Experimental observation

Experimental data are summarized in the sections below. Certain empirical relations between the data should become apparent from these Tables. 

These have often been noted by investigators, and are presented in the discussion below. In other instances they await recognition by readers of this article. In view of the limitations of present theoretical treatments, such empirical relations are important. First, they allow one to assess important structural features of the molecules under study from the data available. In addition, these relations may serve as a guide for future theoretical developments. 

Methods for determining magnetic susceptibility by magnetic resonance have been reported and these should be of general interest 105a, 129b, 133a). 

Compounds containing more than one kind of ligand are cross-referenced in the appropriate Tables. 

Chemical shifts and spin-spin coupling data for cr-bonded organomet llic compounds are summarized in Tables I through IX. Within each table, the 

Serizawa et al. (2002) studied experimentally, through visualization, the two-phase flow patterns in air-water two-phase flows in round tubes. The test section for air-water experiments consisted of a transparent silica or quartz capillary tube with circular cross-section positioned horizontally. The two-phase flow was realized through a mixer with different designs, as shown in Figs. 5.4 and 5.5. The air was injected into the mixer co-axially while water was introduced peripherally. 

Dispersed bubbles are observed (Fig. 5.6a) when the gas flow rate is very small such as [/gs = 0.0083 m/s. Two kinds of bubbles are observed one type is finely dispersed with a size smaller than the tube diameter, and the other type has a length of near to or a little larger than the mbe diameter with spherical cap and tail. The distance between two consecutive bubbles may be longer than ten times the tube diameter. This flow pattern is also considered as a dispersed bubbly flow. Often in air-water flow two kinds of bubbles appear together as pairs of bubbles in which the small-sized bubbles follow the larger ones. 

From the experimental observation it is quite clear that the occurrence of the slug flow is rather an entrance phenomenon than one induced from the tube. Slug flow occurs if the speed of long gas bubbles is not high enough to overcome the strong surface tension force of the liquid bridge between them (Fig. 5.6b). 

Further increase in the gas flow rate in liquid ring flow leads to a liquid lump flow, of which the high-speed core gas entrains the liquid phase and liquid lumps slide 

As demonstrated in Fig. 5.7, the result indicates that two-phase flow patterns observed in a 100 pm quartz tube are almost similar to those observed in a 25 pm silica capillary tube with several exceptions. One such exceptions is that in slug flow encountered at low velocities, small liquid droplets in a gas slug stick to the tube wall (Fig. 5.8). This fact is evidence that no liquid film exisfs befween fhe gas slug and the tube wall. 

Reviews of experimental observations of the efficiency with which dislocations climb under different driving forces have been published [18-22]. A wide range of semi-quantitative results is available only for metals, including  

A rich variety of experimental observations has been reported in the literature on the buckling of compressively stressed thin films on substrates and on the development of secondary buckling phenomena which lead to configurations with reproducible characteristic shapes. Examples of such observations are presented in this section. 

The droplet structure in attractive emulsions can be directly observed under a microscope. Besides direct observations, a precise determination of the structure 

The form factor depends only on intraparticle interferences and is independent of concentration as long as the particles remain unchanged. For example, for a uniform sphere of radius a comparable to Xq  

The structure factor accounts for interparticle interferences. It relates to the so-called pair distribution function, g(r), of particles through  

by adopting the appropriate approximation, it is possible to obtain quantitative information about the pair interaction energy from scattering experiments, over a wide variety of systems and particle concentrations. 

We first consider emulsion droplets submitted to attractive interactions of the order of ks T. Reversible flocculation may be simply produced by adding excess surfactant in the continuous phase of emulsions. As already mentioned in Chapter 2, micelles may induce an attractive depletion interaction between the dispersed droplets. For equal spheres of radius a at center-to-center separation r, the depletion 

FIGURE 9. Concentration-dependent toxicity and mutagenicity of benzo [a]pyrene (O), cyclo-penta[c, i]pyrene (A), fluoranthene (O), and kerosene soot ( ) to HH-4 lymphoblasts. Exposure was for 3 hr in the presence (solid symbols) or absence (open symbols) of 5% (vol./vol.) rat liver PMS. The mutant fractions were determined by quadruplicate platings of 2 X 10 cells after a grow-back period to allow phenotypic expression of the HGPRT state. The control 6TG mutant fraction was subtracted from each experimental point to yield the induced mutant fraction. The data are expressed as S.D. of two independent cultures treated with each concentration. 

Comparison of Mutation at the hgprt Locus in Different Human 

We have observed the presence of MIT-2 cells heritably resistant to the toxic effects of or MNNG and have isolated a population of 

MNU-resistant cells (Penman, unpublished results). Preliminary experiments with tritiated MNU indicate that the total cellular alkylations of GM 130, normal MIT-2, and MNU-resistant MIT-2 lymphoblasts are the same at equivalent exposure conditions (Slapikoff, unpublished results). Therefore, the resistance mechanism does not seem to be a reduced cellular uptake of alkylating agents. 

Equation 2-22 indicates that a plot of 1/(1 p)2 versus t should be linear. This behavior has 

Chave et al. (1962) limited their measurements to changes of pH during the dissolution reaction, and estimated the pH at infinite time by extrapolation of plots of pH versus the reciprocal of the square root of time. These plots were chosen empirically, because they usually yield linear plots as infinite time is approached when calcite, aragonite, or other simple carbonate minerals are used (Garrets et al., 1960). Chave et al. claimed that in the case of magnesian calcites, however, only 

Solubilities of annealed skeletal carbonates were estimated by Land (1967) by allowing the system to reach a steady state pH and by determining dissolved Ca2+ and Mg2+ concentrations. Dissolution of the magnesian calcites in Land s experiments appeared to be congruent in the sense that the steady state solution had a molar Ca2+/Mg2+ ratio similar to that of the solid. 

Bertram (1989) showed, in dissolution studies of magnesian calcites, that their solubilities decrease with increasing temperature. This trend and its relationship to solubility vs. temperature trends for calcite and aragonite are discussed in Chapter 7. 

There are experimental problems inherent to dissolution studies, of which the reader should be aware. Chave and Schmalz (1966) noted the effect of grain 

9 L V (Efl) Libration 270-345 cm-1 t-6 A Out-of-plane bend 1700-1765 cnT1 Q O (Eg) In-plane bend 710-745 cur1 

The complexity of the respiratory system prevents a precise mathematical approach to the problem. Many clinical studies, however, clearly demonstrate the importance of particle size. 

Particles of hygroscopic materials are removed more effectively than are nonhygro-scopic particles, because of the growth of these 

The effect of particle size on the fate of particles inhaled from an aerosol is shown in Fig. 9.45. 

When used by patients, the Spinhaler delivers about 25% by weight of sodium cro-moglicate, which is normally dispersed as particles below 6 m in diameter, about 5% being less than 2 m diameter. The mass medium diameter (and geometric standard deviation) of the sodium cromoglicate particle batches used were, respectively, 2 f.2 and f f.7 f.f m. There is no doubt that the biological effect of the small particle material is 

An alternative dry powder aerosol device is illustrated in Fig. 9.46 and the mechanism of dispersion of powdered dmg in a Ventodisk or Becodisk system is shown in Fig. 9.47 

The surface mass patterning unique to azobenzenes is a fundamentally optical process, whereby the incident light pattern is encoded in the material. In an SRG experiment, two beams are intersected at an angle 26 at the sample surface, giving rise to an SRG with period  

The phase relationship between the incident light field and the resulting surface deformation is crucial in understanding the mechanism of grating formation (Fig. 4.4). Early investigations using the diffraction of an edge (Kumar et al.. 

TABLE 4.1. Polarization Patterns at the Sample Surface During SRG Inscription Using a Variety of Polarized Beam Combinations. The Quality of the SRG (as Determined by Grating Height) Is Shown for Comparison 

Polarization of beams Electric field in xy plane SRG quality 

Crazing in glassy homo-polymers is overwhelmingly a surface phenomenon. In the few instanees when crazing was found to occur in the interior the source of this has always been particulate inclusions surrounded by misfit stresses and signifi-eantly different elastic properties (Kambour 1973). The surface sensitivity of erazing derives from the presence of geometrical imperfections on surfaces. When 

The classification of solute/cosolvent/water systems based on their relative polarity was suggested by Yalkowsky and Roseman. Solutes which are less polar than both water 

It is more difficult to evaluate the effects of cosolvents which have limited miscibility with water. In the literature, such organic solvents have been termed as both cosolvents and eosolutes, and there is no clear criteria for the distinction. Cosolvent is usually miscible with water, or to be used in an attempt to increase the aqueous solubility of the solute. Cosolute, on the oflier hand, may be organic chemicals which have a similar chemical structure or behave similarly with the solute when they exist in water alone. The effects of cosolutes have been examined in a limited number of published papers.  

Partially water-miscible organic solvents (PMOSs) may act as either cosolvents or cosolutes, and the research in the past has shown flic complexity of their effects. It was demonstrated that in order to exert effects on solubility or sorption of HOCs, PMOSs must exist as a component of the solvent mixture in an appreciable amount Munz and Roberts suggested a mole fi action of greater than 0.005 and Rao and coworkers proposed a volume percent of 1% or a concentration above lO mg/L. Cosolvents with relatively high water solubility are likely to demonstrate observable effects on the solubilities of solutes, up to their solubility limits, in a similar manner to cosolvents of complete miscibility with water. A few experimental examples of the effects of PMOSs include 1 -butanol and 

1-pentanol acting on PCB congeners and naphthalene. andbutanone on anthraeene and fluoranthene.  

YaUcowsky and Roseman introduced the log-linear model in 1984 to describe the phenomenon of the exponential increase in aqueous solubility for nonpolar organic compounds as the cosolvent concentration is increased. They showed that 

It is relatively straightforward to predict the stereochemistry and rates of these reactions. The more electron rich the double bond, the faster it will react with the peracid. Also, sterics are the primary factor directing the epoxidation stereochemistry. The least hindered face of a double bond is predominately epoxidized. The reaction is typically 100% stereospecific, with trans-olefins giving trans-epoxides and cis-olefins giving cis-epoxides. 

Much of the chemistry described above required electrophilic activation of the carbonyl or alkene in order for a nucleophile to add. However, many good nucleophiles will directly add to a carbonyl, and we commence this section by looking at the electron pushing for a few examples traditionally covered in introductory organic chemistry. 

In the wake of the researches for oscillatory reactions more than a dozen pH-autoactivated reactions were shown to produce bistability when operated in a CSTR [57]. Theoretical calculations and experiments demonstrate that such systems readily give rise to spatial bistability when conducted in an OSFR. They would provide a large choice of reaction systems to test the chemomechanical instabilities theoretically described above. However, in our selection criteria, we have to take into account that many of these reactions can already exhibit kinetic oscillations over more or less wide ranges of feed parameters. Such complication can make it difficult to discriminate between kinetic and chemomechanic oscillatory instabilities. Furthermore, it has also been shown that in the case of proton-autoactivated system the natural faster diffusion of this species can lead to another source of oscillatory instability in an OSFR, the long range activation instability [58]. 

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While many methods for parameter estimation have been proposed, experience has shown some to be more effective than others. Since most phenomenological models are nonlinear in their adjustable parameters, the best estimates of these parameters can be obtained from a formalized method which properly treats the statistical behavior of the errors associated with all experimental observations. For reliable process-design calculations, we require not only estimates of the parameters but also a measure of the errors in the parameters and an indication of the accuracy of the data. 

If this criterion is based on the maximum-likelihood principle, it leads to those parameter values that make the experimental observations appear most likely when taken as a whole. The likelihood function is defined as the joint probability of the observed values of the variables for any set of true values of the variables, model parameters, and error variances. The best estimates of the model parameters and of the true values of the measured variables are those which maximize this likelihood function with a normal distribution assumed for the experimental errors. 

Relaxations in the double layers between two interacting particles can retard aggregation rates and cause them to be independent of particle size [101-103]. Discrepancies between theoretical predictions and experimental observations of heterocoagulation between polymer latices, silica particles, and ceria particles [104] have promptetl Mati-jevic and co-workers to propose that the charge on these particles may not be uniformly distributed over the surface [105, 106]. Similar behavior has been seen in the heterocoagulation of cationic and anionic polymer latices [107]. 

There are some subtleties with respect to the physicochemical meaning of the contact angle equation, and these are taken up in Section X-7. The preceding, however, serves to introduce the conventional definitions to permit discussion of the experimental observations. 

Most surfaces are heterogeneous so that in Eq. XI-6 will vary with 6. The experimentally observed adsorption isotherm may then be written... 

We consider first some experimental observations. In general, the initial heats of adsorption on metals tend to follow a common pattern, similar for such common adsorbates as hydrogen, nitrogen, ammonia, carbon monoxide, and ethylene. The usual order of decreasing Q values is Ta > W > Cr > Fe > Ni > Rh > Cu > Au a traditional illustration may be found in Refs. 81, 84, and 165. It appears, first, that transition metals are the most active ones in chemisorption and, second, that the activity correlates with the percent of d character in the metallic bond. What appears to be involved is the ability of a metal to use d orbitals in forming an adsorption bond. An old but still illustrative example is shown in Fig. XVIII-17, for the case of ethylene hydrogenation. 

The course of a surface reaction can in principle be followed directly with the use of various surface spectroscopic techniques plus equipment allowing the rapid transfer of the surface from reaction to high-vacuum conditions see Campbell [232]. More often, however, the experimental observables are the changes with time of the concentrations of reactants and products in the gas phase. The rate law in terms of surface concentrations might be called the true rate law and the one analogous to that for a homogeneous system. What is observed, however, is an apparent rate law giving the dependence of the rate on the various gas pressures. The true and the apparent rate laws can be related if one assumes that adsorption equilibrium is rapid compared to the surface reaction. 

The existence of intennolecular interactions is apparent from elementary experimental observations. There must be attractive forces because otherwise condensed phases would not fomi, gases would not liquefy, and liquids would not solidify. There must be short-range repulsive interactions because otherwise solids and liquids could be compressed to much smaller volumes with ease. The kernel of these notions was fomuilated in the late eighteenth century, and Clausius made a clear statement along the lines of this paragraph as early as 1857 [1]. 

It is important to recognize that thennodynamic laws are generalizations of experimental observations on systems of macroscopic size for such bulk systems the equations are exact (at least within the limits of the best experimental precision). The validity and applicability of the relations are independent of the correchiess of any model of molecular behaviour adduced to explain them. Moreover, the usefiilness of thennodynamic relations depends cmcially on measurability, unless an experimenter can keep the constraints on a system and its surroundings under control, the measurements may be worthless. 

It is a universal experimental observation, i.e. a law of nature , that the equations of state of systems 1 and 2 are then coupled as if the wall separating them were diathemiic rather than adiabatic. In other words, there is a relation... 

One may now consider how changes can be made in a system across an adiabatic wall. The first law of thermodynamics can now be stated as another generalization of experimental observation, but in an unfamiliar form the M/ork required to transform an adiabatic (thermally insulated) system, from a completely specified initial state to a completely specifiedfinal state is independent of the source of the work (mechanical, electrical, etc.) and independent of the nature of the adiabatic path. This is exactly what Joule observed the same amount of work, mechanical or electrical, was always required to bring an adiabatically enclosed volume of water from one temperature 0 to another 02. 

In the example of the previous section, the release of the stop always leads to the motion of the piston in one direction, to a final state in which the pressures are equal, never in the other direction. This obvious experimental observation turns out to be related to a mathematical problem, the integrability of differentials in themiodynamics. The differential Dq, even is inexact, but in mathematics many such expressions can be converted into exact differentials with the aid of an integrating factor. 

Figure A3.14.12. The first experimental observation of a Turing pattern in a gel strip reactor. Solutions containing separate components of the CIMA/CDIMA reaction are flowed along each edge of the strip and a spatial pattern along the horizontal axis develops for a range of experimental conditions. (Reprinted with pennission from [38], The American Physical Society.)...

Lee K-J, MoCormiok W D, Pearson J E and Swinney H L 1994 Experimental observation of self-replioating spots in a reaotion-diffusion system Nature 369 215-8... 

All the previous discussion in this chapter has been concerned with absorption or emission of a single photon. However, it is possible for an atom or molecule to absorb two or more photons simultaneously from a light beam to produce an excited state whose energy is the sum of the energies of the photons absorbed. This can happen even when there is no intemrediate stationary state of the system at the energy of one of the photons. The possibility was first demonstrated theoretically by Maria Goppert-Mayer in 1931 [29], but experimental observations had to await the development of the laser. Multiphoton spectroscopy is now a iisefiil technique [30, 31]. 

The Bom approximation for the differential cross section provides the basis for the interpretation of many experimental observations. The discussion is often couched in temis of the generalized oscillator strength. 

This is the seminal book on metastable ions, their chemistry and experimental observation. It is a must for anyone starting out in gas-phase ion chemistry. 

Tunnelling is a phenomenon that involves particles moving from one state to another tlnough an energy barrier. It occurs as a consequence of the quantum mechanical nature of particles such as electrons and has no explanation in classical physical tenns. Tuimelling has been experimentally observed in many physical systems, including both semiconductors [10] and superconductors [11],... 

Mollenauer L F, Stolen R H and Gordon J P 1980 Experimental observation of picosecond pulse narrowing and solitons in optical fibres Phys. Rev. Lett. 45 1095-7... 

This time-dependent method allows one to nieely eoimeet the theoretieal and experimental observations. As mentioned earlier, the eorrelation fiinotion and its generalizations yield the speetra for a large number of other photospeetroseopy proeesses, sueh as Raman proeesses [ ], as well as moleeular seattering [73, 74],... 

Cox A J, Louderback J G and Bloomfield L A 1993 Experimental observation of magnetism in rhodium clusters Phys. Rev. Lett. 71 923... 

In extensively deionized suspensions, tliere are experimental indications for effective attractions between particles, such as long-lived void stmctures [89] and attractions between particles confined between charged walls [90]. Nevertlieless, under tliese conditions tire DLVO tlieory does seem to describe interactions of isolated particles at tire pair level correctly [90]. It may be possible to explain tire experimental observations by taking into account explicitly tire degrees of freedom of botli tire colloidal particles and tire small ions [91, 92]. 

Experimentally, local vibrational modes associated witli a defect or impurity may appear in infra-red absorjrtion or Raman spectra. The defect centre may also give rise to new photoluminescence bands and otlier experimentally observable signature. Some defect-related energy levels may be visible by deep-level transient spectroscopy (DLTS) [23]. 

Figure C3.2.12. Experimentally observed electron transfer time in psec (squares) and theoretical electron transfer times (survival times, Tau a and Tau b) predicted by an extended Sumi-Marcus model. For fast solvents tire survival times are a strong Emction of tire characteristic solvent relaxation dynamics. For slower solvents tire electron transfer occurs tlirough tire motion of intramolecular degrees of freedom. From [451.

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