Supercooled Water and Ice Included in Multilamellar L-α, Distearoyl Phosphatidylcholine in Low-Temperature Regions below 0°C

2000 ◽  
Vol 39 (Part 1, No. 10) ◽  
pp. 5931-5938 ◽  
Author(s):  
Shigenori Utoh ◽  
Nobuaki Okubo
Keyword(s):  
Low Temperature ◽  
Supercooled Water ◽  
Distearoyl Phosphatidylcholine

scholarly journals Supercooling in Dormant Flower Buds of Forsythia, and the Correlation between Pistil Size and Bud Hardiness

1999 ◽  
Vol 17 (2) ◽  
pp. 57-62 ◽  
Author(s):  
Cindy L. Flinn ◽  
Edward N. Ashworth
Keyword(s):  
Low Temperature ◽  
Supercooled Water ◽  
Freeze Tolerance ◽  
Freezing Injury ◽  
Laboratory Studies ◽  
Flower Buds ◽  
Deep Supercooling ◽  
Freeze Stress ◽  
Stem Segments ◽  
Accurate Indicator

Abstract Experiments were conducted to determine if dormant buds of Forsythia taxa exhibit the deep supercooling characteristic. Specimens were collected from thirteen Forsythia taxa including: F. suspensa (Thunb.) Vahl, F. x intermedia cv. Spectabilis (Koehne), F. x intermedia cv. Lynwood (G.E. Peterson), F. europaea (Degen and Baldacci), F. giraldiana (Lingelsh), F. japonica (Makino) var. saxatilis (Nakai), F. mandshurica (Uyeki), F. ovata (Nakai), F. suspensa var. fortunei (Lindl.), F. viridissima (Lindl.), F. x intermedia cv. Arnold Giant (Sax), F. cv. Arnold's Dwarf, and F. cv. Meadowlark (Flint). Buds and attached stem segments, were cooled at 2C (3.6F) per hour, and the temperature at which freezing occurred was determined by thermal analysis. Typically, two distinct freezing events were detected within Forsythia buds. The first freezing event, or high temperature exotherm, occurred just below 0C (32F), while the second freezing event, or low temperature exotherm, occurred between −16C (3.2F) and −28C (−18.4F). The low temperature exotherm corresponded to the freezing of supercooled water within dormant buds, and the detection of low temperature exotherms in buds of all 13 Forsythia taxa indicated that deep supercooling is common among members of this genus. In nine of the 13 Forsythia taxa, the temperature of the low temperature exotherm was an accurate indicator of bud freeze-tolerance (LT50), as determined by a laboratory freeze-stress protocol. The discrepancies noted in the other four taxa were apparently due to the occurrence of field freezing injury prior to conducting these laboratory studies. Evidence indicated a relationship between the extent of supercooling and the size of the pistil in dormant Forsythia buds.

scholarly journals Modelling the effect of condensed-phase diffusion on the homogeneous nucleation of ice in supercooled water

2019 ◽  
Author(s):  
Kathryn Fowler ◽  
Paul Connolly ◽  
David Topping
Keyword(s):  
Low Temperature ◽  
Aerosol Particle ◽  
Condensed Phase ◽  
Homogeneous Nucleation ◽  
Supercooled Water ◽  
Organic Aerosol ◽  
Ice Nucleation ◽  
Cirrus Clouds ◽  
Climate Modelling ◽  
Phase Diffusion

Abstract. In-situ studies of low temperature cirrus clouds have found unexpectedly low ice crystal numbers and consistently high supersaturations, which suggest that our understanding of the freezing mechanisms under these conditions are incomplete. Computational models typically use homogeneous nucleation to predict the ice nucleated in supercooled water. However, the existence of ultra-viscous organic aerosol in the upper troposphere has offered alternative ice nucleation pathways, which have been observed in laboratory studies. The possible effects of aerosol viscosity on cloud micro-physical properties have traditionally been interpreted from simple model simulations of an individual aerosol particle based on equilibration timescales. In this study, to gain insight into the formation of ice in low temperature cirrus clouds, we have developed the first cloud parcel model with bin micro-physics to simulate condensed phase diffusion through each individual aerosol particle. Our findings demonstrate, for the first time, the complex relationship between the rate of ice formation and the viscosity of secondary organic aerosol, driven by two competing effects – which cannot be explained using existing modelling approaches. The first is inhibition of homogeneous ice nucleation below 200 K, due to restricted particle growth and low water volume. The second occurs at temperatures between 200 K and 220 K, where water molecules are slightly more mobile and a layer of water condenses on the outside of the particle, causing an increase in the number of frozen aerosol particles. Our new model provides a basis to better understand and simulate cirrus cloud formation on a larger scale, addressing a major source of uncertainty in climate modelling through the representation of cloud processes.

RELATIONSHIP OF THE LOW TEMPERATURE EXOTHERM TO APPLE AND PEAR PRODUCTION IN NORTH AMERICA

1976 ◽  
Vol 56 (3) ◽  
pp. 493-500 ◽  
Author(s):  
H. A. QUAMME
Keyword(s):  
North America ◽  
Low Temperature ◽  
Cold Hardiness ◽  
Supercooled Water ◽  
Spontaneous Nucleation ◽  
Pyrus Communis L ◽  
Commercial Cultivars ◽  
Malus Pumila Mill ◽  
Apple Production ◽  
Relationship Of

Twig pieces from the current season’s growth of three crabapple (Malus sp.), eight apple (Malus pumila Mill.) and seven year (Pyrus communis L.)cultivars, and limb pieces from 6- to 7-yr-old branches of Starking Red Delicious apple and Bartlett pear were taken during mid-winter and-subjected to a preconditioning treatment to induce maximal cold hardiness. The apple and pear cultivars studied included many of the major commercial cultivars grown in North America. Freezing tests and differential thermal analysis (DTA) were performed on the twig and limb pieces after preconditioning. Xylem was the most susceptible in stem tissue of both preconditioned apple and preconditioned pear. The temperature at which apple and pear xylem of commercial cultivars became injured (−35 to −40 C and −30 to −35 C, respectively) was related to the initiation of the low temperature exotherm on the DTA profile (−37 to −40 C and −33 to −38 C, respectively) and in turn was related to the average annual minimum temperatures at the northern limits of commercial production (−34.4 to −40 C and −28.9 to −34.4 C, respectively). The low temperature exotherm was previously shown to be produced by freezing of supercooled water in the xylem. The spontaneous nucleation temperature of supercooled water in xylem of the cultivars studied appears to be related to the northern limit of pear and apple production in North America.

scholarly journals Supercooling in Floral Buds of `Danka' Black and `Red Lake' Red Currants

1991 ◽  
Vol 116 (6) ◽  
pp. 1030-1034 ◽  
Author(s):  
Michele Warmund ◽  
Milon George ◽  
Fumiomi Takeda
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Floral Morphology ◽  
Thermal Analyses ◽  
Supercooled Water ◽  
Floral Buds ◽  
Red Lake ◽  
The Relationship ◽  
Scanning Electron

Differential thermal analyses (DTA) and freeze viability tests were conducted to investigate the biophysics of freezing in floral buds of `Danka' black (Ribes nigrutn L.) and `Red Lake' red currants [Ribe.s sativum (Rchb.) Syrne] sampled from Nov. 1989 through Mar. 1990. Scanning electron microscopy was also used to determine the relationship between floral morphology and the freezing characteristics of the buds. Floral buds had multiple abrupt low-temperature exotherms (LTEs) and one or two broad LTEs in DTA tests. Abrupt LTEs from DTA were associated with apparent injury to the inflorescence in viability tests. The number of LTEs did not correspond to the number of racemes or flowers per bud, indicating that several flowers froze simultaneously. DTA experiments conducted in Dec. 1990 revealed that the broad exotherm detected between - 14 and - 20C in `Danka' samples resulted from freezing of supercooled water in the outer nonliving region of the periderm of cane tissue attached to the bud.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

Low temperature x-ray microanalysis of frozen-hydrated tobacco leaves

1984 ◽  
Vol 42 ◽  
pp. 284-285
Author(s):  
S. Edith Taylor ◽  
Patrick Echlin ◽  
May McKoon ◽  
Thomas L. Hayes
Keyword(s):  
Low Temperature ◽  
Lemna Minor ◽  
Root Tips ◽  
Tobacco Leaves ◽  
X Ray ◽  
Whole Cells ◽  
Carbon Coated ◽  
The Right ◽  
Beam Currents ◽  
The University

Low temperature x-ray microanalysis (LTXM) of solid biological materials has been documented for Lemna minor L. root tips. This discussion will be limited to a demonstration of LTXM for measuring relative elemental distributions of P,S,Cl and K species within whole cells of tobacco leaves.Mature Wisconsin-38 tobacco was grown in the greenhouse at the University of California, Berkeley and picked daily from the mid-stalk position (leaf #9). The tissue was excised from the right of the mid rib and rapidly frozen in liquid nitrogen slush. It was then placed into an Amray biochamber and maintained at 103K. Fracture faces of the tissue were prepared and carbon-coated in the biochamber. The prepared sample was transferred from the biochamber to the Amray 1000A SEM equipped with a cold stage to maintain low temperatures at 103K. Analyses were performed using a tungsten source with accelerating voltages of 17.5 to 20 KV and beam currents from 1-2nA.

Bulk standards for low-temperature biological x-ray microanalysis

1984 ◽  
Vol 42 ◽  
pp. 282-283
Author(s):  
P. Echlin ◽  
M. McKoon ◽  
E.S. Taylor ◽  
C.E. Thomas ◽  
K.L. Maloney ◽  
...  
Keyword(s):  
Phase Separation ◽  
Low Temperature ◽  
Analytical Method ◽  
Salt Solutions ◽  
Absolute Concentration ◽  
Cooling Process ◽  
X Ray ◽  
The Absolute ◽  
Analytical Procedures ◽  
Electrical Conductors

Although sections of frozen salt solutions have been used as standards for x-ray microanalysis, such solutions are less useful when analysed in the bulk form. They are poor thermal and electrical conductors and severe phase separation occurs during the cooling process. Following a suggestion by Whitecross et al we have made up a series of salt solutions containing a small amount of graphite to improve the sample conductivity. In addition, we have incorporated a polymer to ensure the formation of microcrystalline ice and a consequent homogenity of salt dispersion within the frozen matrix. The mixtures have been used to standardize the analytical procedures applied to frozen hydrated bulk specimens based on the peak/background analytical method and to measure the absolute concentration of elements in developing roots.

Field ion microscopy

1988 ◽  
Vol 46 ◽  
pp. 434-435
Author(s):  
Gert Ehrlich
Keyword(s):  
Low Temperature ◽  
Sample Surface ◽  
Low Pressure ◽  
Radius Of Curvature ◽  
Field Ion Microscopy ◽  
Phosphor Screen ◽  
Ion Microscopy ◽  
Field Ion Microscope

The field ion microscope, devised by Erwin Muller in the 1950's, was the first instrument to depict the structure of surfaces in atomic detail. An FIM image of a (111) plane of tungsten (Fig.l) is typical of what can be done by this microscope: for this small plane, every atom, at a separation of 4.48Å from its neighbors in the plane, is revealed. The image of the plane is highly enlarged, as it is projected on a phosphor screen with a radius of curvature more than a million times that of the sample. Müller achieved the resolution necessary to reveal individual atoms by imaging with ions, accommodated to the object at a low temperature. The ions are created at the sample surface by ionization of an inert image gas (usually helium), present at a low pressure (< 1 mTorr). at fields on the order of 4V/Å.

High-Vacuum Evaporation and a Cryostage to Observe Fractured Yeast

1988 ◽  
Vol 46 ◽  
pp. 256-257
Author(s):  
William P. Wergin ◽  
Eric F. Erbe ◽  
Eugene L. Vigil
Keyword(s):  
Electron Microscope ◽  
Low Temperature ◽  
Standard Specimen ◽  
High Vacuum ◽  
Specimen Holder ◽  
Sputter Coating ◽  
Fresh Frozen ◽  
Gain Access ◽  
Scanning Electron ◽  
Transfer Device

Investigators have long realized the potential advantages of using a low temperature (LT) stage to examine fresh, frozen specimens in a scanning electron microscope (SEM). However, long working distances (W.D.), thick sputter coatings and surface contamination have prevented LTSEM from achieving results comparable to those from TEM freeze etch. To improve results, we recently modified techniques that involve a Hitachi S570 SEM, an Emscope SP2000 Sputter Cryo System and a Denton freeze etch unit. Because investigators have frequently utilized the fractured E face of the plasmalemma of yeast, this tissue was selected as a standard for comparison in the present study.In place of a standard specimen holder, a modified rivet was used to achieve a shorter W.D. (1 to -2 mm) and to gain access to the upper detector. However, the additional height afforded by the rivet, precluded use of the standard shroud on the Emscope specimen transfer device. Consequently, the sample became heavily contaminated (Fig. 1). A removable shroud was devised and used to reduce contamination (Fig. 2), but the specimen lacked clean fractured edges. This result suggested that low vacuum sputter coating was also limiting resolution.

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