Impurity pairs

Appropriate response. From a review of all retained lots and stability samples of API, no impurities were observed that eluted near the API with a resolution that was less than the resolution of known impurities X and Y. No other known impurity pairs have a resolution that is less than that for X and Y, thus these two components form the critical resolution pair. If these components are resolved to 3.0, then all known impurities will be resolved from the API and from each other. 

PAS Data Treatment. The lifetime spectra are resolved into two components, a long lifetime due to positrons trapped at defects (Td) and a short lifetime that mainly comes from free positrons in the matrix. For general interpretation, it can be considered that the positron lifetime (PL) technique is a well-established method for studying open-volume-type atomic defects and defect impurity interactions in metals and alloys. The lifetime of positrons trapped at vacancies, vacancy-impurity pairs, dislocations, microvoids, etc., is longer than that of free positrons in the perfect region of the same material. As a result of the presence of open-volume defects, the average positron lifetime observed in structural materials is found to increase with damage [127,128],... 

In metals the associations between impurity atoms and vacancies have important effects on the rates of age-hardening in alloys by affecting the diffusion of vacancies. The association enthalpy of a vacancy-impurity pair in metals may range from about 2 to 10 kcal/... 

In n type semiconductors, electrons are tire majority carriers. Holes will also be present tlirough accidental incoriioration of acceptor impurities or, more importantly, tlirough tlie intentional creation of electron-hole pairs. Holes in n type and electrons in p type semiconductors are minority carriers. 

There are many ways of increasing tlie equilibrium carrier population of a semiconductor. Most often tliis is done by generating electron-hole pairs as, for instance, in tlie process of absorjition of a photon witli h E. Under reasonable levels of illumination and doping, tlie generation of electron-hole pairs affects primarily the minority carrier density. However, tlie excess population of minority carriers is not stable it gradually disappears tlirough a variety of recombination processes in which an electron in tlie CB fills a hole in a VB. The excess energy E is released as a photon or phonons. The foniier case corresponds to a radiative recombination process, tlie latter to a non-radiative one. The radiative processes only rarely involve direct recombination across tlie gap. Usually, tliis type of process is assisted by shallow defects (impurities). Non-radiative recombination involves a defect-related deep level at which a carrier is trapped first, and a second transition is needed to complete tlie process. 

Example of copredpitation (a) schematic of a chemically adsorbed inclusion or a physically adsorbed occlusion in a crystal lattice, where C and A represent the cation-anion pair comprising the analyte and the precipitant, and 0 is the impurity (b) schematic of an occlusion by entrapment of supernatant solution (c) surface adsorption of excess C. 

Any material which can form a color center contains two types of precursors as shown in Figure 2a. The hole center precursor is an atom, ion, molecule, impurity, or other defect which contains two paired electrons, one of which can be ejected by irradiation, leaving behind a hole center (Fig. 2b). The electron center precursor is an atom, ion, etc, which can produce an electron center by trapping the electron ejected from the hole center precursor. A hole and an electron center are thus formed simultaneously. Either or both can be the color center. Almost all materials have hole center precursors. If there is no electron center precursor, however, the displaced electron returns to its original place and the material remains unchanged. 

PHOTOMETRIC DETERMINATION OF ACIDIC IMPURITIES IN OILS AND ORGANIC LIQUIDS WITH THE USE OF THE ION PAIR OF TRINONYLOCTADECYLAMMONIUM AND BROMOTHYMOL BLUE AS THE COLORED REAGENT... 

The spectra of these ion pairs are largely different, which forms the basis of the determination method for the spectrophotometric determination of acidic impurities. 

Let us assume that a given compound has a purity of 98 % ee, and that this compound is reacted with a derivatizing agent which has also a purity of 98 % ee. The two major compounds plus the minor impurities in the compound to be analyzed and the derivatizing agent will create a set of four diastereomers. Two pairs of diastereomers (-i-)-A(-i-)B and (-)-A(-)-B as well as (- )-A(-i-)-B and (-i-)-A(-)-B are enantiomeric pairs, and thus elute together on an achiral column. Therefore, a peak area of 98.011 % will be detected for (-i-)-A(-i-)-B, which leads to a purity of 96.03 % ee for (-i-)-A. This is a quite significant deviation from the true value for (-i-)-A. 

The aim of the present paper is to apply the impurity KKR Green s function method to the study of nearest-neighbor effective-pair interaction energies (NN-EPIE s) in low-concentrated fee di.sordered alloys (H = host, X = impurity c < 0.1). It is... 

The methanol-ether filtrate has a slight yellow color. It is not known what impurity is removed by this solvent pair. However, the submitters found that this treatment improved the yield of several aryl fluorides prepared according to the present procedure. 

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