Sequential assessment

Embryo/larval viability (see Note 10) and development can be evaluated under a microscope at various timepoints during the incubation period. This ability to do sequential assessments of the same individual embryo/larva is one of the greatest advantages of this model over mammalian systems. 

Bedard K, Smith S, Cribb A. Sequential assessment of an antidrug antibody response in a patient with a systemic delayed-onset sulphonamide hypersensitivity syndrome reaction. Br J Dermatol 2000 142(2) 253-8. 

Buschmann, J.U., and Dambach, M. 1997. Rivalry behaviour in African cave crickets as a test for the sequential assessment game. Adv. in Ethology 32, 144. 

Enquist, M., Leimar, O., Ljungberg, T., Mainer, Y, annd Segerdahl, N. 1990. A test of the sequential assessment game fighting in the cichlid fish Nannacara anomala. Anim. Behav. 40, 1-14. 

Design individuality Consider usage and disposal patterns Evaluate chemical and physical properties Select toxicological tests Relate effects to concentrations Provide sequential assessment Make decisions as early as possible... 

Duthie, J.R., 1977. The importance of sequential assessment in test programs for estimating hazard to aquatic life. In F.L. Mayer and J.L. Hamelink, (Eds.), Aquatic toxicology and hazard evaluation. ASTM STP 634. American Society for Testing Materials, pp. 17-35. 

The behavior of elements (toxicity, bioavailability, and distribution) in the environment depends strongly on their chemical forms and type of binding and cannot be reliably predicted on the basis of the total concentration. In order to assess the mobility and reactivity of heavy metal (HM) species in solid samples (soils and sediments), batch sequential extraction procedures are used. HM are fractionated into operationally defined forms under the action of selective leaching reagents. 

Another approach to assess the partitioning of metals among the phases comprising natural particulate matter is to sequentially and selectively extract or dissolve portions of natural particulate matter. Based on the release of trace metals accompanying each step, associations between the trace metal and the extracted phase are inferred. Both of the above approaches have drawbacks, and at this time it is impossible to predict in advance how and to what extent metals and particulate matter will bond to one another in a natural system. Despite the uncertainties, empirical results can often be interpreted using the framework provided here. 

If a Jessner s-35% TCA peel (Monheit) is performed, Jessner s solution is applied first prior to the TCA in an even sequential fashion from the forehead to the rest of the face, waiting 2 to 3 min to allow for penetration and assessment of frost. Typically this will produce a level 1 frost, erythema with faint reticulate whitening... 

Most plants exhibit "apical dominance" which means that the presence of a terminal (distal) meristem tends to suppress lateral shoot initiation (11). Since lateral shoot production is an important characteristic to assess in hydrilla, the frequency of shoot production was determined in sequentially cut (distal to proximal) explants (Table VI). Even though the 4 cm apical meristem contained several nodes, almost none of these produced new shoots. However, nearly half the 2-node explants subtending the cut apical meristem produced new shoots. There was no apparent difference in percent of new shoots produced once the apical meristem was removed. 

Although sequential fractionation procedures generally do not allow assessing the precise association of elements with each soil mineralogical phase, they can provide operationally defined phase associations and may be a powerful tool for the identification of some of the main binding sites, allowing to assess the potential for remobilisation and bioavailability of arsenic in polluted soils (Wenzel et al. 2001 Martin et al. 2007a). 

Method validation is carried out to provide objective evidence that a method is suitable for a given application. A formal assessment of the validation information against the measurement requirements specification and other important method performance parameters is therefore required. Although validation is described as a sequential process, in reality it can involve more than one iteration to optimize some performance parameters, e.g. if a performance parameter is outside the required limits, method improvement followed by revalidation is needed. 

Solid tailings were collected from test-pits and auger cuttings from boreholes in both the oxidized and reduced tailings. The tailings were analyzed for total metals. Sequential extraction of the tailings allowed the mobility of the metals to be assessed. Evaporites were also collected from the surface of the tailings. 

Chang, D., Hojilla-Evangelista, M.P., Johnson, L.A., and Myers, D.J. 1995. Economic-engineering assessment of sequential extraction processing of com. Trans. ASAE 38, 1129-1138. 

Adapted from Nemati K, Baker NKA, Abas MRB, Sobhanzadeh E, Low KH. Comparison of unmodified and modified BCR sequential extraction schemes for the fractionation of heavy metals in shrimp aquaculture sludge from Selangor, Malaysia. Environ. Mont. Assess. 2011 176 313-320. 

Whalley C, Grant A. Assessment of the phase selectivity of the European Community Bureau of Reference (BCR) sequential extraction procedure for metals in sediment. Anal. Chim. Acta 1994 291 287-295. 

Davidson CM, Duncan AL, Littlejohn D, Garden LM. A critical evaluation of the three-stage BCR sequential extraction procedure to assess the potential mobility and toxicity of heavy metals in industrially-contaminated land. Anal. Chim. Acta 1998 363 45-55. 

Unlike column chromatography approaches that can only process single samples sequentially, one TLC plate can accommodate and analyze multiple samples and standards. Numerous samples are processed simultaneously in a unique solvent tank, separating out the stabilizer or explosive analyte(s) away from the sample matrix. Semi-quantitative assessments with nanogram detection limits are readily obtained by inspection of the plates. This process allows numerous samples to be analyzed by a single operator per day. 

Estimates of service life are usually made either by natural or simulated trials or, most commonly, by accelerated tests with extrapolation to predict performance at longer times under less severe conditions. An alternative approach is to subject the product to environmental exposures which equate to the whole design life, and then to assess performance by real or simulated service tests (the end performance assessment). The exposures usually have to involve accelerated procedures and can be composed of several environmental agents applied simultaneously or sequentially. 

The sequential multiple analysers (SMAs) were later developments and they were much more complex in design and included a computer. They could analyse each sample for several constituents simultaneously, the number of channels determining this capacity, i.e. 6, 12 or 20. These instruments were developed primarily for hospital clinical chemistry laboratories to allow an overall assessment of the chemical composition of blood samples. They have now been superseded by other types of analysers. 

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