scholarly journals Pluto’s Atmosphere in Plateau Phase Since 2015 from a Stellar Occultation at Devasthal

2021 ◽  
Vol 923 (2) ◽  
pp. L31
Author(s):  
Bruno Sicardy ◽  
Nagarhalli M. Ashok ◽  
Anandmayee Tej ◽  
Ganesh Pawar ◽  
Shishir Deshmukh ◽  
...  
Keyword(s):  
Excellent Agreement ◽  
Surface Pressure ◽  
Transport Model ◽  
Imaging Systems ◽  
Plateau Phase ◽  
Pressure Decrease ◽  
Stellar Occultation ◽  
Volatile Transport

Abstract A stellar occultation by Pluto was observed on 2020 June 6 with the 1.3 m and 3.6 m telescopes located at Devasthal, Nainital, India, using imaging systems in the I and H bands, respectively. From this event, we derive a surface pressure for Pluto’s atmosphere of p surf = 12.23 − 0.38 + 0.65 μbar. This shows that Pluto’s atmosphere has been in a plateau phase since mid-2015, a result which is in excellent agreement with the Pluto volatile transport model of Meza et al. This value does not support the pressure decrease reported by independent teams, based on occultations observed in 2018 and 2019 by Young et al. and Arimatsu et al., respectively.

Physical Properties and Hydrostatic Function of the Swimbladder of Herring (Clupea harengus L.)

1962 ◽  
Vol 19 (4) ◽  
pp. 635-656 ◽  
Author(s):  
Vivien M. Brawn
Keyword(s):  
Surface Pressure ◽  
Sea Water ◽  
Gas Production ◽  
Clupea Harengus ◽  
Gas Release ◽  
Pressure Reduction ◽  
Neutral Buoyancy ◽  
Reduced Pressure ◽  
Pressure Decrease ◽  
Mean Pressure

Living herring at the depth of adjustment had a mean sinking factor of 1003, density of 1.026 g/ml, relative sensitivity of 0.8 and percentage swimbladder volume of 4.2. Neutral buoyancy was attained at a mean pressure reduction of 5.5% from the adjusted pressure. Swimbladder gas was under an average excess pressure of 1 cm Hg. Gas was released through the posterior swimbladder duct during pressure reduction in 105 out of 109 herring observed. Gas release occurred at a mean pressure decrease of 6% in rapidly swimming herring, at 32% in moderately swimming fish and brought the herring to within 19% of perfect adjustment to a new reduced pressure within half an hour. Herring could compensate for their increased buoyancy during pressure decrease until this was reduced by gas release. Decompression at rates up to 123 cm Hg/sec was not fatal after 16 hours at the greater pressure. No recovery of buoyancy after gas loss occurred in herring held 24 hours in running sea water even if fine air bubbles were present. Recovery occurred if these fish had access to the surface. Gas production by bacterial activity as a means of restoring buoyancy was not established. Herring responded to rapid pressure increases by swimming upwards. They could compensate for their increased density following pressure increase of 300% and survive increases of 430%. Herring from 10 to 25 feet depth at sea were positively buoyant at surface pressure when anaesthetized. Thus in nature herring are adjusted to pressures greater than surface pressure. It is suggested that they take in air when feeding at the surface at night and slowly pass this to the swimbladder on returning to greater depths by day.

Analytical Solutions for a Family of Gaussian Impinging Jets

2008 ◽  
Vol 75 (2) ◽  
Author(s):  
Zhuyun Xu ◽  
Horia Hangan ◽  
Pei Yu
Keyword(s):  
Boundary Layer ◽  
Excellent Agreement ◽  
Surface Pressure ◽  
Analytical Solutions ◽  
Reynolds Numbers ◽  
Impinging Jets ◽  
Experimental Results ◽  
Jet Flows ◽  
Pressure Distributions ◽  
Circular Plane

Various types of impinging jet flows are analytically modeled using inviscid free Gaussian jet solutions superimposed with experimentally fitted boundary layer models. Improved (more robust) and simplified solutions to existing models are defined. Velocity profiles, surface pressure distributions, and streamline plots are calculated for circular, plane, and annular impinging jets. The models show excellent agreement with existing experimental results in both laminar and turbulent conditions and for different Reynolds numbers.

scholarly journals Lower atmosphere and pressure evolution on Pluto from ground-based stellar occultations, 1988–2016

2019 ◽  
Vol 625 ◽  
pp. A42 ◽  
Author(s):  
E. Meza ◽  
B. Sicardy ◽  
M. Assafin ◽  
J. L. Ortiz ◽  
T. Bertrand ◽  
...  
Keyword(s):  
Transport Model ◽  
Lower Atmosphere ◽  
Seasonal Effects ◽  
Orbital Eccentricity ◽  
Temperature Variations ◽  
New Horizons ◽  
Large Factor ◽  
Stellar Occultations ◽  
Density Values ◽  
Volatile Transport

Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015. Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 μbar to 10 nbar). Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4–7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere.

scholarly journals Study of Pluto’s atmosphere based on 2020 stellar occultation light curve results

2021 ◽  
Vol 653 ◽  
pp. L7
Author(s):  
Atila Poro ◽  
Farzaneh Ahangarani Farahani ◽  
Majid Bahraminasr ◽  
Maryam Hadizadeh ◽  
Fatemeh Najafi Kodini ◽  
...  
Keyword(s):  
Light Curve ◽  
Ray Tracing ◽  
Atmospheric Pressure ◽  
Transport Model ◽  
Atmospheric Model ◽  
Atmospheric Parameters ◽  
Sublimation Process ◽  
Stellar Occultation ◽  
Rapid Pressure ◽  
Pressure Evolution

On 6 June 2020, Pluto’s stellar occultation was successfully observed at a ground-based observatory in Iran, and Pluto’s atmospheric parameters were investigated. We used an atmospheric model of Pluto, assuming a spherical and transparent pure N2 atmosphere. Using ray-tracing code, the stellar occultation light curve was satisfactorily fit to this model. We found that Pluto’s atmospheric pressure at the reference radius of 1215 km was 6.72 ± 0.48 μbar in June 2020. Our estimated pressure shows a continuation of the pressure increase trend observed since 1988 and does not confirm the rapid pressure decrease tentatively reported in 2019. The pressure evolution is consistent with a seasonal transport model. We conclude that the N2 sublimation process from Sputnik Planitia is continuing. This study’s result is shown on the diagram of the annual evolution of atmospheric pressure.

Modeling of external and internal concentration polarization effect on flux behaviour of forward osmosis

2008 ◽  
Vol 8 (5) ◽  
pp. 533-539 ◽  
Author(s):  
C. H. Tan ◽  
H. Y. Ng
Keyword(s):  
Excellent Agreement ◽  
Polarization Effect ◽  
Concentration Polarization ◽  
Transport Model ◽  
Water Flux ◽  
Forward Osmosis ◽  
Selective Membrane ◽  
Internal Concentration ◽  
Internal Concentration Polarization ◽  
The Impact

The forward osmosis process has recently gained more interest from researchers and is being viewed as an alternative to various membrane processes. The primary challenge in developing the process is the severity of both external and internal concentration polarizations, which significantly reduce the water flux across the highly selective membrane. This study investigates the impact of concentration polarization on flux behaviour. A model adopted from the boundary layer concept was used to describe the external concentration polarization effect. A previously developed model for the internal concentration polarization was further improved from the governing convective-diffusion equations, to achieve a better transport model that was in excellent agreement with experimental flux data. Laboratory experiments were carried out to account for both the external and internal concentration polarization and the associated water flux was verified with the improved models. Results showed excellent agreement for both models, which were used to describe external and internal concentration polarization, and these modified models were more accurate than previously used models.

Digital imaging and quantitative image analysis of polymer blends

1996 ◽  
Vol 54 ◽  
pp. 170-171
Author(s):  
Xiao Zhang
Keyword(s):  
Digital Imaging ◽  
Imaging Techniques ◽  
Imaging Systems ◽  
Polymer Science ◽  
Key Factors ◽  
Multiple Imaging ◽  
Quantitative Image ◽  
Digital Imaging Systems ◽  
Multi Phase ◽  
Network Technologies

Polymer microscopy involves multiple imaging techniques. Speed, simplicity, and productivity are key factors in running an industrial polymer microscopy lab. In polymer science, the morphology of a multi-phase blend is often the link between process and properties. The extent to which the researcher can quantify the morphology determines the strength of the link. To aid the polymer microscopist in these tasks, digital imaging systems are becoming more prevalent. Advances in computers, digital imaging hardware and software, and network technologies have made it possible to implement digital imaging systems in industrial microscopy labs.

A Comparison of the Bethesda and New Oxford Methods of Factor VIII Antibody Assay

1982 ◽  
Vol 47 (01) ◽  
pp. 072-075 ◽  
Author(s):  
D E G Austen ◽  
K Lechner ◽  
C R Rizza ◽  
I L Rhymes
Keyword(s):  
Factor Viii ◽  
Excellent Agreement ◽  
International Committee ◽  
The Other ◽  
Antibody Assay ◽  
Collaborative Trial

SummaryA collaborative trial has been carried out under the auspices of the International Committee on Thrombosis and Haemostasis to compare the Bethesda and New Oxford methods of antibody assay. It was found that errors between laboratories were much greater than those within laboratories and each laboratory had a bias whereby it always rated samples high or low with respect to the other laboratories. However there was excellent agreement in the order in which laboratories ranked antibody samples and if a standard antibody sample could be provided there would be a significant improvement in numerical agreement between laboratories. On average, for this exercise, a result for a given sample in Bethesda units was 1.21 times the result in New Oxford units although it must be stressed that this ratio could vary from sample to sample.

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