scholarly journals Effect of Cold Acclimation and Freezing on Spring Dead Spot Severity in Bermudagrass

HortScience ◽  
2005 ◽  
Vol 40 (2) ◽  
pp. 421-423 ◽  
Author(s):  
F.B. Iriarte ◽  
J.D. Fry ◽  
D.L Martin ◽  
T.C. Todd ◽  
N.A. Tisserat
Keyword(s):  
Cold Acclimation ◽  
Disease Severity ◽  
Incubation Temperature ◽  
Freezing Temperature ◽  
Spring Dead Spot ◽  
Freezing Temperatures ◽  
Shoot Mortality

Spring dead spot (SDS), caused by three root-infecting species of Ophiosphaerella, is a destructive disease of bermudagrass (Cynodon spp.L.C. Rich). We tested the effects of incubation temperature and duration, and exposure to decreasing freezing temperatures on bermudagrass shoot survival following inoculation with SDS pathogens. Inoculated plants exposed to freezing temperatures as high as -2 °C following a two month incubation exhibited extensive shoot mortality and had SDS symptoms consistent with those observed in the field. Lowering the freezing temperature from -2 to -8 °C increased disease severity and shoot mortality on noninoculated bermudagrass. Inoculated bermudagrass incubated for 1 month in the greenhouse, then for an additional month at 4 °C had greater shoot mortality following freezing than plants incubated at 25 °C. Although cold acclimation and freezing intensified SDS symptoms, the technique did not reliably distinguish between resistant and susceptible cultivars.

The Spontaneous Freezing Temperatures of Melted Snow and of Small Water Drops

1954 ◽  
Vol 35 (2) ◽  
pp. 52-55 ◽  
Author(s):  
Harry C. Vaughan
Keyword(s):  
Drop Size ◽  
Freezing Temperature ◽  
Bulk Sample ◽  
Bulk Water ◽  
Lower Atmosphere ◽  
Obvious Effect ◽  
Small Water ◽  
Melted Snow ◽  
Freezing Temperatures ◽  
Snow Crystals

The spontaneous freezing temperatures of samples of melted snow collected at hourly intervals during several storms are reported. The freezing temperatures were found to range from −8.3 to −16.8°C. In most cases the freezing temperature remained fairly constant over periods of several hours. Gross variations in the pollution of the lower atmosphere caused no obvious effect on the observed freezing temperatures. It is suggested that the observed freezing temperatures represent the temperatures of initial formation of the snow crystals. A few experiments on the freezing temperatures of small drops were made with a technique such that all drops were formed from the same bulk sample without any danger of contamination. In all cases the freezing temperatures of the drops were well below that of the bulk water. The freezing temperature decreased with decreasing drop size but there was a relatively large variation for a given drop size.

scholarly journals Effects of storage temperature and repeated freeze–thaw cycles on stability of bovine plasma concentrations of haptoglobin and ceruloplasmin

2017 ◽  
Vol 29 (5) ◽  
pp. 738-740 ◽  
Author(s):  
Paulo G. M. A. Martins ◽  
Philipe Moriel ◽  
John D. Arthington
Keyword(s):  
Whole Blood ◽  
Storage Temperature ◽  
Plasma Concentrations ◽  
Freezing Temperature ◽  
Plasma Samples ◽  
Blood Samples ◽  
Freeze Thaw ◽  
Bovine Plasma ◽  
Whole Blood Samples ◽  
Freezing Temperatures

We evaluated the effects of storage temperature (−20 or −80°C) and handling procedure on plasma concentrations of bovine haptoglobin and ceruloplasmin. Within each temperature, whole blood samples were: centrifuged within 2 h of collection and plasma kept frozen until analysis (control); refrigerated at 4°C for 24 h before plasma harvest and freezing (24H); or plasma harvested and frozen within 2 h after collection, but then plasma samples were thawed and refrozen 1 wk (1X), 1 and 2 wk (2X), or 1, 2 and 3 wk (3X) before analyses. Haptoglobin concentrations were greatest at 24H, but similar among remaining treatments. Ceruloplasmin concentrations were not affected by the handling procedures. Storage temperature did not affect haptoglobin concentrations, but ceruloplasmin concentrations decreased when stored at −20 versus −80°C. Except for greater concentrations after 24 h storage at 4°C, haptoglobin concentrations remained stable at either freezing temperature and through freeze–thaw cycles. Ceruloplasmin concentrations decreased after 3 freeze–thaw cycles and required lower freezing temperatures to remain stable.

scholarly journals Ice nucleation efficiency of AgI: review and new insights

2016 ◽  
Vol 16 (14) ◽  
pp. 8915-8937 ◽  
Author(s):  
Claudia Marcolli ◽  
Baban Nagare ◽  
André Welti ◽  
Ulrike Lohmann
Keyword(s):  
Water Adsorption ◽  
Water Saturation ◽  
Experimental Studies ◽  
Freezing Temperature ◽  
Nucleating Agent ◽  
Ice Nucleation ◽  
Lattice Match ◽  
Complex Picture ◽  
Good Lattice ◽  
Freezing Temperatures

Abstract. AgI is one of the best-investigated ice-nucleating substances. It has relevance for the atmosphere since it is used for glaciogenic cloud seeding. Theoretical and experimental studies over the last 60 years provide a complex picture of silver iodide as an ice-nucleating agent with conflicting and inconsistent results. This review compares experimental ice nucleation studies in order to analyze the factors that influence the ice nucleation ability of AgI. The following picture emerges from this analysis: the ice nucleation ability of AgI seems to be enhanced when the AgI particle is on the surface of a droplet, which is indeed the position that a particle takes when it can freely move in a droplet. The ice nucleation by particles with surfaces exposed to air depends on water adsorption. AgI surfaces seem to be most efficient at nucleating ice when they are exposed to relative humidity at or even above water saturation. For AgI particles that are completely immersed in water, the freezing temperature increases with increasing AgI surface area. Higher threshold freezing temperatures seem to correlate with improved lattice matches as can be seen for AgI–AgCl solid solutions and 3AgI·NH4I·6H2O, which have slightly better lattice matches with ice than AgI and also higher threshold freezing temperatures. However, the effect of a good lattice match is annihilated when the surfaces have charges. Also, the ice nucleation ability seems to decrease during dissolution of AgI particles. This introduces an additional history and time dependence for ice nucleation in cloud chambers with short residence times.

scholarly journals An approximation for homogeneous freezing temperature of water droplets

2015 ◽  
Vol 15 (21) ◽  
pp. 31867-31889
Author(s):  
K.-T. O ◽  
R. Wood
Keyword(s):  
Experimental Studies ◽  
Freezing Temperature ◽  
Ice Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Water Droplets ◽  
Wide Range ◽  
The Mean ◽  
Freezing Temperatures ◽  
Homogeneous Freezing

Abstract. In this work, based on the well-known formulae of classical nucleation theory (CNT), the temperature TNc = 1 at which the mean number of critical embryos inside a droplet is unity is derived and proposed as a new approximation for homogeneous freezing temperature of water droplets. Without consideration of time dependence and stochastic nature of the ice nucleation process, the approximation TNc = 1 is able to reproduce the dependence of homogeneous freezing temperature on drop size and water activity of aqueous drops observed in a wide range of experimental studies. We use the TNc = 1 approximation to argue that the distribution of homogeneous freezing temperatures observed in the experiments may largely be explained by the spread in the size distribution of droplets used in the particular experiment. It thus appears that this approximation is useful for predicting homogeneous freezing temperatures of water droplets in the atmosphere.

scholarly journals Metabolic Reprogramming and Its Role in Plant Cold Acclimation

2019 ◽  
Author(s):  
Lisa Fürtauer ◽  
Jakob Weiszmann ◽  
Wolfram Weckwerth ◽  
Thomas Nägele
Keyword(s):  
Low Temperature ◽  
Carbohydrate Metabolism ◽  
Cold Acclimation ◽  
Current Knowledge ◽  
Abiotic Factors ◽  
Freezing Temperature ◽  
Metabolic Reprogramming ◽  
Plant Distribution ◽  
Growth And Yield

Plants have evolved tightly regulated strategies to adapt and acclimate to a changing environment to ensure their survival. Various environmental factors affect plant distribution, growth and yield. Low temperature belongs to those abiotic factors which significantly constrain range boundaries of plant species. Exposing plants to low but non-freezing temperature induces a multigenic processes termed cold acclimation, which finally results in an increased freezing tolerance. Cold acclimation comprises reprogramming of the transcriptome, proteome and metabolome and affects communication and signaling between subcellular organelles. Reprogramming of the central carbohydrate metabolism plays a key role in cold acclimation. This review summarizes current knowledge about the role of carbohydrate metabolism in plant cold acclimation. A focus is laid on subcellular metabolic reprogramming, its thermodynamic constraints under low temperature and mathematical modelling of metabolism.

scholarly journals Heterogeneous freezing of super cooled water droplets in micrometre range-freezing on a chip

2017 ◽  
Author(s):  
Thomas Häusler ◽  
Lorenz Witek ◽  
Laura Felgitsch ◽  
Regina Hitzenberger ◽  
Hinrich Grothe
Keyword(s):  
Active Sites ◽  
Birch Pollen ◽  
Freezing Temperature ◽  
Pure Gold ◽  
Ultrapure Water ◽  
Droplet Sizes ◽  
Temperature Window ◽  
Freezing Temperatures ◽  
Set Up ◽  
Washing Water

Abstract. A new setup to analyse the freezing behaviour of ice nucleation particles (INPs) dispersed in aqueous droplets has been developed with the aim to analyse ensembles of droplets with sizes in the micrometre range, in which INPs are immersed. Major disadvantages of conventional drop-freezing experiments like varying drop sizes or interactions between the water-oil mixture and the INP, were solved by introducing a unique freezing-chip consisting of an etched and sputtered 15 × 15 × 1 mm gold-plated silicon or pure gold film. Using this chip, isolated micrometre-sized droplets can be generated with sizes similar to droplets in real world clouds. The experimental set-up for drop-freezing experiments was revised and improved by establishing automated process control and image evaluation. The new set-up is economical, quick in handling the sample, precise in measurement and the results are more next to real conditions than former approaches. We were able to show the efficiency and accuracy of our setup by comparing measured freezing temperatures of different INPs (Snomax®, K-feldspar, birch pollen (Betula pendula) washing water, juniper pollen suspension (Juniperus communis) and ultrapure water) with already published results. The T50 values of ultrapure water (T50 = −37.2 °C), birch pollen washing water (T50 = −18 °C) and juniper pollen (T50 = −22.7 °C) match the data given in literature. Microcline shows higher freezing temperatures (T50 = −16.4 °C) than literature values from us and others, which can be explained by different preparing/milling parameters. The slightly lower freezing temperature of Snomax® (T50 = −8.9 °C) received by using the freezing-chip, compared to measurements already published, can be explained by different concentrations and droplet sizes. Our measurements and comparisons with the literature data show the important impact of droplet size, INP concentration and number of active sites on the T50 values. Here, the new set-up exhibits its strength in reproducibility and accuracy which is due to the defined and isolated droplets. Finally, it opens a temperature window down to −37 °C for freezing experiments which was not accessible with many former approaches and allows determination of IN also with weak nucleation activity.

scholarly journals Automation and heat transfer characterization of immersion mode spectroscopy for analysis of ice nucleating particles

2017 ◽  
Vol 10 (7) ◽  
pp. 2613-2626 ◽  
Author(s):  
Charlotte M. Beall ◽  
M. Dale Stokes ◽  
Thomas C. Hill ◽  
Paul J. DeMott ◽  
Jesse T. DeWald ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Temperature Measurement ◽  
Measurement Technique ◽  
Freezing Temperature ◽  
Water Volume ◽  
Base Temperature ◽  
Heat Transfer Simulation ◽  
Freezing Temperatures ◽  
Transfer Properties

Abstract. Ice nucleating particles (INPs) influence cloud properties and can affect the overall precipitation efficiency. Developing a parameterization of INPs in global climate models has proven challenging. More INP measurements – including studies of their spatial distribution, sources and sinks, and fundamental freezing mechanisms – must be conducted in order to further improve INP parameterizations. In this paper, an immersion mode INP measurement technique is modified and automated using a software-controlled, real-time image stream designed to leverage optical changes of water droplets to detect freezing events. For the first time, heat transfer properties of the INP measurement technique are characterized using a finite-element-analysis-based heat transfer simulation to improve accuracy of INP freezing temperature measurement. The heat transfer simulation is proposed as a tool that could be used to explain the sources of bias in temperature measurements in INP measurement techniques and ultimately explain the observed discrepancies in measured INP freezing temperatures between different instruments. The simulation results show that a difference of +8.4 °C between the well base temperature and the headspace gas results in an up to 0.6 °C stratification of the aliquot, whereas a difference of +4.2 °C or less results in a thermally homogenous water volume within the error of the thermal probe, ±0.2 °C. The results also show that there is a strong temperature gradient in the immediate vicinity of the aliquot, such that without careful placement of temperature probes, or characterization of heat transfer properties of the water and cooling environment, INP measurements can be biased toward colder temperatures. Based on a modified immersion mode technique, the Automated Ice Spectrometer (AIS), measurements of the standard test dust illite NX are reported and compared against six other immersion mode droplet assay techniques featured in Hiranuma et al. (2015) that used wet suspensions. AIS measurements of illite NX INP freezing temperatures compare reasonably with others, falling within the 5 °C spread in reported spectra. The AIS as well as its characterization of heat transfer properties allows higher confidence in accuracy of freezing temperature measurement, allows higher throughput of sample analysis, and enables disentanglement of the effects of heat transfer rates on sample volumes from time dependence of ice nucleation.

THE FREEZING POINTS OF HIGH PURITY METALS AS PRECISION TEMPERATURE STANDARDS: II. AN INVESTIGATION OF THE FREEZING TEMPERATURES OF ZINC, CADMIUM, AND TIN

1957 ◽  
Vol 35 (9) ◽  
pp. 1086-1106 ◽  
Author(s):  
E. H. McLaren
Keyword(s):  
High Purity ◽  
Freezing Temperature ◽  
Pressure Effects ◽  
Platinum Resistance ◽  
Long Term Stability ◽  
Melting Temperatures ◽  
Three Samples ◽  
Zinc Cadmium ◽  
Precision Temperature ◽  
Freezing Temperatures

An investigation of freezing and melting temperatures with platinum resistance thermometry on high purity zinc, cadmium, and tin has been carried out. Using appropriate techniques, plateaus of essentially constant (< ±0.0001 °C.) temperature with durations of over 1 hour are readily obtained on the cooling curves of these metals. For series of freezes on particular samples, the standard deviations of the respective plateau temperatures were found to be of the order of ±0.0002 °C. It was not possible to distinguish among the plateau temperatures of three samples selected from different distillation batches of New Jersey S.P. zinc. Evidence is presented on the long term stability ([Formula: see text] years) of the plateau freezing temperature of S.P. zinc determined with six standard thermometers. The pressure effects on the freezing temperatures were found to be 0.0043 °C, 0.0062 °C, and 0.0033 °C. per atmosphere for zinc, cadmium, and tin respectively.Thermal analysis of these high purity metals reveals alloy structures and other features associated with nucleation, coring, and annealing phenomena; typical thermal curves are shown.

NOVEL BINARY SPIN GLASS ALLOYS SYNTHESIZED BY MECHANICAL MILLING

1995 ◽  
Vol 09 (03n04) ◽  
pp. 145-162 ◽  
Author(s):  
G. F. ZHOU ◽  
H. BAKKER
Keyword(s):  
Spin Glass ◽  
Mechanical Milling ◽  
Spin Glasses ◽  
Ac Susceptibility ◽  
Freezing Temperature ◽  
High Energy ◽  
Zero Field ◽  
High Concentration ◽  
Freezing Temperatures ◽  
Field Cooling

A few novel binary spin glass alloys have been successfully synthesized by mechanical milling of ordered intermetallic compounds in a high energy ball mill. These alloys are amorphous Co 2 Ge , atomically disordered crystalline GdAl 2, and ball-milled crystalline and amorphous CoZr. The characteristic features of spin glasses are observed; these are (a) the sharp cusps at the freezing temperature T f in both ac and dc magnetic susceptibility versus temperature curves and their peculiar sensitivity to the external magnetic field; (b) the irreversibility, i.e. the difference in value and shape between the magnetisation versus temperature curves after zero field cooling (ZFC) and field cooling (FC) at temperatures below T f and (c) the displacement of the FC magnetisation curve relative to ZFC curve and the corresponding remanence in the FC curve at low temperatures. The freezing temperatures are 41, 65, 35, and 11 K, respectively, which are defined by the sharp cusps in the lowest field ac susceptibility versus temperature curves. The freezing temperatures are lowered with increasing external field. The common feature of these materials is that all are binary alloys with a rather high concentration of the magnetic component. The discovery of these novel spin glasses is of significance because they not only represent new classes of spin glass materials but also demonstrate the use of mechanical milling as a novel technique to synthesize various new materials such as spin glasses. The results are reviewed briefly.

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