Residue endpoints

Example Molecular dynamics simulations of selected portions of proteins can demonstrate the motion of an amino acid sequence while fixing the terminal residues. These simulations can probe the motion of an alpha helix, keeping the ends restrained, as occurs n atiirally m transmembrane proteins. You can also investigate the conformations of loops with fixed endpoints. 

A common procedure for the preparation of vinylated alkyds is as foUows. A base alkyd resin is brought to the desired endpoint. The resin is then cooled to about 160°C and often diluted with aromatic thinner. The desired monomer is added, usually at about 20 —60% based on the final product, foUowed by an appropriate amount of a free radical initiator. Alternatively, a premix of the monomer and the initiator is added at a controUed rate over most of the reaction. The reaction is brought to monomer reflux, until the residual monomer content has fallen below a specified level. Residual monomer, if any, is stripped away before the product is diluted in a solvent, filtered, and packaged. 

One 1-ml aliquot is added to 1.0 ml of freshly-distilled 1,2-dibromo-ethane (bp 132°C) in an oven-dried flask which contains a static atmosphere of nitrogen or argon. After the resulting solution has been allowed to stand at 25°C for 5 min, it Is diluted with 10 rat of water and titrated for base content (residual base) to a phenolphthalein endpoint with standard 0.100 M hydrochloric acid. The second 1-mL aliquot is added cautiously to 10 ml of water and then titrated for base content (total base) to a phenol phthalein endpoint with standard aqueous 0.100 M hydrochloric acid. The methyllithium concentration is the difference between the total base and residual base concentrations.2 Alternatively, the methynithiura concentration may be determined by titration with a standard solution of sec-butyl alcohol employing 2,2 -bipyridyl as an indicator. 

When monitoring efficacy of drug treatment for benign prostatic hyperplasia, subjective endpoints include relief of obstructive and irritative voiding symptoms. Objective endpoints include improvements of urinary flow rates, decreased post-void residual urinary volume, and decreased complications of disease. 

The determination of traces of higher-boiling hydrocarbons and oily matter involves use of a method for residue that involves a preliminary weathering. The residue after weathering is dissolved in a solvent and the solution is applied to a filter paper. The presence of residue is indicated by the formation of an oil stain. The procedure is taken further by combining the oil stain observation with other observed values to calculate an endpoint index (ASTM D2158). The method is not very precise, and work is proceeding in several laboratories to develop a better method for the determination of residue in the form of oily matter. 

Frequently, however, the lack of specificity in an analytical technique can be compensated for with sophisticated data processing, as described in the chemometrics chapter of this text (Chapter 8). Quinn and associates provide a demonstration of this approach, using fiber-optic UV-vis spectroscopy in combination with chemometrics to provide realtime determination of reactant and product concentrations.23 Automatic window factor analysis was used to evaluate the spectra. This technique was able to detect evidence of a reactive intermediate that was not discernable by off-line HPLC, and control charting of residuals was shown to be diagnostic of process upsets. Similarly, fiber-optic NIR was demonstrated by some of the same authors to predict reaction endpoint with suitable precision using a single PLS factor.24... 

The distinguishing features of resid feedstocks are (1) the presence of asphaltenes or pentane-insolubles, (2) high carbon residues, (3) the presence of metals, mainly nickel and vanadium, and (4) unknown endpoints insofar as boiling range is concerned. 

Singhal et al. [306] have determined oxamyl residues (methyl-N. N -dimclh-yl-N- [methylcarbamoyl] oxy-thioaminimidate) by a method based on reaction with carbon disulfide and copper in which excess copper is added to an extract of the soil and the excess copper is determined by titration with 0.001 M EDTA to the l-(2-pyridylazo)-2-naphthol endpoint. 

The primary endpoint was procedural success defined as <20% residual stenosis, Secondary endpoints included death, Ml, unplanned revascularization, or surgical intervention for ischemia, amputation through 30 days and major bleeding. Aspirin was administered in 96.8% of the patients and clopidogrel to 95% of the patients. 

Because experimental error is always present in a measured data matrix, the corresponding row-mode eigenvectors (or eigenspectra) form an orthonormal set of basis vectors that approximately span the row space of the original data set. Figure 4.14 illustrates this concept. The distance between the endpoints of a and a is equal to the variance in a not explained by x and y, that is, the residual variance. 

Inspections on the four mid-distillates are presented in Table II. The 560°F endpoint for the H-Coal mid-distillate is caused by the fact that the 560° F+ material was delivered as process residue containing the ash and unreacted coal. The residue material was very difficult to distill in a batch system. Scheduling pressures forced the H-Coal hydrocracking runs to be done on the available material. 

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