scholarly journals How to Characterize Amorphous Shapes: The Tale of a Reverse Micelle

2021 ◽  
Author(s):  
Christopher Gale ◽  
Mortaza Derakhshani-Molayousefi ◽  
Nancy E. Levinger
Keyword(s):  
Reverse Micelle ◽  
Reverse Micelles ◽  
Experimental Studies ◽  
Regular Structure ◽  
Spherical Shape ◽  
Aerosol Ot ◽  
Curvature Distribution ◽  
Dynamics Simulations ◽  
Changes Over Time ◽  
Over Time

Aerosol-OT reverse micelles represent a chemical construct where surfactant molecules self-assemble to stabilize water nanodroplets ~1-10 nm in diameter. Although commonly assumed to adopt a spherical shape, all-atom molecular dynamics simulations and some experimental studies predict a non-spherical shape. If these aggregates are not spherical, then what shape do they take? Because the tools needed to evaluate the shape of something that lacks regular structure, order, or symmetry are not well developed, we present a set of three intuitive metrics- coordinate-pair eccentricity, convexity, and the curvature distribution- that estimate the shape of an amorphous object and we demonstrate their use on a simulated Aerosol-OT reverse micelle. These metrics are all well-established methods and principles in mathematics, and each provides unique information about the shape. Together, these metrics provide intuitive descriptions of amorphous shapes, facilitate ways to quantify those shapes, and follow their changes over time.

Effects of Water Loading on the Fluorescein/Anti-Fluorescein Antibody System in Aerosol-OT Reverse Micelles Formed in n-Heptane

1998 ◽  
Vol 52 (1) ◽  
pp. 96-100
Author(s):  
Jeffrey S. Lundgren ◽  
A. Neal Watkins ◽  
Frank V. Bright
Keyword(s):  
Binding Site ◽  
Reverse Micelle ◽  
Reverse Micelles ◽  
Site Structure ◽  
Water Loading ◽  
Aerosol Ot ◽  
Aot Reverse Micelles ◽  
Charge Disproportionation

We report on the behavior of monoclonal 4-4-20 mouse anti-fluorescein antibodies sequestered within aerosol-OT (AOT) reverse micelles formed in liquid n-heptane as a function of water loading ( R). Our data suggest that the fluorescein binding site structure is unaffected by R. However, we note that there is a region, at intermediate R values, where the fluorescein apparently binds even more strongly to the monoclonal anti-fluorescein antibodies compared to the native antibody in solution. These results are qualitatively explained in terms of the Ruckenstein–Karpe model, which is based on charge disproportionation and redistribution within the reverse micelle. The results demonstrate that R, within an AOT reverse micelle, influences the apparent anti-fluorescein affinity.

Rotational Reorientation Dynamics of Aerosol-OT Reverse Micelles Formed in Nearcritical Propane

1996 ◽  
Vol 50 (6) ◽  
pp. 732-739 ◽  
Author(s):  
Mark P. Heitz ◽  
Frank V. Bright
Keyword(s):  
Reverse Micelle ◽  
Reverse Micelles ◽  
Lateral Diffusion ◽  
Continuous Phase ◽  
Interfacial Region ◽  
Experimental Conditions ◽  
Correlation Times ◽  
Aerosol Ot ◽  
Rotational Correlation Times ◽  
Rotational Correlation

The rotational reorientation kinetics of two fluorescent solutes (rhodamine 6G, R6G, and rhodamine 101, R101) have been determined in sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT, AOT) reverse micelles formed in liquid and nearcritical propane. We show that the amount of water loading ([water]/[AOT], R), continuous phase density, and temperature all influence the solute rotational dynamics. In all cases, the decay of anisotropy data (i.e., frequency-dependent differential polarized phase angle and polarized modulation ratio) are well-described by a bi-exponential decay law. We find that the faster rotational correlation times are similar to but slightly less than the values predicted for an individual AOT reverse micelle rotating in propane. The recovered rotational correlation times range from 200 to 500 ps depending on experimental conditions. This faster rotational process is explained in terms of lateral diffusion of the fluorophore along the water/headgroup interfacial region within the reverse micelle. The recovered values for the slower rotational correlation times range from 7 to 18 ns. These larger rotational reorientation times are assigned to varying micelle-micelle (i.e., tail-tail) interactions in the low-density, highly compressible fluid region. We also quantify the contribution of the reverse micellar “aggregate” to the total decay of anisotropy.

Comparison of two devices for measuring exercise transcutaneous oxygen pressures in patients with claudication

VASA ◽  
2015 ◽  
Vol 44 (5) ◽  
pp. 355-362 ◽  
Author(s):  
Marie Urban ◽  
Alban Fouasson-Chailloux ◽  
Isabelle Signolet ◽  
Christophe Colas Ribas ◽  
Mathieu Feuilloy ◽  
...  
Keyword(s):  
Oxygen Pressure ◽  
Optical Sensors ◽  
Chemical Sensors ◽  
Transcutaneous Oxygen ◽  
Starting Values ◽  
Two Systems ◽  
Transcutaneous Oxygen Pressure ◽  
New Sensors ◽  
Changes Over Time ◽  
Over Time

Abstract. Summary: Background: We aimed at estimating the agreement between the Medicap® (photo-optical) and Radiometer® (electro-chemical) sensors during exercise transcutaneous oxygen pressure (tcpO2) tests. Our hypothesis was that although absolute starting values (tcpO2rest: mean over 2 minutes) might be different, tcpO2-changes over time and the minimal value of the decrease from rest of oxygen pressure (DROPmin) results at exercise shall be concordant between the two systems. Patients and methods: Forty seven patients with arterial claudication (65 + / - 7 years) performed a treadmill test with 5 probes each of the electro-chemical and photo-optical devices simultaneously, one of each system on the chest, on each buttock and on each calf. Results: Seventeen Medicap® probes disconnected during the tests. tcpO2rest and DROPmin values were higher with Medicap® than with Radiometer®, by 13.7 + / - 17.1 mm Hg and 3.4 + / - 11.7 mm Hg, respectively. Despite the differences in absolute starting values, changes over time were similar between the two systems. The concordance between the two systems was approximately 70 % for classification of test results from DROPmin. Conclusions: Photo-optical sensors are promising alternatives to electro-chemical sensors for exercise oximetry, provided that miniaturisation and weight reduction of the new sensors are possible.

Neuropsychological Symptoms in Posttraumatic Stress Disorder and Changes Over Time

2007 ◽  
Author(s):  
Miranda Olff ◽  
Mirjam Nijdam ◽  
Kristin Samuelson ◽  
Julia Golier ◽  
Mariel Meewisse ◽  
...  
Keyword(s):  
Posttraumatic Stress Disorder ◽  
Posttraumatic Stress ◽  
Stress Disorder ◽  
Neuropsychological Symptoms ◽  
Changes Over Time ◽  
Over Time

Changes Over Time in Adaptive Behavior Functioning of Twice-Exceptional Children

2010 ◽  
Author(s):  
Rebecca D. Stinson ◽  
Zachary Sussman ◽  
Megan Foley Nicpon ◽  
Allison L. Allmon ◽  
Courtney Cornick ◽  
...  
Keyword(s):  
Adaptive Behavior ◽  
Exceptional Children ◽  
Twice Exceptional ◽  
Changes Over Time ◽  
Over Time

Kategorisierung der Schädelform des Cavalier King Charles Spaniels

2019 ◽  
Vol 47 (02) ◽  
pp. 133-133
Keyword(s):  
Pilot Study ◽  
Cavalier King Charles Spaniel ◽  
Conformation Changes ◽  
Veterinary Record ◽  
Changes Over Time ◽  
Over Time

Knowler SP, Gillstedt L, Mitchell TJ et al. Pilot study of head conformation changes over time in the Cavalier King Charles spaniel breed. Veterinary Record 2019. doi:10.1136/vr.105135.

Uneven Decoupling

2019 ◽  
Vol 5 (4) ◽  
pp. 410-427 ◽  
Author(s):  
Ryan P. Thombs ◽  
Xiaorui Huang
Keyword(s):  
Economic Growth ◽  
Co2 Emissions ◽  
Ecological Modernization ◽  
Climate Mitigation ◽  
Data Limitations ◽  
Treadmill Of Production ◽  
Global North ◽  
Organization Of Production ◽  
Changes Over Time ◽  
Over Time

The macro-comparative decoupling literature has often sought to test the arguments made by the treadmill of production (TP) and ecological modernization (EM) theories. However, due to data limitations, these studies have been limited to analyzing the years after 1960. Given that both theories discuss historical processes operating before 1960, analyzing pre-1960 data is warranted to more comprehensively test the propositions made by both theories. We assess the long-term relationship between economic growth and CO2 emissions from 1870 to 2014 using a sample of global North nations. We use Prais-Winsten regression models with time interactions to assess whether, when, and how much CO2 emissions have decoupled from economic growth over time. We find that significant relative decoupling has occurred twice since 1870: during the last 30 years of the nineteenth century, the timing of which is contrary to what both the EM and TP theories might expect, and after 1970. We also observe that the relationship remained relatively stable from the turn of the twentieth century to approximately 1970, which aligns with the arguments made by the classical TP work. We conclude that shifts in the global organization of production have shaped the magnitude of the economic growth–CO2 emissions relationship and its changes over time, which has implications for climate mitigation policy.

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