Probe construction

The eddy currents testing probe realization was satisfactory at the sight of the control and the testing results of coating samples. The fundamental parameters to keep in mind for a probe construction are ... 

Depending on the sensor/probe construction, there may be from one to several capacities, each increasing the inertial error. The inertial error depends not only on the features of the instrument, but also on the character of the... 

The classical cure 131,132), apart from special probe construction precautions, is a pulse sequence using a phase device detection cycle in which one exploits the fact that acoustic ringing increases linearly with pulse width while NMR signal follows the sinusoidal nutation-angle curve. In its most elementary form, the cycle is composed of four steps (ideally with null 5) ... 

Raman probes constructed from fused silica optical fibers have gained much attention recently. Typically, low-OH content fibers are utilized to reduce the fiber fluorescence. The probe design also includes filters at the distal end to suppress the fused silica Raman signal from the excitation fiber and suppress the elastically scattered fight entering the collection fibers.25 Commercial probes are now available and they offer ruggedness and easy access to samples with various special or geometrical constraints. 

Fig. 20.2. Photo-switchable probes constructed from activator-reporter pairs, (a) Spectrally distinct reporters exhibit photo-switching behavior. The lower panel shows the fluorescence time traces of Cy5, Cy5.5, and Cy7 when paired with a Cy3 dye as the activator. The upper panel shows the green laser pulses used to activate the reporters. The red laser was continuously on, serving to excite fluorescence from the reporters and to switch them off to the dark state, (b) The same reporter can be activated by spectrally distinct activators. The lower panel shows the fluorescence time traces of Cy5 paired with different activators, Alexa Fluor 405 (A405), Cy2, and Cy3. The upper panel shows the violet (405nm, magenta line), blue (457nm, blue line), and green (532 nm, green line) activation pulses...

The characteristics of QCM sensors containing mono- or multilayered DNA probe constructed by direct chemical bonding, avidin-biotin interaction or electrostatic adsorption on polyelectrolyte films were compared by Zhou et al. [60]. The use of the polyethyleneimine adhesion, glutaraldehyde cross-linking (PEI-Glu) method to immobilize hepatitis B virus DNA onto gold QCM quartz crystals, enabling the sensor to be regenerated five times, was reported by Hu and co-workers [61],... 

A high-pressure probe constructed to allow the study of supercritical xenon as it interacts with different polymers (bisphenol-A polycarbonate or polytetrafluoro-ethylene) was reported by Nagasaka et al The probe, which has a zirconia cell with a Be-Cu flange and indium o-ring can be used in a range of pressure up to 20 MPa, and temperatures from 150 to 400 K (see Fig. 6). Experiments performed up to 10 MPa showed xenon inside the polymer experienced a very different state from that of free xenon, which was attributed to the limitation on xenon cluster size. Essentially no exchange between the supercritical and confined xenon phases occurred on the second timescale. 

One new approach is to match the magnetic susceptibility of the materials used in probe construction to a non-zero value. Olson et al. have obtained high-resolution NMR spectra using this susceptibility matching approach. A microcoil with an active volume of 5 nL was immersed into a fluid with a magnetic susceptibility similar to that of the copper coil, and thus compensated for the susceptibility mismatch at the air/copper interface. The spectral line width achieved was under 1 Hz, and the LODs were in the 10 to lOOpmol range. 

Probe construction materials were investigated for their signal contribution to ultrashort echo time spectroscopy and imaging. H-1, C-13, and P-31 spectra were obtained at a field strength of 9.4 T for 16 materials considered for use in probe and holder design and construction. Four of the materials were found to be suited for the construction of NMR probes, housing of RF coils, and holders for in vivo experiments. 

Deuteron magnetic resonance (DMR) measurements have been made on plasma-deposited samples of a-Ge D,H a-Si D,F and a-SiGe D,F. The experiments were performed at 30.7 MHz with a Bruker CXP 200 spectrometer and a probe constructed to permit operation at high rf power down to temperatures near 4 K, The 50 to 100 mg samples comprise less than 1 mm flakes in Kel-F containers of 5 mm diameter. 

In terms of immersion probe construction, it should be noted that chlorinated compounds can attack stainless steels and even very slowly dissolve Hastelloy. Thus, when selecting a probe optic, it is important to consider the chemical resistance of the probe material, body, window, O-rings, welds, and so forth to the chemical process under investigation. 

Figure 2. Aluminum-27 NMR spectrum at 104.2 MHz of a solution of composition AICI2CIO4 in anhydrous methyl cyanide. Resonances are observed due to AlCl4, Al(MeCN) (C104) "j , where = 0, 1, 2, 3, due to AlCl (MeCN) " ", where n =, 2, and possibly 3. The broad central resonance is due to aluminum in the solid material used in the probe construction. (Reprinted with permission from Akitt, NMR and Chemistry, 2nd Ed., Chapman and Hall, 1983.)...

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