Pure Ice Crystals Research Articles

A comprehensive investigation of the use of freeze concentration appro aches for the concentration of fish protein hydrolysates

Fish protein hydrolysates (FPH) are inherently unstable in their liquid form, necessitating either freezing or dewatering for stabilization. Gentle methods such as freeze concentration can be used to remove water, this can be achieved by freezing water in solution by decreasing the bulk temperature below freezing point and separating pure ice crystals from concentrated solution. This approach serves as an alternative to techniques like evaporation and reverse osmosis for concentrating solutions that have high water content, significant nutritional value, and thermolabile compounds. This is crucial as many bioactive compounds degrade when exposed to elevated temperatures. Another notable advantage of this technology is its potential to reduce energy consumption by up to 40% when integrated into the FPH drying process. Although this technology is currently industrialized primarily for juices, it can achieve concentrations of up to 60°Brix and manage viscosities up to 400 mPa.s. Numerous studies have been dedicated to enhancing design and processes, leading to a 35% reduction in the system's capital cost and a 20% reduction in energy consumption. Moreover, freeze concentration can synergize with other concentration techniques, creating more efficient hybrid processes. This review aims to introduce freeze concentration as a superior option for preserving fish protein hydrolysates, enhancing their stability, and maintaining their nutritional and bioactive qualities.

Freeze concentration techniques as alternative methods to thermal processing in dairy manufacturing: A review.

Freeze concentration technology is applied to concentrate liquid foods at low temperatures, thus separating pure ice crystals from the final concentrate solution. This method is an interesting alternative to concentrate food with high water levels and significant nutritional value such as dairy products, since several bioactive compounds are reduced when exposed to elevated temperatures. Considered that, this technique may be a great alternative to concentrating and maintaining both nutritional and sensory characteristics of liquid foods. The present review aims to introduce freeze concentration procedures as an eligible choice for conserving dairy products', also addressing its effects on the dairy matrix. PRACTICAL APPLICATION: This study reports the main techniques of freeze concentration applications in dairy products, to be used both on an industrial and laboratory scale, aiming to improve the nutritional quality of the products obtained.

Amorphous and crystalline ices studied by dielectric spectroscopy.

This work reports on frequency dependent ambient-pressure dielectric measurements of hyperquenched glassy water, ice IV, ice VI, as well as a CO2-filled clathrate hydrate, the latter featuring a chiral water network. The dipolar time scales and the spectral shapes of the loss spectra of these specimens are mapped out and compared with literature data on low-density and high-density amorphous ices as well as on amorphous solid water. There is a trend that the responses of the more highly dense amorphous ices are slightly more dynamically heterogeneous than those of the lower-density amorphous ices. Furthermore, practically all of the amorphous ices, for which broadband dielectric spectra are available, display a curved high-frequency wing. Conversely, the high-frequency flanks of the nominally pure ice crystals including ice V and ice XII can be characterized by an approximate power-law behavior. While the spectral shapes of the nominally pure ices thus yield some hints regarding their amorphicity or crystallinity, a comparison of their time scale appears less distinctive in this respect. In the accessible temperature range, the relaxation times of the crystalline ices are between those of low-density and high-density amorphous ice. Hence, with reference also to previous work, the application of suitable doping currently seems to be the best dielectric spectroscopy approach to distinguish amorphous from crystalline ices.

Effects of spherical inclusions on scattering properties of small ice cloud particles

AbstractThe single‐scattering properties of small ice crystals containing four types of spherical inclusions, ammonium sulfate (NH4)2SO4, ammonium nitrate NH3NO3, air bubbles, and soot, are investigated at 0.65 and 2.13 µm. Small, randomly oriented hexagonal ice columns with spherical inclusions that are randomly distributed with standard gamma size distributions in the columns are considered in the present study. Ice crystals with inclusions of (NH4)2SO4 and NH3NO3 essentially have the same features due to their similar refractive indices. Nonzero scattering matrix elements are sensitive to inclusion type and amount, and show differences between 0.65 and 2.13 µm. The extinction efficiency Qe of small ice crystals at 0.65 µm is near 2.0 and essentially unaffected by variations in inclusion volume, in contrast to strong influences of inclusion amount on Qe at 2.13 µm. The single‐scattering albedo ϖ0 of ice crystals, nearly equal to 1.0, is not affected by inclusions of (NH4)2SO4, NH3NO3, and air bubbles. Soot inclusions strongly affect ϖ0, which decreases to about 0.5 with increasing soot amounts. The asymmetry factor g is substantially affected by (NH4)2SO4, NH3NO3, and soot and the variations in their amounts. Full Stokes parameters of cirrus clouds consisting of uniform hexagonal ice columns with inclusions are computed using a polarized radiative transfer model. Sensitivities of light intensity and polarization of cirrus clouds to types and amounts of inclusions and cirrus cloud optical thicknesses are found to depend on wavelength. The present results suggest that different types of inclusions for small ice crystals should be considered when developing realistic ice crystal optical properties, and that light intensity and polarization of cirrus clouds and their angular distribution features, in the absence of other effects such as cavities and surface roughness, imply the potential for identifying pure ice crystals from those with aerosol inclusions.

Modelling the influence of antifreeze proteins on three-dimensional ice crystal melt shapes using a geometric approach

The melting of pure axisymmetric ice crystals has been described previously by us within the framework of so-called geometric crystal growth . Non-equilibrium ice crystal shapes evolving in the presence of hyperactive antifreeze proteins (hypAFPs) are experimentally observed to assume ellipsoidal geometries (‘lemon’ or ‘rice’ shapes). To analyse such shapes, we harness the underlying symmetry of hexagonal ice I h and extend two-dimensional geometric models to three-dimensions to reproduce the experimental dissolution process. The geometrical model developed will be useful as a quantitative test of the mechanisms of interaction between hypAFPs and ice.

The Endoscopic Cryotherapy of Lung and Bronchial Tumors: A Systematic Review -Can We Expect a New Era of Cryotherapy in Lung Cancer?

The Endoscopic Cryotherapy of Lung and Bronchial Tumors: A Systematic Review -Can We Expect a New Era of Cryotherapy in Lung Cancer?

Optical properties of ice particles in young contrails

The single-scattering properties of four types of ice crystals (pure ice crystals, ice crystals with an internal mixture of ice and black carbon, ice crystals coated with black carbon, and soot coated with ice) in young contrails are investigated at wavelengths 0.65 and 2.13 μm using Mie codes for coated spheres. The four types of ice crystals show differences in their single-scattering properties because of the embedded black carbon whose volume ratio is assumed to be 5%. The bulk-scattering properties of young contrails consisting of the four types of ice crystals are further investigated by averaging their single-scattering properties over a typical ice particle size distribution found in young contrails. The effect of the radiative properties of the four types of ice particles on the Stokes parameters I, Q, U, and V is also investigated for different viewing zenith angles and relative azimuth angles with a solar zenith angle of 30° using a vector radiative transfer model based on the adding-doubling technique. The Stokes parameters at a wavelength of 0.65 μm show pronounced differences for the four types of ice crystals, whereas the counterparts at a wavelength of 2.13 μm show similar variations with the viewing zenith angle and relative azimuth angle. However, the values of the results for the two wavelengths are noticeably different.

Biogas (CO2, O2, dimethylsulfide) dynamics in spring Antarctic fast ice

We studied the temporal variations of CO2, O2, and dimethylsulfide (DMS) concentrations within three environments (sea‐ice brine, platelet ice‐like layer, and underlying water) in the coastal area of Adeélie Land, Antarctica, during spring 1999 before ice breakup. Temporal changes were different among the three environments, while similar temporal trends were observed within each environment at all stations. The underlying water was always undersaturated in O2 (around 85%) and oversaturated in CO2 at the deepest stations. O2 concentrations increased in sea‐ice brine as it melted, reaching oversaturation up to 160% due to the primary production by the sea‐ice algae community (chlorophyll a in the bottom ice reached concentrations up to 160 µg L−1 of bulk ice). In parallel, DMS concentrations increased up to 60 nmol L21 within sea‐ice brine and the platelet ice‐like layer. High biological activity consumed CO2 and promoted the decrease of partial pressure of CO2 (pCO2). In addition, melting of pure ice crystals and calcium carbonate (CaCO3) dissolution promoted the shift from a state of CO2 oversaturation to a state of marked CO2 undersaturation (pCO2 < 30 dPa). On the whole, our results suggest that late spring land fast sea ice can potentially act as a sink of CO2 and a source of DMS for the neighbouring environments, i.e., the underlying water or/and the atmosphere.

Laboratory studies about the interaction of ammonia with ice crystals at temperatures between 0 and −20°C

In laboratory experiments the interactions of ammonia with ice crystals were studied within the temperature range between 0 and −20°C. In a first series of experiments dendritic ice crystals were grown from water vapor in presence of ammonia gas in various concentrations between 4 and 400 ppbv. In a second series of experiments pure ice crystals were exposed to a humidified ammonia–air mixture inside a horizontal flow tube. The influence of temperature, ammonia gas concentration (0.6, 1.5, and 10 ppmv), exposure time, and the presence of impurities such as sulfate on the ammonia uptake by the ice surface was investigated by determining the ammonium content in the melt water of the ice crystals by ion chromatography. During the growth of ice crystals significant amounts of ammonia (around 200 μg/l) were taken up even at small gas concentrations. In contrast, even at high gas concentrations the uptake of ammonia by non-growing ice crystals was lower by approximately one order of magnitude. The presence of sulfate on the ice surface affected an enhanced uptake of ammonia by a factor of 5–10. A model is presented which describes the uptake of ammonia by ice considering the chemical processes occurring in the ice surface layer and simultaneous diffusion of ammonia into bulk ice. Even the increased uptake of ammonia by growing ice is rather small compared to the uptake by water droplets; thus, the major process for scavenging of ammonia from the atmosphere via the ice phase might not be the direct uptake by ice crystals but the riming involving super-cooled droplets containing ammonia.

Laboratory investigation of positive streamer discharges from simulated ice hydrometeors

AbstractPositive streamer discharges have been observed from ice crystals grown from the vapour under controlled temperature and air pressure corresponding to the standard atmosphere and also constant air pressure of 850 hPa. Crystals of size comparable to larger precipitation crystals were grown in a vapour diffusion chamber at various temperatures and pressures, and were subject to electric fields using an in situ electrode assembly. Results show that individual positive streamer discharges can occur at temperatures from near freezing down to at least −38°C when subject to electric fields on the order of 500kV m−1, in contrast to previous reports of continuous positive streamer discharges occurring only at temperatures warmer than −18°C for pure ice crystals. These results suggest that positive streamer discharges can occur on frozen precipitation particles at high altitudes in thunderclouds, given a sufficiently strong electric field. Such discharges may be a necessary element of the lightning‐initiation process. Copyright © 2006 Royal Meteorological Society

A laboratory study of the effects of a kerosene-burner exhaust on ice nucleation and the evaporation rate of ice crystals

Laboratory experiments are described during which the influence of gases and particles from the exhaust of a kerosene burner on microphysical processes were studied. In one experimental investigation the evaporation rates of ice crystals polluted with the kerosene-burner exhaust were compared with the evaporation rates of pure ice crystals. During another experimental investigation the ice nucleating ability of the exhaust particles was studied in terms of the efficiency of the exhaust particles to act as deposition and condensation freezing nuclei, as immersion freezing nuclei, and as contact nuclei. The results of our experiments showed that the evaporation rate of ice crystals polluted with the kerosene-burner exhaust was significantly reduced compared to the evaporation rate of pure ice crystals, implying an increased lifetime of aircraft contrails in comparison to a cloud of pure ice crystals. We also found that the kerosene-burner exhaust particles act as ice nuclei in all studied modes of ice formation at temperatures as high as −20°C, particulary freezing between 20 and 70% of the drops at temperatures warmer than −28°C in the immersion mode. Since the temperature at the level of the contrails is typically below −30°C our result allows the speculation that drop formation at the cruising altitude of air planes is immediately followed by ice crystal formation via heterogeneous nucleation.

Thermal expansion measurements of frozen biological tissues at cryogenic temperatures.

Thermal expansion data are essential for analyses of cryodestruction associated with thermal stresses during cryopreservation protocols as well as during cryosurgery. The present study tests a commonly used hypothesis that the thermal expansion of frozen tissues is similar to that of pure water ice crystals. This study further provides insight into the potential effect of the presence of cryoprotectants on thermal expansion. A new apparatus for thermal strain measurements of frozen biological tissues within a cryogenic temperature range is presented. Results are presented for fresh tissue samples taken from beef muscle, chicken muscle, rabbit muscle, rabbit bone, and pig liver. Pilot studies of the effect of cryoprotectants on thermal expansion are further presented for rabbit muscle immersed in dimethyl sulphoxide (2 mols/l) and glycerol (2 mols/l), and for pig liver perfused with dimethyl sulphoxide (2 mols/l). Thermal expansion of frozen soft biological tissues was found to be similar to that of water ice crystals in the absence of cryoprotectant. Thermal expansion of the rabbit bone was found to be about one half of that of frozen soft tissues. A significant reduction in the thermal expansion at higher temperatures was observed in the presence of cryoprotectants. A rapid change of thermal strain near -100 degrees C was also observed, which is likely to be associated with the glass transition process of the cryoprotectant solutions.

The phase evolution of Young Sea Ice

Sea ice forms as a porous matrix consisting of pure ice crystals in equilibrium with brine. We present an experimental and theoretical study that reveals that the brine expelled by growing sea ice initially remains trapped within the crystalline interstices but that drainage into the underlying water is ultimately triggered abruptly due to the onset of buoyancy‐driven convection. The onset is quantified by a critical porous‐medium Rayleigh number, and we present an empirical marginal stability diagram that defines the transition.

A preliminary comparison of the properties of pure ice and sea ice single crystals

An experimental program is carried out to compare the mechanical properties of single crystals of sea ice and pure ice in order to assess the potential importance of individual crystal properties in determining the properties of polycrystalline sea ice and pure ice. The sea ice and pure ice single crystals were grown by similar techniques. Test specimens formed from these crystals had dimensions of 5×5×20 cm. Unconfined compression tests were run at constant strain rate for different c-axis and a-axis orientations to evaluate the effect of crystallographic orientation on material response. Test results showed that the ultimate stress attained by the pure ice single crystals was almost an order of magnitude higher than that for the sea ice crystals. The pure ice crystals had a steady-state flow stress almost three times as large as the sea ice crystals. The sea ice crystals showed an unexpected deformation mechanism associated with flow of brine pocket material to the crystal boundary. In general the test results indicate that much of the difference in the material properties of polycrystalline pure ice and polycrystalline sea ice may be due to the individual crystal properties rather than just due to intergranular effects.

Über die kristallisation von eis aus salzlösungen

In a supercooled aqueous solution of sodium chloride, growing ice has the shape of needles or dendrites. It is difficult to separate the pure ice crystals from the adherent brine. If a layer of ice is deposited on cool walls, it will grow up opaque as it is filled with small inclusions of brine. Under Special conditions, however, a film of clear ice grows up which does not include any brine. It is shown that a relationship exists from which the maximum growing rate for clear ice can be derived.

Density of Single Crystals of Ice from a Temperate Glacier

AbstractDensity of single crystals of ice from the Mendenhall Glacier near Juneau, Alaska, a temperate glacier, was determined by the hydrostatic weighing method. It was found that the densities of single crystals are slightly but measurably variable from one crystal to another. The values range from a minimum of 0.91712 gm./cm.3 to a maximum of 0.91728 gm./cm.3, when corrected for −3.5° C., for the eight crystals measured. Any imperfections such as Tyndall figures (hexagonal prismatic voids) were immediately evident in the density determinations, and correction for these imperfections give a corrected density essentially the same as that of clear specimens. Two clear crystal aggregate specimens tested had a lower density than the pure single ice crystals. An error computation gives the value of the estimated maximum error of the density determinations as ±2.1×10−5 gm./cm.3.