92 research outputs found
Stability Of Hydrophobic Foams
The stability of foams was determined in two-phase regions containing an isotropic hydrocarbon solution and a lamellar liquid crystal. The lamellar liquid crystal showed surface activity with regard to the hydrocarbon solution. This was interpreted as due to the higher frequency of methyl groups at the surface of the liquid-crystalline state compared to the liquid state. The weaker intermolecular forces from the methyl groups were assumed to result in a lower surface tension of the liquid crystal in comparison to the liquid. This hypothesis was tested by the use of a low surface tension hydrocarbon, isooctane. No foam stability was formed in this medium, supporting the claim of the methyl groups as the surface-active element. © 1986, American Chemical Society. All rights reserved
Nonionic Hydrophilic Surfaces: Adsorption and Interactions
An overview is given of recent studies of nonionic, hydrophilic surfaces formed by the adsorption of surfactants or surface active polymers. Hydrophobic surfaces can be easily hydrophilized by the adsorption of nonionic surfactants or block copolymers containing hydrophobic chain segments; the cooperative interaction between the hydrocarbon moieties contributes more to the free energy of adsorption than the interaction with the hydro- phobic surface.
Hydrophilic layers are also readily formed on hydrophilic surfaces provided specific interaction between the hydrophilic end groups and the surface creates a sufficiently hydrophobic surface so that a second layer can be formed through cooperative interaction. The temperature dependence of the interaction forces between layers of surfactants can be closely correlated with their phase equilibria with water.
In order to prevent protein adsorption the surface should be neither charged nor hydrophobic; it is shown that, accordingly, protein adsorption is extremely low on polyethylene oxide-covered surfaces
Optimisation of Over-Expression in E. coli and Biophysical Characterisation of Human Membrane Protein Synaptogyrin 1
Progress in functional and structural studies of integral membrane proteins (IMPs) is lacking behind their soluble counterparts due to the great challenge in producing stable and homogeneous IMPs. Low natural abundance, toxicity when over-expressed and potential lipid requirements of IMPs are only a few reasons for the limited progress. Here, we describe an optimised workflow for the recombinant over-expression of the human tetraspan vesicle protein (TVP) synaptogyrin in Escherichia coli and its biophysical characterisation. TVPs are ubiquitous and abundant components of vesicles. They are believed to be involved in various aspects of the synaptic vesicle cycle, including vesicle biogenesis, exocytosis and endocytotic recycling. Even though TVPs are found in most cell types, high-resolution structural information for this class of membrane proteins is still missing. The optimisation of the N-terminal sequence of the gene together with the usage of the recently developed Lemo21(DE3) strain which allows the balancing of the translation with the membrane insertion rate led to a 50-fold increased expression rate compared to the classical BL21(DE3) strain. The protein was soluble and stable in a variety of mild detergents and multiple biophysical methods confirmed the folded state of the protein. Crosslinking experiments suggest an oligomeric architecture of at least four subunits. The protein stability is significantly improved in the presence of cholesteryl hemisuccinate as judged by differential light scattering. The approach described here can easily be adapted to other eukaryotic IMPs
Taajuudesta riippuvia komponentteja sisältävien piirien aika-alueanalyysi konvoluutiota käyttäen
Csim - a Simple HP48 Circuit Simulator for Educational Purposes
The report presents the theory required to develop and program a simple circuit simulator capable of DC, AC and transient analysis based on modified nodal analysis. Together with the theoretical presentation, the code for a circuit simulating program is developed in order to show how theory is translated into algorithms. The programming language is RPL, which is commonly used by Hewlett-Packard handheld calculators. The program listing presented in this report applies directly to the HP48 scientific calculator. Indexing terms: Circuit simulation. ISBN 951-22-0940-3 ISSN 0784-5979 TKK OFFSET The author is with the Helsinki University of Technology, Faculty of Electrical Engineering, Circuit Theory Laboratory, Otakaari 5A, SF-02150 Espoo, Finland. Contents 1 Introduction 1 1.1 Notation : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 3 2 Modified nodal formulation 4 2.1 The set of equations : : : : : : : : : : : : : : : : : : : : : : : : : : : 4 2.2 Component e..
Surface Characterization of Mechanical Pulp Fibers by Contact Angle Measurement, Polyelectrolyte Adsorption, XPS and AFM
Anbefale metoder for flomberegninger i smĂĄ uregulerte felt
Rapporten anbefaler metoder som bør brukes ved estimering av flomstørrelser i små uregulerte nedbørfelt i Norge på bakgrunn av resultatene fra Stenius m. fl. (2015). Metodene som er brukt er flomfrekvensanalyser, et nytt formelverk for små uregulerte nedbørfelt (Glad m. fl., 2015), flommodulen i PQRUT og den rasjonale formel. Det er brukt data fra opptil 170 målestasjoner i analysene. Rapporten er en del av Naturfareprosjektet (NIFS), aktivitet 5.1 Flom og vann på avveie
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