Site Characteristics Controlling Airflow in the Shallow Unsaturated Zone in Response to Atmospheric Pressure Changes

2005 ◽  
Vol 22 (1) ◽  
pp. 25-37 ◽  
Author(s):  
Fred D. Tillman ◽  
James A. Smith
Keyword(s):  
Atmospheric Pressure ◽  
Unsaturated Zone ◽  
Site Characteristics ◽  
Pressure Changes

Atmospheric pressure changes in the Arctic from 1801 to 1920

2012 ◽  
Vol 33 (7) ◽  
pp. 1730-1760 ◽  
Author(s):  
Rajmund Przybylak ◽  
Przemysław Wyszyński ◽  
Zsuzsanna Vízi ◽  
Joanna Jankowska
Keyword(s):  
Atmospheric Pressure ◽  
The Arctic ◽  
Pressure Changes

scholarly journals Comparison of bacterial microleakage of three bioactive endodontic sealers in simulated underwater diving and aviation conditions

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Mehdi Dastorani ◽  
Behnam Malekpour ◽  
Mohsen AminSobhani ◽  
Mohammadsadegh Alemrajabi ◽  
Arezoo Mahdian ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Mineral Trioxide Aggregate ◽  
In Vitro Study ◽  
Chi Square ◽  
Custom Made ◽  
Single Cone ◽  
Registration Number ◽  
Chi Square Test ◽  
Pressure Changes

Abstract Background Bacterial microleakage is an important cause of apical periodontitis and endodontic treatment failure. This study aimed to assess the bacterial microleakage of nano-mineral trioxide aggregate (nano-MTA) as a sealer, Endoseal MTA, and GuttaFlow Bioseal sealers in atmospheric pressure, and simulated underwater diving and aviation conditions. Methods In this in vitro, experimental study, 180 extracted single-rooted teeth were cleaned and shaped, and were then randomly divided into three groups for single-cone obturation using Endoseal MTA, GuttaFlow Bioseal, or nano-MTA as a sealer. Each group was then randomly divided into three subgroups, and subjected to ambient atmospheric pressure, 2 atm pressure (to simulate underwater diving), and 0.5 atm pressure (to simulate aviation) using a custom-made pressure chamber. The teeth then underwent microbial leakage test using Streptococcus mutans (S. mutans), and the percentage of samples showing microleakage was recorded for up to 1 month, and analyzed using the Chi-square test. Results The three sealer groups were significantly different regarding bacterial microleakage (P < 0.05). The nano-MTA group showed significantly higher microleakage after 15 days than the other two groups (P = 0.006). The effect of pressure on bacterial microleakage was not significant in any sealer group (P > 0.05). Conclusion Within the limitations of this in vitro study, it may be concluded that single-cone obturation technique using nano-MTA as a sealer results in lower resistance to bacterial microleakage compared with the use of GuttaFlow Bioseal, and Endoseal MTA. Pressure changes in simulated underwater diving and aviation conditions had no significant effect on bacterial microleakage. Trial Registration Number This is not a human subject research.

scholarly journals Atmospheric Pressure Changes

Nature ◽  
1946 ◽  
Vol 158 (4025) ◽  
pp. 914-914
Author(s):  
C. H. B. PRIESTLEY
Keyword(s):  
Atmospheric Pressure ◽  
Pressure Changes

scholarly journals Polymer matrix ferroelectric composites under pressure: Negative electric capacitance and glassy dynamics

2019 ◽  
Vol 42 (9) ◽  
Author(s):  
Szymon Starzonek ◽  
Aleksandra Drozd-Rzoska ◽  
Sylwester J. Rzoska ◽  
Kena Zhang ◽  
Emilia Pawlikowska ◽  
...  
Keyword(s):  
High Pressure ◽  
Relaxation Time ◽  
Barium Strontium Titanate ◽  
Atmospheric Pressure ◽  
Polyvinylidene Difluoride ◽  
Broadband Dielectric Spectroscopy ◽  
Electric Capacitance ◽  
Barium Strontium ◽  
Spectroscopy Studies ◽  
Pressure Changes

Abstract. This report presents the results of high-pressure and broadband dielectric spectroscopy studies in polyvinylidene difluoride (PVDF) and barium strontium titanate (BST) microparticles composites (BST/PVDF). It shows that the Arrhenius behaviour for the temperature-related dynamics under atmospheric pressure is coupled to Super-Arrhenius/Super-Barus isothermal pressure changes of the primary relaxation time. Following these results, an explanation of the unique behaviour of the BST/PVDF composite is proposed. Subsequently, it is shown that when approaching the GPa domain the negative electric capacitance phenomenon occurs. Graphical abstract

scholarly journals The atmospheric excitation of rapid polar motions

1988 ◽  
Vol 128 ◽  
pp. 365-370 ◽  
Author(s):  
T. M. Eubanks ◽  
J. A. Steppe ◽  
J. O. Dickey
Keyword(s):  
Atmospheric Pressure ◽  
Normal Modes ◽  
Geodetic Data ◽  
Atmospheric Excitation ◽  
Pressure Changes

Analysis of data from new, highly accurate, geodetic techniques reveals rapid polar motions. Comparison of the new geodetic data and meteorological excitation estimates shows that the observed rapid polar motions are correlated with atmospheric pressure changes, and that these changes are related to atmospheric normal modes.

Determination of the Efficacy of Sterile Barrier Systems Against Microbial Challenges During Transport and Storage

2009 ◽  
Vol 30 (2) ◽  
pp. 179-183 ◽  
Author(s):  
Hartmut Dunkelberg ◽  
Ulrich Schmelz
Keyword(s):  
Atmospheric Pressure ◽  
Pressure Difference ◽  
Film Material ◽  
Plastic Film ◽  
Exposure Test ◽  
Bacterial Aerosol ◽  
Logarithmic Reduction ◽  
Pressure Changes ◽  
And Storage ◽  
Microbial Challenge

Objective.The sterility assurance level of 10−6 is an established standard that defines the quality of sterile products. The aim of the present study was to develop a method that correlated the results from microbial-barrier testing of flexible sterile barrier systems with the estimated microbial challenge that the package encounters during storage and transport.Methods.The effectiveness of microbial-barrier packaging was determined by the use of an exposure chamber test with 20 periodic atmospheric pressure changes of 50 and 70 hPa. Flexible peel pouches were used as sterile barrier systems. The logarithmic reduction value of a sterile barrier system was calculated on the basis of the experimental results and compared with the logarithmic reduction value required for the microbial challenges to maintain sterility during transport and storage.Results.For pouches made of paper and plastic-film material, a logarithmic reduction value of 5.4 was obtained on the basis of 30 of 99 plates becoming nonsterile after being exposed to a 50 hPa difference in periodic atmospheric pressure changes. For pouches made of paper and plastic-film material, a logarithmic reduction value of 5.2 was obtained on the basis of 48 of 100 plates becoming nonsterile after being exposed to a 70 hPa difference in atmospheric pressure. For pouches made of nonwoven and plastic-film material, logarithmic reduction values of 6.38 (ie, 3 of 99 plates became nonsterile after being exposed to a 50 hPa pressure difference) and 6.07 (ie, 3 of the 99 plates became nonsterile after being exposed to a 70 hPa pressure difference) were obtained. Calculating an expected microbial challenge during transport and storage that requires barrier properties corresponding to a logarithmic reduction value of 5.83 and taking the sterility assurance level into account, we found that only the nonwoven pouches fulfilled the European standard EN 556-1.Conclusions.Using the data obtained in a microbial exposure test with a specified flow rate of a bacterial aerosol, we found that the effectiveness of the sterile barrier system against the actual microbial challenge can be examined and evaluated at the sterility assurance level of 10−6.

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