Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 842-848 ◽  
Author(s):  
Duncan C Hone ◽  
Brian H Robinson ◽  
David C Steytler ◽  
Roger W Glyde ◽  
John A Cleverley
Keyword(s):  
Kinetic Studies ◽  
Hydrocarbon Chain ◽  
Water Soluble ◽  
Stopped Flow ◽  
Acid Neutralization ◽  
Ph Indicator ◽  
Ph Indicators ◽  
Hydrocarbon Chain Length ◽  
Overbased Detergent ◽  
Neutralization Rate

We have used stopped-flow kinetic studies to conduct an investigation into the acid neutralization reaction between overbased detergent additives and aqueous acid dispersed as w/o microemulsion droplets. Water-soluble pH indicators have been used to monitor the change in pH during the reaction. The acid neutralization rate was found to be dependent on the concentration of overbased additive, the temperature of the system, and the hydrocarbon chain length of the solvent. The systems are of importance in relation to the mechanism of acid neutralization by engine lubricants.Key words: overbased detergent additive, acid neutralization, pH indicator, stopped flow.

scholarly journals Structure and Interdigitation of Chain-Asymmetric Phosphatidylcholines and Milk Sphingomyelin in the Fluid Phase

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1441
Author(s):  
Moritz P. K. Frewein ◽  
Milka Doktorova ◽  
Frederick A. Heberle ◽  
Haden L. Scott ◽  
Enrico F. Semeraro ◽  
...  
Keyword(s):  
Chain Length ◽  
Hydration Shell ◽  
Fluid Phase ◽  
Hydrocarbon Chain ◽  
Specific Model ◽  
Glycerol Backbone ◽  
Membrane Composition ◽  
Membrane Structures ◽  
Hydrocarbon Chain Length ◽  
Dynamics Simulations

We addressed the frequent occurrence of mixed-chain lipids in biological membranes and their impact on membrane structure by studying several chain-asymmetric phosphatidylcholines and the highly asymmetric milk sphingomyelin. Specifically, we report trans-membrane structures of the corresponding fluid lamellar phases using small-angle X-ray and neutron scattering, which were jointly analyzed in terms of a membrane composition-specific model, including a headgroup hydration shell. Focusing on terminal methyl groups at the bilayer center, we found a linear relation between hydrocarbon chain length mismatch and the methyl-overlap for phosphatidylcholines, and a non-negligible impact of the glycerol backbone-tilting, letting the sn1-chain penetrate deeper into the opposing leaflet by half a CH2 group. That is, penetration-depth differences due to the ester-linked hydrocarbons at the glycerol backbone, previously reported for gel phase structures, also extend to the more relevant physiological fluid phase, but are significantly reduced. Moreover, milk sphingomyelin was found to follow the same linear relationship suggesting a similar tilt of the sphingosine backbone. Complementarily performed molecular dynamics simulations revealed that there is always a part of the lipid tails bending back, even if there is a high interdigitation with the opposing chains. The extent of this back-bending was similar to that in chain symmetric bilayers. For both cases of adaptation to chain length mismatch, chain-asymmetry has a large impact on hydrocarbon chain ordering, inducing disorder in the longer of the two hydrocarbons.

scholarly journals The Phosphate Content of Escherichia coli Alkaline Phosphatase and Its Effect on Stopped Flow Kinetic Studies

1973 ◽  
Vol 248 (16) ◽  
pp. 5794-5805
Author(s):  
Will Bloch ◽  
Milton J. Schlesinger
Keyword(s):  
Escherichia Coli ◽  
Alkaline Phosphatase ◽  
Kinetic Studies ◽  
Stopped Flow ◽  
Phosphate Content

scholarly journals Effect of Hydrocarbon Chain Length of Amphiphilic Ruthenium Dyes on Solid-State Dye-Sensitized Photovoltaics

Nano Letters ◽  
2005 ◽  
Vol 5 (7) ◽  
pp. 1315-1320 ◽  
Author(s):  
Lukas Schmidt-Mende ◽  
Jessica E. Kroeze ◽  
James R. Durrant ◽  
Md. K. Nazeeruddin ◽  
Michael Grätzel
Keyword(s):  
Solid State ◽  
Chain Length ◽  
Hydrocarbon Chain ◽  
Dye Sensitized ◽  
Hydrocarbon Chain Length ◽  
Ruthenium Dyes

Effect of primary amine hydrocarbon chain length for the selective catalytic reduction of NOx from diesel engine exhaust

Fuel ◽  
2010 ◽  
Vol 89 (9) ◽  
pp. 2292-2298 ◽  
Author(s):  
Maria Stanciulescu ◽  
Jean-Pierre Charland ◽  
James F. Kelly
Keyword(s):  
Diesel Engine ◽  
Selective Catalytic Reduction ◽  
Chain Length ◽  
Primary Amine ◽  
Catalytic Reduction ◽  
Hydrocarbon Chain ◽  
Engine Exhaust ◽  
Diesel Engine Exhaust ◽  
Hydrocarbon Chain Length ◽  
Reduction Of Nox

Formation mechanism of self-assembled unilamellar vesiclesSpecial issue on Neutron Scattering in Canada

2010 ◽  
Vol 88 (10) ◽  
pp. 735-740 ◽  
Author(s):  
Mu-Ping Nieh ◽  
Norbert Kučerka ◽  
John Katsaras
Keyword(s):  
Neutron Scattering ◽  
Hydrocarbon Chain ◽  
Lipid Concentration ◽  
Uniform Size ◽  
Lipid Mixtures ◽  
Hydrocarbon Chain Length ◽  
Membrane Rigidity ◽  
Self Assembled ◽  
Best Fit ◽  
Sans Data

Uniform size self-assembled unilamellar vesicles (ULVs) can be produced from mixtures of weakly charged short- and long-chain phospholipids. These lipid mixtures self-assemble into bilayered micelles (so-called bicelles), and a bicelle to ULV transition has been previously reported. Here, we discuss the effect of various parameters (i.e., lipid concentration, charge density, membrane rigidity, lipid composition, and lipid hydrocarbon chain length) on ULV radius as determined by small angle neutron scattering (SANS). SANS data were best fit using a core-shell disk and a spherical-shell model to obtain the size of bicelles and ULVs, respectively. From the present experiments we conclude that a previously proposed mechanism of ULV formation, where bicelles coalesce into large precursor and self-fold into ULVs, is able to explain the present SANS data.

scholarly journals Adsorption of heavy metals by road deposited solids

2013 ◽  
Vol 67 (11) ◽  
pp. 2622-2629 ◽  
Author(s):  
Chandima Gunawardana ◽  
Ashantha Goonetilleke ◽  
Prasanna Egodawatta
Keyword(s):  
Heavy Metals ◽  
Kinetic Studies ◽  
Field Studies ◽  
Water Soluble ◽  
Trivalent Cation ◽  
Urban Road ◽  
High Charge Density ◽  
Road Surfaces ◽  
Adsorption Desorption ◽  
Exchangeable Form

The research study discussed in the paper investigated the adsorption/desorption behaviour of heavy metals commonly deposited on urban road surfaces, namely, Zn, Cu, Cr and Pb, for different particle size ranges of solids. The study outcomes, based on field studies and batch experiments, confirmed that road deposited solids particles contain a significantly high amount of vacant charge sites with the potential to adsorb additional heavy metals. Kinetic studies and adsorption experiments indicated that Cr is the most preferred metal element to associate with solids due to the relatively high electronegativity and high charge density of trivalent cation (Cr3+). However, the relatively low availability of Cr in the urban road environment could influence this behaviour. Comparing total adsorbed metals present in solids particles, it was found that Zn has the highest capacity for adsorption to solids. Desorption experiments confirmed that a low concentration of Cu, Cr and Pb in solids was present in water-soluble and exchangeable form, whilst a significant fraction of adsorbed Zn has a high likelihood of being released back into solution. Among heavy metals, Zn is considered to be the most commonly available metal among road surface pollutants.

Cellulose Acetate-Based pH Indicator Optodes

1995 ◽  
Vol 48 (6) ◽  
pp. 1081 ◽  
Author(s):  
TJ Cardwell ◽  
RW Cattrall ◽  
LW Deady ◽  
M Dorkos ◽  
AJ Kaye ◽  
...  
Keyword(s):  
Cellulose Acetate ◽  
Ph Indicator ◽  
Ph Indicators

Some pH indicators for use in optode membranes based on cellulose acetate have been prepared, and applications of membranes containing octyl bis (2,4-dinitrophenyl)acetate in static and flowing systems are discussed.

scholarly journals Photocatalytic Degradation of Alizarin Red-S by Fe-Co Nanoparticles Prepared By Chemical Co-precipitation Method

2015 ◽  
Vol 11 (9) ◽  
pp. 3950-3958 ◽  
Author(s):  
Chandrakant Vedu Nandre ◽  
C.P. Sawant
Keyword(s):  
Photocatalytic Degradation ◽  
Contact Time ◽  
Oxygen Demand ◽  
Kinetic Studies ◽  
Water Soluble ◽  
Precipitation Method ◽  
Alizarin Red ◽  
Co Nanoparticles ◽  
Co Precipitation ◽  
Red Dye

In the present study photocatalytic degradation of hazardous water soluble alizarin red dye by using Fe-Co nanoparticles  has been investigated. Fe-Co nanoparticles was synthesized by chemical co-precipitation method and characterized by TEM, SEM, EDAX and XRD. The photocatalytic degradation have been studied with the help of variety of parameters such as catalytic dose, dye concentration, pH, contact time and most important chemical oxygen demand. It was observed that The photocatalytic degradation of alizarin red dye by using Fe-Co nanoparticles was an effective ,economic, ecofriendly and faster mode of removing dye from an aqueous solution. The optimum condition for the degradation of the dye was 50 mg/L,pH 8.0, catalyst dose 60 mg/L and contact time 60 minutes. The kinetic studies also have been studied.

scholarly journals Crystal Memory near Discontinuous Triacylglycerol Phase Transitions: Models, Metastable Regimes, and Critical Points

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5631
Author(s):  
David A. Pink ◽  
Marjorie Ladd-Parada ◽  
Alejandro G. Marangoni ◽  
Gianfranco Mazzanti
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Single Phase ◽  
Hydrocarbon Chain ◽  
Temperature Data ◽  
Recent Time ◽  
Recent Experimental Data ◽  
Hydrocarbon Chain Length ◽  
Discontinuous Phase ◽  
Solid Liquid

It is proposed that “crystal memory”, observed in a discontinuous solid-liquid phase transition of saturated triacylglycerol (TAG) molecules, is due to the coexistence of solid TAG crystalline phases and a liquid TAG phase, in a superheated metastable regime. Such a coexistence has been detected. Solid crystals can act as heterogeneous nuclei onto which molecules can condense as the temperature is lowered. We outlined a mathematical model, with a single phase transition, that shows how the time-temperature observations can be explained, makes predictions, and relates them to recent experimental data. A modified Vogel-Fulcher-Tammann (VFT) equation is used to predict time-temperature relations for the observation of “crystal memory” and to show boundaries beyond which “crystal memory” is not observed. A plot of the lifetime of a metastable state versus temperature, using the modified VFT equation, agrees with recent time-temperature data. The model can be falsified through its predictions: the model possesses a critical point and we outline a procedure describing how it could be observed by changing the hydrocarbon chain length. We make predictions about how thermodynamic functions will change as the critical point is reached and as the system enters a crossover regime. The model predicts that the phenomenon of “crystal memory” will not be observed unless the system is cooled from a superheated metastable regime associated with a discontinuous phase transition.

Sign in / Sign up

Export Citation Format

Share Document