Acronyms Experiment

Many variations of the basic homonuclear COSY experiment have been devised to extend its range. A brief guide to some classes of experiment follows, along with a few of the connnon acronyms. 

A H(detected)- C shift correlation spectrum (conmion acronym HMQC, for heteronuclear multiple quantum coherence, but sometimes also called COSY) is a rapid way to assign peaks from protonated carbons, once the hydrogen peaks are identified. With changes in pulse timings, this can also become the HMBC (l eteronuclear multiple bond coimectivity) experiment, where the correlations are made via the... 

ELDOR is tlie acronym for electron-electron double resonance. In an ELDOR experiment [28] one observes a rednction in the EPR signal intensity of one hyperfme transition that results from the saturation of another EPR transition within the spin system. ELDOR measurements are still relatively rare bnt the experiment is fimily established in the EPR repertoire. 

HC HMQC (heteronuclear multiple quantum coherence) and HC HSQC (heteronuclear single quantum coherence) are the acronyms of the pulse sequences used for inverse carbon-proton shift correlations. These sensitive inverse experiments detect one-bond carbon-proton connectivities within some minutes instead of some hours as required for CH COSY as demonstrated by an HC HSQC experiment with a-pinene in Fig. 2.15. 

In 2000, Krishnamurthy et al. have presented the 2/,3/-HMBC experiment (Figure 20), that affords for the first time the means of unequivocally differentiating between 2/ch from 3Jch correlations.59 Their approach is based on a further derivative of the constant-time variable delay introduced in the IMPEACH-MBC experiment. The user-definable /-scaling factor of the CIGAR-HMBC is used in the new experiment, the 2J,3J-HMBC experiment, to differentiate between 2/CH from 3Jch correlations. This new pulse sequence element has been given the acronym STAR (Selectively Tailored Accordion F1 Refocused) operator. 

The AquaTerra acronyms are adopted here to provide an easier understanding of the format of each experiment. The first part of each acronym refers to the RCM and the second to the GCM data used to provide the boundary conditions. Scenario simulations have the further suffix A2. For further details on RCM formulations, see [27]. Some AquaTerra studies used a smaller subset of this ensemble... 

Just as in the COSY type of experiments this cross-relaxation effect is not restricted to protons, but can also involve heteronuclei the acronym HOESY (heteronuclear Overhauser effect) is used in these cases. This can be used, for example, to show that an anion such as IT1., is in close proximity to the ligands of the organometallic compound, as was carried out by Macchioni et al. with a 19F-xH HOESY experiment [24]. 

The acronym COSY stands for Correlated SpectroscopV and this technique is widely used to determine all of the coupling interactions in a single experiment. This proves to be more efficient than the decoupling experiment in which each signal is irradiated in turn to determine its coupling partners. COSY involves a multiple pulse sequence (which we do not need to know anything about in order to use the technique) and is an example of two-dimensional (2D) spectroscopy. 

As DEPT relies on the transfer of polarization from a directly bonded H atom to the carbon - resulting in the increased sensitivity of the carbon atoms - only C atoms that are attached to H atoms are detectable by this method, and so no quaternary carbon atoms are seen on DEPT spectra. Depending upon something called the pulse angle (which is expressed as a number after the acronym, but we do not need to know its significance), there are three different DEPT experiments that can be carried out on a particular sample. 

Based upon the foregoing experiences, some researchers observed that the same reluctance to interact with matter is responsible for the neutrino s long range and ability to resist detection. Tlios, it was reasoned that an apparatus for detecting neutrinos should be massive and shielded from the interference of other particles and radiation. As a solution to these problems, some researchers proposed a deep underwater muon and neutrino detector (acronym DUMAND). 

Finally, in order to relate the acronyms for the various techniques to the scattering and emission experiments on which they are based, we present in Table I an indication of the relationship between these acronyms, the type of information which they provide, and the scattering or emission experiment which they designate. The definition of the acronyms is given in Table II. These tables embody only "commonly used" methods. Considerably more extensive lists may be found elsewhere in the literature (1, 5.-9, 20> 30> 36)- Unfortunately, all authors do not use the same acronyms. Therefore Tables I and II are a guide to but not a glossary of the acronyms used in other papers in this symposium. 

Many readers will already be aware that acronyms for 2-D NMR experiments have proliferated along with available experiments. This chapter attempts neither an encyclopedic approach to describing these acronyms nor their experimental counterparts. This chapter does, however, cover enough important experiments to enable the reader to interpret nearly any 2-D experiment that one is likely to encounter. Acronyms are listed in the index. 

In chemistry the term STP does not refer to an oil additive for cars but rather is an acronym for standard temperature and pressure. Standard temperature has been set by the scientific community to be 0°C, and standard pressure to be 1 atmosphere or 760 mm or 760 torr. Because gas experiments are performed under a variety of temperature and pressure conditions in laboratories all over the world, it is necessary that scientists have some type of standard so that they can compare results. STP is this standard, and results are often said to be corrected to STP. That is, the results have been calculated to be the values that they would be at STP. 

The variety of 2D NMR experiments, each with its own acronym, can easily be understood by knowing the nature of the I and S spins (e.g., XH and 13C) and the type of mixing used (e.g., coherence transfer via one-bond J coupling). Two general distinctions can be made ... 

The shapes of molecules are determined by actual experiments, not by theoretical considerations. But we do not want to have to memorize the shape of each molecule. Instead, we would like to be able to look at a Lewis structure and predict the shape of the molecule. Several models enable us to do this. One of the easiest to use is valence shell electron pair repulsion theory, which is often referred to by its acronym VSEPR (pronounced vesper ). As the name implies, the theory states that pairs of electrons in the valence shell repel each other and try to stay as far apart as possible. You probably remember this theory from your general chemistry class. The parts of VSEPR theory that... 

This technique was extended by Schmidt-Rohr et al.251 and was given the acronym DECODER (direction exchange with correlation for orientation-distribution evaluation and reconstruction). The pulse sequence of the 2D version of this method, which is shown in Fig. 16(a), is basically a typical 2D exchange experiment except that the sample is reoriented during the mixing time. Consequently, the correlation of, for example, the chemical shift interaction at two different sample orientations is obtained. 

STP was said to be an acronym for "Serenity, Tranquility and Peace, although for many it proved to be a foundation-shaking experience. Among the first to try STP was Richard Alpert, who took it in an apartment building on 57th Street in Manhattan and promptly tried to walk out the window. He was so scared by his response that he said the drug should not be released under any circumstances, that it was too intense. Later, considering that... 

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