Detection, remote

D. Rochais, L. Paradis and F. Lepoutre, Remote detection of welds depth penetration by laser generated ultrasonics . Journal de Physique 4, Collogue C7, supp. J. Phys. 3, vol 4. 1994. 

Room-Temperature Fluorescence and the Remote Detection of Solar-Stimulated Luminescence... 

An important consideration for making NMR and MRI suitable for applications in chemical engineering is to provide for flexibility in handling samples of various sizes, materials, shapes or temperatures, while ensuring sufficiently high NMR detection sensitivity. In this chapter, we present a novel technique known as NMR and MRI remote detection [11,12], which addresses these problems in a fundamental fashion, as well as a few examples where remote detection has been applied successfully. 

Fig. 2.6.1 Schematic of an experiment with remote detection. The basic steps are (a) the polarization of the sensor medium, (b) NMR or MRI encoding using rf pulses and magnetic field gradients and (c) signal detection. The NMR or MRI information travels between the locations (b) and (c).

Broadening the Application Range ofNMR and MRI by Remote Detection I 143... 

The most fundamental aspect of a sensitivity discussion of remote detection is the fact that it is inherently a point-by-point technique. Each spectrum recorded by the detector does not contain any information other than its amplitude. Conceptually, a remote NMR experiment is very similar to a 2D NMR experiment with a z filter between encoding and detection, which causes all transverse magnetization to dephase. For 2D NMR experiments, it has been shown that the signal-to-noise ratio (SNR) per square root time, which will be denominated as sensitivity in the following, is the same as in the ID case when neglecting T2 relaxation [20, 21]. To compare the sensitivity of a remotely detected spectrum [Figure 2.6.4(b)] with an equivalent experiment with direct detection [Figure 2.6.4(a)], we can use an expression similar to the discussion in Ref. [20] ... 

Fig. 2.6.4 Sensitivity comparison between direct (a) and remote detection (b). With direct detection, an FID is recorded transiently with M data points, which are marked with the symbols x in the first FID in (a). Remotely, M encoding steps are necessary to obtain the same data set, which allows one to perform M signal averaging steps in the direct dimension in the same time. The encoding and detection steps in the remote experiment are intermingled, therefore only a time overhead correspon-...

In order to use Eqs. (2.6.1) and (2.6.2) to estimate the sensitivity gain obtained by remote detection, knowledge of the relative sensitivity of the detector and the encoding circuit, A, is required. Here we discuss the sensitivity of an rf coil detector as an example, because all the experiments presented in this text use inductive detection at high field. The signal-to-noise ratio of inductive NMR detection can be approximated by the following simplified equation [12] ... 

Application of NMR Remote Detection 2.6.5.1 Broadening the Application Range... 

Fig. 2.6.5 Hardware for high field NMR remote probe in (c) contains a relatively large saddle-detection. Photographs (a) and (b) show la- coil and is used for (flow) imaging. The detec-boratory-built remote detection probes with tor probe in (d) contains a microsolenoid coil both rf coils built into the same body (c), (d) for optimized mass sensitivity, which is parti-and (e) are detector-only remote probes that cularly useful for microfluidic NMR applica-can be inserted from the top or bottom into the tions. The same probe is shown in (e) with a NMR imaging assembly, so that the well mounted holder for a microfluidic chip that is...

High Field NMR Imaging with Remote Detection... 

The flowing sensor medium as an integral part of remote detection naturally leads to the study of flow through porous media [40, 41]. In addition to carrying the... 

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