Incomplete Freezing Research Articles

Incomplete freezing strategies for achieving long-lasting preservation of muscle foods: categories, regulations, efficiencies and challenges

Incomplete freezing strategies for achieving long-lasting preservation of muscle foods: categories, regulations, efficiencies and challenges

The Severe Multi-Day October 2019 Snow Storm Over Southern Manitoba, Canada

ABSTRACT A devastating storm struck southern Manitoba, Canada on 10–13 October 2019, producing a large region of mainly sticky and wet snow. Accumulations reached 75 cm, wind gusts exceeded 100 km h−1, and surface temperature (T) remained near 0°C (−1°C ≤ T ≤ 1°C) for up to 88 h. It produced the largest October snowfall and was the earliest to produce at least 20 cm since 1872 in Winnipeg. These factors led to unparalleled damage and power restoration challenges for Manitoba Hydro and, with leaves still largely on vegetation, the most damaging storm to Winnipeg’s trees ever recorded. The storm’s track was uncommon, and produced elevated convection related to buoyancy-driven instability and conditional symmetric instability (CSI), with a moist absolutely unstable layer (MAUL) near 500 hPa. Instabilities were released via lift through lower-tropospheric warm advection and frontogenesis, differential cyclonic vorticity advection, and jet streak dynamics. Precipitation bands, elevated convection, and lake effect snow bands enhanced local snowfall. Snow adhering to structures was not always wet but, when present, it sometimes occurred because of incomplete freezing of particles partially melted aloft in a near-surface (<100 m deep) inversion. Although other storms over the historical record have produced a similar combination of severe precipitation, temperature and wind conditions, none have done this for such a long period.

Investigations on Polyplex Stability During the Freezing Step of Lyophilization Using Controlled Ice Nucleation—The Importance of Residence Time in the Low-Viscosity Fluid State

The aim of the study was to comprehensively investigate the influence of the freezing step during lyophilization on the stability of gene-delivery particles in order to better understand particle stabilization during freezing. Particle size of plasmid/linear polyethylenimine (LPEI) polyplexes at two DNA concentrations and at increasing sucrose-DNA ratios was investigated separately as a function of freezing procedure, ice-nucleation temperature, residence time of the particles in a partially frozen state, or incomplete freezing. Using a numerical model, the increase in sucrose concentration and system viscosity and corresponding bimolecular reaction rates were theoretically estimated. Freezing with a temperature-hold step after ice nucleation negatively influenced particle stability. Ice-nucleation temperature had an impact only at low DNA concentrations. Particle stability was highly reduced during the early part of freezing (<-3°C), especially at low shelf-ramp rates. In this phase, bimolecular reaction rates increase greatly at still low system viscosity. Below a critical temperature (≤∼-18°C) and at high system viscosity, no further particle aggregation occurred. In conclusion, the initial sample viscosity rather than the unfrozen volume and the residence time of particles in the low-viscosity state are the predominant factors in particle stabilization, which likely apply to aggregation in any system.

Probing Pore Connectivity in Random Porous Materials by Scanning Freezing and Melting Experiments

Freezing and melting behavior of nitrobenzene confined to pores of Vycor porous glass with random pore structure has been studied by means of nuclear magnetic resonance cryoporometry. The two transitions are found to reveal a broad hysteresis. To get deeper insight into the mechanisms leading to this phenomenon, scanning experiments exploiting temperature reversal upon incomplete freezing or melting have been performed. In this way, it was found that different cooling and warming histories result in different solid-liquid configurations within the pore system. Further evolution of the thus-attained configurations with changing temperature unveiled important information about the transition paths. In particular, these experiments indicated the occurrence of a pronounced pore blocking for freezing, resulting in freezing transitions via invasion percolation. The melting, on the other hand, is found to occur homogeneously over the whole pore network.

Application of Computational Fluid Dynamics (CFD) Simulations to Spray-Freezing Operations

A 3D computational fluid dynamics (CFD) simulation for spray-freezing in a cold gas has been developed and used to identify design improvements. This model includes an approximate method to model the latent heat of fusion and is able to track particle trajectories. The simulation predictions agreed reasonably well with experimentally measured gas temperatures and droplet velocities. The results suggest that a hollow-cone spray is more effective in cooling the particles uniformly. The CFD simulation suggested that buildup of an icy layer on the cone walls observed experimentally was due to incomplete freezing of larger particles (>100 µm). Collection efficiencies could be raised (from 20 to 57%) by increasing the diameter of the chamber outlet.

Depth-Dependent Spin Dynamics of Canonical Spin-Glass Films: A Low-Energy Muon-Spin-Rotation Study

We have performed depth dependent muon-spin-rotation and -relaxation studies of the dynamics of single layer films of AuFe and CuMn spin glasses as a function of thickness and of its behavior as a function of distance from the vacuum interface (5-70 nm). A significant reduction in the muon-spin relaxation rate as a function of temperature with respect to the bulk material is observed when the muons are stopped near (5-10 nm) the surface of the sample. A similar reduction is observed for the whole sample if the thickness is reduced to, e.g., 20 nm and less. This reflects an increased impurity spin dynamics (incomplete freezing) close to the surface although the freezing temperature is only modestly affected by the dimensional reduction.

185 POSTER Incomplete freezing of liver tumors in cryosurgery

185 POSTER Incomplete freezing of liver tumors in cryosurgery

The origin and significance of debris‐charged ridges at the surface of storglaciären, northern sweden

Storglaciären is a 3.2 km long polythermal valley glacier in northern Sweden. Since 1994 a number of small (1–2 m high) transverse debris‐charged ridges have emerged at the ice surface in the terminal zone of the glacier. This paper presents the results of a combined structural glaciological, isotopic, sedimentological and ground‐penetrating radar (GPR) study of the terminal area of the glacier with the aim of understanding the evolution of these debris‐charged ridges, features which are typical of many polythermal glaciers. The ridges originate from steeply dipping (50–70°) curvilinear fractures on the glacier surface. Here, the fractures contain bands of sediment‐rich ice between 0.2 and 0.4 m thick composed of sandy gravel and diamicton, interpreted as glaciofluvial and basal glacial material, respectively. Structural mapping of the glacier from aerial photography demonstrates that the curvilinear fractures cannot be traced up‐glacier into pre‐existing structures visible at the glacier surface such as crevasses or crevasse traces. These curvilinear fractures are therefore interpreted as new features formed near the glacier snout. Ice adjacent to these fractures shows complex folding, partly defined by variations in ice facies, and partly by disseminated sediment. The isotopic composition (δ18O) of both coarse‐clear and coarse‐bubbly glacier ice facies is similar to the isotopic composition of the interstitial ice in debris layers that forms the debris‐charged ridges, implying that none of these facies have undergone any significant isotopic fractionation by the incomplete freezing of available water. The GPR survey shows strong internal reflections within the ice beneath the debris‐charged ridges, interpreted as debris layers within the glacier. Overall, the morphology and distribution of the fractures indicate an origin by compressional glaciotectonics near the snout, either at the thermal boundary, where active temperate glacier ice is being thrust over cold stagnant ice near the snout, or as a result of large‐scale recumbent folding in the glacier. Further work is required to elucidate the precise role of each of these mechanisms in elevating the basal glacial and glaciofluvial material to the ice surface.

Defect-mediated condensation of a charge density wave

Symmetry, dimensionality, and disorder play a pivotal role in critical phenomena. The atomic imaging capabilities of the scanning tunneling microscope were used to directly visualize the interaction between charge density oscillations and lattice defects in a two-dimensional charge density wave (CDW) system. Point defects act as nucleation centers of the CDW, which, as the temperature is lowered, results in the formation of pinned CDW domains that are separated by atomically abrupt charge boundaries. Incomplete freezing of substitutional disorder at low temperature indicates a novel CDW-mediated hopping of pinning centers.

Natural Sludge Dewatering. II: Thawing-Drying Process in Full-Scale Sludge Freezing Ditches

The thawing and drying process in full-scale sludge freezing ditches was studied. The ditches are located in northern Sweden. The treated sludge derived from a small wastewater-treatment plant with mechanical and chemical treatment. Due to the relatively warm winter of 1994–1995, it became possible to study the effect of incomplete freezing. The results show that frozen and thawed sludge has a porous and humus-like structure, whereas unfrozen sludge has a compact and smeary consistency. The study also shows that incomplete freezing decreases the dewaterability of the sludge, but that the result measured as solid content is satisfactory even if all the sludge is not well frozen. Moreover, the study indicates that the thawing depth could be estimated by a simple equation based on the number of positive degree-days.

Natural Sludge Dewatering. I: Combination of Freezing, Thawing, and Drying as Dewatering Methods

A Swedish full-scale pilot plant employing all-year-round natural sewage sludge dewatering is presented in this paper. The treatment includes three different types of outdoor ditches: a freezing ditch for the winter months, a drying ditch for the early summer months, and a combined drying-freezing-thawing-drying (DFTD) ditch for sludge produced in late summer and early autumn. The test period included two consecutive winters. Complete freezing of the sludge was achieved in the first winter in contrast to the second when incomplete freezing of the sludge occurred due to an unusually warm winter. The dry matter content for the freezing ditch was, at the harvest in August, 30–70 of the first test year. The second test year yielded a sludge with a dry matter content of 20–40 in the freezing ditch. The final dry matter result for the DFTD ditch was 20–40. The summers included were similar to the extent that both late summers were unusually warm, helping to produce sludge of high final dry matter content. The f...

Microscopic approach to the quadrupolar-glass problem.

We report results of the microscopic approach to the quadrupolar-glass problem in mixed molecular crystals formed by linear and spherical molecules. The temperature-concentration analysis of the orientational order parameter derived from NMR spectroscopy data is given on the two-component vector model of site-diluted ortho-para-hydrogen-type mixtures. Two features of the short-range orientational ordering, characteristically different from the spin-glass case, namely, incomplete freezing and residual ordering, respectively, at low and high temperatures are discussed. It is established that the first effect is due to spatial correlated local molecular and reaction fields and the second caused by quadrupolar intrinsic field. A zero-field freezing temperature is estimated taking into account the threshold concentration for quadrupolar glass formation. \textcopyright{} 1996 The American Physical Society.

Factors influencing cryoprotective activity and drug leakage from liposomes after freezing

The effects of freezing and thawing conditions and cryoprotective additives on release of streptomycin from lecithin liposomes following freeze-thaw cycles have been investigated. Drug retention was maximized by slow cooling (approx. 1 degree C min-1). At temperatures between 0 degree and -20 degrees C, the extent of drug loss was time-dependent indicating incomplete freezing; below -45 degrees C this effect was abolished and the system was stable. Osmotic gradients across the liposome membrane during freezing were found to have little effect on drug loss. Marked cryoprotective activity was shown by dimethylsulphoxide, glycerol, alanine and glycinebetaine at concentrations of 3% w/v or less. At this concentration sucrose and mannitol had little activity.

Solute—Water interactions: Do polyhydroxy compounds alter the properties of water?

The interactions between PHCs and water, like those between water molecules, are governed by hydrogen bonding. The details of these interactions are very sensitive to spacings and orientations of the OH groups on the solute molecules. Where different conformers can coexist in solution, the aqueous solvent acts so as to favor the conformer with the largest number of equatorial OH groups, because of their spatial compatibility with water. Because of this compatibility, aqueous solutions of PHCs have the tendency to supersaturation and incomplete freezing, manifestations of the phenomenon known as bound water which is, however, a misnomer. The range of water structure perturbation is probably governed by hydration forces which appear to dominate at solute-solute distances of < 3 nm and which decay exponentially. Although on a single hydrogen bond basis the hydration effects are marginal, they nevertheless are responsible for many macroscopic phenomena, e.g., gel formation, liquid crystals, and protection against dehydration.

A survey of commercial meat block freezing in the United Kingdom and Fire

The results of a survey of meat block freezing in the UK and Eire have been compared with experimental and calculated data. This comparison showed that only 58% of the throughput is being frozen within ±20% of the actual time required. There was little standardization of block size, type of wrapping and carton, freezing and storage conditions. The weight of the majority of blocks was between 25 and 30 kg and 80% of the meat was frozen in cartons between 14.6 and 15.9 cm thick. The survey concludes that refrigeration and meat companies must aim for more realistic freezing times and conditions in order to avoid either incomplete freezing or wasting energy by freezing for longer than necessary.