Experimental Findings

Considerations about mechanisms of crystallization and melting in polymers require as some basic ingredients 

Time and temperature dependent small angle X-ray scattering (SAXS) experiments made it possible to determine these properties. They were carried out for several polymer systems, including syndiotactic polypropylene 

Over the course of the past hve years we have compiled an exhaustive set of experiments wherein we attempt to ensure we have measured and fully characterized the hfth-order Raman response of liquid CS2. The most important results and conclusions are summarized here. In addition, preliminary results are presented for liquid benzene. 

Now that the signal had been established as measurable and uncontaminated with cascades, the next step was to fully characterize the response. Several papers had been pubUshed examining the merits of various polarization tensor elements and the potentially unique information they might contribute. Tokmakoff et al. had pubhshed a set of two papers examining the third-order [82] and fifth-order [83] tensor elements for the nonresonant Raman case and the dipole resonant case. The result was seven nonzero tensor elements that could be measured for the fifth-order Raman response iiimii, f ii22ii 111122  

The major problem in the comparison of 2D fifth-order Raman spectra to theory is that the theoretical calculations do not include all the contributions to the experiment in their calculated response functions such that there is tendency to selectively isolate certain regions of the spectrum in which one finds coincidences. An additional means of verifying the purity and origin of the fifth-order signal was necessary. One of the most important contributions to the field was the discovery of a mixed-polarization tensor element by Jansen, Snidjers, and Duppen that leads to a factor of 10 increase in contrast against cascaded nuclear contributions (vide infra) [50]. The proposed response 

DRF model. This model is a more accurate description of the intermolecular interactions as discussed previously. From the results it appears that the model used has a profound effect on the node position in the FFMD simulation. The results of Saito and Ohmine predict a node position around 200 fs for both DID and DRF calculations (see Fig. 1.13). In our FFMD simulation, both the DRF model and the DID model predict a much earlier node position, with the DRF model indicating a 50 fs shift to earlier time from the DID approximation (see 

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Figure B3.1.9 [83] displays the errors (in pieometres eompared to experimental findings) in the equilibrium bond lengths for a series of 28 moleeules obtained at the FIF, MP2-4, CCSD, CCSD(T), and CISD levels of theory using three polarized eorrelation-eonsistent basis sets (valenee DZ tlu-ough to QZ).

The BDD approach has been applied in a number of studies that employ the parameters derived from the experimental findings [77-85]. The approach has been extended by Duxbury an co-workers, particularly Alijah in its present version, involving the new stretch-bender Hamiltonian [84,85], which follows the idea by HBl [60], it approaches the methods we tentatively call benchmark. ... 

HCR and co-workers carried out a number of studies by employing 3D potential energy surfaces calculated by means of highly sophisticated ab initio approaches [88,91-101]. The results of these computations are in impressive agreement with the corresponding experimental findings. The discrepancies in the order of 100 wavenumbers, as in early ab initio studies [16,17], have been reduced in the HCR studies to only a few wavenumbers. In conclusion of their paper on the ( H ) system of NH2, Gabriel et al. state We believe... 

The excellent agreement of the results of HCR ab initio studies with the corresponding experimental findings clearly shows that the strongest influence on the numerical accuracy of the vibronic levels have effects outside of the R-T effect, that is, primarly the replacement of the effective bending approaches employed in previous works by a full 3D treatment of the vibrational motions (for an analysis of this matter see, e.g., [17]). Let us note, however, that such a... 

Figure 11. Left Vibronic structure of the X Tl state of HCCS derived by Tang and Saito from experimental findings (Fig. 3 of [139]). Right Corresponding results of the ab initio study presented in [152].

The phenomenon of thermal transpiration was discovered by Osborne Reynolds [82], who gave a clear and detailed description of his experiments, together with a theoretical analysis, in a long memoir read before the Royal Society in February of 1879. He experimented with porous plates of stucco, ceramic and meerschaum and, in the absence of pressure gradients, found that gas passes through the plates from the colder to the hotter side. His experimental findings were summarized in the following "laws" of thermal transpiration. 

This case history presents only a simple account of one of R.B. Woodward s adventures based on ingenious undentanding of structural features and experimental findings described in the literature. The hydrogenation of porphyrins is still one of the most active subjects in heterocyclic natural products chemistry, and the interested reader may find some modem developments in the publications of A. Eschenmoser (C.Angst, 1980 J.E. Johansen, 1980). 

Experimental findings in the intervening years have tended to support and extend this concept. The results obtained by Ramsay and Avery in their studies of the effect of compaction on the nitrogen isotherms of two finely divided powders, one of zirconia and the other of silica, are especially instructive in the present context. As in earlier studies (cf. Chapter 3) the isotherm on the original powder was of Type II, but on compaction it first became Type IV with a well defined hysteresis loop, which moved... 

The procedure we followed in adapting the relaxation model to experimental findings immediately suggests how to handle the discrepancies between the model and experiment in the case of creep ... 

With the Monte Carlo method, the sample is taken to be a cubic lattice consisting of 70 x 70 x 70 sites with intersite distance of 0.6 nm. By applying a periodic boundary condition, an effective sample size up to 8000 sites (equivalent to 4.8-p.m long) can be generated in the field direction (37,39). Carrier transport is simulated by a random walk in the test system under the action of a bias field. The simulation results successfully explain many of the experimental findings, notably the field and temperature dependence of hole mobilities (37,39). 

A Hiickel model used for calculating aromaticity indicated that the isoxazole nucleus is considerably less aromatic than other five-membered heterocycles, including oxazole and furan. SCF calculations predicted that isoxazole is similar to oxazole. Experimental findings are somewhat difficult to correlate with calculations (79AHC(25)147). PRDDO calculations were compared with ab initio values and good agreement for the MO values was reported... 

The usefulness of Eq. (3.41) depends crucially on whether or not the sensitivity factor rjA depends on the presence of other elements in the surface ( matrix effects ). It is an experimental finding that in general neutralization depends only on the atomic number of the scattering center, and matrix effects occur rarely. An instructive example is the neutralization of He by A1 in the pure metal and in alumina. The slopes of the neutralization curves turn out to be the same for both materials, i. e. matrix effects are absent [3.143]. This is a strong indication that in the neutralization process not only the valence/conduction electrons, but also atomic levels below the valence/ conduction band are involved. 

Occasionally a free ketol rather than its acetate may be cleaved successfully in other cases cleavage does not occur. Starr and Smith " have summarized the available data including that covering the reduction of vinylogs of ketols. The experimental findings may be rationalized in several ways, but no firm conclusions seem possible. Smith has discussed some of the pertinent factors that must control the reduction of ketols. 

In order to determine the mesomixing time, a least square fit of the 300 ml eontinuous ealeium oxalate (CaOx) preeipitation results for the number mean size and nueleation rate was performed. From these ealeulations, the faetor A in equation 8.15 was obtained as 17.7. Using the kinetie parameters determined from the laboratory-seale eontinuous experiments (Zauner, 1999), the large-seale experiments were simulated with the SFM and eompared with the experimental findings. 

First, we would like to eonsider a simple hard sphere model in a hard sphere matrix, similar to the one studied in Refs. 20, 21, 39. However, our foeus is on a very asymmetric hard sphere mixture adsorbed in a disordered matrix. Moreover, having assumed a large asymmetry of diameters of the eomponents and a very large differenee in the eoneentration of eomponents, here we restriet ourselves to the deseription of the struetural properties of the model. Our interest in this model is due, in part, to experimental findings eoneerning the potential of the mean foree aeting between eolloids in a eolloidal dispersion in the presenee of a matrix of obstaeles [12-14]. 

The experimental finding was substantiated by high-level ab initio calculations. The unionized acid exists in only minute concentrations (if at all) in aqueous solutions of SOi- However, its salts, the sulfites, are quite stable and many are known... 

Wheland and Pauling (1959) tried to explain the inductive effect in terms of ar-electron theory by varying the ax and ySxY parameters for nearest-neighbour atoms, then for next-nearest-neighbour atoms and so on. But, as many authors have also pointed out, it is always easy to introduce yet more parameters into a simple model, obtain agreement with an experimental finding and then claim that the model represents some kind of absolute truth. 

The computational results (93JA2465) are consistent with the experimental findings of NMR spectroscopic studies (82JOC5132 97MRC35), which showed the presence of only the H tautomer of tetrazole in DMSO-dfi e = 49) solution. The content of H tautomer 27a in dioxane e = 22) at 30°C was estimated as 78% (82JST283) and 85% (75BSF1675) from its dipole moment 4.88 D and those of 1,5- and 2,5-dimethyltetrazoles as models for the H and 2H tautomers respectively. 

DPT calculations confirmed the experimental findings that 2-ZnCl-l,3-oxazole 21 prefers a closed-ring structure while the corresponding 2-Li-l,3-oxazole 22 is not stable and prefers an acyclic structure (Scheme 17) [98CEJ814]. NBO analyses showed that the orbital of the C—M (M = Li, Zn) bond is -hybridized in the Zn... 

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