scholarly journals Experimental investigation and modeling on the dissociation conditions of methane hydrate in clayey silt cores

2021 ◽  
Author(s):  
Changhong Yu ◽  
Baojiang Sun ◽  
Tangyang Yang ◽  
zhiyuan wang ◽  
Yonghai Gao ◽  
...  
Keyword(s):  
Water Activity ◽  
Methane Hydrate ◽  
Equilibrium Temperature ◽  
Activity Measurement ◽  
Efficient Production ◽  
Activity Data ◽  
Clayey Silt ◽  
Step Heating ◽  
Temperature Depression ◽  
Good Agreement

The dissociation conditions of hydrate in clayey silts are of great significance for its efficient production. In this work, the dissociation conditions of methane hydrate in clayey silt cores were experimentally measured by step-heating method. Various cores including quartz powder, montmorillonite and South China Sea sediments were used for investigation. The results showed that the dissociation temperatures of methane hydrate in clayey silt cores depressed compared to bulk hydrate. In comparison to grain size, salinity and lithology had a more significant influence on the equilibrium temperature depression. A water activity meter was used to measure the water activity in clayey silt cores. The influence of salt and minerals on water activity was investigated. By combining the measured water activity data with the Chen-Guo model, a novel water activity measurement method (WAM) for the hydrate dissociation conditions prediction was proposed. The predicted results are in good agreement with the experimental data.

scholarly journals Water activity and activation diameters from hygroscopicity data - Part I: Theory and application to inorganic salts

2005 ◽  
Vol 5 (5) ◽  
pp. 1357-1370 ◽  
Author(s):  
S. M. Kreidenweis ◽  
K. Koehler ◽  
P. J. DeMott ◽  
A. J. Prenni ◽  
C. Carrico ◽  
...  
Keyword(s):  
Sodium Chloride ◽  
Ammonium Sulfate ◽  
Water Activity ◽  
Cloud Condensation Nuclei ◽  
Dry Density ◽  
Published Data ◽  
Activity Data ◽  
Degree Of Dissociation ◽  
Soluble Species ◽  
Good Agreement

Abstract. A method is described that uses particle hygroscopicity measurements, made with a humidified tandem differential mobility analyzer (HTDMA), to determine solution water activity as a function of composition. The use of derived water activity data in computations determining the ability of aerosols to serve as cloud condensation nuclei (CCN) is explored. Results for sodium chloride and ammonium sulfate are shown in Part I. The methodology yields solution water activities and critical dry diameters for ammonium sulfate and sodium chloride in good agreement with previously published data. The approach avoids the assumptions required for application of simplified and modified Köhler equations to predict CCN activity, most importantly, knowledge of the molecular weight and the degree of dissociation of the soluble species. Predictions of the dependence of water activity on the mass fraction of aerosol species are sensitive to the assumed dry density, but predicted critical dry diameters are not.

scholarly journals Water activity and activation diameters from hygroscopicity data – Part I: Theory and application to inorganic salts

2005 ◽  
Vol 5 (1) ◽  
pp. 287-323 ◽  
Author(s):  
S. M. Kreidenweis ◽  
K. Koehler ◽  
P. DeMott ◽  
A. J. Prenni ◽  
C. Carrico ◽  
...  
Keyword(s):  
Sodium Chloride ◽  
Ammonium Sulfate ◽  
Water Activity ◽  
Cloud Condensation Nuclei ◽  
Dicarboxylic Acids ◽  
Dry Density ◽  
Published Data ◽  
Activity Data ◽  
Degree Of Dissociation ◽  
Good Agreement

Abstract. A method is described that uses particle hygroscopicity measurements, made with a humidified tandem differential mobility analyzer (HTDMA), to determine solution water activity as a function of composition. The use of derived water activity data in computations 5 determining the ability of aerosols to serve as cloud condensation nuclei (CCN) is explored. Results for sodium chloride and ammonium sulfate are shown in Part I. In Part II (Koehler et al., to be submitted, 2005), results are reported for several atmospherically-relevant dicarboxylic acids: malonic acid, glutaric acid and oxalic acid. The methodology yields solution water activities and critical dry diameters for 10 ammonium sulfate and sodium chloride in good agreement with previously published data. The approach avoids the assumptions required for application of simplified and modified K¨ohler equations to predict CCN activity, most importantly, knowledge of the molecular weight and the degree of dissociation of the soluble species. Predictions of the dependence of water activity on the mass fraction of aerosol species are sensitive 15 to the assumed dry density, but predicted critical dry diameters are not.

scholarly journals An instrument for quantifying heterogeneous ice nucleation in multiwell plates using infrared emissions to detect freezing

2018 ◽  
Vol 11 (10) ◽  
pp. 5629-5641 ◽  
Author(s):  
Alexander D. Harrison ◽  
Thomas F. Whale ◽  
Rupert Rutledge ◽  
Stephen Lamb ◽  
Mark D. Tarn ◽  
...  
Keyword(s):  
Active Sites ◽  
Freezing Temperature ◽  
Equilibrium Temperature ◽  
Ice Nucleation ◽  
Ir Camera ◽  
Low Concentrations ◽  
Immersion Freezing ◽  
Mixed Phase Clouds ◽  
The City ◽  
Good Agreement

Abstract. Low concentrations of ice-nucleating particles (INPs) are thought to be important for the properties of mixed-phase clouds, but their detection is challenging. Hence, there is a need for instruments where INP concentrations of less than 0.01 L−1 can be routinely and efficiently determined. The use of larger volumes of suspension in drop assays increases the sensitivity of an experiment to rarer INPs or rarer active sites due to the increase in aerosol or surface area of particulates per droplet. Here we describe and characterise the InfraRed-Nucleation by Immersed Particles Instrument (IR-NIPI), a new immersion freezing assay that makes use of IR emissions to determine the freezing temperature of individual 50 µL droplets each contained in a well of a 96-well plate. Using an IR camera allows the temperature of individual aliquots to be monitored. Freezing temperatures are determined by detecting the sharp rise in well temperature associated with the release of heat caused by freezing. In this paper we first present the calibration of the IR temperature measurement, which makes use of the fact that following ice nucleation aliquots of water warm to the ice–liquid equilibrium temperature (i.e. 0 ∘C when water activity is ∼1), which provides a point of calibration for each individual well in each experiment. We then tested the temperature calibration using ∼100 µm chips of K-feldspar, by immersing these chips in 1 µL droplets on an established cold stage (µL-NIPI) as well as in 50 µL droplets on IR-NIPI; the results were consistent with one another, indicating no bias in the reported freezing temperature. In addition we present measurements of the efficiency of the mineral dust NX-illite and a sample of atmospheric aerosol collected on a filter in the city of Leeds. NX-illite results are consistent with literature data, and the atmospheric INP concentrations were in good agreement with the results from the µL-NIPI instrument. This demonstrates the utility of this approach, which offers a relatively high throughput of sample analysis and access to low INP concentrations.

scholarly journals Limitations of Canada’s physical activity data: implications for monitoring trendsThis article is part of a supplement entitled Advancing physical activity measurement and guidelines in Canada: a scientific review and evidence-based foundation for the future of Canadian physical activity guidelines co-published by Applied Physiology, Nutrition, and Metabolism and the Canadian Journal of Public Health. It may be cited as Appl. Physiol. Nutr. Metab. 32(Suppl. 2E) or as Can. J. Public Health 98(Suppl. 2).

2007 ◽  
Vol 32 (S2E) ◽  
pp. S185-S194 ◽  
Author(s):  
Peter T. Katzmarzyk ◽  
Mark S. Tremblay
Keyword(s):  
Public Health ◽  
Physical Activity ◽  
Activity Patterns ◽  
Health Concern ◽  
Activity Measurement ◽  
Clear Understanding ◽  
Activity Data ◽  
Scientific Review ◽  
Physical Activity Guidelines ◽  
Applied Physiology

The current low level of physical activity among Canadians is a dominant public health concern. Accordingly, a clear understanding of physical activity patterns and trends is of paramount importance. Irregularities in monitoring, analysis, and reporting procedures create potential confusion among researchers, policy-makers, and the public alike. The purpose of this paper is to consolidate reported findings and provide a critical assessment of the physical activity surveillance procedures, analytical practices, and reporting protocols currently employed in Canada to provide insights for accurate and consistent interpretation of data, as well as recommendations for future surveillance efforts.

scholarly journals ROCK MAGNETIC AND PALAEOMAGNETIC ANALYSES ON LITHIC FRAGMENTS FROM THE ARCHAEOLOGICAL SITE OF AKROTIRI, SANTORINI

2017 ◽  
Vol 50 (3) ◽  
pp. 1250
Author(s):  
E. Tema
Keyword(s):  
Principal Component Analysis ◽  
Deposition Temperature ◽  
Principal Component ◽  
Archaeological Site ◽  
Equilibrium Temperature ◽  
Component Analysis ◽  
Temperature Data ◽  
Minoan Eruption ◽  
Pumice Fall ◽  
Good Agreement

Rock magnetic and palaeomagnetic analyses on lithic clasts collected from the pumice fall deposited inside the archaeological site of Akrotiri have been applied in order to estimate the deposition temperature of the first volcanic products of the Minoan eruption. A total of 50 lithic clasts have been collected from four different locations inside the excavation of Akrotiri. All samples have been stepwise thermally demagnetized and the obtained results have been interpreted through principal component analysis. The equilibrium temperature obtained after the deposition of the pumice fall varies from sample to sample but generally shows temperatures around 240-280oC. These temperatures are in good agreement with those estimated from lithic clasts from the Megalochori Quarry while they are higher compared with those from ceramic fragments from Akrotiri. The new temperature data presented here show that the pumice fall was still relatively hot when deposited inside the archaeological site and even if it interacted with the buildings, often causing the collapse of roofs, it still remained hot with mean temperature around 260oC.

Modeling the Effect of Water Activity, pH, and Temperature on the Probability of Enterotoxin A Production by Staphylococcus aureus

2016 ◽  
Vol 79 (1) ◽  
pp. 148-152 ◽  
Author(s):  
TIAN DING ◽  
YAN-YAN YU ◽  
CHENG-AN HWANG ◽  
QING-LI DONG ◽  
SHI-GUO CHEN ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Water Activity ◽  
Storage Temperature ◽  
Probability Model ◽  
Toxin Production ◽  
Factors Affecting ◽  
Model Predictions ◽  
And Storage ◽  
Storage Temperatures ◽  
Good Agreement

ABSTRACT The objectives of this study were to develop a probability model of Staphylococcus aureus enterotoxin A (SEA) production as affected by water activity (aw), pH, and temperature in broth and assess its applicability for milk. The probability of SEA production was assessed in tryptic soy broth using 24 combinations of aw (0.86 to 0.99), pH (5.0 to 7.0), and storage temperature (10 to 30°C). The observed probabilities were fitted with a logistic regression to develop a probability model. The model had a concordant value of 97.5% and concordant index of 0.98, indicating that the model satisfactorily describes the probability of SEA production. The model showed that aw, pH, and temperature were significant factors affecting the probability of toxin production. The model predictions were in good agreement with the observed values obtained from milk. The model may help manufacturers in selecting product pH and aw and storage temperatures to prevent SEA production.

WATER ADSORPTION IN CEREAL FOODS AND WATER ACTIVITY MEASUREMENT

1980 ◽  
pp. 97-119 ◽  
Author(s):  
Jean-Louis Multon ◽  
Hervé Bizot ◽  
Bernadette Savet
Keyword(s):  
Water Activity ◽  
Water Adsorption ◽  
Activity Measurement

scholarly journals Sn-Ni-Bi liquid phase thermodynamic properties

2011 ◽  
Vol 9 (1) ◽  
pp. 149-156 ◽  
Author(s):  
Nikolina Milcheva ◽  
Jolanta Romanowska ◽  
Gueorgui Vassilev
Keyword(s):  
Experimental Data ◽  
Liquid Phase ◽  
Thermodynamic Properties ◽  
Binary Systems ◽  
Isopiestic Method ◽  
Miscibility Gap ◽  
Calphad Approach ◽  
Activity Data ◽  
General Solution Model ◽  
Good Agreement

AbstractExperimental data of bismuth activity coefficients at 1773 K were obtained by isopiestic method and compared to calculated values. Thermodynamic properties of the Sn-Ni-Bi liquid phase were estimated by means of the general solution model and by the methods of Kohler. Description of the ternary liquid phase (Gibbs excess energy dependence on the temperature and the composition) was achieved by using available thermodynamic data of the constitutive binary systems (Ni-Bi, Sn-Bi, Sn-Ni). A comparison between calculated quantities and experimental data wasconducted. The present assessment with thermodynamically optimized values of the system Sn-Ni-Bi (obtained by the CALPHAD approach) was in good agreement. The suggested appearance of a liquid phase miscibility gap at high temperatures is in agreement with the experimental bismuth activity data and with the assessed thermochemical functions.

Temperature diagnostics of plasma under optically-thin conditions

2017 ◽  
Vol 31 (31) ◽  
pp. 1750292
Author(s):  
Zhiqiang Zhen ◽  
Jian He
Keyword(s):  
Intensity Ratio ◽  
Equilibrium Temperature ◽  
Spectral Lines ◽  
Ionization Equilibrium ◽  
Average Cell ◽  
Quiet Sun ◽  
Solar Transition Region ◽  
Solar Transition ◽  
Temperature Diagnostics ◽  
Good Agreement

For temperature diagnostics of plasma, using the silicon spectral lines emitted from the solar transition region, under the optically-thin conditions, we discuss temperature diagnostics of the quiet sun in some typical features. For the silicon IV 112.8325 nm and 140.2770 nm spectral lines, using the observed intensity ratio, we calculate the temperature of faint cell center, average cell center, average quiet sun, average network, bright network and very bright network of the quiet sun, and results are in good agreement with those predicted at the [Formula: see text] ionization equilibrium temperature of formation of the silicon IV, and we discuss the temperature when the observed intensity varies from 0.05 to 0.2. This investigation will be significant for temperature diagnostics of plasma under the optically-thin conditions.

Metastable Phenomena in the Thermally Activated Conductivity of Hydrogenated Amorphous Germanium (a-Ge:H)

1993 ◽  
Vol 297 ◽  
Author(s):  
T. DrÜsedau ◽  
D. Pang ◽  
E. Sauvain ◽  
P. Wickboldt ◽  
E.Z. Liu ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Room Temperature ◽  
Equilibrium Temperature ◽  
Cooling Curves ◽  
Thermally Activated ◽  
Heating And Cooling ◽  
Higher Temperature ◽  
Hydrogenated Amorphous ◽  
Hydrogenated Amorphous Germanium ◽  
Good Agreement

The activated conductivity of a-Ge:H between room temperature and 460K was investigated using heating and cooling rates in the range between .001 and 0.1 K/s. A splitting of the cooling curves obtained at different rates, which defines the so called equilibrium temperature TE, is observed mainly between 420 and 430K. Taking into consideration that TE depends on the maximum cooling rate, the present results are in good agreement with those reported by Eberhardt et al. The higher cooling rate always leads to the lower conductivity at any temperature below TE. These effects can be rationalized in terms of a reversible shift of the Fermi level towards midgap at higher temperature. Though reversible changes of the mobility cannot be excluded, they cannot account for our set of experimental data. Rather, changes in the density of electronic states within the mobility gap can explain the effects observed.

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