Flat sample

Flartmann U 1991 van der Waals interactions between sharp probes and flat sample surfaces Phys. Rev. B 43 2404... 

Transmission. The spectral transmission of glass is determiaed by reflectioa at the glass surfaces and the optical absorption within the glass. Overall transmission of a flat sample at a particular wavelength is equal to (1 — R), where P is the absorption coefficient, t the thickness of glass, and... 

For flat samples such as press cured slabs the resistivity may be computed from the foUowiag formula where p = resistivity, R = resistance, A = area of the sample (the effective area of the smaller electrode if two electrodes of different sizes ate used), and t = thickness of the sample. 

Radioactivity in environmental waters can originate from both natural and artificial sources. The natural or background radioactivity usuaUy amounts to <100 mBq/L. The development of the nuclear power industry as weU as other industrial and medical uses of radioisotopes (qv) necessitates the deterrnination of gross alpha and beta activity of some water samples. These measurements are relatively inexpensive and are useful for screening samples. The gross alpha or beta activity of an acidified sample is deterrnined after an appropriate volume is evaporated to near dryness, transferred to a flat sample-mounting dish, and evaporated to dryness in an oven at 103—105°C. The amount of original sample taken depends on the amount of residue needed to provide measurable alpha or beta activity. 

Sample requirements Vacuum-compatible material flat samples best size accepted depends on instrumentation... 

Electron Probe Microanalysis, EPMA, as performed in an electron microprobe combines EDS and WDX to give quantitative compositional analysis in the reflection mode from solid surfaces together with the morphological imaging of SEM. The spatial resolution is restricted by the interaction volume below the surface, varying from about 0.2 pm to 5 pm. Flat samples are needed for the best quantitative accuracy. Compositional mapping over a 100 x 100 micron area can be done in 15 minutes for major components Z> 11), several hours for minor components, and about 10 hours for trace elements. 

A typical LIMS instrument accepts specimens up to 19 mm (0.75 in) in diameter and up to 6 mm in thickness. Custom designed instruments exist, with sample manipulation systems that accept much larger samples, up to a 6-in wafer. Although a flat sample is preferable and is easier to observe with the instrument s optical system, irregular samples are often analyzed. This is possible because ions are produced and extracted from pm-sized regions of the sample, without much influence from nearby topography. However, excessive sample relief is likely to result in reduced ion signal intensity. 

The aims of sampling are to establish whether eontaminants are present, their distribution and eoneentrations. Commonly-used sampling regimes inelude square grid, stratified random or simple random teehniques. Evenly-spaeed sampling points may be appropriate if the eontamination is visible otherwise judgement is required based on whether the land slopes or is flat. Samples are also taken near to the point of release. 

The elasticity was quantitatively determined by analyzing the recorded force curves with the help of the Hertz model. The Hertz model describes the elastic deformation of two spherical surfaces touching imder the load, which was calculated theoretically in 1882 by Hertz. Other effects, such as adhesion or plastic deformation, were not included in this model. Sneddon extended the calculation to other geometries. For a cone pushing onto a flat sample, the relation between the indentation 5 and the loading force F can be expressed as ... 

The gas-permeability coefficient K of the material is obtained by measuring the gas flow J through a flat sample with thickness L under a total pressure difference AP. The gas-permeability coefficient K is a two terms sum ... 

The second requirement is related to chemical imaging applications. Very flat samples are required to avoid problems of depth of field. Even if this is common to every imaging technique, it is in this case coupled with surface pollution problems. Sample preparation must then lead to flat surfaces without surface pollution. For cultural heritage samples,... 

Texture observed for a flat sample between crossed polarizers, showing a network of black brushes connecting centers of point and line defects. 

Figure 9. Changes in annual Corrosion rate of mild steel flat samples, annual average Chloride deposition rate determined by the dry plate method and annual average Sulfur compounds deposition rate determined by alkaline surfaces method in the west side of the Cuban Isle.

The rate g in a linear heating program AT = q At should be carefully considered. Usually, a compromise between fast heating (for signal-to-noise ratio to be improved) and uniform heating of the sample is chosen. The temperature difference between the back (heated) and front surface of a flat sample for a given heating rate q may be estimated from... 

Hirayama and Lewis (131) studied the fluorescent decay of the 3/2 state of neodymium in a very large number of alkali silicate and alkali germanate glasses. Data were taken by exciting a flat sample with a xenon... 

Reflection Meter. A photometer arranged to pick up diffusely reflected light from the surface of a flat sample. The spectral evaluation of the reflected light permits quantitative color evaluation as seen by the human observer. 

The test samples were cut from pieces of peel with a razor. It was not easy to produce large flat samples without crushing or deforming the... 

TMA consists of a quartz probe which rests on top of a flat sample (a few mms square) in a temperature controlled chamber. When setup in neutral buoyancy (with flat probe ) then as the temperature is increased the probe rises in direct response to the expansion of the sample yielding... 

There are numerous ways to prepare a solid sample for XPS-analysis 17K Because of the 360° angle of acceptance, the optimum sample geometry is a cylinder of 11 mm diameter and 2 mm width. However, with a certain loss in sensitivity, flat samples as well as odd shaped samples can be analyzed as well, if they do not exceed the maximum size defined by the vacuum interlock. Sample powders are normally mounted on sticky tape or pressed into a metal grid 17). Excellent results were also obtained by pressing pellets 31) or by subliming the sample directly unto the sample holder. 

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