In situ investigations

The main advantage of these methods is that they can potentially produce a continuous profile of sediment properties that can be correlated witii geophysical data (i.e., bulk density, water content, classification, strength, and compressibility) (Ehlers et al., 2008). However, the effect of the steel drill pipe and the unknown size of the annulus outside the drill pipe obscure the interpretability of the results (Anderson 1985 Pelletier et al., 1997). Detailed information on in situ investigations is presented in Chapter 4. 

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The AFM is now fmnly established as a unique tool for the in situ investigation of biologieal surfaees [144], whether these be biomoleeules, eell stnietures, or even viruses [145]. Often, a sueeessfril innnobilization strategy has been key to suoeessful imaging of the biologieal surfaee [146]. 

Hunger M and Horvath T 1995 A new MAS NMR probe for in situ investigations of hydrooarbon oonversions on solid oatalysts under oontinuous-flow oonditions Chem. Commun. 1995 1423-4... 

C.G. Vayenas, A. loannides, and S. Bebelis, Solid Electrolyte Cyclic Voltammetry for in situ Investigation of Catalyst Surfaces, J. Catal. 129, 67-87 (1991). 

EXAFS spectroscopy was introduced as a further tool for the in situ investigation of electrode coatings... 

Hunger, M. and Horvath, T.J. (1995) A new mas NMR probe for in-situ investigations of hydrocarbon conversion on solid catalysts under continuous-flow conditions, Chem. Soc. Client. Comm., 14, 1423. 

For in situ investigations of electrode surfaces, that is, for the study of electrodes in an electrochemical environment and under potential control, the metal tip inevitably also becomes immersed into the electrolyte, commonly an aqueous solution. As a consequence, electrochemical processes will occur at the tip/solution interface as well, giving rise to an electric current at the tip that is superimposed on the tunnel current and hence will cause the feedback circuit and therefore the imaging process to malfunction. The STM tip nolens volens becomes a fourth electrode in our system that needs to be potential controlled like our sample by a bipotentiostat. A schematic diagram of such an electric circuit, employed to combine electrochemical studies with electron tunneling between tip and sample, is provided in Figure 5.4. To reduce the electrochemical current at the tip/solution... 

Fagerholm, U., Nilsson, D., Knutson, L., Lennernas, H., Jejunal permeability in humans in vivo and rats in situ investigation of molecular size selectivity and solvent drag, Acta Physiol. Scand. 1999, 165, 315-324. 

Having defined our near electrode region, we turn now to consider the various techniques that can be employed in the in situ investigation of the reactions that occur within it. The various methods that can be employed will each provide different types of information on the processes occurring there. As has already been discussed, cyclic voltammetry is the most common technique first employed in the investigation of a new electrochemical system. However, in contrast to the LSV and CV of adsorbed species, the voltammetry of electroactivc species in solution is complicated by the presence of an additional factor in the rate, the mass transport of species to the electrode. Thus, it may be more useful to consider first the conceptually more simple chronoamperometry and chronocoulometry techniques, in order to gain an initial picture of the role of mass transport. 

Resch, R. Prohaska, T. Friedbacher, G. Grasserbauer, M. Kanniainen, T. Lindroos, S. Leskela, M. Niinisto, L. Broekaert, J. A. C. 1998. In-situ investigation of ZnS deposition on mica by successive ionic layer adsorption and reaction method as studied with atomic force microscopy. Fresenius J. Anal. Chem. 353 772-777. 

Another interesting application of high-pressure tubes is the in-situ investigation of reactions in supercritical solvents such as carbon dioxide. For example, the iridium-catalyzed enantioselective hydrogenation of imines was investigated in a sapphire tube at 313 K [32]. 

VIII.A. In Situ Investigations of Gas Solid Reactions and Active Sites. 196... 

In recent years, increasing use has been made of in situ methods in EM—as is true of other techniques of catalyst characterization such as IR, Raman, and NMR spectroscopy, or X-ray diffraction. Although the low mean-free path of electrons prevents EM from being used when model catalysts are exposed to pressures comparable to those prevailing in industrial processes, Gai and Boyes (4) reported early investigations of in situ EM with atomic resolution under controlled reaction conditions to probe the dynamics of catalytic reactions. Direct in situ investigation permits extrapolation to conditions under which practical catalysts operate, as described in Section VIII. 

A great advantage of infrared spectroscopy is that the technique can be used to study catalysts in situ. Several cells for in situ investigations have been described in the literature [4, 5]. The critical point is the construction of infrared-transparent windows that withstand high temperatures and pressures. 

Fein, A.P. J. Vac. Sci. Technol. A. in press)(3). Electronic structure measurements of occupied states are typically made with UPS, while unoccupied states are probed by IPS (49). EELS probes both filled and unfilled states simultaneously, and is therefore used in conjunction with either UPS or IPS to complete a band structure determination (44,49). A new electronic spectroscopy technique, Field Emission Scanning Auger Microscopy (50), utilizes STM-like technology to effect highly localized (c.a. 1 /im) Auger electron spectroscopy. The local electronic information afforded by STM is a valuable complement to these other techniques, and STM is the only one of these methods that may be applied to in situ investigations in condensed media. 

J. P. Owejan, T. A. Trabold, D. L. Jacobson, et al. In situ investigation of water transport in an operating PEM fuel cell using neutron radiography. Part 2. Transient water accumulation in an interdigitated cathode flow field. International Journal of Heat Mass Transfer 49 (2006) 4721-4731. 

For more sophisticated spectroelectrochemical analysis, electrochemical cycling is coupled with X-ray absorption spectroscopy (XAS) methods, which probe electronic and local atomic structures with element specificity.266-234 Because XAS techniques are compatible with in situ investigations and do not require long-range structural order for analysis, they are... 

Figure 2.12 Exploded (left) and assembled (right) view of a toroid cavity autoclave probe for in situ investigations under high gas pressures or in supercritical fluids. Autoclave base (A) and autoclave body (P-bronze, B) thermocouple (C) coaxial heater (D) PTFE ring (E) central conductor (Cu/Be ring, F) nonmagnetic pin from male coaxial connection (G) RF feedthrough (from Rathke [28], H) base-plate (MACOR, I) fixing screws (P-bronze, J) PEEK capillary (l<) ceramic ball (Si3N4, L) PTFE seal (M).

Schneider et al. have reported a cell for HP IR spectroscopy which combines both transmission and reflectance methods for in situ investigations of multiphase reactions [47]. The upper part of the cell can be monitored by variable pathlength... 

Figure 4.1 Schematic diagram of a general-purpose CSTR recycle system for in situ investigations of liquid-phase homogeneous catalyzed reactions. The blocks represent in-line instruments and their signals, namely, (i) sets of scalar valued measurements (sensors), (ii) sets of vector valued measurements (ID spectroscopies) and (iii) sets of matrix valued measurements (2D spectroscopies). The recycle time for the system is given by t.

The inference of reactive surface formate species formed on zeolite CsOH/ Cs,NaX was further supported by CF MAS NMR spectroscopy (Fig. 27) (235,236). This in situ investigation was performed under CF conditions at a... 

Over the last years the utilisation of supramolecular arrays of surfactant molecules as structure-directing templates [1] has been applied to the synthesis of numerous mesostructured aluminophosphates [2-11]. In most cases the preparations were carried out in aqueous systems under hydrothermal conditions, but tetraethylene glycol and/or unbranched primary alcohols were also used [2,4]. Several discussions have been made on the reaction mechanisms that are involved in the syntheses of mesostructured materials [1,12-15] and recently a number of in-situ investigations on the formation processes of mesostructured silica phases in aqueous media have been reported these studies employed small angle X-ray diffraction [16-19] as well as 2H, 13C, 29Si, and 8lBr NMR spectroscopy and polarised light optical microscopy [17]. 

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