Phase-stepping technique

In recenf sfudies, if has been proved possible to examine the birefiingence in the matrix around a fibre-end or break. Using a phase-stepping technique, contours of principal... 

Very accrrrate measrrrements of the optical path differences in the interference pattern can be made by the digital phase-stepping technique. The data from three or more such measrrrements made with different directions of illumination can then be processed to obtain the surface displacements and the principal strains. 

The digital phase-stepping technique can also be used with electronic speckle pattern interferometry. Indus case each speckle is treated as an individual interference pattern, the hght from the object having a particular ampli-mde and phase. If the optical path difference at each such point with respect to the reference beam is meastrred by the phase-stepping technique before and after the strrface moves, the change gives a direct measure of the strrface displacement at that point. 

Preparation of soil—sediment of water samples for herbicide analysis generally has consisted of solvent extraction of the sample, followed by cleanup of the extract through Uquid—Uquid or column chromatography, and finally, concentration through evaporation (285). This complex but necessary series of procedures is time-consuming and is responsible for the high cost of herbicide analyses. The advent of soUd-phase extraction techniques in which the sample is simultaneously cleaned up and concentrated has condensed these steps and thus gready simplified sample preparation (286). 

Although the mechanisms discussed above are still topics of debate, it is now firmly established that the electrodeposition of conducting polymers proceeds via some kind of nucleation and phase-growth mechanism, akin to the electrodeposition of metals.56,72-74 Both cyclic voltammetry and potential step techniques have been widely used to investigate these processes, and the electrochemical observations have been supported by various types of spectroscopy62,75-78 and microscopy.78-80... 

Thermal treatments can be applied to modify the properties of a material, for example, dealumination and optimization of crystalHne phases. These techniques do not require oxidants. Oxidative thermal treatments are generally employed to activate molecular sieves, by removing the organic templates employed during synthesis. This is one of the key steps when preparing porous catalysts or adsorbents. In air-atmosphere calcination, the templates are typically combusted between 400... 

Exudate collection in trap solutions usually requires subsequent concentration steps (vacuum evaporation, lyophilization) due to the low concentration of exudate compounds. Depending on the composition of the trap solution, the reduction of sample volume can lead to high salt concentrations, which may interfere with subsequent analysis or may even cause irreversible precipitation of certain exudate compounds (e.g., Ca-citrate, Ca-oxalate, proteins). Therefore, if possible, removal of interfering salts by use of ion exchange resins prior to sample concentration is recommended. Alternatively, solid-phase extraction techniques may be employed for enrichment of exudate compounds from the diluted trap solution (11,22). High-molecular-weight compounds may be concentrated by precipitation with organic solvents [methanol, ethanol, acetone 80% (v/v) for polysaccharides and proteins] or acidification [trichloroacetic acid 10% (w/v), per-... 

Sample preparation—Analytes of interest were extracted from human plasma using the online solid phase extraction technique. The steps required are noted below ... 

Whereas the optical method indicates attainment of saturation coverage by the dye in its /-state, results obtained with the phase-separation technique show that, after reaching apparent saturation, further adsorption occurs as the dye concentration in solution is increased. The horizontal step observed with the phase separation measurement is in approximate agreement with the maximum surface concentration of dye in its /-state as determined by the optical method. Hence, it is concluded that, contrary to earlier suppositions (70), only the first layer of this dye is adsorbed in its /-state subsequent dye layers must be adsorbed in different states. 

Aminoquinolines 62 have been prepared in a two-step, one-pot, three-component reaction of 2-azidobenzophenones, secondary amines and arylac-etaldehydes [110]. The microwave-assisted reaction proceeded via the initial formation of enamines 59. Subsequent addition of 2-azidobenzophenones 60 afforded the triazoline intermediates 61, which underwent thermal rearrangement and cyclocondensation to furnish 2-aminoquinolines 62 (Scheme 41). Direct comparison with conventional thermal conditions demonstrated the superiority of microwave dielectric heating in terms of yields (73% vs. 31% of heterocycle 63 after 10 min at 180 °C). Furthermore, the formation of by-products due to decomposition of azide 60 was diminished in the microwave-assisted synthesis. Purification of the products was achieved using solid-phase extraction techniques. 

In a subsequent study, solvent partitioning and solid-phase extraction techniques were used to produce a partial ly -pur If led extract (15). The first step In the purification scheme Involved partitioning of a highly oonoentrated ethanol 1c extract of house fly ovaries between chloroform and water. Further processing of the chloroform layer (I.e., evaporation, solvent exchange, and filtration through a bed of Porapac Q) eventually produced a methanol 1c extract with a 23-fold Increeee In OH activity over the crude extract. 

The formation of liposomes [or better arsonoliposomes (ARSL)], composed solely of arsonolipids (Ars with R=lauric acid (C12) myristic acid (C14) palmitic acid (C16) and stearic acid (C18) (Fig. 1) have been used for ARSL construction), mixed or not with cholesterol (Choi) (plain ARSL), or composed of mixtures of Ars and phospholipids (as phosphatidylcholine [PC] or l,2-distearoyl- -glyceroyl-PC [DSPC]) and containing or not Choi (mixed ARSL), was not an easy task. Several liposome preparation techniques (thin-film hydration, sonication, reversed phase evaporation, etc.) were initially tested, but were not successful to form vesicles. Thereby a modification of the so called one step or bubble technique (8), in which the lipids (in powder form) are mixed at high temperature with the aqueous medium, for an extended period of time, was developed. This technique was successfiil for the preparation of arsonoliposomes (plain and mixed) (9). If followed by probe sonication, smaller vesicles (compared to those formed without any sonication [non-sonicated]) could be formed [sonicated ARSL] (9). Additionally, sonicated PEGylated ARSL (ARSL that contain polyethyleneglycol [PEG]-conjugated phospholipids in their lipid bilayers) were prepared by the same modified one-step technique followed by sonication (10). 

The shake-flask method is based on the phase solubility technique that was developed 40 years ago and is still the most reliable and widely used method for solubility measurement today (Higuchi and Connors, 1965). The method can be divided into hve steps sample preparation, equilibration, separation of phases, analysis of the saturated solution and residual solid, and data analysis and interpretation (Yalkowsky and Banerjee, 1992, Winnike, 2005). 

---