scholarly journals Intercomparing different devices for the investigation of ice nucleating particles using Snomax<sup>®</sup> as test substance

2015 ◽  
Vol 15 (3) ◽  
pp. 1463-1485 ◽  
Author(s):  
H. Wex ◽  
S. Augustin-Bauditz ◽  
Y. Boose ◽  
C. Budke ◽  
J. Curtius ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Protein Complexes ◽  
Test Substance ◽  
Angle Distribution ◽  
Active Protein ◽  
Experimental Conditions ◽  
Slow Cooling ◽  
Suitable Material ◽  
Temperature Range ◽  
Immersion Freezing

Abstract. Seven different instruments and measurement methods were used to examine the immersion freezing of bacterial ice nuclei from Snomax® (hereafter Snomax), a product containing ice-active protein complexes from non-viable Pseudomonas syringae bacteria. The experimental conditions were kept as similar as possible for the different measurements. Of the participating instruments, some examined droplets which had been made from suspensions directly, and the others examined droplets activated on previously generated Snomax particles, with particle diameters of mostly a few hundred nanometers and up to a few micrometers in some cases. Data were obtained in the temperature range from −2 to −38 °C, and it was found that all ice-active protein complexes were already activated above −12 °C. Droplets with different Snomax mass concentrations covering 10 orders of magnitude were examined. Some instruments had very short ice nucleation times down to below 1 s, while others had comparably slow cooling rates around 1 K min−1. Displaying data from the different instruments in terms of numbers of ice-active protein complexes per dry mass of Snomax, nm, showed that within their uncertainty, the data agree well with each other as well as to previously reported literature results. Two parameterizations were taken from literature for a direct comparison to our results, and these were a time-dependent approach based on a contact angle distribution (Niedermeier et al., 2014) and a modification of the parameterization presented in Hartmann et al. (2013) representing a time-independent approach. The agreement between these and the measured data were good; i.e., they agreed within a temperature range of 0.6 K or equivalently a range in nm of a factor of 2. From the results presented herein, we propose that Snomax, at least when carefully shared and prepared, is a suitable material to test and compare different instruments for their accuracy of measuring immersion freezing.

scholarly journals Intercomparing different devices for the investigation of ice nucleating particles using Snomax<sup>®</sup> as test substance

2014 ◽  
Vol 14 (16) ◽  
pp. 22321-22384 ◽  
Author(s):  
H. Wex ◽  
S. Augustin-Bauditz ◽  
Y. Boose ◽  
C. Budke ◽  
J. Curtius ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Protein Complexes ◽  
Test Substance ◽  
Angle Distribution ◽  
Active Protein ◽  
Experimental Conditions ◽  
Slow Cooling ◽  
Suitable Material ◽  
Temperature Range ◽  
Immersion Freezing

Abstract. Seven different instruments and measurement methods were used to examine the immersion freezing of bacterial ice nuclei from Snomax® (hereafter Snomax), a product containing ice active protein complexes from non-viable Pseudomonas syringae bacteria. The experimental conditions were kept as similar as possible for the different measurements. Of the participating instruments, some examined droplets which had been made from suspensions directly, and the others examined droplets activated on previously generated Snomax particles, with particle diameters of mostly a few hundred nanometers and up to a few micrometers in some cases. Data were obtained in the temperature range from −2 to −38 °C, and it was found that all ice active protein complexes were already activated above −12 °C. Droplets with different Snomax mass concentrations covering 10 orders of magnitude were examined. Some instruments had very short ice nucleation times down to below 1 s, while others had comparably slow cooling rates around 1 K min−1. Displaying data from the different instruments in terms of numbers of ice active protein complexes per dry mass of Snomax, nm, showed that within their uncertainty the data agree well with each other as well as to previously reported literature results. Two parameterizations were taken from literature for a direct comparison to our results, and these were a time dependent approach based on a contact angle distribution Niedermeier et al. (2014) and a modification of the parameterization presented in Hartmann et~al.~(2013) representing a time independent approach. The agreement between these and the measured data were good, i.e. they agreed within a temperature range of 0.6 K or equivalently a range in nm of a factor of 2. From the results presented herein, we propose that Snomax, at least when carefully shared and prepared, is a suitable material to test and compare different instruments for their accuracy of measuring immersion freezing.

scholarly journals Immersion freezing of ice nucleation active protein complexes

2013 ◽  
Vol 13 (11) ◽  
pp. 5751-5766 ◽  
Author(s):  
S. Hartmann ◽  
S. Augustin ◽  
T. Clauss ◽  
H. Wex ◽  
T. Šantl-Temkiv ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Pseudomonas Syringae ◽  
Nucleation Rate ◽  
Protein Complex ◽  
Protein Complexes ◽  
Ice Nucleation ◽  
Minor Importance ◽  
Class Iii ◽  
Temperature Range ◽  
Immersion Freezing

Abstract. Utilising the Leipzig Aerosol Cloud Interaction Simulator (LACIS), the immersion freezing behaviour of droplet ensembles containing monodisperse particles, generated from a Snomax™ solution/suspension, was investigated. Thereto ice fractions were measured in the temperature range between −5 °C to −38 °C. Snomax™ is an industrial product applied for artificial snow production and contains Pseudomonas syringae} bacteria which have long been used as model organism for atmospheric relevant ice nucleation active (INA) bacteria. The ice nucleation activity of such bacteria is controlled by INA protein complexes in their outer membrane. In our experiments, ice fractions increased steeply in the temperature range from about −6 °C to about −10 °C and then levelled off at ice fractions smaller than one. The plateau implies that not all examined droplets contained an INA protein complex. Assuming the INA protein complexes to be Poisson distributed over the investigated droplet populations, we developed the CHESS model (stoCHastic modEl of similar and poiSSon distributed ice nuclei) which allows for the calculation of ice fractions as function of temperature and time for a given nucleation rate. Matching calculated and measured ice fractions, we determined and parameterised the nucleation rate of INA protein complexes exhibiting class III ice nucleation behaviour. Utilising the CHESS model, together with the determined nucleation rate, we compared predictions from the model to experimental data from the literature and found good agreement. We found that (a) the heterogeneous ice nucleation rate expression quantifying the ice nucleation behaviour of the INA protein complex is capable of describing the ice nucleation behaviour observed in various experiments for both, Snomax™ and P. syringae bacteria, (b) the ice nucleation rate, and its temperature dependence, seem to be very similar regardless of whether the INA protein complexes inducing ice nucleation are attached to the outer membrane of intact bacteria or membrane fragments, (c) the temperature range in which heterogeneous droplet freezing occurs, and the fraction of droplets being able to freeze, both depend on the actual number of INA protein complexes present in the droplet ensemble, and (d) possible artifacts suspected to occur in connection with the drop freezing method, i.e., the method frequently used by biologist for quantifying ice nucleation behaviour, are of minor importance, at least for substances such as P. syringae, which induce freezing at comparably high temperatures. The last statement implies that for single ice nucleation entities such as INA protein complexes, it is the number of entities present in the droplet population, and the entities' nucleation rate, which control the freezing behaviour of the droplet population. Quantities such as ice active surface site density are not suitable in this context. The results obtained in this study allow a different perspective on the quantification of the immersion freezing behaviour of bacterial ice nucleation.

scholarly journals Immersion freezing of ice nucleating active protein complexes

2012 ◽  
Vol 12 (8) ◽  
pp. 21321-21353 ◽  
Author(s):  
S. Hartmann ◽  
S. Augustin ◽  
T. Clauss ◽  
J. Voigtländer ◽  
D. Niedermeier ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Nucleation Rate ◽  
Protein Complex ◽  
Protein Complexes ◽  
Ice Nucleation ◽  
Temperature Range ◽  
Immersion Freezing ◽  
New Perspective ◽  
Lower Temperature ◽  
Heterogeneous Ice Nucleation

Abstract. Biological particles, e.g. bacteria and their Ice Nucleating Active (INA) protein complexes, might play an important role for the ice formation in atmospheric mixed-phase clouds. Therefore, the immersion freezing behavior of INA protein complexes generated from a SnomaxTM solution/suspension was investigated as function of temperature in a range of −5 °C to −38 °C at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). The immersion freezing of droplets containing small numbers of INA protein complexes occurs in a temperature range of −7 °C and −10 °C. The experiments performed in the lower temperature range, where all droplets freeze which contain at least one INA protein complex, are used to determine the average number of INA protein complexes present, assuming that the INA protein complexes are Poisson distributed over the droplet ensemble. Knowing the average number of INA protein complexes, the heterogeneous ice nucleation rate and rate coefficient of a single INA protein complex is determined by using the newly-developed CHESS model (stoCHastic model of idEntical poiSSon distributed ice nuclei). Therefore, we assume the ice nucleation process to be of stochastic nature, and a parameterization of the INA protein complex's nucleation rate. Analyzing the results of immersion freezing experiments from literature (SnomaxTM and Pseudomonas syringae bacteria), to results gained in this study, demonstrates that first, a similar temperature dependence of the heterogeneous ice nucleation rate for a single INA protein complex was found in all experiments, second, the shift of the ice fraction curves to higher temperatures can be explained consistently by a higher average number of INA protein complexes being present in the droplet ensemble, and finally the heterogeneous ice nucleation rate of one single INA protein complex might be also applicable for intact Pseudomonas syringae bacteria cells. The results obtained in this study allow a new perspective on the interpretation of immersion freezing experiments considering INA protein complexes and the derived simple parameterization of the heterogeneous ice nucleation rate can be used in cloud resolving models for studying the effect of bacteria induced ice nucleation.

scholarly journals Heterogeneous ice nucleation activity of bacteria: new laboratory experiments at simulated cloud conditions

2008 ◽  
Vol 5 (5) ◽  
pp. 1425-1435 ◽  
Author(s):  
O. Möhler ◽  
D. G. Georgakopoulos ◽  
C. E. Morris ◽  
S. Benz ◽  
V. Ebert ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Cloud Condensation Nuclei ◽  
Bacterial Species ◽  
Ice Nucleation ◽  
Cloud Chamber ◽  
Bacterial Cells ◽  
Active Fraction ◽  
Temperature Range ◽  
Spray Droplets ◽  
Immersion Freezing

Abstract. The ice nucleation activities of five different Pseudomonas syringae, Pseudomonas viridiflava and Erwinia herbicola bacterial species and of Snomax™ were investigated in the temperature range between −5 and −15°C. Water suspensions of these bacteria were directly sprayed into the cloud chamber of the AIDA facility of Forschungszentrum Karlsruhe at a temperature of −5.7°C. At this temperature, about 1% of the Snomax™ cells induced immersion freezing of the spray droplets before the droplets evaporated in the cloud chamber. The living cells didn't induce any detectable immersion freezing in the spray droplets at −5.7°C. After evaporation of the spray droplets the bacterial cells remained as aerosol particles in the cloud chamber and were exposed to typical cloud formation conditions in experiments with expansion cooling to about −11°C. During these experiments, the bacterial cells first acted as cloud condensation nuclei to form cloud droplets. Then, only a minor fraction of the cells acted as heterogeneous ice nuclei either in the condensation or the immersion mode. The results indicate that the bacteria investigated in the present study are mainly ice active in the temperature range between −7 and −11°C with an ice nucleation (IN) active fraction of the order of 10−4. In agreement to previous literature results, the ice nucleation efficiency of Snomax™ cells was much larger with an IN active fraction of 0.2 at temperatures around −8°C.

scholarly journals Two generations of exsolution lamellae in pyroxene from Asuka 09545: Clues to the thermal evolution of silicates in mesosiderite

2019 ◽  
Vol 104 (11) ◽  
pp. 1663-1672
Author(s):  
Lidia Pittarello ◽  
Seann McKibbin ◽  
Akira Yamaguchi ◽  
Gang Ji ◽  
Dominique Schryvers ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
Parent Body ◽  
Cooling History ◽  
Equilibrium Conditions ◽  
Slow Cooling ◽  
Temperature Range ◽  
Fine Grained ◽  
Two Generations ◽  
Mantle Component ◽  
The Antarctic

Abstract Mesosiderite meteorites consist of a mixture of crustal basaltic or gabbroic material and metal. Their formation process is still debated due to their unexpected combination of crust and core materials, possibly derived from the same planetesimal parent body, and lacking an intervening mantle component. Mesosiderites have experienced an extremely slow cooling rate from ca. 550 °C, as recorded in the metal (0.25–0.5 °C/Ma). Here we present a detailed investigation of exsolution features in pyroxene from the Antarctic mesosiderite Asuka (A) 09545. Geothermobarometry calculations, lattice parameters, lamellae orientation, and the presence of clinoenstatite as the host were used in an attempt to constrain the evolution of pyroxene from 1150 to 570 °C and the formation of two generations of exsolution lamellae. After pigeonite crystallization at ca. 1150 °C, the first exsolution process generated the thick augite lamellae along (100) in the temperature interval 1000–900 °C. By further cooling, a second order of exsolution lamellae formed within augite along (001), consisting of monoclinic low-Ca pyroxene, equilibrated in the temperature range 900–800 °C. The last process, occurring in the 600–500 °C temperature range, was likely the inversion of high to low pigeonite in the host crystal, lacking evidence for nucleation of orthopyroxene. The formation of two generations of exsolution lamellae, as well as of likely metastable pigeonite, suggest non-equilibrium conditions. Cooling was sufficiently slow to allow the formation of the lamellae, their preservation, and the transition from high to low pigeonite. In addition, the preservation of such fine-grained lamellae limits long-lasting, impact reheating to a peak temperature lower than 570 °C. These features, including the presence of monoclinic low-Ca pyroxene as the host, are reported in only a few mesosiderites. This suggests a possibly different origin and thermal history from most mesosiderites and that the crystallography (i.e., space group) of low-Ca pyroxene could be used as parameter to distinguish mesosiderite populations based on their cooling history.

Thermopolarization Phenomena in the Temperature Range of Glass Transition of Amorphous Polydiethylsiloxane

2018 ◽  
Vol 773 ◽  
pp. 15-19
Author(s):  
I.V. Popov
Keyword(s):  
Glass Transition ◽  
Amorphous Phase ◽  
Elastic State ◽  
Structural Units ◽  
Flexible Chain ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Maximum Value ◽  
Temperature Dependences ◽  
Amorphous Phase Formation

The transition from the glass to the highly elastic state in polydiethylsiloxane (PDES) is not reflected on the temperature dependences of the relative permittivity, the dielectric loss tangent, and the specific volumetric electrical conductivity. But, the peak of the current of thermostimulated depolarization (TSD) is fixed in the temperature range of the transition to the highly elastic state. The peak of the TSD current at T ~ 130K indicates a continuous amorphous phase formation in the experimental conditions. The maximum value of the TSD current directly depends on the content of the amorphous phase in the polymer. The cooling of the polymer in an electric field reduces the magnitude of the peak. Exposure in the mesophase leads to an almost complete absence of thermopolarization effects near the glass transition temperature. This peak of the TSD current in the absence of preliminary polarization is characteristic, presumably, only for flexible-chain polymers where structural units have pyroelectric properties. Under certain conditions, PDES demonstrates itself as an active dielectric in the temperature range of 90 - 180K.

scholarly journals The influence of pressure on the spontaneous ignition of inflammable gas-air mixtures - IV—methane-, ethane-, and propane-air mixtures

1936 ◽  
Vol 154 (881) ◽  
pp. 95-112 ◽  
Keyword(s):  
Critical Pressure ◽  
Spontaneous Ignition ◽  
Lower Range ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Limited Temperature ◽  
Tentative Hypothesis ◽  
Temperature Ranges ◽  
Higher Temperature ◽  
Temperature And Pressure

In previous papers the results of investigations into the influence of varying initial pressures up to 15-20 atmospheres on the spontaneous ignition of mixtures with air of butane, iso -butane, pentane, and hexane were described. On the attainment of a critical pressure, which varied both with the hydrocarbon concerned and the composition of its mixture with air, the ignition points were always found to fall sharply from a higher temperature range above 500°C to a lower range at about 300°C. At pressures just exceeding the critical transition pressures ignition occurred at first only within limited temperature ranges which widened and ultimately merged with increasing pressure. The striking relationship between the behaviours of the hydrocarbons referred to under the experimental conditions and their “knocking” propensities in an engine was also indicated. While the data available were inadequate for drawing any final con­clusion as to the character of the phenomena referred to, a tentative hypothesis was advanced that while ignition in the higher temperature range pertains mainly to the thermal decomponents of intermedially formed compounds, ignition in the lower system occurs when temperature and pressure conditions favour the survival and further oxidation of such bodies, particularly aldehydes.

Low-temperature storage of mammalian spermatozoa

1957 ◽  
Vol 147 (929) ◽  
pp. 498-508 ◽  
Keyword(s):  
Critical Temperature ◽  
Low Temperatures ◽  
Freezing Point ◽  
Egg Yolk ◽  
Slow Cooling ◽  
Temperature Range ◽  
Low Temperature Storage ◽  
The Media ◽  
Extent Of Damage ◽  
Mammalian Spermatozoa

Experiments in this and other countries on the preservation of spermatozoa at very low temperatures have shown that no mammalian spermatozoa so far examined survive freezing when they are cooled ultra-rapidly from temperatures above freezing point to temperatures of — 79° C or below. Slow cooling and the addition of glycerol to the media in which the spermatozoa are suspended, however, permits survival of the spermatozoa of many species. In different animals, there are marked variations in the resistance of their spermatozoa to freezing and the proportion of spermatozoa which can be revived from very low temperatures may be influenced both by the concentration of glycerol added to the semen and by the composition of the diluting fluid. In experiments with the spermatozoa of the bull, ram, stallion and boar it has been found that during slow cooling to — 79° C there is a critical temperature range between — 15 and — 25° C at which the greatest amount of damage occurs. The rate at which the capacity for motility of the spermatozoa is destroyed within this critical temperature range is considerably reduced by allowing the spermatozoa to stand at 2° C in contact with a medium containing egg yolk and glycerol for 18 h before freezing. The extent of damage in the critical temperature range may also be reduced by cooling the specimens at a rate of 0-25 to 0-5° per second between —15 and —25° C.

The Rate-Constant for the Recombination of Methyl Radicals

1986 ◽  
Vol 39 (8) ◽  
pp. 1257 ◽  
Author(s):  
NL Arthur ◽  
JC Biordi
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Rate Constant ◽  
Rate Constants ◽  
The Other ◽  
Methyl Radicals ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Best Value ◽  
Limiting Value

Rate constants for the recombination of CH3 radicals have been measured by means of the rotating sector technique in the temperature range 373- 463 K, and at a pressure of 30 Torr . CH3 radicals were produced by the photolysis of acetone, and the experimental data were fitted to sector curves generated from Shepp's theory. The results give kb = (2.81�0.22)×1013 cm3 mol-1 s-1, which, under the chosen experimental conditions, is close to its high-pressure limiting value. A comparison is made with the other values of the rate constant reported in the literature, and a best value is suggested.

scholarly journals Studies on Pyrolysis Kinetic of Newspaper Wastes in a Packed Bed Reactor: Experiments, Modeling, and Product Characterization

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Aparna Sarkar ◽  
Sudip De Sarkar ◽  
Michael Langanki ◽  
Ranjana Chowdhury
Keyword(s):  
Packed Bed ◽  
Nitrogen Atmosphere ◽  
Packed Bed Reactor ◽  
Experimental Conditions ◽  
Deactivation Model ◽  
Temperature Range ◽  
Product Characterization ◽  
Kinetic Rate Constants ◽  
Ft Ir ◽  
Pyrolysis Kinetic

Newspaper waste was pyrolysed in a 50 mm diameter and 640 mm long reactor placed in a packed bed pyrolyser from 573 K to 1173 K in nitrogen atmosphere to obtain char and pyro-oil. The newspaper sample was also pyrolysed in a thermogravimetric analyser (TGA) under the same experimental conditions. The pyrolysis rate of newspaper was observed to decelerate above 673 K. A deactivation model has been attempted to explain this behaviour. The parameters of kinetic model of the reactions have been determined in the temperature range under study. The kinetic rate constants of volatile and char have been determined in the temperature range under study. The activation energies 25.69 KJ/mol, 27.73 KJ/mol, 20.73 KJ/mol and preexponential factors 7.69 min−1, 8.09 min−1, 0.853 min−1of all products (solid reactant, volatile, and char) have been determined, respectively. A deactivation model for pyrolysis of newspaper has been developed under the present study. The char and pyro-oil obtained at different pyrolysis temperatures have been characterized. The FT-IR analyses of pyro-oil have been done. The higher heating values of both pyro-products have been determined.

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