Methods indirect

The indirect methods for measuring cell mass are based on the overall stoichiometry for growth and product formation, which may be written in the general form  

The change of the cell mass can be monitored indirectly by measuring nutrient consumption, product formation, cell components, heat evolution, or other physical properties of broth. 

Nutrient Consumption It is necessary to choose a nutrient which is not likely to be used to synthesize a metabolic product. Phosphate, sulfate, or magnesium can be good candidates. When cell mass is the major product, the concentration of a carbon source can be measured to estimate the cell mass. 

Product Formation It is important to check that the product formed is growth associated. Some products are formed after cell mass reaches the stationary phase of the growth cycle and, therefore, are not growth associated. The evolution of carbon dioxide can be measured and related stoichiometrically to the cell growth. One product that is quite general to many fermentations is the hydrogen ion. The amount of alkali added to the fermentation broth to maintain the pH may be proportional to the growth. 

Cell Components For cultures undergoing balanced growth, the macro-molecular cell components such as protein, RNA, and DNA can be measured instead of cell mass. However, care is needed because the proportion of these materials in a cell can change with time if the culture does not undergo balanced growth. 

All the indirect methods that are based on the determination of the colloidal properties of crude oil measure macroscopic properties such as density, viscosity, and molecular weight. An example is that the molecular weight of asphaltene 

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Molecular weight (MWt) of CPs can be determined by a number of direct and indirect methods, most direct methods unfortunately requiring some maimer of solubility or processibility of the polymer. The three types of MWt applicable to 

In contrast to the approach utilized in the direct determination of lignin, indirect methods do not involve the isolation of a lignin residue. Instead, the lignin content may be calculated as the difference between 100% and the polysaccharide content of an extractive-free sample or, more commonly, by measuring some characteristic structural functionality, property, or chemical response and relating the result to concentration. 

The method is called direct if the atomic absorption of the analyte is related to its concentration. Indirect methods in turn are based on the chemical reaction of the analyte with one or more species, where one should be a metal easily measurable by AAS. The reaction must be stoichiometric and a relationship between the atomic absorption of the metal and the concentration of the analyte must be established. Indirect methods are not common in routine analysis, because most of them are time-consuming and difficult to automate. 

Indirect methods for the determination of anions and organic compounds may be classified into the three groups (i) Methods based on the formation of compounds in solution (ii) Methods based on the formation of compounds in the atomization cell and (iii) Methods based on the formation of volatile compounds. 

An inorganic or organic anion is precipitated with a solution of a cation of appropriate concentration. The compound formed should have a very low solubility. An excess of the cation is used in order to obtain complete precipitation. The mixture is filtered, centrifuged, or decanted, and the cation is determined by AAS either in the filtrate or in the precipitate. These methods are specific only if the sample solution does not contain other species that might be precipitated. 

The determination of the unreacted metal ion used as the precipitation reagent, in the supernatant solution, is more often employed than the determination of the precipitated metal after dissolution of the precipitate, as less manipulation is required. Calibration solutions are generally prepared from the anion standard solutions treated in the same way as the sample solutions. 

Indirect methods for the determination of sulfur and chlorine by precipitation with metal cations and measurement by FAAS of the excess metal in solution are given in Table 17. 

The methods discussed could be classified as direct methods, since they measure the nanoparticles directly in some way. It is common in analytical measurements to have methods that measure some effect that originates from the true quantity that is of interest. These methods are commonly classified as indirect. In order to yield the highest accuracy in these methods, a direct method must be utilized to correlate the indirect measurement to the quantity of interest. 

In polymer nanocomposites, there are two common indirect methods. The first is the measurement of melt viscosity. In this method a rheometer is normally utilized where the viscosity can be measured as a function of shear rate. Clay nanoparticles normally impart thixotropic rheology to the nanocomposite melt. In this type of rheology the melt viscosity at low shear will be much higher than the pure 

It transpires that the shear rate in most extruders utilized to process polymers is in the high range and so the torque observed in the extruder is not normally markedly different than that of the pure polymer. When the shear rate is lowered, thixotropes undergo hysteresis, with the viscosity returning more slowly than it did when the shear was increased. 

The type of correlation between experimentally measured variable parameters in the system is changing as a result of phase transformations within that system. The indirect methods are used to identify the changes in those correlations. For example, the p-V-T-x curves (pressure as a function of temperature (p-T curves) pressure or temperature as a function of volume (p-V or T-V curves) pressure drop during salt dissolution as a function of solution composition (p-x curves)) show a break at the location of the phase transformation. Not only pressure or temperature or composition could be considered as variables. The properties of the solution or the whole system itself as well as heating or cooling period in thermal analysis can be used as variables to find the phase transitions. 

In the case of the water - salt equilibrium L-G, one can concentrate a solution until a saturated solution (L-G-S) is reached by releasing steam at a constant temperature until the vapor pressure remains constant, notwithstanding the removal of steam. 

The method of p-x curves was used for solubility measurements of noble gases in water at elevated temperatures (Potter and Clynne, 1978). The known amounts of water were injected in increments into the thermostated bomb with the known quantity of gas and pressure measured after thermal equilibration. As long as gas phase remains in the bomb along with liquid, those water injections alter pressure moderately. Only after the last bubble of gas dissolves in the water, further addition of water cause a relatively large increase in pressure. 

Method of p-V curves. An increase of the volume of a system in a homogeneous state (by release of mercmy from the autoclave at constant temperature) results in a pressme drop and may result in an appearance of a new phase. The change of the phase state is determined as the break in the p-V curve. The change in volmne of the system is measmed by weighing the mercury vented from the autoclave through the valve p-V curves are in fact pressme - weight of mercmy curves, while T-V curves are temperatme - weight of mercmy cmves. 

The otiier apparatus used to obtain the p-T curves for solubihty determinations (i.e. phase transition from a single phase to a two-phase equihbrium L-S) is described in Potter et al. (1976, 1977). The method of p-T curves in a set-up with visual ceU and a piston (Figme 1.1) was employed for the determination of phase transitions in Gehrig et al. (1986) 

Inferential Method The inferential technique for determining dry deposition rates is based on the direct application of (19.1). Measured ambient concentrations at a particular reference height are multiplied by a deposition velocity assumed to be representative of the local surface to compute the dry deposition rate. This approach is most suited when routine monitoring data are available, but the values of the derived flux values are clearly dependent on the validity of the estimates for v,j. Detailed canopy models using information about the surface and meteorology surrounding the concentration monitor can be used to calculate the deposition velocity. 

Affinity Chromatography - Mass Spectrometry for Ligand Discovery and Characterization 

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Keywords d rec methods, indirect methods, rock properties, coring, core barrel, standard core analysis, special core analysis, slabbed core, sidewall samples, direct indications, microfossils, sonde, logging unit, invasion, mudcake, formation pressure measurement, fluid sampling, measurement while drilling, formation evaluation while drilling. 

The basic data gathering methods are direct methods which allow visual inspection or at least direct measurement of properties, and indirect methods whereby we infer reservoir parameters from a number of measurements taken in a borehole. The main techniques available within these categories are summarised in the following table ... 

The Institute has many-year experience of investigations and developments in the field of NDT. These are, mainly, developments which allowed creation of a series of eddy current flaw detectors for various applications. The Institute has traditionally studied the physico-mechanical properties of materials, their stressed-strained state, fracture mechanics and developed on this basis the procedures and instruments which measure the properties and predict the behaviour of materials. Quite important are also developments of technologies and equipment for control of thickness and adhesion of thin protective coatings on various bases, corrosion control of underground pipelines by indirect method, acoustic emission control of hydrogen and corrosion cracking in structural materials, etc. 

Many experimental methods may be distinguished by whether and how they achieve time resolution—directly or indirectly. Indirect methods avoid the requirement for fast detection methods, either by detemiining relative rates from product yields or by transfonuing from the time axis to another coordinate, for example the distance or flow rate in flow tubes. Direct methods include (laser-) flash photolysis [27], pulse radiolysis [28]... 

There are many compounds in existence which have a considerable positive enthalpy of formation. They are not made by direct union of the constituent elements in their standard states, but by some process in which the necessary energy is provided indirectly. Many known covalent hydrides (Chapter 5) are made by indirect methods (for example from other hydrides) or by supplying energy (in the form of heat or an electric discharge) to the direct reaction to dissociate the hydrogen molecules and also possibly vaporise the other element. Other known endothermic compounds include nitrogen oxide and ethyne (acetylene) all these compounds have considerable kinetic stability. 

None of the halogens reacts directly with oxygen but all form oxides by indirect methods. 

When the ascending solvent-front has reached a convenient height, the strip is removed, the position of the solvent-front marked, and the paper strip dried. The positions of the various solutes, if they are coloured compounds, now appear as clear separate spots. Frequently however, the solutes are colourless, and the position of their spots must be determined by indirect methods, such as their fluorescence in ultraviolet light, or their absorption in such light (when the spots appear almost black), or by spraying the paper with a dilute solution of a reagent which will give a coloured insoluble derivative with the solutes. 

Since aliphatic hydrocarbons (unlike aromatic hydrocarbons, p. 155) can be directly nitrated only under very special conditions, indirect methods are usually employed for the preparation of compounds such as nitroethane, CjHsNO. When ethyl iodide is heated with silver nitrite, two isomeric compounds are formed, and can be easily separated by fractional distillation. The first is the true ester, ethyl nitrite, C,HiONO, of b.p. 17° its identity is shown by the action of hot sodium hydroxide solution, which hydrolyses it, giving ethanol and... 

This direct sulphonation should be compared with the indirect methods for the preparation of aliphatic sulphonic acids, e.g., oxidation of a thiol (RSH -> RSOjH), and interaction of an alkyl halide with sodium sulphite to give the sodium sulphonate (RBr + Na,SO, -> RSO,Na + NaBr). 

The described direct derivation of shape functions by the formulation and solution of algebraic equations in terms of nodal coordinates and nodal degrees of freedom is tedious and becomes impractical for higher-order elements. Furthermore, the existence of a solution for these equations (i.e. existence of an inverse for the coefficients matrix in them) is only guaranteed if the elemental interpolations are based on complete polynomials. Important families of useful finite elements do not provide interpolation models that correspond to complete polynomial expansions. Therefore, in practice, indirect methods are employed to derive the shape functions associated with the elements that belong to these families. 

Preparation of primary allylamines by the selective monoallylation of ammonia is not possible and they are prepared by indirect methods. The monoallylation of Li and Na amides of di-/-butoxycarbonyl (Boc) (305), followed by hydrolysis, affords a primary allylamine (306)[184],... 

The most general pathways to thiazoles bearing such groups as alkyl, aryl, aralkyl, and alkenyl, substituted or not by functional groups, are the cyclization reactions described in Chapter II. A certain number of indirect methods also exist, though only a few examples of each are given here. Others are discussed in the following chapters, with the more important references cited here. 

The measurement of pK for bases as weak as thiazoles can be undertaken in two ways by potentiometric titration and by absorption spectrophotometry. In the cases of thiazoles, the second method has been used (140, 148-150). A certain number of anomalies in the results obtained by potentiometry in aqueous medium using Henderson s classical equation directly have led to the development of an indirect method of treatment of the experimental results, while keeping the Henderson equation (144). 

Types of Chelometric Titrations. Chelometric titrations may be classified according to their manner of performance direct titrations, back titrations, substitution titrations, redox titrations, or indirect methods. 

Representative Method Although each volatilization gravimetric procedure has its own unique characteristics, the following indirect method for the determination of Si in ores and alloys by formation of volatile SiF4 provides an instructive example of a typical procedure. 

This is an indirect method of analysis because the chlorine-containing species do not react with the titrant. Instead the total chlorine residual oxidizes l to l3 , and the amount of 13 is determined by the redox titration with Na282 03. 

Prada and colleagues recently described a new indirect method for determining sulfate in natural samples, such as sea water and industrial effluents. The method is based on... 

Scavengers such as diphenylpicrylhydrazyl radicals [II] react with other radicals and thus provide an indirect method for analysis of the number of free radicals in a system ... 

We saw in Section 9.3.8 that spectroscopy, in the form of LIDAR, is a very important tool for measuring ozone concentration directly in the atmosphere. A useful indirect method involves the measurement of the concentration of oxygen which is formed from ozone by photolysis ... 

The other commercially important routes to alkyltin chloride intermediates utilize an indirect method having a tetraalkjitin intermediate. Tetraalkyltins are made by transmetaHation of stannic chloride with a metal alkyl where the metal is typicaHy magnesium or aluminum. Subsequent redistribution reactions with additional stannic chloride yield the desired mixture of monoalkyl tin trichloride and dialkyltin dichloride. Both / -butjitin and / -octjitin intermediates are manufactured by one of these schemes. 

Monoisopinocampheylborane [64234-27-17, IpcBH2 (6) is an important asymmetric hydroborating agent. It is prepared from a-pinene (7) either directiy or better by indirect methods. The product obtained by hydroboration of a-pinene [80-56-8] is an equiUbrium mixture. Optically pure monoisopinocampheylborane is best prepared from a-pinene via diisopinocampheylborane [1091-56-1] IPC2BH (8) (64,65). Both enantiomers are readily available. 

A number of less hindered monoalkylboranes is available by indirect methods, eg, by treatment of a thexylborane—amine complex with an olefin (69), the reduction of monohalogenoboranes or esters of boronic acids with metal hydrides (70—72), the redistribution of dialkylboranes with borane (64) or the displacement of an alkene from a dialkylborane by the addition of a tertiary amine (73). To avoid redistribution, monoalkylboranes are best used /V situ or freshly prepared. However, they can be stored as monoalkylborohydrides or complexes with tertiary amines. The free monoalkylboranes can be hberated from these derivatives when required (69,74—76). Methylborane, a remarkably unhindered monoalkylborane, exhibits extraordinary hydroboration characteristics. It hydroborates hindered and even unhindered olefins to give sequentially alkylmethyl- and dialkylmethylboranes (77—80). 

Determination of Lignin Content. Lignin content in plants (wood) is determined by direct or indirect methods (21). The direct method includes measurement of acid-insoluble (ie, Klason) lignin after digesting wood with 72% sulfuric acid to solubilize carbohydrates (22). The Klason lignin contents of representative lignifted materials are shown in Table 2. 

Nitration. Naphthalene is easily nitrated with mixed acids, eg, nitric and sulfuric, at moderate temperatures to give mostly 1-nitronaphthalene and small quantities, 3—5%, of 2-nitronaphthalene. 2-Nitronaphthalene [581-89-5] is not made in substantial amounts by direct nitration and must be produced by indirect methods, eg, the Bucherer reaction starting with 2-naphthalenol (2-naphthol [135-19-3]). However, the 2-naphthylamine [91-59-8] made using this route is a carcinogen thus the Bucherer method is seldom used in the United States. 

If pure isomers are required, the ortho and meta compounds can be prepared by indirect methods. o-Nitrotoluene can be obtained by treating 2,4-dinitrotoluene with ammonium sulfide followed by diazotization and boiling with ethanol. / -Nitrotoluene can be prepared from -toluidine by acetylation, nitration deacetylation, diazotization, and boiling with ethanol. A fairly pure -nitrotoluene, which has been isolated from the isomeric mixture, can be purified further by repeated crystallization. 

Indirect methods have also been used to form the monooxime (8) and the phenyUiydrazone (9). 

Ha.logena.tlon, One review provides detailed discussion of direct and indirect methods for both mono- and polyhalogenation (20). As with nitration, halogenation under acidic conditions favors reaction in the benzenoid ring, whereas reaction at the 3-position takes place in the neutral molecule. Radical reactions in the pyridine ring can be important under more vigorous conditions. 

Indirect methods of estimating sorption have been used when actual measurement of sorption isotherm is impossible (44). For instance, sorption coefficients have been estimated from soil organic carbon and a specific surface of soil, and from semiempidcal equations using pesticide properties. 

Analytical and Test Methods. Analysis and test methods are similar to those for sodium thiosulfate. Sulfite is determined by an indirect method based on the titration of the acid Hberated when both the sulfite and thiosulfate are oxidized with iodine solution (69). 

Reduction of Acid Chlorides to Aldehydes. Palladium catalysis of acid chlorides to produce aldehydes is known as the Rosenmund reduction and is an indirect method used in the synthesis of aldehydes from organic acids. 

No significant amounts of diacylated products are obtained under Vilsmeier-Haack conditions an indirect method for preparing pyrrole-2,5-dicarbaldehydes is outlined in Scheme 16 (78S295, 82CJC383). 

Other carbon electrophiles which are frequently employed include aldehydes, ketones, esters, nitriles and amides of the type RCONMei. An indirect method of acylation involves the initial reaction of a lithio compound with an aldehyde followed by oxidation of the resulting secondary alcohol to the corresponding acyl derivative. 

This can be achieved by an indirect method. The lithio derivative is first reacted with a borate ester. Sequential acid hydrolysis and oxidation yields the corresponding hydroxy derivative. This procedure is illustrated by the conversion of 2-lithiobenzo[6]thiophene to 2-hydroxybenzo[6]thiophene, which exists predominantly in the 2(3//)-one tautomeric form (200) <70JCS(C)1926). 

Thermal conversion of diazirines to linear diazo compounds was postulated occasionally and proved by indirect methods. The existence of a diazo compound isomeric to diazirine (197) was proved spectroscopically on short thermolysis in DMSO (76JA6416). An intermediate diazoalkane was trapped by reaction with acetic acid, yielding the ester (198) (77JCS(P2)1214). 

The second class of multivariable optimization techniques in principle requires the use of partial derivatives, although finite difference formulas can be substituted for derivatives such techniques are called indirect methods and include the following classes ... 

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