Problems in determination

The presence of a Faradaic electrode reaction of any kind competing with the double layer charging presents a problem in determining the purely capacitive current needed to calculate the surface charge. From a plot of 1 vs. (/ = total electrode current) with a fixed concentration of the ions of the electrode metal dissolved in solution, the surface charge can be obtained [65Butl]. (Data obtained with this method are labelled TC). 

Konieczka P, Wolska L, Namiesnik J (2010) Quality problems in determination of organic compounds in environmental samples, such as PAHs and PCBs. TrAC, Trends Anal Chem 29(7) 706-717... 

This variation attempts to address a real problem in determining the optimum level of water addition. Some flour samples need more water added than others. 

As well as the solid solution formula given above, there have been suggestions that compositions off the join may also give single-phase NASICON. Part of the problem in determining solid solution stoichiometries and limits in materials such as NASICON arises because of the... 

Schrap, S.M., de Vries, P.J., and Opperhuizen, A. Experimental problems in determining sorption coefficients of organic chemicals an example of chlorobenzenes, Chemosphere, 28(5) 931-945, 1994. 

The basic problem in determining phase equilibria in multicomponent systems is the existence of a large number of variables, necessitating extensive experimental work. If ten measurements are considered satisfactory for acceptable characterization of the solubility in a two-component system in a particular temperature range, then the attainment of the same reliability with a three-component system requires as many as one hundred measurements. Therefore, a reliable correlation method permitting a decrease in the number of measurements would be extremely useful. Two different methods - the first of them based on geometrical considerations, and the second on thermodynamic condition of phase equilibria - are presented and their use is demonstrated on worked examples. 

The problem in determining resonance energies is to single out of the total energy of the molecule the contribution from the cyclic bond delocalization. 

Most psychiatric patients do not meet the criteria of one particular disorder as presently defined, but show signs and symptoms of a multitude of disorders, or rather they display a patchwork of parts of different disorders. This situation faces biological psychiatry with insurmountable problems in determining which of the disorders in a given patient is the behavioral correlate of a particular biological disturbance. The hierarchical principle as applied in the later DSM editions—albeit inconsistently— provides no more than an ostrich solution. The problems of comorbidity do not disappear by concealing them. 

For polymers, a problem in identifying the reflections causes a problem in determining atomic arrangements from X-ray diffraction results. Polymers do not usually exhibit reflections greater than 4 or 5. Using oriented materials greatly simplifies data. 

Experimental determination of ATP, ADP, and Pj concentrations in brain, muscle, and liver, and a discussion of the problems in determining the real free-energy change for ATP synthesis in cells. 

The fact that the complex has a great affinity for water presents a problem in determining its density. However, by placing the samples of the complex in desiccators at different relative humidities it could be determined when the free (or adsorbed) water had been lost and when the water of hydration (or crystallization) had been lost. That is, by watching the weight loss in the samples as the relative humidity varied (Table I) and by comparing this with the x-ray powder... 

One major problem in determining phase transition lines is associated with the use of finite systems, so that near criticality the correlation length of the fluctuations begins to exceed the size of the simulation box. Finite-size... 

The inversed hexagonal structure, with water cylinders arranged in a matrix formed by the disordered hydrocarbon chains (Figure 1, left), is a common structure in aqueous systems of lipids of biological origin. There is usually no problem in determining the true alternative between the two hexagonal structures from the x-ray data, and the molecular dimensions can then be calculated. The occurrence of this structure in complex lipids results from the molecular shape two hydrocarbon chains are usually... 

The principal problems in determining size distribution parameters with cascade impactors are wall losses, inefficient collection due to particle bounce, deposition of gas-phase species on impaction substrates, and deposition of fine particles from boundary layers. 

In structure determination from X-ray diffraction data, it sometimes happens that, on the Fourier maps, parts of the coming out structure are unclear. Fuzzy electron density maps may present problems in determining even the approximate positions of the respective fragments of the structure being analyzed. For example, the layered structure of the inclusion (intercalation) compound formed by Ni(NCS)2 (4-methylpyridine)4 (host) and methylcellosolve (guest) [1], The guest molecules are (Fig. 11.1) located on twofold crystal axes of unit cell symmetry and are orientationally disordered as shown in the picture. 

One important problem in determining efficacy of treatment seems to be the choice of the type of control. While in most cases the same volume of saline is injected into the intervertebral disk as a control 96], little or no rf ia are available that compare the effect of chymopapain treatment with the natural history of the disease [97]. This problem was discussed in an editorial in the Lancet in 1986 [98]. However, a number of studies have been published that compare chemonucleolysis with traditional surgical disc removal [99-1021. These studies indicate that surgical disc removal has an equal or slightly better overall success rate than chemonucleolysis. It has been argued that if chymopapain treatment fails, subsequent surgery may be less successful, especially if the operation Is delayed [103], but recent results indicate that this is not the case [104],... 

There are problems in determining crystallite size from line broadening alone, since factors other than crystallite size contribute to the broadening, including local strain in the crystallites and shape anisotropy. Some of these problems can be overcome by the use of Fourier analysis of the peak shape. The cosine coefficients of the Fourier series can be used to determine a surface weighted average size for the crystallites. 

Grob, K. and Bronz, M. (1994) Analytical problems in determining 3,5-stigmastadiene and campestadiene in edible oils. Riv. Ital. Sost. Grasse, 71, 291-295. 

The chemical art creates great problems in determining a correct chemical inventor entity. One built-in problem is the frequent later determination of a utility for a chemical compound or composition. An invention is not complete until its usefulness is determined, and this utility may be established either by an extended technical arm of the chemist who made the compound or by someone who is not such an arm. 

Spear, R.C. (1980). Technical problems in determining safe re-entry intervals, J. Environ. Pathol Toxicol, 4, 293-304. 

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