Preference test

The correct viscose age or ripeness for spinning varies according to the type of fiber being made. Ripeness can be assessed by estabHshing the salt concentration necessary to just coagulate the viscose dope. The preferred test uses sodium chloride (salt figure) although ammonium chloride is the basis of the alternative method (Hottenroth number). 

Filtered-Particle Inspection. Solids containing extensive inteiconnected porosity, eg, sintered metallic or fired ceramic bodies formed of particles that ate typically of 0.15-mm (100-mesh) screen size, are not inspectable by normal Hquid penetrant methods. The preferred test medium consists of a suspension of dyed soHd particles, which may be contained in a Hquid vehicle dyed with a different color. Test indications can form wherever suspensions can enter cracks and other discontinuities open to the surface and be absorbed in porous material along interior crack walls. The soHd particles that form test indications ate removed by filtration along the line of the crack at the surface where they form color or fluorescent indications visible under near-ultraviolet light (1,3). 

Evaluations have been conducted using deer, a multiple-choice preference-testing apparatus, and tetramethylthiuram disulfide [137-26-8] (TMTD) (29) or the fungicide thiram as a standard repeUent for competitive tests with repeUent-treated food (78). 

In paired comparison tests two different samples are presented and one asks which of the two samples has most of the sensory property of interest, e.g. which of two products has the sweetest taste (Fig. 38.3). The pairs are presented in random order to each assessor and preferably tested twice, reversing the presentation order on the second tasting session. Fairly large numbers (>30) of test subjects are required. If there are more than two samples to be tested, one may compare all possible pairs ( round robin ). Since the number of possible pairs grows rapidly with the number of different products this is only practical for sets of three to six products. By combining the information of all paired comparisons for all panellists one may determine a rank order of the products and determine significant differences. For example, in a paired comparison one compares three food products (A) the usual freeze-dried form, (B) a new freeze-dried product, (C) the new product, not freeze-dried. Each of the three pairs are tested twice by 13 panellists in two different presentation orders, A-B, B-A, A-C, C-A, B-C, C-B. The results are given in Table 38.3. 

For these reasons and other complex influences (e.g., large-diameter pipelines, particle-wall friction, particle shape, bends, etc.), it has been accepted that if high accuracy is needed, then some form of empiricism must be adopted. The preferred test-design procedure is listed below. 

Fig. 23.1 Results of the odor preference test in a Y-maze (A). Female mice carrying lesions in either the MOE (B) or VNO (C) were given a choice between volatile odors derived from an intact or a gonadectomized male...

Physical withdrawal phenomena drug preference tests... 

Place preference tests drug discrimination tests self administration procedures... 

Nicotiana glauca and anabasine as a preferred test plant/alkaloid... 

Plochberger, K. and A. Velimirov (1992). Are Food Preference Test with Laboratory Rats a Proper Method for Evaluating Nutritional Quality Biological Agriculture and Horticulture 8 221-233. 

Support for the pheromone hypothesis has come from preference tests in Atlantic salmon parr and experiments with sea lampreys migrating upstream to spawn. 

Campbell, D. L. and Bullard, R. W. (1972). A preference-testing system for evaluating repellents for black-tailed deer. Proceedings of the Vertebrate Pest Conference 5, 56-63. 

In general, bioequivalence is demonstrated if the mean difference between two products is within 20% at the 95% confidence level. This is a statistical requirement, which may require a large number of samples (e.g. volunteers), if the drug exhibits variable absorption and disposition pharmacokinetics. For drugs for which there is a small therapeutic window or low therapeutic index, the 20% limit may be reduced. The preferred test method is an in vivo crossover study and, since this occurs in the development phase, necessitates the emplo)unent of volim-teers. These studies are, therefore, expensive and animal experiments may be substituted, or in vitro experiments if they have been correlated with in vivo studies. 

Aramendia et al. (22) investigated three separate organic test reactions such as, 1-phenyl ethanol, 2-propanol, and 2-methyl-3-butyn-2-ol (MBOH) on acid-base oxide catalysts. They reached the same conclusions about the acid-base characteristics of the samples with each of the three reactions. However, they concluded that notwithstanding the greater complexity in the reactivity of MBOH, the fact that the different products could be unequivocally related to a given type of active site makes MBOH a preferred test reactant. Unfortunately, an important drawback of the decomposition of this alcohol is that these reactions suffer from a strong deactivation caused by the formation of heavy products by aldolization of the ketone (22) and polymerization of acetylene (95). The occurrence of this reaction can certainly complicate the comparison of basic catalysts that have different intrinsic rates of the test reaction and the reaction causing catalyst decay. 

Similar feeding preference tests have been conducted with penultimate and final instars of Paplllo g. glaucus and suggest... 

It is possible to build a basic system with chart-recorder output using components from various manufacturers. Suppliers of used equipment are another possible source. Sometimes there are equipment auctions but, having learnt from bitter experience, unless one can actually go and see (and preferably test) the items listed in the catalogue, this method of purchase should be avoided. Very often parts will be missing and, being obsolete, no longer obtainable. Used equipment suppliers always include some form of guarantee, and that is worth its cost. Some used or refurbished equipment suppliers are listed in Appendix 1. 

The result is always expressed as a transmission rate, not a permeability, and is, hence, dependent on test piece thickness. Generally, transmission rate is not a linear function of temperature or relative humidity and, preferably, test conditions are chosen to be as close as possible to those found in service. 

Exercise 11-17 Suppose you were given four unlabeled bottles, each of which is known to contain one of the following compounds pentane, 1-pentene, 2-pentyne, or 1-pentyne. Explain how you could use simple chemical tests (preferably test-tube reactions) to identify the contents of each bottle. (Notice that all four compounds are low-boiling liquids.)... 

How would you distinguish between the compounds in each of the following pairs using chemical methods (preferably test-tube reactions) ... 

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