Small punch analysis

A novel method is the small punch analysis, or pin on disk test, which is used to evaluate the weight loss of friction material. It is performed with a metallic pin in friction contact on a sample (small disk) the pin, moving cyclically, yields a stress-strain curve related to the specimen wear. This test is generally performed on retrieved, or aged, UHMWPE components. 

During the development of the small pimch test for UHMWPE, a validation analysis was performed comparing the results obtained from small punch... 

Acylcarnitine analysis of dried blood or bile spots is very similar to the analysis of plasma. A small disk (diameter typically 5 mm or less) is punched out of the blood spot and the acylcarnitines extracted by the addition of methanol and known concentrations of isotopically labeled acylcarnitines, which function as internal standards. The extract is dried under a stream of nitrogen, and derivatized by the addition of either n-butanol HC1 or n-methanol HC1. The acylcarnitines are measured as their butyl or methyl esters by MS-MS. The concentrations of the analytes are established by computerized comparison of ion intensities of these analytes to that of the internal standards. 

Linear profiles are the simplest profiles to use for powder compressions. Typically, a sawtooth or v-shaped profile is used where the punch is extended at a constant velocity and retracts at a constant velocity. In theory, during a sawtooth profile, the punch reverses its motion instantaneously between the compression and a decompression strokes. At low speeds (e.g.. <1 mm/sec), the hydraulic response system can easily accommodate this discontinuity. However, at high speeds (>100mm/.sec), the control system may show a small lag in the position-time waveform (<10 milliseconds) as it attempts to rapidly reverse the direction of punch. The sawtooth waveform is commonly used for more fundamental compression studies (e.g.. Heckel analysis), where the desired powder volume reduction is proportional to time. It is also u.seful when evaluating instrument performance during factory acceptance testing. 

Fig. 3.14 Concentration profiles of pore water from anoxic sediments obtained from an upwelling area off Namibia at a water depth of approximately 1300 m. The analysis of sulfide and methane was carried out in samples that were punched out with syringes from small and quickly sawed-out windows in the fresh sediment core. As for sulfide, these syringe-drawn samples were brought into an alkaline environment, whilst for methane analysis the samples were stored in head space vials for subsequent gas-chromatography analysis. The arrow points to a methane sample that originated from a sealed sediment core obtained by using a sample from the core catcher (after Niewohner et al. 1998).

The so-called Delves cup method was applied in many laboratories for PbB determination before the graphite furnace technique reached its highly developed present stage. The method was published by Delves (1970) and at that time it was one of the first reliable micro methods requiring only very small amounts of blood. It has been adopted by several authors for the analysis of capillary blood as well as for lead determinations on disks punched from filter paper previously spotted with a drop of blood (Cernik and Sayers, 1971 Cernik, 1974 Delves, 1977). 

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