treated starch (FTS), as evidenced by the cracking surface on starch granules. More dry matter concentration was leached, which was characterized by high amylopectin concentration (4.34 mg/mL). The leaching was accompanied by a decrease in relative crystallinity from 35.19% in native starch to 31.34% in 10 FTS. Freezing treatment also led to significant deviations in the functional characteristics, for instance decreased gelatinization temperature range, enthalpy, and pasting viscosities. The resistant starch content of 10FTS significantly decreased from 58.9% to 19%, whereas the slowly digested starch content greatly increased from 23.8% in native starch to 50.3%. The increase in susceptibility to enzyme hydrolysis may be attributed to porous granular surface, amylopectin leaching, and the decrease in the relative crystallinity caused by freezing water.

Biochemical, sensory and microbiological attributes of bream (Megalobrama amblycephala) during partial freezing and chilled storage.

PubMed

Song, Yongling; Luo, Yongkang; You, Juan; Shen, Huixing; Hu, Sumei

2012-01-15

Bream is one of the main farmed freshwater fish species in China. This study aimed to examine the nucleotide degradation of bream during partial freezing and chilled storage and to assess the possible usefulness of nucleotide ratios (K, Ki, H, P, Fr and G values) as freshness indices in comparison with sensory assessment and total viable counts. Total viable counts were 5.74 and 4.66 log(colony-forming units g(-1)) on the day of sensory rejection under chilled storage and partial freezing storage respectively. The inosine 5-monophosphate decrease and inosine increase were faster in chilled storage than in partial freezing storage. Hypoxanthine levels increased continuously with time under both storage regimes. Among the nucleotide ratios, the K, Ki, P, G and Fr values were superior to the H value and provided useful freshness indicators for both storage conditions. Bream in chilled storage were sensorially acceptable only up to 10 days, compared with 33 days for bream in partial freezing storage. Partial freezing delayed the nucleotide degradation of bream. Copyright © 2011 Society of Chemical Industry.

Pre rigor processing, ageing and freezing on tenderness and colour stability of lamb loins.

PubMed

Kim, Yuan H Brad; Luc, Genevieve; Rosenvold, Katja

2013-10-01

Forty eight lamb carcasses with temperature and pH monitored were obtained from two commercial plants. At 24h post mortem both loins (M. longissimus) from each carcass were randomly allocated to a) unaged frozen at -18°C, (b) aged at -1.5°C for 2weeks before freezing, (c) aged for 3 weeks before freezing and (d) aged for 9 weeks without freezing. Shear force, colour stability and proteolysis were analyzed. Carcasses with a slower temperature and more rapid pH decline had more calpain autolysis, slightly higher shear force and less colour stable compared to that counterpart in general (P<0.05). However, the shear force values of the loins were all acceptable (<6 kgF) regardless of different pre rigor processing and ageing/freezing treatments. Furthermore, the loins aged for 2 weeks-then-frozen/thawed had a similar shear force to the loins aged only for 9 weeks suggesting that ageing-then-freezing would result in equivalent tenderness compared to aged only loins for the long-term storage. Copyright © 2013 Elsevier Ltd. All rights reserved.

Protoplasmic Swelling as a Symptom of Freezing Injury in Onion Bulb Cells 1

PubMed Central

Arora, Rajeev; Palta, Jiwan P.

1986-01-01

Freezing injury, in onion bulb tissue, is known to cause enhanced K+ efflux accompanied by a small but significant loss of Ca2+ following incipient freezing injury and swelling of protoplasm during the postthaw secondary injury. The protoplasmic swelling of the cell is thought to be caused by the passive influx of extracellular K+ into the cell followed by water uptake. Using outer epidermal layer of unfrozen onion bulb scales (Allium cepa L. cv Big Red), we were able to stimulate the irreversible freezing injury symptoms, by bathing epidermal cells in 50 millimolar KCl. These symptoms were prevented by adding 20 millimolar CaCl2 to the extracellular KCl solution. Our results provide evidence that loss of cellular Ca2+ plays an important role in the initiation and the progression of freezing injury. Images Fig. 1 PMID:16665083

Delay in the Freezing of Supercooled Water Drops on Superhydrophobic Surfaces of Silicone Rubber at Negative Temperatures

NASA Astrophysics Data System (ADS)

Bezdomnikov, A. A.; Emel'yanenko, A. M.; Emel'yanenko, K. A.; Boinovich, L. B.

2018-01-01

A method is proposed for fabricating textured superhydrophobic surfaces of silicone rubber with mechanical resistance toward liquid or freezing aqueous solutions. The anti-icing characteristics of silicone rubber samples that differ in the wetting characteristics and mechanical stability of their micro- and nanotextures are derived by analyzing the delays in the freezing of supercooled sessile water drops deposited on the sample surface. The longest delay in freezings are observed for sessile water drops on superhydrophobic surfaces prepared by laser texturing with subsequent application of a layer of a hydrophobic agent to consolidate the textural elements. Delay in freezings can be as long as tens of hours on such surfaces at T = -18°C. The prepared superhydrophobic surfaces exhibit greater anti-icing ability with respect to aqueous salt solutions than to deionized water.

In vitro culture thawed human ovarian tissue: NIV versus slow freezing method.

PubMed

Xiao, Zhun; Wang, Yan; Li, Ling-Ling; Li, Shang-wei

2013-01-01

The aim of this study was to determine if the needle immersed vitrification method (NIV) can improve the growth potential of thawed ovarian tissue in vitro culture. Human ovarian cortical tissues were cryopreserved using NIV and slow freezing method. After 14 days of culture, the preservation outcomes of NIV and slow freezing groups were analyzed histologically using light microscope and apoptosis was assessed by TUNEL assay. The result showed that the percentage of morphologically abnormal primordial follicles was lower in NIV group than in slow freezing group (P < 0.05). The incidence of TUNEL-positive primordial follicles was lower in NIV group than in slow freezing group (P < 0.05). The study showed that cryopreservation of human ovarian tissue with NIV was effective in improving the growth potential of frozen-thawed ovarian tissue in vitro culture.

Sperm Preservation by Freeze-Drying for the Conservation of Wild Animals

PubMed Central

Kaneko, Takehito; Ito, Hideyuki; Sakamoto, Hidefusa; Onuma, Manabu; Inoue-Murayama, Miho

2014-01-01

Sperm preservation is a useful technique for the maintenance of biological resources in experimental and domestic animals, and in wild animals. A new preservation method has been developed that enables sperm to be stored for a long time in a refrigerator at 4°C. Sperm are freeze-dried in a solution containing 10 mM Tris and 1 mM EDTA. Using this method, liquid nitrogen is not required for the storage and transportation of sperm. We demonstrate that chimpanzee, giraffe, jaguar, weasel and the long-haired rat sperm remain viable after freeze-drying. In all species, pronuclei were formed after the injection of freeze-dried sperm into the mouse oocytes. Although preliminary, these results may be useful for the future establishment of “freeze-drying zoo” to conserve wild animals. PMID:25409172

Impact of freezing and thawing on the quality of meat: review.

PubMed

Leygonie, Coleen; Britz, Trevor J; Hoffman, Louwrens C

2012-06-01

This comprehensive review describes the effects of freezing and thawing on the physical quality parameters of meat. The formation of ice crystals during freezing damages the ultrastructure and concentrates the solutes in the meat which, in turn, leads to alterations in the biochemical reactions that occur at the cellular level and influence the physical quality parameters of the meat. The quality parameters that were evaluated are moisture loss, protein denaturation, lipid and protein oxidation, colour, pH, shear force and microbial spoilage. Additionally mechanisms employed to mitigate the effects of freezing and thawing were also reviewed. These include the use of novel methods of freezing and thawing, ante and post mortem antifreeze protein inclusion and vitamin E supplementation, brine injection and modified atmospheric packaging. Copyright © 2012 Elsevier Ltd. All rights reserved.

In-line and real-time process monitoring of a freeze drying process using Raman and NIR spectroscopy as complementary process analytical technology (PAT) tools.

PubMed

De Beer, T R M; Vercruysse, P; Burggraeve, A; Quinten, T; Ouyang, J; Zhang, X; Vervaet, C; Remon, J P; Baeyens, W R G

2009-09-01

The aim of the present study was to examine the complementary properties of Raman and near infrared (NIR) spectroscopy as PAT tools for the fast, noninvasive, nondestructive and in-line process monitoring of a freeze drying process. Therefore, Raman and NIR probes were built in the freeze dryer chamber, allowing simultaneous process monitoring. A 5% (w/v) mannitol solution was used as model for freeze drying. Raman and NIR spectra were continuously collected during freeze drying (one Raman and NIR spectrum/min) and the spectra were analyzed using principal component analysis (PCA) and multivariate curve resolution (MCR). Raman spectroscopy was able to supply information about (i) the mannitol solid state throughout the entire process, (ii) the endpoint of freezing (endpoint of mannitol crystallization), and (iii) several physical and chemical phenomena occurring during the process (onset of ice nucleation, onset of mannitol crystallization). NIR spectroscopy proved to be a more sensitive tool to monitor the critical aspects during drying: (i) endpoint of ice sublimation and (ii) monitoring the release of hydrate water during storage. Furthermore, via NIR spectroscopy some Raman observations were confirmed: start of ice nucleation, end of mannitol crystallization and solid state characteristics of the end product. When Raman and NIR monitoring were performed on the same vial, the Raman signal was saturated during the freezing step caused by reflected NIR light reaching the Raman detector. Therefore, NIR and Raman measurements were done on a different vial. Also the importance of the position of the probes (Raman probe above the vial and NIR probe at the bottom of the sidewall of the vial) in order to obtain all required critical information is outlined. Combining Raman and NIR spectroscopy for the simultaneous monitoring of freeze drying allows monitoring almost all critical freeze drying process aspects. Both techniques do not only complement each other, they also provided mutual confirmation of specific conclusions.

Lipophilic components of the brown seaweed, Ascophyllum nodosum, enhance freezing tolerance in Arabidopsis thaliana.

PubMed

Rayirath, Prasanth; Benkel, Bernhard; Mark Hodges, D; Allan-Wojtas, Paula; Mackinnon, Shawna; Critchley, Alan T; Prithiviraj, Balakrishnan

2009-06-01

Extracts of the brown seaweed Ascophyllum nodosum enhance plant tolerance against environmental stresses such as drought, salinity, and frost. However, the molecular mechanisms underlying this improved stress tolerance and the nature of the bioactive compounds present in the seaweed extracts that elicits stress tolerance remain largely unknown. We investigated the effect of A. nodosum extracts and its organic sub-fractions on freezing tolerance of Arabidopsis thaliana. Ascophyllum nodosum extracts and its lipophilic fraction significantly increased tolerance to freezing temperatures in in vitro and in vivo assays. Untreated plants exhibited severe chlorosis, tissue damage, and failed to recover from freezing treatments while the extract-treated plants recovered from freezing temperature of -7.5 degrees C in in vitro and -5.5 degrees C in in vivo assays. Electrolyte leakage measurements revealed that the LT(50) value was lowered by 3 degrees C while cell viability staining demonstrated a 30-40% reduction in area of damaged tissue in extract treated plants as compared to water controls. Moreover, histological observations of leaf sections revealed that extracts have a significant effect on maintaining membrane integrity during freezing stress. Treated plants exhibited 70% less chlorophyll damage during freezing recovery as compared to the controls, and this correlated with reduced expression of the chlorphyllase genes AtCHL1 and AtCHL2. Further, the A. nodosum extract treatment modulated the expression of the cold response genes, COR15A, RD29A, and CBF3, resulting in enhanced tolerance to freezing temperatures. More than 2.6-fold increase in expression of RD29A, 1.8-fold increase of CBF3 and two-fold increase in the transcript level of COR15A was observed in plants treated with lipophilic fraction of A. nodosum at -2 degrees C. Taken together, the results suggest that chemical components in A. nodosum extracts protect membrane integrity and affect the expression of stress response genes leading to freezing stress tolerance in A. thaliana.

Effects of freezing-induced cell-fluid-matrix interactions on the cells and extracellular matrix of engineered tissues.

PubMed

Teo, Ka Yaw; DeHoyos, Tenok O; Dutton, J Craig; Grinnell, Frederick; Han, Bumsoo

2011-08-01

The two most significant challenges for successful cryopreservation of engineered tissues (ETs) are preserving tissue functionality and controlling highly tissue-type dependent preservation outcomes. In order to address these challenges, freezing-induced cell-fluid-matrix interactions should be understood, which determine the post-thaw cell viability and extracellular matrix (ECM) microstructure. However, the current understanding of this tissue-level biophysical interaction is still limited. In this study, freezing-induced cell-fluid-matrix interactions and their impact on the cells and ECM microstructure of ETs were investigated using dermal equivalents as a model ET. The dermal equivalents were constructed by seeding human dermal fibroblasts in type I collagen matrices with varying cell seeding density and collagen concentration. While these dermal equivalents underwent an identical freeze/thaw condition, their spatiotemporal deformation during freezing, post-thaw ECM microstructure, and cellular level cryoresponse were characterized. The results showed that the extent and characteristics of freezing-induced deformation were significantly different among the experimental groups, and the ETs with denser ECM microstructure experienced a larger deformation. The magnitude of the deformation was well correlated to the post-thaw ECM structure, suggesting that the freezing-induced deformation is a good indicator of post-thaw ECM structure. A significant difference in the extent of cellular injury was also noted among the experimental groups, and it depended on the extent of freezing-induced deformation of the ETs and the initial cytoskeleton organization. These results suggest that the cells have been subjected to mechanical insult due to the freezing-induced deformation as well as thermal insult. These findings provide insight on tissue-type dependent cryopreservation outcomes, and can help to design and modify cryopreservation protocols for new types of tissues from a pre-developed cryopreservation protocol. Copyright © 2011 Elsevier Ltd. All rights reserved.

Salvaging urospermic ejaculates from brown bear (Ursus arctos).

PubMed

Gomes-Alves, S; Alvarez, M; Nicolas, M; Martínez-Rodríguez, C; Borragán, S; Chamorro, C A; Anel, L; de Paz, P

2014-11-30

The objective of this study was to reverse the osmotic stress of sperm in urine contaminated bear ejaculates that were obtained by electroejaculation using pre-freezing washing or density gradient centrifugation isolation. In Experiment 1, ejaculates were divided into six aliquots, five were diluted in each washing extender: 200, 300, 400, 500 and 700 mOsm/kg (prepared from a Tes-Tris-Fructose base, adding water or fructose as corresponds), at a 1:2 ratio (raw semen: washing solution, v/v); and the other aliquot was handled without washing (Control group). Samples were centrifuged at 600 × g for 6 min prior to freezing. In Experiment 2, ejaculates were divided into two aliquots: one was diluted 1:1 with TCG (Tris-Citric acid-Glucose) and centrifuged at 600 × g for 6 min (Centrifugation Control; C-Control); the other was treated with PureSperm density gradient column. After treatments, samples were cryopreserved. Sperm motility, viability (SYBR-14/propidium iodide (PI)) and acrosomal status (peanut agglutinin-fluorescein isothiocyanate (PNA-FITC)/PI) were analyzed before and after freezing. Ejaculates with an initial osmolality of less than 120 mOsm/kg treated with pre-freezing washing, and the Control sample had greater pre-freezing sperm motility than the raw ejaculate, but sperm viability was not different among these groups. The samples washed with 700 mOsm/kg solutions had the least pre-freezing viability. In the post-thawing evaluation, pre-freezing washing treatments did not provide any improvement in comparison with the Control sample, and treatment with 700 mOsm/kg extender had deleterious effects in all urospermic samples. PureSperm density gradient centrifugation applied to urospermic raw semen was suitable for improving sperm motility and viability of pre-freezing samples and the selected spermatozoa had greater freezing capacity. Copyright © 2014 Elsevier B.V. All rights reserved.

Evaluation of specimen preparation techniques for micro-PIXE localisation of elements in hyperaccumulating plants

NASA Astrophysics Data System (ADS)

Kachenko, Anthony G.; Siegele, Rainer; Bhatia, Naveen P.; Singh, Balwant; Ionescu, Mihail

2008-04-01

Hybanthus floribundus subsp. floribundus, a rare Australian Ni-hyperaccumulating shrub and Pityrogramma calomelanos var. austroamericana, an Australian naturalized As-hyperaccumulating fern are promising species for use in phytoremediation of contaminated sites. Micro-proton-induced X-ray emission (μ-PIXE) spectroscopy was used to map the elemental distribution of the accumulated metal(loid)s, Ca and K in leaf or pinnule tissues of the two plant species. Samples were prepared by two contrasting specimen preparation techniques: freeze-substitution in tetrahydrofuran (THF) and freeze-drying. The specimens were analysed to compare the suitability of each technique in preserving (i) the spatial elemental distribution and (ii) the tissue structure of the specimens. Further, the μ-PIXE results were compared with concentration of elements in the bulk tissue obtained by ICP-AES analysis. In H. floribundus subsp. floribundus, μ-PIXE analysis revealed Ni, Ca and K concentrations in freeze-dried leaf tissues were at par with bulk tissue concentrations. Elemental distribution maps illustrated that Ni was preferentially localised in the adaxial epidermal tissues (1% DW) and least concentration was found in spongy mesophyll tissues (0.53% DW). Conversely, elemental distribution maps of THF freeze-substituted tissues indicated significantly lower Ni, Ca and K concentrations than freeze-dried specimens and bulk tissue concentrations. Moreover, Ni concentrations were uniform across the whole specimen and no localisation was observed. In P. calomelanos var. austroamericana freeze-dried pinnule tissues, μ-PIXE revealed statistically similar As, Ca and K concentrations as compared to bulk tissue concentrations. Elemental distribution maps showed that As localisation was relatively uniform across the whole specimen. Once again, THF freeze-substituted tissues revealed a significant loss of As compared to freeze-dried specimens and the concentrations obtained by bulk tissue analysis. The results demonstrate that freeze-drying is a suitable sample preparation technique to study elemental distribution of ions in H. floribundus and P. calomelanos plant tissues using μ-PIXE spectroscopy. Furthermore, cellular structure was preserved in samples prepared using this technique.

Response of changes in seasonal soil freeze/thaw state to climate change from 1950 to 2010 across china

NASA Astrophysics Data System (ADS)

Peng, Xiaoqing; Frauenfeld, Oliver W.; Cao, Bin; Wang, Kang; Wang, Huijuan; Su, Hang; Huang, Zhe; Yue, Dongxia; Zhang, Tingjun

2016-11-01

Variations in seasonal soil freeze/thaw state are important indicators of climate change and influence ground temperature, hydrological processes, surface energy, and the moisture balance. Previous studies mainly focused on the active layer and permafrost, while seasonally frozen ground research in nonpermafrost regions has received less attention. In this study, we investigate the response of changes in seasonal soil freeze/thaw state to changes in air temperatures by combining observations from more than 800 stations with gridded mean monthly air temperature data across China. The results show that mean annual air temperature (MAAT) increased statistically significantly by 0.29 ± 0.03°C/decade from 1967 to 2013, with greater warming on the Qinghai-Tibetan Plateau. There is a statistically significant decrease in the freeze/thaw cycle (FTC) at 0.39 ± 0.05 cycles/decade. In addition, there are strong negative correlations between FTC and MAAT. Estimating the soil freeze/thaw state classification based on the number of days in the month, we find that changes of mean annual area extent of seasonal soil freeze/thaw state decreased significantly for completely frozen (CF) ground, while the area extent of partially frozen (PF) and unfrozen (UF) ground both increased. Changes in mean monthly area extent of seasonal soil freeze/thaw state indicate that the extent of CF and UF area was decreasing and increasing, respectively. But for the extent of PF areas, both increasing and decreasing trends were observed. Quantifying the spatial pattern of the seasonal soil freeze/thaw, we find that CF and PF areas are located in northern China and the Tibetan Plateau from December to March, and UF areas are located in southern China. The variations of mean annual area extent departure of soil freeze/thaw states are consistent with MAAT changes in different land cover types across China.

Effect of freeze-thaw cycles on greenhouse gas fluxes from peat soils

NASA Astrophysics Data System (ADS)

Oh, H. D.; Rezanezhad, F.; Markelov, I.; McCarter, C. P. R.; Van Cappellen, P.

2017-12-01

The ongoing displacement of climate zones by global warming is increasing the frequency and intensity of freeze-thaw cycles in middle and high latitude regions, many of which are dominated by organic soils such as peat. Repeated freezing and thawing of soils changes their physical properties, geochemistry, and microbial community structure, which together govern the biogeochemical cycling of carbon and nutrients. In this presentation, we focus on how freeze-thaw cycles influence greenhouse gas fluxes from peat using a newly developed experimental soil column system that simulates realistic soil temperature profiles during freeze-thaw cycles. We measured the surface and subsurface changes to gas and aqueous phase chemistry to delineate the diffusion pathways and quantify soil greenhouse gas fluxes during freeze-thaw cycles using sulfur hexafluoride (SF6) as a conservative tracer. Three peat columns were assembled inside a temperature controlled chamber with different soil structures. All three columns were packed with 40 cm of undisturbed, slightly decomposed peat, where the soil of two columns had an additional 10 cm layer on top (one with loose Sphagnum moss and one with an impermeable plug). The results indicate that the release of SF6 and CO2 gas from the soil surface was influenced by the recurrent development of a physical ice barrier, which prevented gas exchange between the soil and atmosphere during freezing conditions. With the onset of thawing a pulse of SF6 and CO2 occurred, resulting in a flux of 3.24 and 2095.52 µmol/m2h, respectively, due to the build-up of gases in the liquid-phase pore space during freezing. Additionally, we developed a model to determine the specific diffusion coefficients for each peat column. These data allow us to better predict how increased frequency and intensity of freeze-thaw cycles will affect greenhouse gas emissions in northern peat soils.

Investigation of the Stability of Human Freezing-Like Responses to Social Threat From Mid to Late Adolescence.

PubMed

Niermann, Hannah C M; Figner, Bernd; Tyborowska, Anna; Cillessen, Antonius H N; Roelofs, Karin

2018-01-01

Freezing behavior, a commonly observed defensive stress response, shows relatively high stability over time in animals. Given the relevance of freezing for stress-coping and human psychopathology, it is relevant to know whether freezing behavior is also stable in humans, particularly during adolescence, when most affective symptoms develop. In a prospective longitudinal study, we investigated freezing-like behavior in response to social threat in 75 adolescents at age 14, repeated 3 years later at age 17. We used a well-established method combining electrocardiography (ECG; heart rate) and posturography (body sway) in response to emotional picture-viewing of angry, happy, and neutral faces. We hypothesized that individual differences in freezing-like behavior in response to social threat-operationalized by contrasting angry vs. neutral faces-would be relatively stable over time. Our results indeed showed relative stability between ages 14 and 17 in individual differences in freezing-like behavior in heart rate ( r = 0.82), as well as in combined heart rate and body sway measures ( r = 0.65). These effects were not specific for the angry vs. neutral contrast; they were also visible in other emotion contrasts. Exploratory analysis in males and females separately showed stability in body sway specifically for angry vs. neutral faces only in females. Together, these results suggest moderate to strong stability in human freezing-like behavior in response to social threat from mid to late adolescence (with exception for the body sway measure in males). This relative stability was not specific for threat-induction and may reflect a general stability that is particularly strong for heart rate. The fact that this relative stability was found over a relatively long time range of 3 years is promising for studies aiming to use freezing-like behavior as a marker for internalizing symptoms in adolescent development.

Investigation of the Stability of Human Freezing-Like Responses to Social Threat From Mid to Late Adolescence

PubMed Central

Niermann, Hannah C. M.; Figner, Bernd; Tyborowska, Anna; Cillessen, Antonius H. N.; Roelofs, Karin

2018-01-01

Freezing behavior, a commonly observed defensive stress response, shows relatively high stability over time in animals. Given the relevance of freezing for stress-coping and human psychopathology, it is relevant to know whether freezing behavior is also stable in humans, particularly during adolescence, when most affective symptoms develop. In a prospective longitudinal study, we investigated freezing-like behavior in response to social threat in 75 adolescents at age 14, repeated 3 years later at age 17. We used a well-established method combining electrocardiography (ECG; heart rate) and posturography (body sway) in response to emotional picture-viewing of angry, happy, and neutral faces. We hypothesized that individual differences in freezing-like behavior in response to social threat—operationalized by contrasting angry vs. neutral faces—would be relatively stable over time. Our results indeed showed relative stability between ages 14 and 17 in individual differences in freezing-like behavior in heart rate (r = 0.82), as well as in combined heart rate and body sway measures (r = 0.65). These effects were not specific for the angry vs. neutral contrast; they were also visible in other emotion contrasts. Exploratory analysis in males and females separately showed stability in body sway specifically for angry vs. neutral faces only in females. Together, these results suggest moderate to strong stability in human freezing-like behavior in response to social threat from mid to late adolescence (with exception for the body sway measure in males). This relative stability was not specific for threat-induction and may reflect a general stability that is particularly strong for heart rate. The fact that this relative stability was found over a relatively long time range of 3 years is promising for studies aiming to use freezing-like behavior as a marker for internalizing symptoms in adolescent development. PMID:29867396

Time-to-isolation guided titration of freeze duration in 3rd generation short-tip cryoballoon pulmonary vein isolation - Comparable clinical outcome and shorter procedure duration.

PubMed

Pott, Alexander; Kraft, Christoph; Stephan, Tilman; Petscher, Kerstin; Rottbauer, Wolfgang; Dahme, Tillman

2018-03-15

The optimal freeze duration in cryoballoon pulmonary vein isolation (PVI) is unknown. The 3rd generation cryoballoon facilitates observation of the time-to-isolation (TTI) and thereby enables individualized cryoenergy titration. To evaluate the efficacy of an individualized freeze duration we compared the clinical outcome of patients treated with a TTI-guided ablation protocol to the outcome of patients treated with a fixed ablation protocol. We compared 100 patients treated with the 3rd generation cryoballoon applying a TTI-based protocol (TTI group) to 100 patients treated by a fixed freeze protocol (fixed group). In the fixed group a 240s freeze cycle was followed by a 240s bonus freeze after acute PV isolation. In the TTI group freeze duration was 180s if TTI was ≥30s and reduced to only 120s, if TTI was <30s. In case of a TTI >60s a 180s bonus freeze was applied. Freedom from atrial arrhythmia recurrence off class I/III antiarrhythmic drugs after one year was not different between the TTI group (73.6%) and the fixed group (75.7%; p=0.75). Mean procedure duration was 85.8±27.3min in the TTI group compared to 115.7±27.1min in the fixed group (p<0.001). Mean fluoroscopy time was 17.5±6.6min in the TTI group and 22.5±9.8min in the fixed group (p<0.001). TTI-guided cryoenergy titration leads to reduced procedure duration and fluoroscopy time and appears to be as effective as a fixed ablation strategy. A single 2-minute freeze seems to be sufficient in case of short TTI. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Effects of drying-wetting and freezing-thawing cycle on leachability of metallic elements in mine soils

NASA Astrophysics Data System (ADS)

Bang, H.; Kim, J.; Hyun, S.

2016-12-01

Mine leachate derived from contaminated mine sites with metallic elements can pose serious risks on human society and environment. Only labile fraction of metallic elements in mine soils is subject to leaching and movement by rainfall. Lability of metallic element in soil is a function of bond strengths between metal and soil surfaces, which is influenced by environmental condition (e.g., rainfall intensity, duration, temperature, etc.) The purpose of this study was to elucidate the effects of various climate conditions on the leaching patterns and lability of metallic elements in mine soils. To do this, two mine soils were sampled from two abandoned mine sites located in Korea. Leaching test were conducted using batch decant-refill method. Various climatic conditions were employed in leaching test such as (1) oven drying (40oC) - wetting cycles, (2) air drying (20oC) - wetting cycle, and (3) freezing (-40oC) - thawing cycles. Duration of drying and freezing were varied from 4 days to 2 weeks. Concentration of metallic elements, pH, Eh and concentration of dissolved iron and sulfate in leachate from each leaching process was measured. To identify the changes of labile fraction in mine soils after each of drying or freezing period, sequential extraction procedure (five fraction) was used to compare labile fraction (i.e., F1 + F2) of metallic elements. The concentration of metallic elements in mine leachate was increased after drying and freezing procedure. The amounts of released metallic element from mine soils was changed depending on their drying or freezing period. In addition, labile fraction of metallic elements in soil was also changed after drying and freezing. The changes in labile fraction after drying and freezing might be due to the increased soil surface area by pore water volume expansion. Further study is therefore needed to evaluate the impact of altered physical properties of soils such as hydration of soil surface area and shrinking by drying and freezing cycles.

Stability of an aluminum salt-adjuvanted protein D-conjugated pneumococcal vaccine after exposure to subzero temperatures

PubMed Central

Fortpied, Juliette; Wauters, Florence; Rochart, Christelle; Hermand, Philippe; Hoet, Bernard; Moniotte, Nicolas; Vojtek, Ivo

2018-01-01

ABSTRACT Accidental exposure of a vaccine containing an aluminum-salt adjuvant to temperatures below 0°C in the cold chain can lead to freeze damage. Our study evaluated the potential for freeze damage in a licensed aluminum-salt-containing protein-D-conjugated pneumococcal vaccine (PHiD-CV; Synflorix, GSK) in conditions that included static storage, single subzero-temperature excursions, and simulated air-freight transportation. Several parameters were assessed including freezing at subzero temperatures, aluminum-salt-particle size, antigen integrity and immunogenicity in the mouse. The suitability of the WHO's shake test for identifying freeze-damaged vaccines was also assessed. During subzero-temperature excursions, the mean temperatures at which PHiD-CV froze (−16.7°C to −18.1°C) appeared unaffected by the type of vaccine container (two-dose or four-dose vial, or single-dose syringe), vaccine batch, rotational agitation, or the rate of temperature decline (−0.5 to −10°C/hour). At constant subzero temperature and in simulated air-freight transportation, the freezing of PHiD-CV appeared to be promoted by vibration. At −5°C, no PHiD-CV sample froze in static storage (>1 month), whereas when subjected to vibration, a minority of samples froze (7/21, 33%) within 18 hours. At −8°C with vibration, nearly all (5/6, 83%) samples froze. In these vibration regimes, the shake test identified most samples that froze (10/12, 93%) except two in the −5°C regime. Nevertheless, PHiD-CV-antigen integrity appeared unaffected by freezing up to −20°C or by vibration. And although aluminum-salt-particle size was increased only by freezing at −20°C, PHiD-CV immunogenicity appeared only marginally affected by freezing at −20°C. Therefore, our study supports the use of the shake test to exclude freeze-damaged PHiD-CV in the field. PMID:29337646

Maple sap uptake, exudation, and pressure changes correlated with freezing exotherms and thawing endotherms.

PubMed

Tyree, M T

1983-10-01

Sap flow rates and sap pressure changes were measured in dormant sugar maple trees (Acer saccharum Marsh.). In the forest, sap flow rates and pressure changes were measured from tap holes drilled into tree trunks in mature trees and sap flow rates were measured from the base of excised branches. Excised branches were also brought into the laboratory where air temperature could be carefully controlled in a refrigerated box and sap flow rates and sap pressures were measured from the cut base of the branches.Under both forest and laboratory conditions, sap uptake occurred as the wood temperature declined but much more rapid sap uptake correlated with the onset of the freezing exotherm. When sap pressures were measured under conditions of negligible volume displacement, the sap pressure rapidly fell to -60 to -80 kilopascals at the start of the freezing exotherm. The volume of water uptake and the rate of uptake depended on the rate of freezing. A slow freezing rate correlated with a large volume of water uptake, a fast freezing rate induced a smaller volume of water uptake. The volume of water uptake ranged from 0.02 to 0.055 grams water per gram dry weight of sapwood. The volume of water exuded after thawing was usually less than the volume of uptake so that after several freezing and thawing cycles the sapwood water content increased from 0.7 to 0.8 grams water per gram dry weight.These results are discussed in terms of a physical model of the mechanism of maple sap uptake and exudation first proposed by P. E. R. O'Malley. The proposed mechanism of sap uptake is by vapor distillation in air filled wood fiber lumina during the freezing of minor branches. Gravity and pressurized air bubbles (compressed during freezing) cause sap flow from the canopy down the tree after the thaw.

Maple Sap Uptake, Exudation, and Pressure Changes Correlated with Freezing Exotherms and Thawing Endotherms 1

PubMed Central

Tyree, Melvin T.

1983-01-01

Sap flow rates and sap pressure changes were measured in dormant sugar maple trees (Acer saccharum Marsh.). In the forest, sap flow rates and pressure changes were measured from tap holes drilled into tree trunks in mature trees and sap flow rates were measured from the base of excised branches. Excised branches were also brought into the laboratory where air temperature could be carefully controlled in a refrigerated box and sap flow rates and sap pressures were measured from the cut base of the branches. Under both forest and laboratory conditions, sap uptake occurred as the wood temperature declined but much more rapid sap uptake correlated with the onset of the freezing exotherm. When sap pressures were measured under conditions of negligible volume displacement, the sap pressure rapidly fell to −60 to −80 kilopascals at the start of the freezing exotherm. The volume of water uptake and the rate of uptake depended on the rate of freezing. A slow freezing rate correlated with a large volume of water uptake, a fast freezing rate induced a smaller volume of water uptake. The volume of water uptake ranged from 0.02 to 0.055 grams water per gram dry weight of sapwood. The volume of water exuded after thawing was usually less than the volume of uptake so that after several freezing and thawing cycles the sapwood water content increased from 0.7 to 0.8 grams water per gram dry weight. These results are discussed in terms of a physical model of the mechanism of maple sap uptake and exudation first proposed by P. E. R. O'Malley. The proposed mechanism of sap uptake is by vapor distillation in air filled wood fiber lumina during the freezing of minor branches. Gravity and pressurized air bubbles (compressed during freezing) cause sap flow from the canopy down the tree after the thaw. PMID:16663208

A proteome analysis of freezing tolerance in red clover (Trifolium pratense L.).

PubMed

Bertrand, Annick; Bipfubusa, Marie; Castonguay, Yves; Rocher, Solen; Szopinska-Morawska, Aleksandra; Papadopoulos, Yousef; Renaut, Jenny

2016-03-10

Improvement of freezing tolerance of red clover (Trifolium pratense L.) would increase its persistence under cold climate. In this study, we assessed the freezing tolerance and compared the proteome composition of non-acclimated and cold-acclimated plants of two initial cultivars of red clover: Endure (E-TF0) and Christie (C-TF0) and of populations issued from these cultivars after three (TF3) and four (TF4) cycles of phenotypic recurrent selection for superior freezing tolerance. Through this approach, we wanted to identify proteins that are associated with the improvement of freezing tolerance in red clover. Freezing tolerance expressed as the lethal temperature for 50 % of the plants (LT50) increased markedly from approximately -2 to -16 °C following cold acclimation. Recurrent selection allowed a significant 2 to 3 °C increase of the LT50 after four cycles of recurrent selection. Two-dimensional difference gel electrophoresis (2D-DIGE) was used to study variations in protein abundance. Principal component analysis based on 2D-DIGE revealed that the largest variability in the protein data set was attributable to the cold acclimation treatment and that the two genetic backgrounds had differential protein composition in the acclimated state only. Vegetative storage proteins (VSP), which are essential nitrogen reserves for plant regrowth, and dehydrins were among the most striking changes in proteome composition of cold acclimated crowns of red clovers. A subset of proteins varied in abundance in response to selection including a dehydrin that increased in abundance in TF3 and TF4 populations as compared to TF0 in the Endure background. Recurrent selection performed indoor is an effective approach to improve the freezing tolerance of red clover. Significant improvement of freezing tolerance by recurrent selection was associated with differential accumulation of a small number of cold-regulated proteins that may play an important role in the determination of the level of freezing tolerance.

The Impact of Freeze-Thaw Cycles on Epinephrine.

PubMed

Beasley, Heather; Ng, Pearlly; Wheeler, Albert; Smith, William R; McIntosh, Scott E

2015-12-01

Epinephrine is the first-line medical treatment for anaphylaxis, a life-threatening allergic syndrome. To treat anaphylaxis, backcountry recreationalists and guides commonly carry epinephrine autoinjectors. Epinephrine may be exposed to cold temperatures and freezing during expeditions. An epinephrine solution must contain 90% to 115% of the labeled epinephrine amount to meet United States Pharmacopeia standards. The purpose of this study was to determine whether freeze-thaw cycles alter epinephrine concentrations in autoinjectors labeled to contain 1.0 mg/mL epinephrine. A further objective was to determine whether samples continued to meet United States Pharmacopeia concentration standards after freeze-thaw cycles. Epinephrine from 6 autoinjectors was extracted and divided into experimental and control samples. The experimental samples underwent 7 consecutive 12-hour freeze cycles followed by 7 12-hour thaw cycles. The control samples remained at an average temperature of 23.1°C for the duration of the study. After the seventh thaw cycle, epinephrine concentrations were measured using a high-performance liquid chromatography assay with mass spectrometry detection. The mean epinephrine concentration of the freeze-thaw samples demonstrated a statistically significant increase compared with the control samples: 1.07 mg/mL (SD ± 8.78; 95% CI, 1.04 to 1.11) versus 0.96 mg/mL (SD ± 6.81; 95% CI, 0.94 to 0.99), respectively. The maximal mean epinephrine concentration in the experimental freeze-thaw group was 1.12 mg/mL, which still fell within the range of United States Pharmacopeia standards for injectables (0.90 to 1.15 mg/mL). Although every attempt should be made to prevent freezing of autoinjectors, this preliminary study demonstrates that epinephrine concentrations remain within 90% to 115% of 1.0 mg/mL after multiple freeze-thaw cycles. Copyright © 2015 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.

Design and evaluation of aircraft heat source systems for use with high-freezing point fuels

NASA Technical Reports Server (NTRS)

Pasion, A. J.

1979-01-01

The objectives were the design, performance and economic analyses of practical aircraft fuel heating systems that would permit the use of high freezing-point fuels on long-range aircraft. Two hypothetical hydrocarbon fuels with freezing points of -29 C and -18 C were used to represent the variation from current day jet fuels. A Boeing 747-200 with JT9D-7/7A engines was used as the baseline aircraft. A 9300 Km mission was used as the mission length from which the heat requirements to maintain the fuel above its freezing point was based.

Mechanisms of deterioration of nutrients. [freeze drying methods for space flight food

NASA Technical Reports Server (NTRS)

Karel, M.; Flink, J. M.

1974-01-01

Methods are reported by which freeze dried foods of improved quality will be produced. The applicability of theories of flavor retention has been demonstrated for a number of food polymers, both proteins and polysacchardies. Studies on the formation of structures during freeze drying have been continued for emulsified systems. Deterioration of organoleptic quality of freeze dried foods due to high temperature heating has been evaluated and improved procedures developed. The influence of water activity and high temperature on retention of model flavor materials and browning deterioration has been evaluated for model systems and food materials.

Ice nucleation and antinucleation in nature.

PubMed

Zachariassen, K E; Kristiansen, E

2000-12-01

Plants and ectothermic animals use a variety of substances and mechanisms to survive exposure to subfreezing temperatures. Proteinaceous ice nucleators trigger freezing at high subzero temperatures, either to provide cold protection from released heat of fusion or to establish a protective extracellular freezing in freeze-tolerant species. Freeze-avoiding species increase their supercooling potential by removing ice nucleators and accumulating polyols. Terrestrial invertebrates and polar marine fish stabilize their supercooled state by means of noncolligatively acting antifreeze proteins. Some organisms also depress their body fluid melting point to ambient temperature by evaporation and/or solute accumulation. Copyright 2000 Academic Press.

Theory of freezing in simple systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cerjan, C.; Bagchi, B.

The transition parameters for the freezing of two one-component liquids into crystalline solids are evaluated by two theoretical approaches. The first system considered is liquid sodium which crystallizes into a body-centered-cubic (bcc) lattice; the second system is the freezing of adhesive hard spheres into a face-centered-cubic (fcc) lattice. Two related theoretical techniques are used in this evaluation: One is based upon a recently developed bifurcation analysis; the other is based upon the theory of freezing developed by Ramakrishnan and Yussouff. For liquid sodium, where experimental information is available, the predictions of the two theories agree well with experiment and eachmore » other. The adhesive-hard-sphere system, which displays a triple point and can be used to fit some liquids accurately, shows a temperature dependence of the freezing parameters which is similar to Lennard-Jones systems. At very low temperature, the fractional density change on freezing shows a dramatic increase as a function of temperature indicating the importance of all the contributions due to the triplet direction correlation function. Also, we consider the freezing of a one-component liquid into a simple-cubic (sc) lattice by bifurcation analysis and show that this transition is highly unfavorable, independent of interatomic potential choice. The bifurcation diagrams for the three lattices considered are compared and found to be strikingly different. Finally, a new stability analysis of the bifurcation diagrams is presented.« less

Evaluation of Physicochemical Deterioration and Lipid Oxidation of Beef Muscle Affected by Freeze-thaw Cycles

PubMed Central

Rahman, M. H.; Hossain, M. M.; Rahman, S. M. E.; Amin, M. R.; Oh, Deog-Hwan

2015-01-01

This study was performed to explore the deterioration of physicochemical quality of beef hind limb during frozen storage at −20℃, affected by repeated freeze-thaw cycles. The effects of three successive freeze-thaw cycles on beef hind limb were investigated comparing with unfrozen beef muscle for 80 d by keeping at −20±1℃. The freeze-thaw cycles were subjected to three thawing methods and carried out to select the best one on the basis of deterioration of physicochemical properties of beef. As the number of repeated freeze-thaw cycles increased, drip loss decreased and water holding capacity (WHC) increased (p<0.05) till two cycles and then decreased. Cooking loss increased in cycle one and three but decreased in cycle two. Moreover, drip loss, WHC and cooking loss affected (p<0.05) by thawing methods within the cycles. However, pH value decreased (p<0.05), but peroxide value (p<0.05), free fatty acids value (p<0.05) and TBARS value increased (p<0.05) significantly as the number of repeated freeze-thaw cycles increased. Moreover, significant (p<0.05) interactive effects were found among the thawing methods and repeated cycles. As a result, freeze-thaw cycles affected the physicochemical quality of beef muscle, causing the degradation of its quality. PMID:26877637

Enhancing freezing tolerance of Brassica napus L. by overexpression of a stearoyl-acyl carrier protein desaturase gene (SAD) from Sapium sebiferum (L.) Roxb.

PubMed

Peng, Dan; Zhou, Bo; Jiang, Yueqiao; Tan, XiaoFeng; Yuan, DeYi; Zhang, Lin

2018-07-01

Sapium sebiferum (L.) Roxb. is an important woody oil tree and traditional herbal medicine in China. Stearoyl-acyl carrier protein desaturase (SAD) is a dehydrogenase enzyme that plays a key role in the transformation of saturated fatty acids into unsaturated fatty acids in oil; these fatty acids greatly influence the freezing tolerance of plants. However, it remains unclear whether freezing tolerance can be regulated by the expression level of SsSAD in S. sebiferum L. Our research indicated that SsSAD expression in S. sebiferum L. increased under freezing stress. To further confirm this result, we constructed a pEGAD-SsSAD vector and transformed it into B. napus L. W10 by Agrobacterium tumefaciens-mediated transformation. Transgenic plants that overexpressed the SsSAD gene exhibited significantly higher linoleic (18:2) and linolenic acid (18:3) content and advanced freezing tolerance. These results suggest that SsSAD overexpression in B. napus L. can increase the content of polyunsaturated fatty acids (PUFAs) such as linoleic (18:2) and linolenic acid (18:3), which are likely pivotal in improving freezing tolerance in B. napus L. plants. Thus, SsSAD overexpression could be useful in the production of freeze-tolerant varieties of B. napus L. Copyright © 2018 Elsevier B.V. All rights reserved.

Uptake of erythromycin by first-feeding sockeye salmon, Oncorhynchus nerka (Walbaum), fed live or freeze-dried enriched adult Artemia or medicated pellets.

PubMed

Cook, M A; Rust, M B; Massee, K; Majack, T; Peterson, M E

2003-05-01

The potential to use adult Artemia to deliver erythromycin to first-feeding sockeye salmon, Oncorhynchus nerka (Walbaum), was investigated in three trials. In the first trial, first-feeding sockeye were fed live erythromycin enriched adult Artemia or pellets containing equal amounts of erythromycin for 35 days. At the end of the trial, tissue erythromycin concentration of the fish fed the live Artemia was significantly greater (P < 0.05, 25.52 +/- 1.29 microg mL(-1); mean +/- SEM), than the tissue concentration of the fish fed the pellets (0.72 +/- 0.01 microg mL(-1)). In the second trial, first-feeding sockeye were fed either live or freeze-dried bioencapsulated erythromycin (adult Artemia) or pellets containing erythromycin daily for 21 days. Mean daily erythromycin concentration in fish fed the freeze-dried Artemia, live Artemia, or pellets did not differ significantly. In the third trial, apparent erythromycin digestibility was determined. Significantly more (P < 0.05) erythromycin was retained by juvenile sockeye fed freeze-dried bioencapsulated erythromycin (98.3 +/- 1.0%) compared with medicated pellets (89.2 +/- 1.7%). Uptake of bioencapsulated erythromycin from adult Artemia (live or freeze-dried) appears to be greater than uptake from pellets. Freeze-dried and live Artemia were equally effective at delivery suggesting enriched freeze-dried adult Artemia could be produced into a highly palatable, consistent, off-the-shelf product.

Transcriptome Analysis of Spartina pectinata in Response to Freezing Stress

PubMed Central

Nah, Gyoungju; Lee, Moonsub; Kim, Do-Soon; Rayburn, A. Lane; Voigt, Thomas; Lee, D. K.

2016-01-01

Prairie cordgrass (Spartina pectinata), a perennial C4 grass native to the North American prairie, has several distinctive characteristics that potentially make it a model crop for production in stressful environments. However, little is known about the transcriptome dynamics of prairie cordgrass despite its unique freezing stress tolerance. Therefore, the purpose of this work was to explore the transcriptome dynamics of prairie cordgrass in response to freezing stress at -5°C for 5 min and 30 min. We used a RNA-sequencing method to assemble the S. pectinata leaf transcriptome and performed gene-expression profiling of the transcripts under freezing treatment. Six differentially expressed gene (DEG) groups were categorized from the profiling. In addition, two major consecutive orders of gene expression were observed in response to freezing; the first being the acute up-regulation of genes involved in plasma membrane modification, calcium-mediated signaling, proteasome-related proteins, and transcription regulators (e.g., MYB and WRKY). The follow-up and second response was of genes involved in encoding the putative anti-freezing protein and the previously known DNA and cell-damage-repair proteins. Moreover, we identified the genes involved in epigenetic regulation and circadian-clock expression. Our results indicate that freezing response in S. pectinata reflects dynamic changes in rapid-time duration, as well as in metabolic, transcriptional, post-translational, and epigenetic regulation. PMID:27032112

Unprecedented Cell-Selection Using Ultra-Quick Freezing Combined with Aquaporin Expression

PubMed Central

Kato, Yasuhiro; Miyauchi, Takayuki; Abe, Youichiro; Kojić, Dušan; Tanaka, Manami; Chikazawa, Nana; Nakatake, Yuhki; Ko, Shigeru B. H.; Kobayashi, Daisuke; Hazama, Akihiro; Fujiwara, Shoko; Uchida, Tatsuya; Yasui, Masato

2014-01-01

Freezing is usually used for preservation and storage of biological samples; however, this process may have some adverse effects such as cell membrane damage. Aquaporin (AQP), a water channel protein, has been suggested to play some roles for cryopreservation although its molecular mechanism remains unclear. Here we show that membrane damage caused by ultra-quick freezing is rescued by the expression of AQP4. We next examine if the expression of AQP combined with ultra-quick freezing can be used to select cells efficiently under freezing conditions where most cells are died. CHO cells stably expressing AQP4 were exclusively selected from mixed cell cultures. Having identified the increased expression of AQP4 during ES cell differentiation into neuro-ectoderm using bioinformatics, we confirmed the improved survival of differentiated ES cells with AQP4 expression. Finally we show that CHO cells transiently transfected with Endothelin receptor A and Aqp4 were also selected and concentrated by multiple cycles of freezing/thawing, which was confirmed with calcium imaging in response to endothelin. Furthermore, we found that the expression of AQP enables a reduction in the amount of cryoprotectants for freezing, thereby decreasing osmotic stress and cellular toxicity. Taken together, we propose that this simple but efficient and safe method may be applicable to the selection of mammalian cells for applications in regenerative medicine as well as cell-based functional assays or drug screening protocols. PMID:24558371

Jasmonate Regulates the INDUCER OF CBF EXPRESSION–C-REPEAT BINDING FACTOR/DRE BINDING FACTOR1 Cascade and Freezing Tolerance in Arabidopsis[W

PubMed Central

Hu, Yanru; Jiang, Liqun; Wang, Fang; Yu, Diqiu

2013-01-01

The INDUCER OF CBF EXPRESSION (ICE)–C-REPEAT BINDING FACTOR/DRE BINDING FACTOR1 (CBF/DREB1) transcriptional pathway plays a critical role in modulating cold stress responses in Arabidopsis thaliana. Dissecting crucial upstream regulatory signals or components of the ICE-CBF/DREB1 cascade will enhance our understanding of plant cold-tolerance mechanisms. Here, we show that jasmonate positively regulates plant responses to freezing stress in Arabidopsis. Exogenous application of jasmonate significantly enhanced plant freezing tolerance with or without cold acclimation. By contrast, blocking endogenous jasmonate biosynthesis and signaling rendered plants hypersensitive to freezing stress. Consistent with the positive role of jasmonate in freezing stress, production of endogenous jasmonate was triggered by cold treatment. In addition, cold induction of genes acting in the CBF/DREB1 signaling pathway was upregulated by jasmonate. Further investigation revealed that several JASMONATE ZIM-DOMAIN (JAZ) proteins, the repressors of jasmonate signaling, physically interact with ICE1 and ICE2 transcription factors. JAZ1 and JAZ4 repress the transcriptional function of ICE1, thereby attenuating the expression of its regulon. Consistent with this, overexpression of JAZ1 or JAZ4 represses freezing stress responses of Arabidopsis. Taken together, our study provides evidence that jasmonate functions as a critical upstream signal of the ICE-CBF/DREB1 pathway to positively regulate Arabidopsis freezing tolerance. PMID:23933884

Jasmonate regulates the inducer of cbf expression-C-repeat binding factor/DRE binding factor1 cascade and freezing tolerance in Arabidopsis.

PubMed

Hu, Yanru; Jiang, Liqun; Wang, Fang; Yu, Diqiu

2013-08-01

The inducer of cbf expression (ICE)-C-repeat binding factor/DRE binding factor1 (CBF/DREB1) transcriptional pathway plays a critical role in modulating cold stress responses in Arabidopsis thaliana. Dissecting crucial upstream regulatory signals or components of the ICE-CBF/DREB1 cascade will enhance our understanding of plant cold-tolerance mechanisms. Here, we show that jasmonate positively regulates plant responses to freezing stress in Arabidopsis. Exogenous application of jasmonate significantly enhanced plant freezing tolerance with or without cold acclimation. By contrast, blocking endogenous jasmonate biosynthesis and signaling rendered plants hypersensitive to freezing stress. Consistent with the positive role of jasmonate in freezing stress, production of endogenous jasmonate was triggered by cold treatment. In addition, cold induction of genes acting in the CBF/DREB1 signaling pathway was upregulated by jasmonate. Further investigation revealed that several jasmonate ZIM-domain (JAZ) proteins, the repressors of jasmonate signaling, physically interact with ICE1 and ICE2 transcription factors. JAZ1 and JAZ4 repress the transcriptional function of ICE1, thereby attenuating the expression of its regulon. Consistent with this, overexpression of JAZ1 or JAZ4 represses freezing stress responses of Arabidopsis. Taken together, our study provides evidence that jasmonate functions as a critical upstream signal of the ICE-CBF/DREB1 pathway to positively regulate Arabidopsis freezing tolerance.

Immersion freezing of internally and externally mixed mineral dust species analyzed by stochastic and deterministic models

NASA Astrophysics Data System (ADS)

Wong, B.; Kilthau, W.; Knopf, D. A.

2017-12-01

Immersion freezing is recognized as the most important ice crystal formation process in mixed-phase cloud environments. It is well established that mineral dust species can act as efficient ice nucleating particles. Previous research has focused on determination of the ice nucleation propensity of individual mineral dust species. In this study, the focus is placed on how different mineral dust species such as illite, kaolinite and feldspar, initiate freezing of water droplets when present in internal and external mixtures. The frozen fraction data for single and multicomponent mineral dust droplet mixtures are recorded under identical cooling rates. Additionally, the time dependence of freezing is explored. Externally and internally mixed mineral dust droplet samples are exposed to constant temperatures (isothermal freezing experiments) and frozen fraction data is recorded based on time intervals. Analyses of single and multicomponent mineral dust droplet samples include different stochastic and deterministic models such as the derivation of the heterogeneous ice nucleation rate coefficient (J­­het), the single contact angle (α) description, the α-PDF model, active sites representation, and the deterministic model. Parameter sets derived from freezing data of single component mineral dust samples are evaluated for prediction of cooling rate dependent and isothermal freezing of multicomponent externally or internally mixed mineral dust samples. The atmospheric implications of our findings are discussed.

Reversed phase HPLC analysis of stability and microstructural effects on degradation kinetics of β-carotene encapsulated in freeze-dried maltodextrin-emulsion systems.

PubMed

Harnkarnsujarit, Nathdanai; Charoenrein, Sanguansri; Roos, Yrjö H

2012-09-26

Degradation of dispersed lipophilic compounds in hydrophilic solids depends upon matrix stability and lipid physicochemical properties. This study investigated effects of solid microstructure and size of lipid droplets on the stability of dispersed β-carotene in freeze-dried systems. Emulsions of β-carotene in sunflower oil were dispersed in maltodextrin systems (M040/DE6, M100/DE11, and M250/DE25.5) (8% w/w oil) and prefrozen at various freezing conditions prior to freeze-drying to control nucleation and subsequent pore size and structural collapse of freeze-dried solids. The particle size, physical state, and β-carotene contents of freeze-dried emulsions were measured during storage at various water activity (a(w)) using a laser particle size analyzer, differential scanning calorimeter, and high performance liquid chromatography (HPLC), respectively. The results showed that M040 stabilized emulsions in low temperature freezing exhibited lipid crystallization. Collapse of solids in storage at a(w) which plasticized systems to the rubbery state led to flow and increased the size of oil droplets. Degradation of β-carotene analyzed using a reversed-phase C(30) column followed first-order kinetics. Porosity of solids had a major effect on β-carotene stability; however, the highest stability was found in fully plasticized and collapsed solids.

Characteristics, atmospheric drivers and occurrence patterns of freezing precipitation and ice pellets over the Prairie Provinces and Arctic Territories of Canada: 1964-2005

NASA Astrophysics Data System (ADS)

Kochtubajda, Bohdan; Mooney, Curtis; Stewart, Ronald

2017-07-01

Freezing precipitation and ice pellet events on the Canadian Prairies and Arctic territories of Canada often lead to major disruptions to air and ground transportation, damage power grids and prevent arctic caribou and other animals from accessing the plants and lichen they depend on for survival. In a warming climate, these hazards and associated impacts will continue to happen, although their spatial and temporal characteristics may vary. In order to address these issues, the occurrence of freezing rain, freezing drizzle, and ice pellets from 1964 to 2005 is examined using hourly weather observations at 27 manned 24 h weather stations across the different climatic regions of the Prairie Provinces and Arctic Territories of Canada. Because of the enormous size of the area and its diverse climatic regions, many temporal and spatial differences in freezing precipitation and ice pellet characteristics occur. The 12 most widespread freezing rain events over the study area are associated with only two atmospheric patterns with one linked to strong warm advection between low and high pressure centres and the other pattern associated with chinooks occurring east of the Rocky Mountains. Given the annual patterns of freezing rain occurrence found in this study, it is proposed that a maximum of five regimes exist and three occur within the Prairies and Arctic.

An RNA-Cleaving Catalytic DNA Accelerated by Freezing.

PubMed

Yu, Tianmeng; Zhou, Wenhu; Liu, Juewen

2018-05-18

The EtNa DNAzyme was isolated during the isopropanol precipitation step of an in vitro selection effort. Although inactive with the intended cofactor, its RNA cleavage activity was observed under a few conditions. With Na + , EtNa was highly active in ∼50 % ethanol, whereas in water, it was highly active with Ca 2+ . In this work, we showed that the EtNa DNAzyme was accelerated by freezing in water in the presence of Na + . The apparent K d value reached 6.2 mm Na + under the frozen condition, over 20 times tighter than that in water at room temperature. With 10 mm Na + , EtNa had a cleavage rate of 0.12 h -1 after freezing at -20 °C. This effect was unique to EtNa, as all other tested DNAzymes were inhibited by freezing except for the Na + -specific NaA43. Freezing also inhibited EtNa if Ca 2+ was used. We attributed this to the concentrations of EtNa and Na + in the micropockets between ice crystals, but divalent metals might misfold DNA. Overall, we have systematically studied the effect of freezing on the RNA-cleavage activity of DNAzymes. The DNAzyme sequence and the metal ion species are both crucial to determine the effect of freezing. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Considering the formation of hematite spherules on Mars by freezing aqueous hematite nanoparticle suspensions

NASA Astrophysics Data System (ADS)

Sexton, M. R.; Elwood Madden, M. E.; Swindle, A. L.; Hamilton, V. E.; Bickmore, B. R.; Elwood Madden, A. S.

2017-04-01

The enigmatic and unexpected occurrence of coarse crystalline (gray) hematite spherules at Terra Meridiani on Mars in association with deposits of jarosite-rich sediments fueled a variety of hypotheses to explain their origin. In this study, we tested the hypothesis that freezing of aqueous hematite nanoparticle suspensions, possibly produced from low-temperature weathering of jarosite-bearing deposits, could produce coarse-grained hematite aggregate spherules. We synthesized four hematite nanoparticle suspensions with a range of sizes and morphologies and performed freezing experiments. All sizes of hematite nanoparticles rapidly aggregate during freezing. Regardless of the size or shape of the initial starting material, they rapidly collect into aggregates that are then too big to push in front of a stable advancing ice front, leading to incohesive masses of particles, rather than solid spherules. We also explored the effects of "seed" silicates, a matrix of sand grains, various concentrations of NaCl and CaCl2, and varying the freezing temperature on hematite nanoparticle aggregation. However, none of these factors resulted in mm-scale spherical aggregates. By comparing our measured freezing rates with empirical and theoretical values from the literature, we conclude that the spherules on Mars could not have been produced through the freezing of aqueous hematite nanoparticle suspensions; ice crystallization front instability disrupts the aggregation process and prevents the formation of mm-scale continuous aggregates.

Near-freezing effects on the proteome of industrial yeast strains of Saccharomyces cerevisiae.

PubMed

Ballester-Tomás, Lidia; Pérez-Torrado, Roberto; Rodríguez-Vargas, Sonia; Prieto, Jose A; Randez-Gil, Francisca

2016-03-10

At near-freezing temperatures (0-4°C), the growth of the yeast Saccharomyces cerevisiae stops or is severely limited, and viability decreases. Under these conditions, yeast cells trigger a biochemical response, in which trehalose and glycerol accumulate and protect them against severe cold and freeze injury. However, the mechanisms that allow yeast cells to sustain this response have been not clarified. The effects of severe cold on the proteome of S. cerevisiae have been not investigated and its importance in providing cell survival at near-freezing temperatures and upon freezing remains unknown. Here, we have compared the protein profile of two industrial baker's yeast strains at 30°C and 4°C. Overall, a total of 16 proteins involved in energy-metabolism, translation and redox homeostasis were identified as showing increased abundance at 4°C. The predominant presence of glycolytic proteins among those upregulated at 4°C, likely represents a mechanism to maintain a constant supply of ATP for the synthesis of glycerol and other protective molecules. Accumulation of these molecules is by far the most important component in enhancing viability of baker's yeast strains upon freezing. Overexpression of genes encoding certain proteins associated with translation or redox homeostasis provided specifically protection against extreme cold damage, underlying the importance of these functions in the near-freezing response. Copyright © 2016 Elsevier B.V. All rights reserved.

Cross-tolerance between osmotic and freeze-thaw stress in microbial assemblages from temperate lakes.

PubMed

Wilson, Sandra L; Frazer, Corey; Cumming, Brian F; Nuin, Paulo A S; Walker, Virginia K

2012-11-01

Osmotic stress can accompany increases in solute concentrations because of freezing or high-salt environments. Consequently, microorganisms from environments with a high-osmotic potential may exhibit cross-tolerance to freeze stress. To test this hypothesis, enrichments derived from the sediment and water of temperate lakes with a range of salt concentrations were subjected to multiple freeze-thaw cycles. Surviving isolates were identified and metagenomes were sampled prior to and following selection. Enrichments from alkali lakes were typically the most freeze-thaw resistant with only 100-fold losses in cell viability, and those from freshwater lakes were most susceptible, with cell numbers reduced at least 100,000-fold. Metagenomic analysis suggested that selection reduced assemblage diversity more in freshwater samples than in those from saline lakes. Survivors included known psychro-, halo- and alkali-tolerant bacteria. Characterization of freeze-thaw-resistant isolates from brine and alkali lakes showed that few isolates had ice-associating activities such as antifreeze or ice nucleation properties. However, all brine- and alkali-derived isolates had high intracellular levels of osmolytes and/or appeared more likely to form biofilms. Conversely, these phenotypes were infrequent amongst the freshwater-derived isolates. These observations are consistent with microbial cross-tolerance between osmotic and freeze-thaw stresses. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Imaging ion and molecular transport at subcellular resolution by secondary ion mass spectrometry

NASA Astrophysics Data System (ADS)

Chandra, Subhash; Morrison, George H.

1995-05-01

The transport of K+, Na+, and Ca2+ were imaged in individual cells with a Cameca IMS-3f ion microscope. Strict cryogenic frozen freeze-dry sample preparations were employed. Ion redistribution artifacts in conventional chemical preparations are discussed. Cryogenically prepared freeze-fractured freeze-dried cultured cells allowed the three-dimensional ion microscopic imaging of elements. As smaller structures in calcium images can be resolved with the 0.5 [mu]m spatial resolution, correlative techniques are needed to confirm their identity. The potentials of reflected light microscopy, scanning electron microscopy and laser scanning confocal microscopy are discussed for microfeature recognition in freeze-fractured freeze-dried cells. The feasibility of using frozen freeze-dried cells for imaging molecular transport at subcellular resolution was tested. Ion microscopy successfully imaged the transport of the isotopically tagged (13C, 15N) amino acid, -arginine. The labeled amino acid was imaged at mass 28 with a Cs+ primary ion beam as the 28(13C15N)- species. After a 4 h exposure of LLC-PK1 kidney cells to 4 mM labeled arginine, the amino acid was localized throughout the cell with a preferential incorporation into the nucleus and nucleolus. An example is also shown of the ion microscopic imaging of sodium borocaptate, an experimental therapeutic drug for brain tumors, in cryogenically prepared frozen freeze-dried Swiss 3T3 cells.

The detection of Giardia muris and Giardia lamblia cysts by immunofluorescence in animal tissues and fecal samples subjected to cycles of freezing and thawing.

PubMed

Erlandsen, S L; Sherlock, L A; Bemrick, W J

1990-04-01

The effects of freezing and thawing on the detection of selected Giardia spp. cysts were investigated using immunofluorescence, bright field microscopy, and low voltage scanning electron microscopy (SEM). Giardia muris cysts were obtained from either animal carcasses, fecal pellets, or isolated cyst preparations, whereas Giardia lamblia cysts were isolated from fecal samples. These samples were stained using an immunofluorescence technique after 1-3 freezing (-16 C) and thawing (20 C) cycles. Cysts were detected successfully by immunofluorescence in all samples. However, in those samples subjected to freeze-thawing, the cyst walls often became distorted and then were not detectable by bright field microscopy. Low voltage SEM demonstrated that the filaments in the distorted cyst wall underwent rearrangements of interfilament spacing. Quantitation of cyst recovery after freezing and thawing demonstrated that a substantial loss occurred after 1 cycle of alternating temperature when low concentrations of cysts were used, but not with high concentrations of cysts. Cyst recovery, after 3 freezing and thawing cycles, was dramatically lowered irrespective of the initial cyst concentration. These results demonstrated that immunofluorescence was an effective technique for the detection of Giardia spp. cysts in frozen samples and would suggest that freezing and thawing of fecal samples could prevent the detection of cysts when only bright field microscopy was employed.

Optimization of a protective medium for freeze-dried Pichia membranifaciens and application of this biocontrol agent on citrus fruit.

PubMed

Niu, X; Deng, L; Zhou, Y; Wang, W; Yao, S; Zeng, K

2016-07-01

To optimize a protective medium for freeze-dried Pichia membranifaciens and to evaluate biocontrol efficacies of agents against blue and green mould and anthracnose in citrus fruit. Based on the screening assays of saccharides and antioxidants, response surface methodology was used to optimize sucrose, sodium glutamate and skim milk to improve viability of freeze-dried Pi. membranifaciens. Biocontrol assays were conducted between fresh and freeze-dried Pi. membranifaciens against Penicillium italicum, Penicillium digitatum and Colletotrichum gloeosporioides in citrus fruit. Solving the regression equation indicated that the optimal protective medium was 6·06% (w/v) sucrose combined with 3·40% (w/v) sodium glutamate and 5·43% (w/v) skim milk. Pi. membranifaciens freeze-dried in the optimal protective medium showed 76·80% viability, and retained biocontrol efficacy against Pe. italicum, Pe. digitatum and Co. gloeosporioides in citrus fruit. The optimal protective medium showed more effective protective properties than each of the three protectants used alone. The viability of freeze-dried Pi. membranifaciens finally reached 76·80%. Meanwhile, the biocontrol efficacies showed no significant difference between fresh and freeze-dried yeast against Pe. italicum, Pe. digitatum and Co. gloeosporioides in citrus fruit. The results showed the potential value of Pi. membranifaciens CICC 32259 for commercialization. © 2016 The Society for Applied Microbiology.

Gelatinization and freeze-concentration effects on recrystallization in corn and potato starch gels.

PubMed

Ronda, Felicidad; Roos, Yrjö H

2008-04-07

Freeze-concentration of starch gels was controlled by temperature and gelatinization with glucose and lactose. The aim of the study was to evaluate the effects of freezing temperature and gel composition on starch recrystallization behaviour of corn and potato starch gels (water content 70%, w/w) in water or glucose or lactose (10%, w/w) solutions. Starch gels were obtained by heating in differential scanning calorimetry (DSC). Samples of starch gels were frozen at -10 degrees C, -20 degrees C and -30 degrees C for 24h and, after thawing, stored at +2 degrees C for 0, 1, 2, 4 and 8 days. The extent of starch recrystallization was taken from the enthalpy of melting of the recrystallized starch by DSC. Freezing temperatures, glucose, lactose and the origin of the starch affected the recrystallization behaviour greatly. The recrystallization of amorphous starch during storage was enhanced by freeze-concentration of gels at temperatures above T'(m). Molecular mobility was enhanced by unfrozen water and consequently molecular rearrangements for nucleation could take place. Further storage at a higher temperature enhanced the growth and the maturation of crystals. In particular, glucose decreased the T'(m) of the gels and consequently lower freezing temperatures were needed to reduce enhanced recrystallization during storage. Freeze-concentration temperatures also showed a significant effect on the size and the perfection of crystals formed in starch recrystallization.

Freeze-dried, mucoadhesive system for vaginal delivery of the HIV microbicide, dapivirine: optimisation by an artificial neural network.

PubMed

Woolfson, A David; Umrethia, Manish L; Kett, Victoria L; Malcolm, R Karl

2010-03-30

Dapivirine mucoadhesive gels and freeze-dried tablets were prepared using a 3x3x2 factorial design. An artificial neural network (ANN) with multi-layer perception was used to investigate the effect of hydroxypropyl-methylcellulose (HPMC): polyvinylpyrrolidone (PVP) ratio (X1), mucoadhesive concentration (X2) and delivery system (gel or freeze-dried mucoadhesive tablet, X3) on response variables; cumulative release of dapivirine at 24h (Q(24)), mucoadhesive force (F(max)) and zero-rate viscosity. Optimisation was performed by minimising the error between the experimental and predicted values of responses by ANN. The method was validated using check point analysis by preparing six formulations of gels and their corresponding freeze-dried tablets randomly selected from within the design space of contour plots. Experimental and predicted values of response variables were not significantly different (p>0.05, two-sided paired t-test). For gels, Q(24) values were higher than their corresponding freeze-dried tablets. F(max) values for freeze-dried tablets were significantly different (2-4 times greater, p>0.05, two-sided paired t-test) compared to equivalent gels. Freeze-dried tablets having lower values for X1 and higher values for X2 components offered the best compromise between effective dapivirine release, mucoadhesion and viscosity such that increased vaginal residence time was likely to be achieved. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Investigation of the Influence of Heat Balance Shifts on the Freeze Microstructure and Composition in Aluminum Smelting Bath System: Cryolite-CaF2-AlF3-Al2O3

NASA Astrophysics Data System (ADS)

Liu, Jingjing; Fallah-Mehrjardi, Ata; Shishin, Denis; Jak, Evgueni; Dorreen, Mark; Taylor, Mark

2017-12-01

In an aluminum electrolysis cell, the side ledge forms on side walls to protect it from the corrosive cryolitic bath. In this study, a series of laboratory analogue experiments have been carried out to investigate the microstructure and composition of side ledge (freeze linings) at different heat balance steady states. Three distinct layers are found in the freeze linings formed in the designed Cryolite-CaF2-AlF3-Al2O3 electrolyte system: a closed (columnar) crystalline layer, an open crystalline layer, and a sealing layer. This layered structure changes when the heat balance is shifted between different steady states, by melting or freezing the open crystalline layer. Phase chemistry of the freeze lining is studied in this paper to understand the side ledge formation process upon heat balance shifts. Electron probe X-ray microanalysis (EPMA) is used to characterize the microstructure and compositions of distinct phases existing in the freeze linings, which are identified as cryolite, chiolite, Ca-cryolite, and alumina. A freeze formation mechanism is further developed based on these microstructural/compositional investigations and also thermodynamic calculations through the software—FactSage. It is found that entrapped liquid channels exist in the open crystalline layer, assisting with the mass transfer between solidified crystals and bulk molten bath.

Quality Evaluation of Pork with Various Freezing and Thawing Methods

PubMed Central

2014-01-01

In this study, the physicochemical and sensory quality characteristics due to the influence of various thawing methods on electro-magnetic and air blast frozen pork were examined. The packaged pork samples, which were frozen by air blast freezing at −45℃ or electro-magnetic freezing at −55℃, were thawed using 4 different methods: refrigeration (4±1℃), room temperature (RT, 25℃), cold water (15℃), and microwave (2450 MHz). Analyses were carried out to determine the drip and cooking loss, water holding capacity (WHC), moisture content and sensory evaluation. Frozen pork thawed in a microwave indicated relatively less thawing loss (0.63-1.24%) than the other thawing methods (0.68-1.38%). The cooking loss after electro-magnetic freezing indicated 37.4% by microwave thawing, compared with 32.9% by refrigeration, 36.5% by RT, and 37.2% by cold water in ham. The thawing of samples frozen by electro-magnetic freezing showed no significant differences between the methods used, while the moisture content was higher in belly thawed by microwave (62.0%) after electro-magnetic freezing than refrigeration (54.8%), RT (61.3%), and cold water (61.1%). The highest overall acceptability was shown for microwave thawing after electro-magnetic freezing but there were no significant differences compared to that of the other samples. PMID:26761493

Evidence for a freezing tolerance-growth rate trade-off in the live oaks (Quercus series Virentes) across the tropical-temperate divide.

PubMed

Koehler, Kari; Center, Alyson; Cavender-Bares, Jeannine

2012-02-01

• It has long been hypothesized that species are limited to the north by minimum temperature and to the south by competition, resulting in a trade-off between freezing tolerance and growth rate. We investigated the extent to which the climatic origins of populations from four live oak species (Quercus series Virentes) were associated with freezing tolerance and growth rate, and whether species fitted a model of locally adapted populations, each with narrow climatic tolerances, or of broadly adapted populations with wide climatic tolerances. • Acorns from populations of four species across a tropical-temperate gradient were grown under common tropical and temperate conditions. Growth rate, seed mass, and leaf and stem freezing traits were compared with source minimum temperatures. • Maximum growth rates under tropical conditions were negatively correlated with freezing tolerance under temperate conditions. The minimum source temperature predicted the freezing tolerance of populations under temperate conditions. The tropical species Q. oleoides was differentiated from the three temperate species, and variation among species was greater than among populations. • The trade-off between freezing tolerance and growth rate supports the range limit hypothesis. Limited variation within species indicates that the distributions of species may be driven more strongly by broad climatic factors than by highly local conditions. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

Isochoric and isobaric freezing of fish muscle.

PubMed

Năstase, Gabriel; Lyu, Chenang; Ukpai, Gideon; Şerban, Alexandru; Rubinsky, Boris

2017-04-01

We have recently shown that, a living organism, which succumbs to freezing to -4 °C in an isobaric thermodynamic system (constant atmospheric pressure), can survive freezing to -4 °C in an isochoric thermodynamic system (constant volume). It is known that the mechanism of cell damage in an isobaric system is the freezing caused increase in extracellular osmolality, and, the consequent cell dehydration. An explanation for the observed survival during isochoric freezing is the thermodynamic modeling supported hypothesis that, in the isochoric frozen solution the extracellular osmolality is comparable to the cell intracellular osmolality. Therefore, cells in the isochoric frozen organism do not dehydrate, and the tissue maintains its morphological integrity. Comparing the histology of: a) fresh fish white muscle, b) fresh muscle frozen to -5 °C in an isobaric system and c) fresh muscle frozen to -5 °C I in an isochoric system, we find convincing evidence of the mechanism of cell dehydration during isobaric freezing. In contrast, the muscle tissue frozen to -5 °C in an isochoric system appears morphologically identical to fresh tissue, with no evidence of dehydration. This is the first experimental evidence in support of the hypothesis that in isochoric freezing there is no cellular dehydration and therefore the morphology of the frozen tissue remains intact. Copyright © 2017 Elsevier Inc. All rights reserved.

Preservation of beluga (Delphinapterus leucas) spermatozoa using a trehalose-based cryodiluent and directional freezing technology.

PubMed

O'Brien, J K; Robeck, T R

2010-01-01

A beluga (Delphinapterus leucas) sperm preservation method was developed for use in genome banking and AI. In Study 1, glycerol-based cryodiluents (modified BF5F and modified Platz Diluent Variant (PDV)) were unable to maintain adequate progressive motility using straws (fast and slow freezing rate (FR)) or pellets (slow FR). Neither freezing method nor FR affected in vitro sperm characteristics (P > 0.05), but retention of prefreeze progressive motility following thawing was greater (P < 0.05) for BF5F (21%) than PDV (15%). In Study 2, examining the effects of straw freeze-thawing using BF5F with glycerol (1 and 3%, v/v) or trehalose (46 and 91 mM) on sperm characteristics, samples cryopreserved in trehalose exhibited superior (P < 0.05) in vitro parameters compared with their glycerol-treated counterparts. In Study 3, compared with a straw method, directional freezing using 91 mM trehalose enhanced (P < 0.05) sperm characteristics, with samples retaining 38%, 75% and 61% of their prefreeze progressive motility, curvilinear velocity and viability, respectively. A higher (P < 0.05) proportion of motile spermatozoa displayed rapid velocity after directional (21 +/- 1%) compared with straw (12 +/- 3%) freezing. Systematic development of a cryodiluent and the use of directional freezing resulted in beluga spermatozoa exhibiting adequate post-thaw quality for genome banking and use in AI.

Adapting and Modifying the Apparatus for Students to Accurately Determine the Freezing Point of a Solvent and Solution

ERIC Educational Resources Information Center

Li, Shirong; Guo, Jianzhong; Wang, Kewang; Chen, Lin; Hu, Daodao; Bai, Yunshan

2017-01-01

An improved apparatus for measuring freezing points has been developed. Compared to the traditional Beckmann freezing point instrument, the improved one overcame prior difficulties with solidification of liquid and made the solid-liquid equilibrium reversible with heat compensation from a heating tube. The reliability and accuracy were carefully…

Influence of simulated snow cover on the cold tolerance and freezing injury of yellow-cedar seedlings

Treesearch

Paul G. Schaberg; Paul E. Hennon; David V. D' amore; Gary J.  Hawley

2008-01-01

It has been hypothesized that yellow-cedar [Chamaecyparis nootkatensis (D. Don) Spach] decline may result from root freezing injury following climate change-induced reductions in protective snow cover. To test this hypothesis, we measured the freezing tolerance and injury expression of yellow-cedar seedlings in three treatments that differed in the...

St. Lawrence River Freeze-Up Forecast Procedure.

ERIC Educational Resources Information Center

Assel, R. A.

A standard operating procedure (SOP) is presented for calculating the date of freeze-up on the St. Lawrence River at Massena, N.Y. The SOP is based on two empirical temperature decline equations developed for Kingston, Ontario, and Massena, N.Y., respectively. Input data needed to forecast freeze-up consist of the forecast December flow rate and…

21 CFR 864.9225 - Cell-freezing apparatus and reagents for in vitro diagnostic use.

Code of Federal Regulations, 2012 CFR

2012-04-01

... use are devices used to freeze human red blood cells for in vitro diagnostic use. (b) Classification. Class I (general controls). The device is exempt from the premarket notification procedures in subpart E... Establishments That Manufacture Blood and Blood Products § 864.9225 Cell-freezing apparatus and reagents for in...

21 CFR 864.9225 - Cell-freezing apparatus and reagents for in vitro diagnostic use.

Code of Federal Regulations, 2014 CFR

2014-04-01

... use are devices used to freeze human red blood cells for in vitro diagnostic use. (b) Classification. Class I (general controls). The device is exempt from the premarket notification procedures in subpart E... Establishments That Manufacture Blood and Blood Products § 864.9225 Cell-freezing apparatus and reagents for in...

21 CFR 864.9225 - Cell-freezing apparatus and reagents for in vitro diagnostic use.

Code of Federal Regulations, 2013 CFR

2013-04-01

... use are devices used to freeze human red blood cells for in vitro diagnostic use. (b) Classification. Class I (general controls). The device is exempt from the premarket notification procedures in subpart E... Establishments That Manufacture Blood and Blood Products § 864.9225 Cell-freezing apparatus and reagents for in...

Influence of Beet necrotic yellow vein virus and freezing temperatures on sugar beet roots in storage

USDA-ARS?s Scientific Manuscript database

Rhizomania caused by Beet necrotic yellow vein virus (BNYVV) is a yield limiting sugar beet disease that was observed to influence root resistance to freezing in storage. Thus, studies were conducted to gain a better understanding of the influence BNYVV and freezing on sugar beet roots to improve p...

Freezing Point of Milk: A Natural Way to Understand Colligative Properties

ERIC Educational Resources Information Center

Novo, Mercedes; Reija, Belen; Al-Soufi, Wajih

2007-01-01

A laboratory experiment is presented in which the freezing point depression is analyzed using milk as solution. The nature of milk as a mixture of different solutes makes it a suitable probe to learn about colligative properties. The first part of the experiment illustrates the analytical use of freezing point measurements to control milk quality,…

Induction of DREB2A pathway with repression of E2F, Jasmonic acid biosynthetic and photosynthesis pathways in cold acclimation specific freeze resistant wheat crown

USDA-ARS?s Scientific Manuscript database

Winter wheat lines can achieve cold acclimation (development of tolerance to freezing temperatures) and vernalization (delay in transition from vegetative to reproductive phase) in response to low non-freezing temperatures. To describe cold acclimation specific processes and pathways, we utilized co...

Analysis of isothermal and cooling rate dependent immersion freezing by a unifying stochastic ice nucleation model

NASA Astrophysics Data System (ADS)

Alpert, P. A.; Knopf, D. A.

2015-05-01

Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature (T) and relative humidity (RH) at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling rate dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nuclei (IN) all have the same IN surface area (ISA), however the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses physically observable parameters including the total number of droplets (Ntot) and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time dependent isothermal frozen fractions exhibiting non-exponential behavior with time can be readily explained by this model considering varying ISA. An apparent cooling rate dependence ofJhet is explained by assuming identical ISA in each droplet. When accounting for ISA variability, the cooling rate dependence of ice nucleation kinetics vanishes as expected from classical nucleation theory. The model simulations allow for a quantitative experimental uncertainty analysis for parameters Ntot, T, RH, and the ISA variability. In an idealized cloud parcel model applying variability in ISAs for each droplet, the model predicts enhanced immersion freezing temperatures and greater ice crystal production compared to a case when ISAs are uniform in each droplet. The implications of our results for experimental analysis and interpretation of the immersion freezing process are discussed.

Analysis of isothermal and cooling-rate-dependent immersion freezing by a unifying stochastic ice nucleation model

NASA Astrophysics Data System (ADS)

Alpert, Peter A.; Knopf, Daniel A.

2016-02-01

Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature, T, and relative humidity, RH, at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling-rate-dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nucleating particles (INPs) all have the same INP surface area (ISA); however, the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. Descriptions of ice active sites and variability of contact angles have been successfully formulated to describe ice nucleation experimental data in previous research; however, we consider the ability of a stochastic freezing model founded on classical nucleation theory to reproduce previous results and to explain experimental uncertainties and data scatter. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses parameters including the total number of droplets, Ntot, and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA-dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous-flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time-dependent isothermal frozen fractions exhibiting non-exponential behavior can be readily explained by this model considering varying ISA. An apparent cooling-rate dependence of Jhet is explained by assuming identical ISA in each droplet. When accounting for ISA variability, the cooling-rate dependence of ice nucleation kinetics vanishes as expected from classical nucleation theory. The model simulations allow for a quantitative experimental uncertainty analysis for parameters Ntot, T, RH, and the ISA variability. The implications of our results for experimental analysis and interpretation of the immersion freezing process are discussed.

The application of A.C. impedance spectroscopy on the durability of hydrated cement paste subjected to various environmental conditions

NASA Astrophysics Data System (ADS)

Perron, Stacey

Harsh Canadian winters cause many problems in reinforced concrete structures due to damaging freezing-thawing cycles which is exacerbated by the heavy use of de-icing salts on roadways. Evaluation of concrete durability with current ASTM methods may give unreliable results and are destructive to the structure. A relatively new and novel approach to evaluating the durability of concrete uses A. C. Impedance Spectroscopy (ACIS). Hydrated cement paste (hcp), mortar, brick and vycor glass were evaluated using ACIS during drying-rewetting and freezing-thawing cycles. Thermal mechanical analysis (TMA), and differential scanning calorimetry (DSC) tests were also conducted and used as references. Results indicate that ACIS can be used to successfully evaluate the pore structure of hcp. The results from the drying-rewetting cycles are consistent with the pore coarsening theory. ACIS revealed pore structure changes consistent with the mechanical strains and pore solution chemistry. Increased pore continuity with each drying-rewetting cycle was indicated by a reduction in sample resistance. Unique tests were conducted on hydrated cement paste, mortar, brick and vycor glass that measured the ACIS and mechanical strains simultaneously while undergoing temperature changes. The temperature was lowered from 5°C to -80°C and then raised to +20°C. The ACIS results indicate that durability of the material can be assessed using the parameters R, material resistance, and phi, indicative of the frequency dispersion angle. The resistance on freezing values correlates with the amount of pore water freezing. The phi values on freezing are representative of the pore size distribution of the test sample. Resistance and phi data from freezing-thawing tests can be analyzed to assess durability of the sample. A material that is durable to freezing-thawing cycles can be described as having a high resistance at room temperature, a low freezing resistance and small changes in phi. Results were consistent among all the materials tested. Freezing-thawing tests were also conducted on specimens resaturated with salt solutions (5%, 10%, 15%). The results of these tests indicated a lower incipient freezing temperature, increase in pore blockage temperatures, and increased mobility of the pore water during freezing (increase in the change to phi). A series of test were conducted to evaluate the electrode polarization effects associated with the permittivity values at low frequencies. Teflon sheets were used to minimize the electrode polarization effects. It is shown that electrode polarization effects dominate over bulk polarization effects. Effects vary with the porosity of the material.

Does freeze-all policy affect IVF outcomes in poor responders?

PubMed

Roque, Matheus; Valle, Marcello; Sampaio, Marcos; Geber, Selmo

2017-12-27

To evaluate whether the freeze-all strategy affects in vitro fertilization (IVF) outcomes in poor ovarian responders following the Bologna criteria. We performed a retrospective cohort study conducted between January 2012 and December 2016. A total of 433 poor responders (per the Bologna criteria) fulfilled the inclusion/exclusion criteria and were included in the study, with 277 patients included in the fresh group and 156 in the freeze-all group. All patients were submitted to controlled ovarian stimulation (COS) with a gonadotropin-releasing hormone antagonist protocol and cleavage-stage embryo transfer (ET). The main outcome measure was ongoing pregnancy rate. Secondary outcomes included implantation and clinical pregnancy rates. The freeze-all strategy was implemented when the progesterone serum level was >1.5 ng/mL on the trigger day, when the endometrium was <7 mm on the trigger day, or as a patient preference. Patients with previous failed fresh embryo transfer were also submitted to fresh or freeze-all strategy considering the indications mentioned above. The patients' mean age in the freeze-all group was 39.5±3.6 years, while that of patients in the fresh group was 39.7±3.8 years (P=0.54). The mean number of embryos transferred (nET) was 1.53±0.6 and 1.60±0.6 (P=0.12) in the freeze-all and fresh groups, respectively. Ongoing pregnancy rates did not significantly differ between the freeze-all and fresh groups (9.6% versus 10.1%, respectively; Relative Risk [RR]: 0.95; 95% CI: 0.52-1.73), nor did the clinical pregnancy rates (14.1% versus 13.7%, respectively; RR: 1.03; 95% CI: 0.63-1.76). Implantation rates were 9.6% and 9.8% (P=0.82) in the freeze-all and fresh groups, respectively. The logistic regression analysis (including age, antral follicle count [AFC], the number of retrieved oocytes, the number of mature oocytes, nET, and fresh versus freeze-all strategy) indicated that age (P<0.001) and the nET (P=0.039) were the only independent variables associated with ongoing pregnancy rates. In this study, the freeze-all strategy had no impact on IVF outcomes among poor responders according to the Bologna criteria. Multi-centric study including a large number of patients should be carried out to extend the results of our study to reach conclusions about the benefits offered to poor responders. This article is protected by copyright. All rights reserved.

New Processes for Freeze-Drying in Dual-Chamber Systems.

PubMed

Werk, T; Ludwig, I S; Luemkemann, J; Huwyler, J; Mahler, H-C; Haeuser, C R; Hafner, M

2016-01-01

Dual-chamber systems can offer self-administration and home care use for lyophilized biologics. Only a few products have been launched in dual-chamber systems so far-presumably due to dual-chamber systems' complex and costly drug product manufacturing process. Within this paper, two improved processes (both based on tray filling technology) for freeze-drying pharmaceuticals in dual-chamber systems are described. Challenges with regards to heat transfer were tackled by (1) performing the freeze-drying step in a needle-down orientation in combination with an aluminum block, or (2) freeze-drying the drug product "externally" in a metal cartridge with subsequent filling of the lyophilized cake into the dual-chamber system. Metal-mediated heat transfer was shown to be efficient in both cases and batch (unit-to-unit) homogeneity with regards to sublimation rate was increased. It was difficult to influence ice crystal size using different methods when in use with an aluminum block due to its heat capacity. Using such a metal carrier implies a large heat capacity leading to relatively small ice crystals. Compared to the established process, drying times were reduced by half using the new processes. The drying time was, however, longer for syringes compared to vials due to the syringe design (long and slim). The differences in drying times were less pronounced for aggressive drying cycles. The proposed processes may help to considerably decrease investment costs into dual-chamber system fill-finish equipment. Dual-chamber syringes offer self-administration and home care use for freeze-dried pharmaceuticals. Only a few products have been launched in dual-chamber syringes so far-presumably due to their complex and costly drug product manufacturing process. In this paper two improved processes for freeze-drying pharmaceuticals in dual-chamber syringes are described. The major challenge of freeze-drying is to transfer heat through a vacuum. The proposed processes cope with this challenge by (1) freeze-drying the drug product in the syringe in an orientation in which the product is closest to the heat source, or (2) freeze-drying the drug product outside the syringe in a metal tube. The latter requires filling the freeze-dried product subsequently into the dual-chamber syringe. Both processes were very efficient and promised to achieve similar freeze-drying conditions for all dual-chamber syringes within one production run. The proposed processes may help to considerably decrease investment costs into dual-chamber syringe fill-finish equipment. © PDA, Inc. 2016.

Freezing resistance in Patagonian woody shrubs: the role of cell wall elasticity and stem vessel size.

PubMed

Zhang, Yong-Jiang; Bucci, Sandra J; Arias, Nadia S; Scholz, Fabian G; Hao, Guang-You; Cao, Kun-Fang; Goldstein, Guillermo

2016-08-01

Freezing resistance through avoidance or tolerance of extracellular ice nucleation is important for plant survival in habitats with frequent subzero temperatures. However, the role of cell walls in leaf freezing resistance and the coordination between leaf and stem physiological processes under subzero temperatures are not well understood. We studied leaf and stem responses to freezing temperatures, leaf and stem supercooling, leaf bulk elastic modulus and stem xylem vessel size of six Patagonian shrub species from two sites (plateau and low elevation sites) with different elevation and minimum temperatures. Ice seeding was initiated in the stem and quickly spread to leaves, but two species from the plateau site had barriers against rapid spread of ice. Shrubs with xylem vessels smaller in diameter had greater stem supercooling capacity, i.e., ice nucleated at lower subzero temperatures. Only one species with the lowest ice nucleation temperature among all species studied exhibited freezing avoidance by substantial supercooling, while the rest were able to tolerate extracellular freezing from -11.3 to -20 °C. Leaves of species with more rigid cell walls (higher bulk elastic modulus) could survive freezing to lower subzero temperatures, suggesting that rigid cell walls potentially reduce the degree of physical injury to cell membranes during the extracellular freezing and/or thaw processes. In conclusion, our results reveal the temporal-spatial ice spreading pattern (from stem to leaves) in Patagonian shrubs, and indicate the role of xylem vessel size in determining supercooling capacity and the role of cell wall elasticity in determining leaf tolerance of extracellular ice formation. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Immersion and contact freezing experiments in the Mainz wind tunnel laboratory

NASA Astrophysics Data System (ADS)

Eppers, Oliver; Mayer, Amelie; Diehl, Karoline; Mitra, Subir; Borrmann, Stephan; Szakáll, Miklós

2016-04-01

Immersion and contact freezing are of outmost important ice nucleation processes in mixed phase clouds. Experimental studies are carried out in the Mainz vertical wind tunnel laboratory in order to characterize these nucleation processes for different ice nucleating particles (INP), such as for mineral dust or biological particles. Immersion freezing is investigated in our laboratory with two different experimental techniques, both attaining contact-free levitation of liquid droplets and cooling of the surrounding air down to about -25 °C. In an acoustic levitator placed in the cold room of our laboratory, drops with diameters of 2 mm are investigated. In the vertical air stream of the wind tunnel droplets with diameter of 700 micron are freely floated at their terminal velocities, simulating the flow conditions of the free atmosphere. Furthermore, the wind tunnel offers a unique platform for contact freezing experiments. Supercooled water droplets are floated in the vertical air stream at their terminal velocities and INP are injected into the tunnel air stream upstream of them. As soon as INP collides with the supercooled droplet the contact freezing is initiated. The first results of immersion and contact freezing experiments with cellulose particles both in the acoustic levitator and in the wind tunnel will be presented. Cellulose is considered as typical INP of biological origin and a macrotracer for plant debris. Nucleating properties of cellulose will be provided, mainly focusing on the temperature, INP concentration, and specific surface area dependences of the freezing processes. Direct comparison between the different experimental techniques (acoustic levitator and wind tunnel), as well as between nucleation modes (immersion and contact freezing) will be presented. The work is carried out within the framework of the German research unit INUIT.

An investigation of voids formation mechanisms and their effects on freeze and thaw processes of lithium and lithium fluoride

NASA Technical Reports Server (NTRS)

El-Genk, Mohamed S.; Yang, Jae-Young

1991-01-01

The mechanisms of void formation during the cooldown and freezing of lithium coolant within the primary loop of SP-100 type systems are investigated. These mechanisms are: (1) homogeneous nucleation; (2) heterogeneous nucleation; (3) normal segregation of helium gas dissolved in liquid lithium; and (4) shrinkage of lithium during freezing. To evaluate the void formation potential due to segregation, a numerical scheme that couples the freezing and mass diffusion processes in both the solid and liquid regions is developed. The results indicated that the formation of He bubbles is unlikely by either homogeneous or heterogeneous nucleation during the cooldown process. However, homogeneous nucleation of He bubbles following the segregation of dissolved He in liquid lithium ahead of the solid-liquid interface is likely to occur. Results also show that total volume of He void is insignificant when compared to that of shrinkage voids. In viewing this, the subsequent research focuses on the effects of shrinkage void forming during freezing of lithium on subsequent thaw processes are investigated using a numerical scheme that is based on a single (solid/liquid) cell approach. The cases of lithium-fluoride are also investigated to show the effect of larger volume shrinkage upon freezing on the freeze and thaw processes. Results show that a void forming at the wall appreciably reduces the solid-liquid interface velocity, during both freeze and thaw, and causes a substantial rise in the wall temperature during thaw. However, in the case of Li, the maximum wall temperature was much lower than the melting temperature of PWC-11, which is used as the structure material in the SP-100 system. Hence, it is included that a formation of hot spots is unlikely during the startup or restart of the SP-100 system.

Brown bear sperm double freezing: Effect of elapsed time and use of PureSperm(®) gradient between freeze-thaw cycles.

PubMed

Alvarez-Rodríguez, Manuel; Alvarez, Mercedes; López-Urueña, Elena; Martínez-Rodriguez, Carmen; Borragan, Santiago; Anel-López, Luis; de Paz, Paulino; Anel, Luis

2013-12-01

The use of sexed spermatozoa has great potential to captive population management in endangered wildlife. The problem is that the sex-sorting facility is a long distance from the semen collection place and to overcome this difficulty two freeze-thaw cycles may be necessary. In this study, effects of refreezing on brown bear electroejaculated spermatozoa were analyzed. We carried out two experiments: (1) to assess the effects of the two freezing-thawing cycles on sperm quality and to analyze three different elapsed times between freezing-thawing cycles (30, 90 and 180 min), and (2) to analyze the use of PureSperm between freezing-thawing cycles to select a more motile and viable sperm subpopulation which better survived first freezing. The motility, viability and undamaged acrosomes were significantly reduced after the second thawing respect to first thawing into each elapsed time group, but the elapsed times did not significantly affect the viability and acrosome status although motility was damaged. Our results with the PureSperm gradient showed higher values of viability in freezability of select sample (pellet) respect to the rest of the groups and it also showed a significant decrease in the number of acrosome damaged. In summary, the double freezing of bear semen selected by gradient centrifugation is qualitatively efficient, and thus could be useful to carry out a sex-sorting of frozen-thawed bear spermatozoa before to send the cryopreserved sample to a biobank. Given the low recovery of spermatozoa after applying a selection gradient, further studies will be needed to increase the recovery rate without damaging of the cell quality. Copyright © 2013 Elsevier Inc. All rights reserved.

Could Sensory Mechanisms Be a Core Factor That Underlies Freezing of Gait in Parkinson’s Disease?

PubMed Central

Ehgoetz Martens, Kaylena A.; Pieruccini-Faria, Frederico; Almeida, Quincy J.

2013-01-01

The main objective of this study was to determine how manipulating the amount of sensory information available about the body and surrounding environment influenced freezing of gait (FOG), while walking through a doorway. It was hypothesized that the more limited the sensory information, the greater the occurrence of freezing of gait. Nineteen patients with Parkinsoǹs disease who experience freezing of gait (PD-FOG) walked through a doorway or into open space in complete darkness. The three doorway conditions included: (i) FRAME (DARK) – walking through the remembered door frame; (ii) FRAME - walking through the door with the door frame illuminated; (iii) FRAME+BODY - walking through the door (both the door and the limbs illuminated). Additionally, two conditions of walking away from the doorway included: (iv) NO FRAME (DARK) - walking into open space; (v) NO FRAME+BODY - walking into open space with the limbs illuminated, to evaluate whether perception (or fear) of the doorway might account for FOG behaviour. Key outcome measures included: the number of freezing of gait episodes recorded, total duration of freezing of gait, and the percentage of time spent frozen. Significantly more freezing of gait episodes occurred when participants walked toward the doorway in complete darkness compared to walking into open space (p<0.05). Similar to previous studies, velocity (p<0.001) and step length (p<0.0001) significantly decreased when walking through the door in complete darkness, compared to all other conditions. Significant increases in step width variability were also identified but only when walking into open space (p<0.005). These results support the notion that sensory deficits may have a profound impact on freezing of gait that need to be carefully considered. PMID:23667499

The Mechanism of Freezing Injury in Xylem of Winter Apple Twigs 1

PubMed Central

Quamme, H.; Weiser, C. J.; Stushnoff, C.

1973-01-01

In acclimated winter twigs of Haralson apple (Pyrus Malus L.), a lag in temperature during cooling at a constant rate was observed at about −41 C by differential thermal analysis. The temperature at which this low temperature exotherm occurred was essentially unaffected by the cooling rate. During thawing there was no lag in temperature (endotherm) near the temperature at which the low temperature exotherm occurred, but upon subsequent refreezing the exotherm reappeared at a somewhat higher temperature when twigs were rewarmed to at least −5 C before refreezing. These observations indicate that a small fraction of water may remain unfrozen to as low as −42 C after freezing of the bulk water in stems. The low temperature exotherm was not present in twigs freeze-dried to a water content below 8.5% (per unit fresh weight), but it reappeared when twigs were rehydrated to 20% water. When freeze-dried twigs were ground to a fine powder prior to rehydration, no exotherm was observed. Previous work has shown that the low temperature exotherm arises from xylem and pith tissues, and that injury to living cells in these tissues invariably occurs only when twigs are cooled below, but not above the temperature of the low temperature exotherm. This study revealed that the low temperature exotherm resulted from the freezing of a water fraction, that the freezing of this water was independent of the freezing of the bulk water, that the exotherm was associated with some gross structural feature but not the viability of the tissue, and that injury to living cells in the xylem and pith was closely and perhaps causally related to the initial freezing of this water. PMID:16658314

Antifreeze proteins govern the precipitation of trehalose in a freezing-avoiding insect at low temperature.

PubMed

Wen, Xin; Wang, Sen; Duman, John G; Arifin, Josh Fnu; Juwita, Vonny; Goddard, William A; Rios, Alejandra; Liu, Fan; Kim, Soo-Kyung; Abrol, Ravinder; DeVries, Arthur L; Henling, Lawrence M

2016-06-14

The remarkable adaptive strategies of insects to extreme environments are linked to the biochemical compounds in their body fluids. Trehalose, a versatile sugar molecule, can accumulate to high levels in freeze-tolerant and freeze-avoiding insects, functioning as a cryoprotectant and a supercooling agent. Antifreeze proteins (AFPs), known to protect organisms from freezing by lowering the freezing temperature and deferring the growth of ice, are present at high levels in some freeze-avoiding insects in winter, and yet, paradoxically are found in some freeze-tolerant insects. Here, we report a previously unidentified role for AFPs in effectively inhibiting trehalose precipitation in the hemolymph (or blood) of overwintering beetle larvae. We determine the trehalose level (29.6 ± 0.6 mg/mL) in the larval hemolymph of a beetle, Dendroides canadensis, and demonstrate that the hemolymph AFPs are crucial for inhibiting trehalose crystallization, whereas the presence of trehalose also enhances the antifreeze activity of AFPs. To dissect the molecular mechanism, we examine the molecular recognition between AFP and trehalose crystal interfaces using molecular dynamics simulations. The theory corroborates the experiments and shows preferential strong binding of the AFP to the fast growing surfaces of the sugar crystal. This newly uncovered role for AFPs may help explain the long-speculated role of AFPs in freeze-tolerant species. We propose that the presence of high levels of molecules important for survival but prone to precipitation in poikilotherms (their body temperature can vary considerably) needs a companion mechanism to prevent the precipitation and here present, to our knowledge, the first example. Such a combination of trehalose and AFPs also provides a novel approach for cold protection and for trehalose crystallization inhibition in industrial applications.

Antifreeze proteins govern the precipitation of trehalose in a freezing-avoiding insect at low temperature

PubMed Central

Wen, Xin; Wang, Sen; Duman, John G.; Arifin, Josh Fnu; Juwita, Vonny; Goddard, William A.; Rios, Alejandra; Liu, Fan; Kim, Soo-Kyung; Abrol, Ravinder; DeVries, Arthur L.; Henling, Lawrence M.

2016-01-01

The remarkable adaptive strategies of insects to extreme environments are linked to the biochemical compounds in their body fluids. Trehalose, a versatile sugar molecule, can accumulate to high levels in freeze-tolerant and freeze-avoiding insects, functioning as a cryoprotectant and a supercooling agent. Antifreeze proteins (AFPs), known to protect organisms from freezing by lowering the freezing temperature and deferring the growth of ice, are present at high levels in some freeze-avoiding insects in winter, and yet, paradoxically are found in some freeze-tolerant insects. Here, we report a previously unidentified role for AFPs in effectively inhibiting trehalose precipitation in the hemolymph (or blood) of overwintering beetle larvae. We determine the trehalose level (29.6 ± 0.6 mg/mL) in the larval hemolymph of a beetle, Dendroides canadensis, and demonstrate that the hemolymph AFPs are crucial for inhibiting trehalose crystallization, whereas the presence of trehalose also enhances the antifreeze activity of AFPs. To dissect the molecular mechanism, we examine the molecular recognition between AFP and trehalose crystal interfaces using molecular dynamics simulations. The theory corroborates the experiments and shows preferential strong binding of the AFP to the fast growing surfaces of the sugar crystal. This newly uncovered role for AFPs may help explain the long-speculated role of AFPs in freeze-tolerant species. We propose that the presence of high levels of molecules important for survival but prone to precipitation in poikilotherms (their body temperature can vary considerably) needs a companion mechanism to prevent the precipitation and here present, to our knowledge, the first example. Such a combination of trehalose and AFPs also provides a novel approach for cold protection and for trehalose crystallization inhibition in industrial applications. PMID:27226297

Lesion of the Ventral Periaqueductal Gray Reduces Conditioned Fear but Does Not Change Freezing Induced by Stimulation of the Dorsal Periaqueductal Gray

PubMed Central

Vianna, Daniel M.L.; Graeff, Frederico G.; Landeira-Fernandez, Jesus; Brandão, Marcus L.

2001-01-01

Previously-reported evidence showed that freezing to a context previously associated with footshock is impaired by lesion of the ventral periaqueductal gray (vPAG). It has also been shown that stepwise increase in the intensity of the electrical stimulation of the dorsal periaqueductal gray (dPAG) produces alertness, then freezing, and finally escape. These aversive responses are mimicked by microinjections of GABA receptor antagonists, such as bicuculline, or blockers of the glutamic acid decarboxylase (GAD), such as semicarbazide, into the dPAG. In this work, we examined whether the expression of these defensive responses could be the result of activation of ventral portion of the periaqueductal gray. Sham- or vPAG electrolytic–lesioned rats were implanted with an electrode in the dPAG for the determination of the thresholds of freezing and escape responses. The vPAG electrolytic lesions were behaviorally verified through a context-conditioned fear paradigm. Results indicated that lesion of the vPAG disrupted conditioned freezing response to contextual cues associated with footshocks but did not change the dPAG electrical stimulation for freezing and escape responses. In a second experiment, lesion of the vPAG also did not change the amount of freezing and escape behavior produced by microinjections of semicarbazide into the dPAG. These findings indicate that freezing and escape defensive responses induced by dPAG stimulation do not depend on the integrity of the vPAG. A discussion on different neural circuitries that might underlie different inhibitory and active defensive behavioral patterns that animals display during threatening situations is presented. PMID:11390636

Characteristics of ultrasonic acoustic emissions from walnut branches during freeze-thaw-induced embolism formation.

PubMed

Kasuga, Jun; Charrier, Guillaume; Uemura, Matsuo; Améglio, Thierry

2015-04-01

Ultrasonic acoustic emission (UAE) methods have been applied for the detection of freeze-thaw-induced embolism formation in water conduits of tree species. Until now, however, the exact source(s) of UAE has not been identified especially in angiosperm species, in which xylem tissues are composed of diverse types of cells. In this study, UAE was recorded from excised branches of walnut (Juglans regia cv. Franquette) during freeze-thaw cycles, and attempts were made to characterize UAEs generated by cavitation events leading to embolism formation according to their properties. During freeze-thaw cycles, a large number of UAEs were generated from the sample segments. However, the cumulative numbers of total UAE during freeze-thawing were not correlated with the percentage loss of hydraulic conductivity after thawing, suggesting that the sources of UAE were not only cavitation leading to embolism formation in vessels. Among the UAEs, cumulative numbers of UAEs with absolute energy >10.0 fJ strongly correlated with the increase in percentage loss of hydraulic conductivity. The high absolute energy of the UAEs might reflect the formation of large bubbles in the large lumen of vessels. Therefore, UAEs generated by cavitation events in vessels during freeze-thawing might be distinguished from other signals according to their magnitudes of absolute energy. On the other hand, the freezing of xylem parenchyma cells was followed by a certain number of UAEs. These results indicate the possibility that UAE methods can be applied to the detection of both freeze-thaw-induced embolism and supercooling breakdown in parenchyma cells in xylem. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Combining reduced glutathione and ascorbic acid has supplementary beneficial effects on boar sperm cryotolerance.

PubMed

Giaretta, Elisa; Estrada, Efrén; Bucci, Diego; Spinaci, Marcella; Rodríguez-Gil, Joan E; Yeste, Marc

2015-02-01

The main aim of this work was to evaluate how supplementing freezing and thawing media with reduced glutathione (GSH) and l-ascorbic acid (AA) affected the quality parameters of frozen-thawed boar spermatozoa. With this purpose, semen samples of 12 ejaculates coming from 12 boars were used. Each ejaculate was split into seven aliquots to which 5 mM of GSH and 100 μM of AA were added separately or together at two different steps of freeze-thawing. Various sperm parameters (levels of free cysteine residues in sperm nucleoproteins, sperm viability, acrosome membrane integrity, intracellular peroxide and superoxide levels [ROS], and total and progressive motility) were evaluated before freezing and at 30 and 240 minutes after thawing. Both GSH and AA significantly improved boar sperm cryotolerance when they were separately added to freezing and thawing media. However, the highest improvement was recorded when both freezing and thawing media were supplemented with 5 mM of GSH plus 100 μM of AA. This improvement was observed in sperm viability and acrosome integrity, sperm motility, and nucleoprotein structure. Although ROS levels were not much increased by freeze-thawing procedures, the addition of GSH and AA to both freezing and thawing extenders significantly decreased intracellular peroxide levels and had no impact on superoxide levels. According to our results, we can conclude that supplementation of freezing and thawing media with both GSH and AA has a combined, beneficial effect on frozen-thawed boar sperm, which is greater than that obtained with the separate addition of either GSH or AA. Copyright © 2015 Elsevier Inc. All rights reserved.