Semi-quantitative

The behaviour of the BZ system ean be modelled semi-quantitatively by the oregonator model [15] ... 

At equilibrium, in order to achieve equality of chemical potentials, not only tire colloid but also tire polymer concentrations in tire different phases are different. We focus here on a theory tliat allows for tliis polymer partitioning [99]. Predictions for two polymer/colloid size ratios are shown in figure C2.6.10. A liquid phase is predicted to occur only when tire range of attractions is not too small compared to tire particle size, 5/a > 0.3. Under tliese conditions a phase behaviour is obtained tliat is similar to tliat of simple liquids, such as argon. Because of tire polymer partitioning, however, tliere is a tliree-phase triangle (ratlier tlian a triple point). For smaller polymer (narrower attractions), tire gas-liquid transition becomes metastable witli respect to tire fluid-crystal transition. These predictions were confinned experimentally [100]. The phase boundaries were predicted semi-quantitatively. 

Circular dicliroism has been a useful servant to tire biophysical chemist since it allows tire non-invasive detennination of secondary stmcture (a-helices and P-sheets) in dissolved biopolymers. Due to tire dissymmetry of tliese stmctures (containing chiral centres) tliey are biaxial and show circular birefringence. Circular dicliroism is tlie Kramers-Kronig transfonnation of tlie resulting optical rotatory dispersion. The spectral window useful for distinguishing between a-helices and so on lies in tlie region 200-250 nm and hence is masked by certain salts. The metliod as usually applied is only semi-quantitative, since tlie measured optical rotations also depend on tlie exact amino acid sequence. 

For more than three components extremely heavy algebra is generated in attempting to solve the implicit flux relations, and in general no usefully compact explicit solution is obtained. However, there are two interesting special cases in which explicit flux relations can be obtained with an arbitrary nutr er of components in the mixture. Neither would be expected to correspond accurately with physical situations of practical interest, but they may provide useful qualitative, or semi-quantitative pointers to the behavior of more accurate models. 

Study of the solubility behaviour of the compound. A semi-quantitative study of the solubility of the substance in a hmited number of solvents (water, ether, dilute sodium hydroxide solution, dilute hydrochloric acid, sodium bicarbonate solution, concentrated sulphuric and phosphoric acid) will, if intelligently apphed, provide valuable information as to the presence or absence of certain classes of organic compounds. 

As a result of the researeh earried out samples of modified BD siliea gel has been obtained. Their behaviour (eoloring ehange) in the presenee of different anions simple (ehlorides, nitrates, sulphates) and metal eomplexes (tetraehloraurate) has been studied. Siliea gel modifieation by astrafloxin FF has been shown possibility of ereation of semi-quantitative AuCl determination test system. 

Typical values of the energy to form vacancies are for silver, lOSkJmol and for aluminium, 65.5kJmol These values should be compared with the values for the activation enthalpy for diffusion which are given in Table 6.2. It can also be seen from the Table 6.2 that die activation enthalpy for selfdiffusion which is related to the energy to break metal-metal bonds and form a vacant site is related semi-quantitatively to the energy of sublimation of the metal, in which process all of the metal atom bonds are broken. 

Notice on tliis graph that the 25°C experiments were informative, and results were in the measurable range. At 135°C some intermediate, semi-quantitative results could be seen. At 285°C no detectable adsorption could be seen. Taking the high adsorption result at 25°C as 22.4 mL/kg, this converts to 0.001 mole/kg. Compare this with the 0.22 mole/kg needed for measurable result in the CSTR case in the previous section. 

Ethylene oxide secondary oxidation with C-tagged ethylene oxide, to clarify the source of CO2, was done at Union Carbide but not published. This was about 10 years before the publication of Happel (1977). With very limited radioactive supply only a semi-quantitative result could be gained but it helped the kinetic modeling work. It became clear that most CO2 comes from ethylene directly and only about 20% from the secondary oxidation of ethylene oxide. 

Page 3 gives a summary of the most important result in a figure illustrating in a semi-quantitative way the conditions in the specified CSTR. As can be seen on line 74, Dar is somewhat larger than the critical value but the concentration difference on line 75 is small, so this result can be accepted with some reservations. The Carberry number is also larger than the criteria, therefore these experimental results are marginal for Nox abatement... 

In Laser Ionization Mass Spectrometry (LIMS, also LAMMA, LAMMS, and LIMA), a vacuum-compatible solid sample is irradiated with short pulses ("10 ns) of ultraviolet laser light. The laser pulse vaporizes a microvolume of material, and a fraction of the vaporized species are ionized and accelerated into a time-of-flight mass spectrometer which measures the signal intensity of the mass-separated ions. The instrument acquires a complete mass spectrum, typically covering the range 0— 250 atomic mass units (amu), with each laser pulse. A survey analysis of the material is performed in this way. The relative intensities of the signals can be converted to concentrations with the use of appropriate standards, and quantitative or semi-quantitative analyses are possible with the use of such standards. 

Local Thermodynamic Equilibrium (LTE). This LTE model is of historical importance only. The idea was that under ion bombardment a near-surface plasma is generated, in which the sputtered atoms are ionized [3.48]. The plasma should be under local equilibrium, so that the Saha-Eggert equation for determination of the ionization probability can be used. The important condition was the plasma temperature, and this could be determined from a knowledge of the concentration of one of the elements present. The theoretical background of the model is not applicable. The reason why it gives semi-quantitative results is that the exponential term of the Saha-Eggert equation also fits quantum-mechanical expressions. 

A bulk sample is the last choice and the least desirable. It should be submitted "for laboratory use only" if there is a possibility of contamination by other matter. The type of bulk sample submitted to the laboratory should be cross-referenced to the appropriate air samples. A reported bulk sample analysis for quartz (or cristobalite) will be semi-quantitative in nature because (1) The XRD analysis procedure requires a thin layer deposition for an accurate analysis. (2) The error for bulk samples analyzed by XRD is unknown because the particle size of nonrespirable bulk samples varies from sample to sample. 

Semi quantitive speetrographie analysis of other elements 2ppm... 

Good semi-quantitative agreements are found in diffraction patterns and proposed models obtained by molecular-dynamics[14], because the results of the ex-periments[31-34] are consistent with the atomic models proposed by us[14]. However, in the present state of high-resolution electron microscopy, taking into account, moreover, the number of sheets and the complicated geometry of the helix, it seems unlikely to directly visualize the pentagon-hexagon pairs. 

Risk Indices - A risk index is a single-number measure of tlie risk associated with a facility. Some risk indices are qualitative or semi-quantitative, ranking risks in various general categories. Risk indices may also be quantitative averages or bencluiiarks based on otlier risk measures. 

To obtain qualitative information about a molecule, such as its moleculip orbitals, atomic charges or vibrational normal modes. In some cast semi-empirical methods may also be successfully used to predict energy-trends arising from alternate conformations or substituent effects in qualitative or semi-quantitative way (but care must be taken in this area). 

AMI does not even get the correct sign for the energy difference. PM3 orders the isomers properly, but substantially underestimates the energy difference, and the Hartree-Fock value is only somewhat better. Electron correlation is needed to obtain even semi-quantitative results for this problem. ... 

Conclusions and predictions concerning the reactivity of monocyclic azines are derived from three sources a) the kinetic data of Section III, A, 2, (6) qualitative or semi-quantitative comparisons in preparative organic chemistry (Section III,B), and (c) theoretical considerations presented in Section II, B. Reactivity can be described by four generalizations ... 

No kinetic data or semi-quantitative comparisons among themselves or with other diazines are available. The most reactive derivative is expected to be the 4-substituted-l,6-naphthyridine (425), with 2-substituted-1,6- and l-substituted-2,7-naphthyridines (426) somewhat less reactive, all three positions being activated by two ring-nitrogens by resonance. Other positions also activated in this way... 

This technique provides quantitative information about tautomeric equilibria in the gas phase. The results are often complementary to those obtained by mass spectrometry (Section VII,E). In principle, gas-phase proton affinities, as determined by ICR, should provide quantitative data on tautomeric equilibria. The problem is the need to correct the measured values for the model compounds, generally methyl derivatives, by the so-called N-, 0-, or S-methylation effect. Since the difference in stability between tautomers is generally not too large (otherwise determination of the most stable tautomer is trivial) and since the methylation effects are difficult to calculate, the result is that proton affinity measurements allow only semi-quantitative estimates of individual tautomer stabilities. This is a problem similar to but more severe than that encountered in the method using solution basicities (76AHCS1, p. 20). 

G. M. Frame, A collaborative study of 209 PCB congeners and 6 Aroclor s on 20 different HRGC columns. Part 2. Semi-quantitative Aroclor congener distributions . Anal. Chem. 70 714-722(1997). 

A semi-quantitative indication of the effects of different elements on the resistance to oxidation of nickel is given in Table 7.15 which lists values for the relative oxidation rate with respect to that of nickel for different concentrations of solute element. These values are approximately valid over quite wide ranges of time and temperature. ... 

This simple expression can be used to obtain only a semi-quantitative idea of the effect of an alloying element because the assumptions of randomness and a constant pairwise energy of interaction between atoms are only approximations to the truth in most systems. 

Surface finish is increasingly referred to as surface cleanliness . This can be misleading because the standards refer to the appearance of the blasted steel and do not deal with chemical contamination. Site tests for assessing the level of soluble salts on freshly blast-cleaned surfaces, and which allow the semi-quantitative determination of the chlorides, soluble sulphates and soluble iron salts, are urgently needed. 

In these ways, then, concentration factors of up to five orders of magnitude may be developed, depending upon the circumstances. Despite much work in this area, theory has not yet developed to the stage where accurate predictions can be made reliably, but the state of the art is such that semi-quantitative assessments can be of considerable value in interpreting occurrences. 

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