Common methods

Depending on the problem to be solved, different methods of evaluation are used. For quantitative investigations, only the amplitudes of the signals are relevant, and the real position of the extrema are not important if the conditions of data handling are not altered and a calibration curve is taken. But if the exact positions of the extrema are desired to identify peaks in a spectrupi or to calculate excitation energies, shifting the maxima and minima must be avoided, or if this is not possible, the deviations must be corrected. 

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As pointed out previously, the separation of homogeneous fluid mixtures requires the creation or addition of another phase. The most common method is by repeated vaporization and condensation— distillation. The three principal advantages of distillation are... 

Probably the most common method used for sequence selection for simple distillation columns is heuristic. Many heuristics have been proposed, but they can be summarized by the following four ... 

Bag filters. Bag filters, as discussed in Chap. 3 and illustrated in Fig. 3.66, are probably the most common method of separating particulate materials from gases. A cloth or felt filter material is used that is impervious to the particles. Bag filters are suitable for use in very high dust load conditions. They have an extremely high efficiency, but they suflFer from the disadvantage that the pressure drop across them may be high. ... 

This is the most common method. It is used for gasolines, kerosenes, gas oiis and similar products. The test is conducted at atmospheric pressure and is not recommended for gasolines having high dissolved gas contents or solvents whose cut points are close together. 

Reservoir porosity can be measured directly from core samples or indirectly using logs. However as core coverage is rarely complete, logging is the most common method employed, and the results are compared against measured core porosities where core material is available. 

If oil and water are mixed as an emulsion, dehydration becomes much more difficult. Emulsions can form as oil-in-water or water-in-oil if mixed production streams are subjected to severe turbulence, as might occur in front of perforations in the borehole. Emulsions can be encouraged to break (or destabilise) using chemicals, heat or just gentle agitation. Chemical destabilisation is the most common method and laboratory tests would normally be conducted to determine the most suitable combination of chemicals. 

Fiscal allowances for investment in capital items (i.e. capex) are made through capital allowances. The method of calculating the capital allowance is set by the fiscal legislation of the host government, but three common methods are discussed below. 

Table 9-1 summarizes common methods for unsupervised and supervised learning. 

To stop this we protect the ketone by a reversible FGl. A common method is to make the eyclie ketal ... 

Sulfur ylides contain a carbanion, which is stabilizea oy an adjacent positively-charged sulfur. Ylides derived from alkylsulfonium salts are usually generated and utilized at low temperatures. Oxosulfonium ylides are, however, stable near room temperature. The most common method of ylide formation is deprotonation of a sulfonium salt. What has been said... 

We therefore felt it timely to attempt a critical exposition and assessment of the common methods for the evaluation of the surface area and pore size distribution of solids from adsorption measurements. Our main concern has therefore been with the use of adsorption data for these purposes rather than with adsorption per se and it is for this reason that our treatment of theoretical matters, whilst sufficiently detailed to bring out the nature of the assumptions underlying the various methods, is not exhaustive we have not set out to write a text-book or a treatise on adsorption, and our choice of material from the literature has been dictated solely by its seeming suitability for the explanation or illustration of the topic under discussion. 

Quantitative Analysis for a Single Analyte The concentration of a single analyte is determined by measuring the absorbance of the sample and applying Beer s law (equation 10.5) using any of the standardization methods described in Chapter 5. The most common methods are the normal calibration curve and the method of standard additions. Single-point standardizations also can be used, provided that the validity of Beer s law has been demonstrated. 

Atomization and Excitation Atomic emission requires a means for converting an analyte in solid, liquid, or solution form to a free gaseous atom. The same source of thermal energy usually serves as the excitation source. The most common methods are flames and plasmas, both of which are useful for liquid or solution samples. Solid samples may be analyzed by dissolving in solution and using a flame or plasma atomizer. 

Lasers can be used in either pulsed or continuous mode to desorb material from a sample, which can then be examined as such or mixed or dissolved in a matrix. The desorbed (ablated) material contains few or sometimes even no ions, and a second ionization step is frequently needed to improve the yield of ions. The most common methods of providing the second ionization use MALDI to give protonated molecular ions or a plasma torch to give atomic ions for isotope ratio measurement. By adjusting the laser s focus and power, laser desorption can be used for either depth or surface profiling. 

Suitable inlets commonly used for liquids or solutions can be separated into three major classes, two of which are discussed in Parts A and C (Chapters 15 and 17). The most common method of introducing the solutions uses the nebulizer/desolvation inlet discussed here. For greater detail on types and operation of nebulizers, refer to Chapter 19. Note that, for all samples that have been previously dissolved in a liquid (dissolution of sample in acid, alkali, or solvent), it is important that high-purity liquids be used if cross-contamination of sample is to be avoided. Once the liquid has been vaporized prior to introduction of residual sample into the plasma flame, any nonvolatile impurities in the liquid will have been mixed with the sample itself, and these impurities will appear in the results of analysis. The problem can be partially circumvented by use of blanks, viz., the separate examination of levels of residues left by solvents in the absence of any sample. 

There are a variety of possible linked scanning methods, but only those in more frequent use are discussed here. They differ from the linked scanning methods used in triple quadrupole instruments and ion traps in that two of the three fields (V, E, and B) are scanned simultaneously and automatically under computer control. The most common methods are listed in Table 34.1, which also defines the type of scanning with regard to precursor and product ions. 

An introduction to several of the more common methods of surface and interface analysis has been presented in this article. This treatment is certainly not comprehensive. An ever-expanding number of methods for the interrogation of surfaces and interfaces are available to the analyst. The ones chosen for discussion here were meant to be representative of methods that can answer the more general questions posed at the beginning of this article. The reader is encouraged to pursue further reading on other techniques for specific appHcations in the many excellent monographs on the subject of surface and interface analysis. 

The common method of naming aldehydes corresponds very closely to that of the related acids (see Carboxylic acids), in that the term aldehyde is added to the base name of the acid. For example, formaldehyde (qv) comes from formic acid, acetaldehyde (qv) from acetic acid, and butyraldehyde (qv) from butyric acid. If the compound contains more than two aldehyde groups, or is cycHc, the name is formed using carbaldehyde to indicate the functionaUty. The lUPAC system of aldehyde nomenclature drops the final e from the name of the parent acycHc hydrocarbon and adds al If two aldehyde functional groups are present, the suffix -dialis used. The prefix formjlis used with polyfunctional compounds. Examples of nomenclature types are shown in Table 1. 

A fan blade is continuously vibrating millions of cycles up and down ia operatioa over a short period of time. Each time a blade tip moves past an obstmction it is loaded and then unloaded. If forced by virtue of tip speed and number of blades to vibrate at its natural frequency, the ampHtude is greatly iacreased and internal stresses result. It is very important when selecting or rating a fan to avoid operation near the natural frequency. The most common method of checking for a resonance problem is by usiag the relatioa ... 

Thermoforming. Thermoforming is the most common method of fabricating sheet into three-dimensional packaging. In conventional thermoforming, the sheet is heated to its softening point or just below the melting temperature. The softened plastic is forced by differential air pressure into an open-top mold to assume the shape of the female mold. The mold is chilled and the plastic sheet solidifies and is then removed from the mold. 

Charge reduction (pH, temperature) and other precipitation are common methods of FVIII fractionation, d. ... 

Plasmids can be introduced into ceUs by several methods. The most common method is transformation, where the recipient ceUs are made competent to receive DNA by washing with a solution of or other inorganic ions. Then the naked DNA is added direcdy a fraction of the ceUs take... 

Hydrolysis. Although hydantoins can be hydroly2ed under strongly acidic conditions, the most common method consists of heating ia an alkaline medium to give iatermediate ureido acids (the so-called hydantoic acids), which are finally hydroly2ed to a-amino acids. 

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