Influence of surface micellar head group neutralized in hexadecyltrimethylammonium bromide (CTAB) and hydroxide (CTAOH) on the dehydrochlorination of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD)

1985 ◽  
Vol 63 (11) ◽  
pp. 2892-2898 ◽  
Author(s):  
C. Otero ◽  
E. Rodenas
Keyword(s):  
Experimental Results ◽  
Head Group ◽  
Hexadecyltrimethylammonium Bromide ◽  
Empirical Expressions ◽  
Theoretical Approaches ◽  
Cationic Micelles

The basic dehydrohalogenation reactions of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD) have been studied in cationic micelles of hexadecyltrimethylammonium bromide (CTAB) and hexadecyltrimethylammonium hydroxide (CTAOH). Different theoretical approaches are discussed, considering the fraction of micellar head group neutralized, β, as a constant, or supposing different kinds of variation in its value. The following two empirical expressions for β have been found: β = 0.8 + 0.5 ([NaOH] + [KBr]) for DDT, and β = 0.8 + 1 ([NaOH] + [KBr]) for DDD, and this is the best way to explain the experimental results.

Cleavage of 4-Nitrophenyl Diphenyl Phosphate by Isomeric Quaternary Pyridinium Ketoximes - How Can Structure and Lipophilicity of Functional Surfactants Influence Their Reactivity in Micelles and Microemulsions?

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1642-1658 ◽  
Author(s):  
Milan Kivala ◽  
Radek Cibulka ◽  
František Hampl
Keyword(s):  
Model Reaction ◽  
Head Group ◽  
Hexadecyltrimethylammonium Bromide ◽  
Polar Head Group ◽  
Cationic Micelles ◽  
Brij 35 ◽  
Ionic Micelles ◽  
Diphenyl Phosphate ◽  
Functional Surfactants ◽  
Triton X

Amphiphilic pyridinium ketoximes 4-[1-(hydroxyimino)alkyl]-1-methylpyridinium bromides (1) and 1-alkyl-4-[1-(hydroxyimino)ethyl]pyridinium bromides (2) are isomeric cationic surfactants bearing the nucleophilic hydroxyimino group. They differ in the position of the nucleophilic function relative to polar head group and hydrophobic alkyl chain. The 4-nitrophenyl diphenyl phosphate (PNPDPP) cleavage by the oximate anions generated from 1 and 2 was used as a model reaction for the investigation of the influence of the structure and lipophilicity of functional surfactants on their reactivity in micelles and microemulsions. The investigation of the model reaction in cationic micelles of hexadecyltrimethylammonium bromide (CTAB), in non-ionic micelles (Triton X-100 and Brij 35) and in o/w microemulsion (isooctane/phosphate buffer/CTAB and butan-1-ol) has revealed that it is the lipophilicity which is the most important factor influencing the localization and reactivity of functional surfactants in nanoaggregates.

A Quantitative Analysis of the Effects of Head Group Bulk on SN2 and E2 Reactions in Cationic Micelles

Langmuir ◽  
1997 ◽  
Vol 13 (17) ◽  
pp. 4583-4587 ◽  
Author(s):  
Lucia Brinchi ◽  
Pietro Di Profio ◽  
Raimondo Germani ◽  
Gianfranco Savelli ◽  
Clifford A. Bunton
Keyword(s):  
Quantitative Analysis ◽  
Head Group ◽  
Cationic Micelles

Discussion of Different Kinetic Models for Explaining Experimental Results in Cationic Micelles

1989 ◽  
pp. 211-227 ◽  
Author(s):  
E. Rodenas ◽  
F. Ortega ◽  
S. Vera ◽  
C. Otero ◽  
S. Maestro
Keyword(s):  
Kinetic Models ◽  
Experimental Results ◽  
Cationic Micelles

scholarly journals Superactivity and conformational changes on alpha-chymotrypsin upon interfacial binding to cationic micelles

2004 ◽  
Vol 378 (3) ◽  
pp. 1059-1066 ◽  
Author(s):  
M. Soledad CELEJ ◽  
Mariana G. D'ANDREA ◽  
Patricia T. CAMPANA ◽  
Gerardo D. FIDELIO ◽  
M. Lucia BIANCONI
Keyword(s):  
Conformational Changes ◽  
Tertiary Structure ◽  
Enzyme Stability ◽  
Catalytic Efficiency ◽  
Tryptophan Fluorescence ◽  
Enzyme Activation ◽  
Hexadecyltrimethylammonium Bromide ◽  
Negative Band ◽  
Cationic Micelles ◽  
Α Helix

The catalytic behaviour of α-CT (α-chymotrypsin) is affected by cationic micelles of CTABr (hexadecyltrimethylammonium bromide). The enzyme–micelle interaction leads to an increase in both the Vmax and the affinity for the substrate p-nitrophenyl acetate, indicating higher catalytic efficiency for bound α-CT. The bell-shaped profile of α-CT activity with increasing CTABr concentrations suggests that the micelle-bound enzyme reacts with the free substrate. Although more active with CTABr micelles, the enzyme stability is essentially the same as observed in buffer only. Enzyme activation is accompanied by changes in α-CT conformation. Changes in tertiary structure were observed by the increase in intensity and the red shift in the α-CT tryptophan fluorescence spectrum, suggesting the annulment of internal quenching and a more polar location of tryptophan residues. Near-UV CD also indicated the transfer of aromatic residues to a more flexible environment. CTABr micelles also induces an increase in α-helix, as seen by far-UV CD and FTIR (Fourier-transform infrared) spectroscopies. The far-UV CD spectrum of α-CT shows an increase in the intensity of the positive band at 198 nm and in the negative band at 222 nm, indicating an increased α-helical content. This is in agreement with FTIR studies, where an increase in the band at 1655 cm−1, corresponding to the α-helix, was shown by fitting analysis and difference spectroscopy. Spectral deconvolution indicated a reduction in the β-sheet content in micelle-bound α-CT. Our data suggest that the higher catalytic efficiency of micelle-bound α-CT results from significant conformational changes.

Origin of the Magnetic Proximity Effect

2002 ◽  
Vol 746 ◽  
Author(s):  
Miguel Kiwi
Keyword(s):  
Proximity Effect ◽  
Experimental Results ◽  
Metal Insulator ◽  
Theoretical Approaches ◽  
Metal Metal ◽  
The Subject ◽  
The Relationship ◽  
Magnetic Proximity Effect

ABSTRACTThe magnetic proximity effect (MPE) has attracted the attention of theorists and experimentalists for at least three decades. Lately, the relevance of the effect for the development of nanodevices has revived interest on the subject. Here we review how the field has evolved, centering our attention on metal-metal and metal-insulator systems. We describe, and critically compare, the different theoretical approaches that have been put forward, as well as their limitations. An evaluation of the relationship between existing theories and available experimental results is also attempted.

scholarly journals SN2 Mechanism of Cationic Micelles on the Hydrolysis of Bis-p-Methoxyphenyl Phosphate Ester

2015 ◽  
Vol 58 (3) ◽  
pp. 117-121
Author(s):  
Abanish Kumar
Keyword(s):  
Head Group ◽  
Phosphate Ester ◽  
Polar Head Group ◽  
Polar Groups ◽  
First Order Kinetics ◽  
Cationic Micelles ◽  
Pseudophase Model ◽  
Group Form ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

Hydrolysis of bis-p-methoxyphenyl phosphate ester (bis-p-MPPE) was studied in micellar solutions of cityltrimethylammoniumbromide n-C16H33N+(CH3)3Br- (CTABr) at pH-9.0. The hydrolysis followed first order kinetics with respect to bis-p-MPPE concentration. At the concentration of critical micelle concentration (CMC) the rate of hydrolysis increased with increasing CTABr concentration. Surfactant with cationic or polar head group form micelles in water with hydrocarbon like interior or polar groups at the surface and bind cationic solute. The binding constant of micelle for bis-p-MPPE and the rate constant in micellar pseudo phase were determined from kinetic data using the pseudophase model. 

Lying, Implicating, and Presupposing

2018 ◽  
pp. 192-202
Author(s):  
Jörg Meibauer
Keyword(s):  
Experimental Results ◽  
Theoretical Approaches

The notions of ‘indirect lying’, ‘falsely implicating’, or ‘misleading’ refer to the phenomenon of lying by deliberately suggesting what is false in order to deceive the addressee. Thus, what the speaker asserts may be sincere and true, while what she implicates may be deceptive and false. This chapter reviews theoretical approaches that deal with untruthful implicature and untruthful presupposition, ‘untruthfulness’ meaning a subjective attitude towards truth. In these cases, an additional proposition is introduced into the discourse with the intention to deceive the addressee. Arguably, cases of so-called misleading can be reduced to untruthful implicatures. If so, untruthful additional propositions such as the untruthful implicature and presupposition can be seen as a part of the overall act of lying, i.e., the total signification of an utterance. Moreover, experimental results providing further evidence are sketched.

scholarly journals VANESA - A Software Application for the Visualization and Analysis of Networks in Systems Biology Applications

2014 ◽  
Vol 11 (2) ◽  
pp. 43-57 ◽  
Author(s):  
Christoph Brinkrolf ◽  
Sebastian Jan Janowski ◽  
Benjamin Kormeier ◽  
Martin Lewinski ◽  
Klaus Hippe ◽  
...  
Keyword(s):  
Systems Biology ◽  
Petri Net ◽  
Biological Networks ◽  
Life Science ◽  
Experimental Results ◽  
Biological Processes ◽  
Molecular Systems ◽  
Software Application ◽  
Theoretical Approaches ◽  
Modeling Software

Summary VANESA is a modeling software for the automatic reconstruction and analysis of biological networks based on life-science database information. Using VANESA, scientists are able to model any kind of biological processes and systems as biological networks. It is now possible for scientists to automatically reconstruct important molecular systems with information from the databases KEGG, MINT, IntAct, HPRD, and BRENDA. Additionally, experimental results can be expanded with database information to better analyze the investigated elements and processes in an overall context. Users also have the possibility to use graph theoretical approaches in VANESA to identify regulatory structures and significant actors within the modeled systems. These structures can then be further investigated in the Petri net environment of VANESA. It is platform-independent, free-of-charge, and available at http://vanesa.sf.net.

scholarly journals Kinetics and Mechanism of Counterionic Salt-Catalysed Piperidinolysis of Anionic Phenyl Salicylate in the Presence of Cationic–Nonionic Mixed Micelles

2018 ◽  
Vol 43 (1) ◽  
pp. 41-52
Author(s):  
Ibrahim I. Fagge ◽  
W. Hamdah W. Ahmad ◽  
Sharifuddin Md Zain ◽  
M. Niyaz Khan
Keyword(s):  
Nonionic Surfactant ◽  
Binding Constants ◽  
Mean Value ◽  
Hexadecyltrimethylammonium Bromide ◽  
Quantitative Correlation ◽  
Cationic Micelles ◽  
Micellar Growth ◽  
Spherical Micelles ◽  
Poly Ethylene ◽  
Semi Empirical

The quantitative correlation of counterion-affinity to aqueous hexadecyltrimethylammonium bromide (HDAB, cationic micelles/nanoparticles) and the counterion-induced HDAB micellar growth, in the presence of different amounts of poly(ethylene glycol hexadecyl ether) (C16E20, nonionic surfactant), was achieved by the use of a semi-empirical kinetic (SEK) method. The values of the ratio of cationic HDAB, as well as mixed HDAB–C16E20, micellar binding constants of X and Br, KX/ KBr (= KXBr or RXBr) for X = 4-ClC6H4CO2-, were obtained by the SEK method. The concentration range (0.006–0.015 M) of pure HDAB was found to have no influence on the values of KXBr or RXBr. These observations were also recorded upon addition of a nonionic surfactant, C16E20, in an aqueous solution of HDAB. The mean value of KXBr or RXBr obtained in the presence of pure HDAB ( KXBr or RXBr = 50.3) is 2.3 times larger than that in the presence of mixed HDAB–C16E20 (m KXBr or m RXBr = 21.7). From rheometric measurements of aqueous HDA+/4-ClC6H4CO2- with 0.015 M HDAB, single symmetric maxima (at both 25 and 35 °C) were obtained at [4-ClC6H4CO2Na] = 0.03 M. This is evidence for the existence of wormlike micelles/nanoparticles. However, the absence of a maximum in rheometric data for aqueous HDA+/C16E20/4-ClC6H4CO2- with 0.015 M HDAB and 0.006 M C16E20 at various [4-ClC6H4CO2Na] revealed the existence of spherical micelles.

Two Different Theoretical Approaches to the Base Pressure Problem in Two-Dimensional Supersonic Flow

1978 ◽  
Vol 29 (2) ◽  
pp. 114-130 ◽  
Author(s):  
M. Tanner
Keyword(s):  
Supersonic Flow ◽  
Flow Model ◽  
The Body ◽  
Experimental Results ◽  
Base Pressure ◽  
Two Dimensional ◽  
Reattachment Point ◽  
Fundamental Idea ◽  
Entropy Increase ◽  
Theoretical Approaches

SummaryThe basic physical idea underlying the theories based on the flow model of CHAPMAN and KORST is that the base pressure can be predicted if the pressure at the reattachment point is known. In the new theory of TANNER the fundamental idea is the connection between the drag of the body and the entropy increase in the flow. This paper presents the essence of both theories together with theoretical and experimental results.

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