Type-specimen

Type specimens are the designated standard for a given name. There are types for family, genus and species. A certain species may be designated as the type (ideal standard) for a family or genus. Types fall into several categories  

Obsolete terms that may be found on type or related specimens include  

Illustrated specimens that are not designated as primary types may be called vouchers or hypotypes. These are important specimens, although not as much so as primary types of the same species. 

In mineralogy, the same terms are used, but with different meaning. The holotype of a mineral species is the specimen from which the characterizing data was obtained, such as unit cell dimensions and shape, chemical formula, etc. Type specimens rarely exist for species defined before 1800. Since most modem analytical methods are, at least in part, destructive, sometimes the only existing sample is destroyed or processed in order to obtain the data needed to define a new species. 

Type collections should be maintained separately from a general collection, or at least in secure storage. Scientifically, they are the most important specimens in a collection. The type collection should include a reference for 

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In a few special cases, the standard spool-type specimen holder is not apphcable and a suitable special test method must be devised to apply to the corrosion conditions being studied. 

For conducting tests in pipe lines of 75-mm (3-in) diameter or larger, a spool holder as shown in Fig. 28-21, which employs the same disk-type specimens used on the standard spool holder, has been used. This frame is so designed that it may be placed in a pipe line in any position without permitting the disk specimens to touch the wall of the pipe. As with the strip-type holder, this assembly does not materially interfere with the fluid through the pipe and permits the study of corrosion effects prevailing in the pipe line. 

FIG. 28-21 Sp ool-type specimen holder for use in 3-in-diameter or larger pipe. (Mantell, ed., Engineering Materials Handbook, McGraw-Hill, New York, 1958.)... 

Syrett and Davis conducted in-vivo studies wherein they implanted crevice corrosion specimens of Co-Cr-Mo in dogs and rhesus monkeys for up to two years. Their results indicated the alloy was not susceptible to crevice corrosion. Galante and Rostoker implanted crevice-type specimens of Co-Cr-Mo and Ti-6A1-4V in the back of rabbits for 12 months. Although no evidence of severe corrosion was found in any of the specimens, several of the titanium and cobalt specimens did show signs of single pits in the crevice regions. 

As a plastic is subjected to a fixed stress or strain, the deformation versus time curve will show an initial rapid deformation followed by a continuous action. Examples of the standard type tests are included in Fig. 2-1. Details on using these type specimens under static and dynamic loads will be reviewed throughout this chapter. (Review also Fig. 8-9 that relates elasticity to strain under different conditions.)... 

Test specimens can also be used to simulate some degree of warpage. Figure 5-8 compares unreinforced and reinforced glass fiber-TS polyester flexural-type specimens at different temperatures in a droop test (with a center support), sag test (end supports), and an expansion test (bolted at three points). The study for this particular test is conducted at various temperatures. 

We prepared a strip-type specimen (100 X 50 X 2 mm) from the rubber sheet of SBR filled with HAH carbon black (50 phr), vulcanized for 30 min at 155°C. On the specimen, a slit of different lengths (si = 30 mm, S2 = 20 mm, S3= 10 mm) parallel to the extension direction and a notch of different lengths (2 or 5 mm) at the center of the side surface of the specimen perpendicular to the extension direction were made by razor-cutting (see the inserted figure in Figure 18.14). The distance 8 between slits and between the slit Si and the tip of notch was 1 and 3 mm, respectively. The no-slit specimen means that it only includes a notch, without slits. 

Anodic processes (p-type specimen or photodecomposition of n-type semiconductors) in aqueous electrolytes... 

A formal description of a mineral presents all the physical and chemical properties of the species. In particular, distinctive attributes that might facilitate identification are noted, and usually a chemical analysis of the first or type specimen on which the name was originally bestowed is included. As an example, the complete description of the mineral brucite (Mg(OH)2), as it appears in Dana s System of Mineralogy, is presented as Appendix 3. Note the complexity of this chemically simple species and the range of information available. In the section on Habit (meaning shape or morphology) both acicular and fibrous forms are noted. The fibrous variety, which has the same composition as brucite, is commonly encountered (see Fig. I.ID) and is known by a separate name, nemalite. ... 

Jat. Arrows point to populations found during fieldwork in the winter 1984-85. In addition to the locations shown, the type specimen was collected in (near ) San Jose Tenango. Miguel Aleman Dam refers to the lake. (Adapted from McMahon 1973.)... 

The family for Jerusalem artichoke is therefore frequently written as Asteraceae (Compositae). The modem names were introduced as a way of standardizing taxonomic terms (e.g., all family names now end in aceae for ease of recognition), and to realign certain groupings so that each family has a nomenclatural-type specimen. The family Asteraceae contains 476 genera in total. The genus Helianthus has sometimes been placed in the subtribe Helianthinae of the family Asteraceae (e.g., Robinson, 1981). 

Table 8.2. The amount of adsorbed carbon nanotubes on the surface of suspension polymers PS and PMMA with various surfactants, and electrical conductivities of prepared compression moulded discs-type specimens (61)...

A problem concerning DNA as the type specimen has been considered by Reynolds and Taylor [146] and Haines and Cooper [147]. Prillinger et al. [148] found that phenotypically identified strains of Sporothrix schenckii may be heterogeneous and stressed the importance of culture collections in modem genotypic identification. 

On semiconductors light emission is induced by injection of electrons into the conduction band and subsequent band-to-band radiative recombination with holes (Fig. 38a). The process is reminiscent of electroluminescence or cathodolumines-cence and works with p-type substrates only (at n-type specimens no hole is available at the surface). Tunnel biases of 1.5-2 V are necessary in the case of GaAs, for instance. Figure 38b is a photon map of a GaAlAs/GaAs multiquantum well obtained by Alvarado et al. [140], The white stripes are regions where photons are emitted and correspond to the GaAs layers. The lateral resolution is about 1 nm and is limited by the diffusion distance of minority carriers. In Sec. 5.1 we have seen an example of the application of this technique in the case of porous silicon layers. 

In-situ SPV measurements seem possible with minor modifications (1) the tip potential (versus the reference) is set at a value close to the rest potential of the semiconductor in darkness (this must be compatible with the electrochemical response of the tip), and (2) the tip current is quenched by adjusting the sample voltage (versus the reference) with the second feedback system. With p-type materials the method seems more obvious than with n-type specimens, since illumination promotes surface electrons. At n-type materials SPV measurements will induce corrosion since holes are driven to the interface. If absolute measurements of the SPV seem difficult, because they depend on the adjustment of the tip potential, differential measurements appear accessible to experiment. 

M. Krings, H. Geisert, R.W. Schmitz, H. Krainitzki, and S. Paabo. 1999. DNA sequence of the mitochondrial hypervariable region II for the Neandertal type specimen Proc. Natl. Acad. Sci. U.S.A. 96 5581-5585. (PubMed) (Full Text in PMC)... 

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