Signal enhancement techniques

The data matrix is preprocessed using any signal enhancement technique to obtain the spectroscopic data of greatest interest as it relates to the spatial characteristics of the material or sample surface under study. In this particular case each data point represents the absorbance difference between a no absorbing wavelength for the paper surface and an absorbing wavelength for the transparent ink added to the paper. The difference in... 

Other examples of use of methods based on population transfers in NMR were provided in fhe comprehensive work by Cahill et al. ° These authors used FSG-RAPT as a routine signal-enhancement technique... 

Signal enhancement, if performed as a selective method, is very helpful for the assignment of NMR lines. In a more general manner, the application of signal enhancement techniques may improve the signal-to-noise ratio of the NMR spectrum, which is important for investigations of samples at elevated temperatures (Section II.D). 

Digital filter — A mathematical algorithm implemented by software used to eliminate unwanted frequencies from a measured signal and thus, increase the - SNR. Some of the most commonly used numerical signal enhancement techniques are ... 

The small cross sections in multiphoton processes are of course a weakness of nonlinear spectroscopy. Especially in microscopy, this problem becomes serious because of the small volume of a sample. By the use of the signal enhancement techniques, however, the disadvantage can be turned into an advantage of back-ground-free selective measurements. For example, the combined use of HRS with the plasmonic enhancement provides us a chemical imaging with nanoscale spatial resolution when a laser-illuminated metal tip is located adjacent to a sample surface, signal enhancement is locally induced near the tip. This spatial resolution is expected to overcome optical diffraction limit. Such tip-enhanced spectroscopy has already been reported in conventional CARS [15]. 

Increased sensitivity due to signal enhancement techniques, rapid relaxation, and the fact that a higher concentration of nuclei are between the poles of the magnet ... 

Raman scattering is known to be an extremely weak process. Its scattering cross-section is approximately 10" cm some 14 orders of magnitude smaller than the absorption cross-section of fluorescence. In order to collect a spectrum with a reasonable signal-to-noise ratio (SNR) and speed, signal enhancement techniques are required, and this is made possible by using TERS. 

Wiedorn KH, Goldmann T, Henne C, et al. EnVision+, a new dextran polymer-based signal enhancement technique for in situ hybridization (ISH). J Histochem Cytochem. 2001 49 1067. 

Flow cytometry protocols for defining cell surface or intracellular antibody staining are discussed. Various staining protocols are provided. Routine cell surface and intracellular techniques as well as more advanced signal enhancement techniques are detailed. 

The chemical shifts of phosphonates in P n.m.r. spectra are considerably different from those of phosphates, and with the advent of signal-enhancing techniques, P n.m.r, spectroscopy appears to be an ideal method for the determination of the relative amounts of phosphonates present in biological systems. Spectroscopic methods are preferable to those based on the... 

Since the introduction of MQMAS, much effort has been expended on developing methods to enhance the signal of the CT, and thus to extend the utility of the technique. A common signal enhancement technique is fast amplitude modulation (FAM). Shaped pulses, including the HS pulses introduced above,as well as p)psi78.208 been used for signal enhancement in MQMAS experiments. Kwak et have combined RAPT with the... 

Cross-polarization (CP) combined with MAS is the most important signal enhancement technique in SSNMR for... 

Hyperpolarization is a term which collects a set of dilferent signal-enhancement techniques in NMR spectroscopy. They have in common that they create population differences (polarizations) of the nuclear spin, which are far larger than the thermal equilibrium value (Boltzmann polarization). Following a proposal by Overhauser in 1953, which was experimentally verified by Carver and Slichter Dynamic Nuclear Polarization (DNP) schemes were developed. These techniques employ an auxiliary reservoir of fast and effectively polarizable spins to generate spin order which is subsequently transferred to the spin system of interest. In case of DNP experiments the strong polarization of electron spins is transferred to the nuclear spins by means of microwave irradiation. In the early days DNP experiments were restricted to relatively low fields ( H-frequency below 60 MHz) due to the technical limitations of klystrons used as microwave sources. 

As in threshold photoionization experiments, photofragment ion concentrations are extremely low and it is necessary to utilize signal-enhancement techniques. Although phase-sensitive detection has been used, it is more usual to employ signal-averaged pulse counting. For photodissociation with a pulsed laser, an appropriate gating system synchronized... 

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