Intensity visual estimation

Column 14 These entries give the observed intensities, visually estimated according to the following simple scale, from the original film for copper in Fig. 3-13 (vs = very strong, s = strong, m = medium, w = weak). 

A number of rotation photographs were made with molybdenum. K-radiation filtered through a zirconium oxide filter to isolate the Ka line. The positions of useful reflections, the indices of the planes producing them, and their visually estimated intensities are given in Table V. The factor placed beside the estimated intensity is a correction for the varying time of reflection, namely Vi — (wl/dsin 20)2, where l is the wave-length, and u and d represent respectively the index of the axis of rotation and the unit translation along it1). (A number of reflections... 

Observed and calculated intensities of reflections on two oscillation photographs, one of which is reproduced in Fig. 5, are given in Table III. The first number below each set of indices (hkl) is the visually estimated observed intensity, and the second the intensity calculated by the usual Bade-methode formula with the use of the Pauling-Sherman /0-values1), the Lorentz and polarization factors being included and the temperature factor omitted. No correction for position on the film has been made. It is seen that the agreement is satisfactory for most of the... 

The values of G2 (calc.), calculated with the final parameters, are given in Table 2, where they are compared with G2 (obs.). Considering that the intensities were estimated visually from photographs, the agreement is excellent. The conventional reliability factor R, as applied here to the G2 rather than to structure factors, i.e. 

Because of the difficulty of obtaining satisfactory photometer records of electron diffraction photographs of gas molecules, we have adapted and extended the visual method to the calculation of radial distribution curves, by making use of the values of (4t sin d/2)/X obtained by the measurement of ring diameters (as in the usual visual method) in conjunction with visually estimated intensities of the rings, as described below. Various tests of the method indicate that the important interatomic distances can be determined in this way to within 1 or 2% (probable error). 

The s values and the visually estimated intensities for the four rings observed in the photographs are given in Table IV. The radial distribution function (Fig. 1) shows maxima at 1.27 and 2.29 A., the second being about twice as large as the first. 

The chitobiose unit has been treated as a rigid body, and by using the full-matrix, least-squares, rigid-body, refinement procedure, the structure was refined to an R factor of 40.7%. Visually estimated intensities were used. The structure was found to be free from short contacts, and to be stabilized by an intrachain OH-3—0-5 hydrogen-bond and one interchain N-H—O hydrogen-bond. 

Natural budworm densities were determined by sampling 6 sprays, each 40 cm long, In the same quarter of the tree used to collect tissue for chemical analysis and to collect defoliation data. Densities were expressed as the average number of budworm larvae per 100 buds per tree. A visual estimate of the amount of defoliation eilso was made In the same area of the crown where the densities and needle tissue were collected. Since budworm may disperse from heavily defoliated trees, (Greenback, 1963) budworm densities from each tree were weighted by the level of defoliation that each tree sustained. This resulted In an Infestation Intensity measurement (dependent variable) which was subjected to multiple stepwise correlation analysis using various foliage quality and physical tree parameters as the Independent variables. Thirty-one parameters were used as Independent variables In this analysis. 

Although only visual estimates of intensities were used, the number of reflections for which calculations were made is so large that the parameters may be accepted with considerable confidence. A view of the structure seen along the h axis is shown in Fig. 183. 

The structure of 2 was first determined in 1969 from the visual estimation of diffraction intensities obtained from Weissenburg rotational photographic data.26 This study established that the octahedral cluster contained an interstitial C atom and also showed the distribution of ligands around... 

The same data collection and reduction techniques are commonly used by the same workers for many different polymers. Therefore, data for these other polymers may contain errors on a similar scale, but that the errors have usually, but not always, gone undetected (8). If more than 500 reflections are observed, from single crystals of simple molecules, recognizable electron-density distributions have been derived from visually estimated data classified only a "weak", "medium" or "strong". The calculation of the structure becomes more sensitive to the accuracy of the intensity data as the number of data points approaches the number of variables in the structure. One problem encountered in crystal structure analyses of fibrous polymers is that of a very limited number of reflections (low data to parameter ratio). In addition, fibrous polymers usually scatter x-rays too weakly to be accurately measured by ionization or scintillation counter techniques. Therefore, the need for a critical study of the photographic techniques of obtaining accurate diffraction intensities is paramount. 

Witnauer (27,28) determined, from visually estimated intensities, that filaments of hydrated KBr-amylose have the space group 432 2 (D ) with cell constants as a = b = 10.7A, c = 16.1A. 

In some instances, intensities are still measured by visual estimation, although in general this practice has now been superseded by the use of one-dimensional microdensitometers. Typically, a radial scan is taken through the centre of each spot, the shape of the background is estimated and sketched in, and overlapping reflections are apportioned. The area under each reflection profile is then measured, and an empirical "arcing factor" is applied. In correcting for the Lorentz and... 

Visual comparison of spot intensity and/or size to a standard amount of the same pesticide run on the same TLC plate. This provides an estimation of the substance with approximately 20% accuracy. A detailed description of this method of visual estimation of thin layer chromatographs has been given by Johnson(21), who has very wisely commented that it is better to be "approximately right than precisely wrong". 

Because of the less than satisfactory results obtained in the first study of the Agri-screen test kit when used with peanut products and corn, a second collaborative study was run. In this second study of the Neogen kit, twelve coded test samples of raw and roasted peanuts and corn, with blind replicates, were analyzed by fourteen laboratories. The determination was slightly modified in that tetramethylbenzidine was used instead of ABTS as substrate for color development, and the analysts were instructed to compare color intensity with standards of varying concentration when using visual estimation. The results of this study are shown In Table III (9). 

In the examples just given, the observed intensity was estimated simply by visual comparison of one line with another. Although this simple procedure is satisfactory in a surprisingly large number of cases, there are problems in which a more precise measurement of diffracted intensity is necessary. Two methods are available for making such measurements, one dependent on the photographic effect of x-rays and the other on the ability of x-rays to activate an electronic counter. These methods have already been mentioned briefly in Sec. 1-8 and will be described more fully in Chaps. 6 and 7, respectively. 

The observed values of sin 0 for the first 16 lines are listed in Table 10-5, together with the visually estimated relative line intensities. This pattern can be indexed on the basis of a cubic unit cell, and the indices of the observed lines are given in the table. The lattice parameter, calculated from the sin 6 value for the highest-angle line, is 6.46 A. 

Coffee in the cup is usually poured black for the drinker to adjust its colour by adding milk or cream. The drinker uses the combination of milk and coffee as an indication of its anticipated taste although he or she may not know the actual concenfration of coffee in the drink. The most obvious appearance attribute of milk in coffee is the intensity of its colour, but translucency has also been shown to affect visual estimation of coffee strength (Hutchings 1999 Mackinney and... 

Dichlorostannic phthalocyanine undergoes a very interesting reaction with disodium phthalocyanine to form the unique bis(phthalocyanine)-tin(IV) (XLVI) (10), which is a distinct homogeneous phase (374), and which has been shown to contain quadrivalent tin by quantitative oxidation (89). Two polymorphs of (XLVI) are known, a and /J. The form purified by vacuum sublimation is converted to the a form when crystallized from naphthalene or 1,2,4-trimethylbenzene. Their infrared spectra are very similar, but they differ in their X-ray powder photographs. The d spacings (A) of the three strongest lines (visually estimated intensities in parentheses) are (195) ... 

The visual estimation is performed under field conditions by dropping 10% HCl onto a soil clod and observing its decomposition. Depending on the intensity of the gas release the CaCOg is estimated as follows hardly observable, short-term effervescence > 0.3% CaCOg weak, short-term effervescence distinct effervescence violent effervescence with long-term decomposition... 

The inclusion of the extra optical elements (e.g., the four extra bounces from the two detuned channel-cut postmonochromator crystals) in the optical path while producing the desired effect of increasing the XSW phase (or atomic positional) resolution, come at the cost of reducing the X-ray intensity incident on the sample. Using Figure 12a one can visually estimate this effect by comparing the emittance from the second Si(004)... 

In the Zn3As2 ZnTe system the additional mean-square displacement of the cations amounted to 0.034 of the lattice constant (0.2 A). The solid solutions of the ZngAsg-CdTe system were less homogeneous and it was not possible to determine individually the line intensities with odd khZ and h + k + Z = 4n + 2. A visual estimate convinced us that the intensities of these reflections increased at the same rate as in the ZngAsg-ZnTe system, hi the calculations we therefore assumed in all cases that the additional mean-square displacement of the cations was 0.034 of the lattice constant. The nature of the cation distribution over the tetrahedral voids affected only the ratios of the intensities of the reflections with an even or an odd sum of the indices. 

---