Situ Methods

It would be interesting to use magnetic methods for the study of catalyst structure during the time when the catalyst is actually promoting a chemical reaction. As yet no method has been developed for doing this, but several posabilities will be mentioned. 

It should be pointed out, in connection with all the in situ methods, that future developments in nuclear magnetism may make unnecessary any procedure such as described (Spooner and Selwood, 10). 

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University of Arkansas and Louisiana State University. In-Situ Methods for the Control of Emissions from Surface Impoundments and Landfills. Draft Final Report. Prepared for U.S. Environmental Protection Agency. Contract No. CR810856. June 1985. pp. 95. 

The in situ method using rat living intestine was simple and qualitative. However, it was difficult to evaluate the weak interaction between polymers and cell membranes quantitatively. Therefore, the lipid bilayer of liposome was used as a model of cell membranes for the quantitative evaluation for the affinity of the hydrophobized polymers (15). 

Ferrite is introduced into the aqueous media by two techniques. With the in situ method, ferrite is formed within the actinide-containing solution by addition of Fe(II), Fe(III), and sodium hydroxide. With the preformed ferrite method, ferrite solids are prepared separately and added to the actinide solution. 

Various in situ and ex situ methods have been used to determine the real surface area of solid electrodes. Each method10,15 32 67,73 74 218 is applicable to a limited number of electrochemical systems so that a universal method of surface area measurement is not available at present. On the other hand, a number of methods used in electrochemistry are not well founded from a physical point of view, and some of them are definitely questionable. In situ and ex situ methods used in electrochemistry have been recently reviewed by Trasatti and Petrii.73 A number of methods are listed in Table 3. 

The in situ methods more commonly used to obtain the surface roughness R = SRa/S8ram (where and Sgeom are the working surface and the geometric area, respectively) of electrodes are10 24 63 73 74 218 (1)... 

Valette-Hamelin approach,67 and other similar methods 24,63,74,218,225 (2) mass transfer under diffusion control with an assumption of homogeneous current distribution73 226 (3) adsorption of radioactive organic compounds or of H, O, or metal monolayers73,142,227 231 (4) voltammetry232,233 and (5) microscopy [optical, electron, scanning tunneling microscopy (STM), and atomic force microscopy (AFM)]234"236 as well as a number of ex situ methods.237 246... 

The huge literature on the electronic conductivity of dry conducting polymer samples will not be considered here because it has limited relevance to their electrochemistry. On the other hand, in situ methods, in which the polymer is immersed in an electrolyte solution under potential control, provide valuable insights into electron transport during electrochemical processes. It should be noted that in situ and dry conductivities of conducting polymers are not directly comparable, since concentration polarization can reduce the conductivity of electrolyte-wetted films considerably.139 Thus in situ conductivities reported for polypyrrole,140,141 poly thiophene,37 and poly aniline37 are orders of magnitude lower than dry conductivities.15... 

Ex Situ Methods XPS and HREELS will continne to be very usefnl ex sitn methods for the stndy of electrode surfaces. Soft X-ray XAS in both the EY and FY modes shonld find wider application. 

Mazurek M, Benker N, Roth C, Buhrmester T, Fuess H. 2006. Electrochemical impedance and X-ray absorption spectroscopy (EXAFS) as in situ methods to study PEMFC anode. Fuel Cells 6 16-20. 

The reaction can be carried out efficiently using aryl diazonium tetrafluoroborates with crown ethers, polyethers, or phase transfer catalysts.103 In solvents that can act as halogen atom donors, the radicals react to give aryl halides. Bromotrichloromethane gives aryl bromides, whereas methyl iodide and diiodomethane give iodides.104 The diazonium ions can also be generated by in situ methods. Under these conditions bromoform and bromotrichloromethane have been used as bromine donors and carbon tetrachloride is the best chlorine donor.105 This method was used successfully for a challenging chlorodeamination in the vancomycin system. 

J. M. Thomas, The ineluctable need for in situ methods of characterising solid catalysts as a prerequisite to engineering active sites, Chem. Fur. J., 1997, 3, 1557. 

The presence of an active site in the modifier is essential for the formation of polymer-modifier adduct by the in-situ method (method 2) above. Figure 3 compares the degree of binding which can be achieved... 

In Situ Methods for the Biological Treatment of Organic Contaminants. 539... 

Another classification of remediation technologies describes where the action is taking place. Ex situ methods are those applied to excavated soil and in situ processes are those applied to the soil in its original location. On-site techniques are those that take place on the contaminated site they can be either ex situ or in situ. Off-site processes treat the excavated soil in fixed industrial facilities, away from the contaminated site. 

A permeable reactive barrier (PRB) is defined as an in situ method for remediating contaminated groundwater that combines a passive chemical or biological treatment zone with subsurface fluid flow management. Treatment media may include zero-valent iron, chelators, sorbents, and microbes to address a wide variety of groundwater contaminants, such as chlorinated solvents, other organics,... 

In situ methods have potential use as an interim or emergency measure until dredging can be undertaken or as a primary remedial action where it is determined to be more cost-effective than removal. The biggest advantages are that they are much less costly than dredging, eliminate the need for dredged material management, and minimize the resuspension of contained sediments.15... 

The big difference in application from the in situ flushing method is that this ex situ method can apply to soils with lower permeability, because soil is excavated and can be sufficiently washed. The following presents two ex situ soil washing processes for organic contaminants the BioGenesis soil cleaning process and the BioTrol soil washing system. 

In principle, the analysis of molecules, ions and adsorbed intermediates is possible if they survive the emersion (no potential control) and UH V conditions (elimination of most of the solvent). The use of ex situ methods for the analysis of sub-monolayer quantities of oxygen-sensitive substances requires an extremely inert atmosphere when the electrode is emersed. In order to check whether a given adsorbate survives the experimental conditions, a control experiment must be carried out, as we describe here for adsorbed CO on Pt. 

Before the widespread adoption of FRET imaging techniques, the only optical, in situ method of assessing whether two proteins were... 

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