In situ measurement

In organic-rich and highly reactive sediments, the depletion of oxygen previously imported by means of diffusion already occurs in the uppermost millimeters of the sediment (cf. Sect. 

However, these organic-rich and young sediments are mostly extremely rich in water (porosity values up to 0.9) and very soft, so that every sample removal will most likely induce a perturbation of the boundary zone which is, in a crucial way, maintained by diffusion. 

Main ballast release Secondary ballast release (1 of 3) (7) Electronic pressure case (7) Sampling racks Syringes 

The lander technique described above is, especially in the deep sea, more easily outlined in brief theory than to put into operation, as the involved workers need to invest a considerable 

By using such electrodes it is now possible to describe a diffusive boundary layer at the transition zone between the sediment and the bottom water with a sufficient degree of depth resolution (Fig. 3.22). This layer characterizes a zone which lies directly over the sediment and is not influenced by any current. Instead, a diffusion controlled transport of material characterizes the exchange between bottom water and sediment. This layer which possesses a thickness of 0.2 - 1 mm still belongs to the bottom water with regard to its 

From the intensity of the emitted radiation, the abundance of such surface elements can be derived. This process is illustrated in Fig. 9.2. 

For example hydrogen emits a strong signal at 2223 keV due to prompt gamma emission following neutron capture on hydrogen (Boynton et al 2002 [42]). 

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In situ measurement of the concentration of radioactive tracers in the different phases requires that the phases are separated and arranged according to density difference over the measurement cross section in a horizontal pipe. In general, the measurements are performed with two spectral gamma radiation detectors placed on top and bottom of the pipe respectively. 

Figure C2.10.2. Cyclic voltammogram of Cu(l 11)/10 mM HCl and in situ measured STM micrographs revealing tire bare Cu(l 1 l)surface (-1.05 V, left) and tire (V3 x A/3)R30°-Cladsorbate superstmcture (-0.6 V, right) (from [39]).

Carman equation is not vahd at void fractions greater than 0.7 to 0.8 (Billings and Wilder, op. cit.). In addition, in situ measurement of the void fraction of a dust layer on a filter fabric is extremely difficult and... 

A wide selection of metal reference foils and powder films of ideal thickness for tranmission EXAFS is available from The EXAFS Materials Company, Danville, CA, USA. The transmission method is well-suited for in situ measurements of materials under industrially relevant conditions of extreme temperature and controlled atmosphere. Specially designed reactors for catalysis experiments and easy-... 

PL measurements are generally nondestructive, and can be obtained in just about any configuration that allows some optically transparent access within several centimeters of the sample. This makes it adaptable as an in situ measurement tool. Little sample preparation is necessary other than to eliminate any contamination that may contribute its own luminescence. The sample may be in air, vacuum, or in any transparent, nonfluorescing medium. 

In-situ measurements into vacuum systems In these experiments the light beams enter and leave via optical ports (usually at a 70° or 75° angle of incidence), and... 

Dunuwila, D. and Berglund, K.A. 1997. ATR FTIR spectroscopy for in situ measurement of supersaturation. Journal of Crystal Growth, 179, 185-193. 

Larson, M.A. and Klekar, S. A., 1973. In-situ measurement of supersaturation in crystallization from solution. Presented at American Institute of Chemical Engineers 66th Annual Meeting, Philadelphia, November. 

In mechanistic studies of stress corrosion and also in the collection of data for remaining-life predictions for plant there is need for stress-corrosion crack velocity measurements to be made. In the simplest way these can be made by microscopic measurement at the conclusion of tests, the assumption being made that the velocity is constant throughout the period of exposure, or, if the crack is visible during the test, in situ measurements may be made by visual observation, the difficulty then being that it is assumed that the crack visible at a surface is representative of the behaviour below the surface. Indirect measurements must frequently be resorted to, and these... 

The physical methods mostly require ultra high vacuum conditions having the disadvantage of not being applicable directly to solvent swollen films, but recent developments of in situ measurements in SIMS X-ray diffraction surface enhanced Raman spectroscopy (SERS) and scanning electrochemical tunneling microscopy... 

A typical field test involves several steps (a) transporting the mobile unit to the site (b) instrument warmup (c) system check out, consisting of mobile unit measurements of distilled water and a 1-ppm stock phenol solution and (d) in situ measurements of the well water, repeated three times for statistical analysis. Signal levels recorded at a field site may be reported as equivalents of phenol (or other calibrant) using the calibration curves. Therefore, this method allows us to report the upper bounds of pollution levels. 

Note When this reagent sequence is combined with the in situ measurement of the UV spectra of the chromatogram zones before derivatization this reagent sequence becomes virtually specific for hydrochlorothiazide and its related derivatives in the analysis of urine. Hence, it is possible to use it for drug monitoring and doping control. 

We are first concentrating on commercially-available instrument technologies providing in situ measurements in polymer reactors, as opposed to those requiring new instrument development or external sampling loops. 

Fig. 5. Estimated characteristic strength of typical biological particles of interest to biotechnology data are based on in-situ measurements of the minimum stresses necessary to cause permanent breakage of particles. For comparison data are shown based on Van der Waals and pendular liquid bridges between two 10-pm particles, 0.01 pm apart...

Tools shape how we think when the only tool you have is an axe, everything resembles a tree or a log. The rapid advances in instrumentation in the last decade, which allow us to measure and manipulate individual molecules and structures on the nanoscale, have caused a paradigm shift in the way we view molecular behavior and surfaces. The microscopic details underlying interfacial phenomena have customarily been inferred from in situ measurements of macroscopic quantities. Now we can see and fmgeT physical and chemical processes at interfaces. 

Ideally, it should be possible to use the physical methods for time-resolved in situ measurements. The use of these methods requires the existence of a well-developed theoretical basis for each method. 

W. Cheng, D. Coleman, C. R. Carroll, and C. A. Hoffman, In situ measurement of root respiration and soluble C concentrations in the rhizosphere. Soil Biology and Biochemistry 25 1189 (1993). 

Residue chemists will need to continue to improve the speed of analysis. In situ measuring methods that can be applied in the field or processing plant or retail outlet would be particularly useful, so that decisions can be made rapidly which might avert toxicity to humans or wildlife, potential residue problems or unnecessary economic loss. 

Kim, H.-B., Hayashi, M., Nakatani, K., Kitamura, N., Sasaki, K., Hotta, J.-I., and Masuhara, H., In situ measurements of ion exchange processes in single polymer particles laser trapping microspectroscopy and confocal fluorescence microspectroscopy, Anal. Chem., 68, 409, 1996. 

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