MRAs

G. Szajer, in Ve -Mra, Analyses of Fats, Oik andEipoproteins, American Oil Chemists Society, Champaign, hi., 1991, Chapt. 18 T. Schmitt, ibid., Chapt. 19. 

The absorption spectrum of poly(2-methoxy-5-(2 -ethyI-hexyIoxy)-/mra-phenyIene vinylene) (MEH-PPV) is shown in Figure 7-8a. Phcnylene-based conducting polymers such as MEH-PPV exhibit multiple absorption features extending well into... 

This reaction cannot be elementary. We can hardly expect three nitric acid molecules to react at all three toluene sites (these are the ortho and para sites meta substitution is not favored) in a glorious, four-body collision. Thus, the fourth-order rate expression 01 = kab is implausible. Instead, the mechanism of the TNT reaction involves at least seven steps (two reactions leading to ortho- or /mra-nitrotoluene, three reactions leading to 2,4- or 2,6-dinitrotoluene, and two reactions leading to 2,4,6-trinitrotoluene). Each step would require only a two-body collision, could be elementary, and could be governed by a second-order rate equation. Chapter 2 shows how the component balance equations can be solved for multiple reactions so that an assumed mechanism can be tested experimentally. For the toluene nitration, even the set of seven series and parallel reactions may not constitute an adequate mechanism since an experimental study found the reaction to be 1.3 order in toluene and 1.2 order in nitric acid for an overall order of 2.5 rather than the expected value of 2. 

MRA describes any of the several MRI techniques that are used to depict arteries. These can be divided into contrast-based techniques and noncontrast-based techniques. 

Perfusion imaging techniques study pathophysiologic events that occur in capillaries and other microscopic blood vessels that cannot be seen by angiographic techniques like CTA or MRA. The perfusion imaging techniques in most widespread clinical use are performed using CT or MRl, and generally obtain or... 

Jacobs A, Lanfermann H, Neveling M, Szelies B, Schroder R, Heiss WD. MRI- and MRA-guided therapy of carotid and vertebral artery dissections. J Neurol Sci 1997 147 27-34. 

CTA and MRA are described in more detail in Chapter 2 therefore, this section will focus on CDUS. CDUS is widely available, well-validated, and is free of the risks and complications of radiographic contrast administration. Using ROC analysis, velocity criteria for detecting a residual lumen diameter of <1.5 mm have been developed based on pathological correlation with CEA plaques.In addition, transcranial Doppler can play an adjunctive role in dehning the hemodynamic signihcance of a lesion. ... 

Johnston and Goldstein found that compared to DSA, there was a misclassifi-cation rate of 7.9% for combined US and time-of-flight (TOE) MRA compared to... 

Patel SG, Collie DA, Wardlaw JM, Lewis SC, Wright AR, Gibson RJ, Sellar RJ. Outcome, observer reliability, and patient preferences if CTA, MRA, or Doppler ultrasound were used, individually or together, instead of digital subtraction angiography before carotid endarterectomy. J Neurol Neurosurg Psychiatry 2002 73(l) 21-28. 

Fraction of the variance The fraction of the variance of an MRA model is expressed by r. It is beheved that the closer the value of to unity, the better the QSAR model. The values of for these QSAR models are from 0.787 to 0.993, which suggests that these QSAR models explain 78.7-99.3% of the variance of the data. According to the literature, the predictive QSAR model must have > 0.6 [73,74]. 

Blomberg MRA, Siegbahn PEM. 2006. Quantum chemistry applied to the mechanisms of transition metal containing enzymes—Cytochrome c oxidase, a particularly challenging case. J Comput Chem 27 1373. 

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