Surface waters complementary methods

As a complementary method, the wetting behavior of dry photoresist surfaces that have been pretreated with surfactant solutions was investigated. Pieces of the photoresist-covered wafers were inserted in surfactant solutions of various concentrations for 3 minutes. Afterwards, the solution was removed and the surface dried with a nitrogen flow. After several hours, the contact angle of water droplets was measured with the Dynamic Contact Angle Tester FIBRO DAT 1100 (FIBRO Systems, Sweden). A water droplet of 8 il volume was placed onto the surface. Its contact angle was measured in time intervals of 20 ms. From the slope of the contact angle curve... 

In contrast to the physico/chemical measurement systems, BEWS are sensitive to many toxic compounds, even to those that are not included in the routine monitoring programmes. They operate continuously (24/24h, 7/7d) and provide early results. In the case of an accidental spill they should generate an alarm within minutes to one hour (van der Schalie el al., 1999). BEWS have recently been included in the WFD Common Implementation Strategy Guideline 19 on surface water chemical monitoring as complementary method (European Communities, 2009). 

The studies on the mode of interaction of prothrombin with phospholipid monolayers, using complementary methods of surface measurement are reviewed. They were investigated at air-water and Hg-water interfaces respectively by radioactivity and electrochemistry. A process more complex than a simple adsorption could be detected. Indeed, the variation of the differential capacity of a mercury electrode in direct contact with phospholipid monolayer, induced by the interaction with prothrombin could be interpreted as a model of its penetration into the layer this was confirmed by the study of the dynamic properties of the direct adsorption of this protein at the e-lectrode, followed in part by the reduction of S-S bridges at the electrode. It could be also concluded that prothrombin resists complete unfolding at these interfaces. 

As an example of a membrane model, phospholipid monolayers with negative charge of different density were used. It had already been found ( ) and discussed O) that the physical and biological behavior of phospholipid monolayers at air-water interfaces and of suspensions of liposomes are comparable if the monolayer is in a condensed state. Two complementary methods of surface measurements (using radioactivity and electrochemical measurements), were used to investigate the adsorption and the dynamic properties of the adsorbed prothrombin on the phospholipid monolayers. Two different interfaces, air-water and mercury-water, were examined. In this review, the behavior of prothrombin at these interfaces, in the presence of phospholipid monolayers, is presented as compared with its behavior in the absence of phospholipids. An excess of lipid of different compositions of phos-phatidylserine (PS) and phosphatidylcholine (PC) was spread over an aqueous phase so as to form a condensed monolayer, then the proteins were inject underneath the monolayer in the presence or in the absence of Ca. The adsorption occurs in situ and under static conditions. The excess of lipid ensured a fully compressed monolayer in equilibrium with the collapsed excess lipid layers. The contribution of this excess of lipid to protein adsorption was negligible and there was no effect at all on the electrode measurements. 

A prototypical example of a molecular probe used extensively to study the mineral adsorbent-solution interface is the ESR spin-probe, Cu2+ (Sposito, 1993), whose spectroscopic properties are sensitive to changes in coordination environment. Since water does not interfere significantly with Cu11 ESR spectra, they may be recorded in situ for colloidal suspensions. Detailed, molecular-level information about coordination and orientation of both inner- and outer-sphere Cu2+ surface complexes has resulted from ESR studies of both phyllosilicates and metal oxyhydroxides. In addition, ESR techniques have been combined with closely related spectroscopic methods, like electron-spin-echo envelope modulation (ESEEM) and electron-nuclear double resonance (ENDOR), to provide complementary information about transition metal ion behaviour at mineral surfaces (Sposito, 1993). The level of sophistication and sensitivity of these kinds of surface speciation studies is increasing continually, such that the heterogeneous colloidal particles in soils can be investigated ever more accurately. 

IR spectroscopy is one of the useful methods to study the hydrogen-bonded pairing between the bases. The measurements are generally carried out in aptotic solvents and the hydrogen-bonded pairing is discussed from the shift of v(NH) and v(C=0). Unfortunately, this approach cannot be used for the studies at the solid/water interface, because both adenine moiety of the SAM and thymidine are hydrated in water and the distinction between hydrogen bonds between the complementary base pair and those between the bases and water is practically impossible from the v(NH) and v(C=0) modes only. The interaction between the surface-confined 6-amino-8-purinethiol and thymidine was discussed from the potential dependence of the band intensities of the v(OH) mode of water and some modes of adenine moiety in this study. 

Bubble-film extraction is an advanced flotation method by means of air bubbles. It provides much better removal from treated water bulk of surface-active substances (SASs) and surface-inactive impurities, which have complementary structure in relation to removed SAS. The improvanent consists in a way of surfactants separating from the space of bubble flotator. In this connection, let us note at first the main features of flotation with air bubbles. 

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