Some Controversial Issues

As mentioned above, the two most popular reaction mechanisms involved in the absorption of free radicals by the monomer-swoUen micelles and polymer particles are the diffusion- and propagation-controlled models. Nevertheless, liotta et al. [39] were inclined to support the colUsion-controlled model. A dynamic competitive particle growth model was developed to study the emulsion polymerization of styrene in the presence of two distinct populations of latex particles (i.e., bimodal particle size distribution). Comparing the on-line density and particle size data with model predictions suggests that absorption of free radicals by the latex particles follows the collision-controlled mechanism. 

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In the context of the structural perturbations at fluid-solid interfaces, it is interesting to investigate the viscosity of thin liquid films. Eaily work on thin-film viscosity by Deijaguin and co-workers used a blow off technique to cause a liquid film to thin. This work showed elevated viscosities for some materials [98] and thin film viscosities lower than the bulk for others [99, 100]. Some controversial issues were raised particularly regarding surface roughness and contact angles in the experiments [101-103]. Entirely different types of data on clays caused Low [104] to conclude that the viscosity of interlayer water in clays is greater than that of bulk water. 

In the second place, we shall study rotational dynamics. Rotational processes are of fundamental importance for dielectric relaxation. To shed light on some controversial issues in dielectric relaxation, Brot and co-workers did a computer simulation of a system of disks interacting via both Lennard-Jones potentials and electric dipole-dipole couplings. This is pre-... 

Let us address some controversial issues on what is emerging now. 

Legator MS, Singleton CR, Morris DL, et al Health effects from chronic low-level exposure to hydrogen sulfide. Arch Environ Health 56 123-131, 2001 Matsuo F, Cummins JW Neurological sequelae of massive hydrogen sulfide inhalation (letter). Arch Neurol 36 451-452,1979 Milby TH, Baselt RC Hydrogen sulfide poisoning clarification of some controversial issues. AmJIndMed 35 192-195, 1999... 

The other problems mentioned in this section (the fact that so many people with alcohol and other drug problems do not acknowledge the need for help, the problem of retaining chents in treatment, and the frequency of relapse among chents fohowing treatment) are related to each other. In order to understand this relationship, it is necessary to examine some controversial issues in treatment. 

Other courts addressing this problem have refused to adopt a rule of proportional recovery. Some have asserted that such a fundamental change of a basic tort principle is more appropriately a legislative function. Others have expressed concern that the long latency period renders any reconstmction of market shares highly speculative. The Restatement notes the opposing views but takes no position on this controversial issue. 

The data presented here has provided a chronological picture of the evolution and current state of the possible positive or negative association of some methylxanthine-containing products and various types of cancer. Perhaps the best conclusion at this time is an extension to tea and other methylxanthine-containing products of the statement by Stavric" who in 1990 wrote that certain controversial issues about the effect of coffee on human health remains unresolved. Future work should focus on types and methods of preparation of teas, roasting and preparation methods for coffees, and consider the whole beverage rather than caffeine or other methylxanthine per se. Meanwhile it appears that both tea and coffee and... 

There is some controversy in the theoretical literature about the relationship between health insurance and efficiency. Puig-Junoy3 has conducted an excellent review of this issue. The scope of the welfare loss associated with health insurance has also been the object of empirical research with econometric procedures. 

Finally, a relatively new area in the computer simulation of confined polymers is the simulation of nonequilibrium phenomena [72,79-87]. An example is the behavior of fluids undergoing shear flow, which is studied by moving the confining surfaces parallel to each other. There have been some controversies regarding the use of thermostats and other technical issues in the simulations. If only the walls are maintained at a constant temperature and the fluid is allowed to heat up under shear [79-82], the results from these simulations can be analyzed using continuum mechanics, and excellent results can be obtained for the transport properties from molecular simulations of confined liquids. This avenue of research is interesting and could prove to be important in the future. 

The corrections for basis set superposition errors (BSSE) with the counterpoise correction are still a controversial issue [120-122], However, some type of correction is needed for calculations on systems with weak interactions. It has been proved that only considering the BSSE meaningful results can be obtained on large systems [122], Of course, by using good quality basis sets the BSSE is less troublesome and the results obtained can be accepted, readily, as reliable. The BSSE in DFT calculations is less important than in conventional ab-initio calculations. We compute the counterpoise correction as ... 

As with other controversial issues, activists on both sides of the gun issue have created many useful web sites. Because they offer overviews and links to news and source materials, such sites provide a good jumping-off place for research. Of course, as you explore the web, you will encounter many references to books and other printed materials that are not available online. It will then be time to use the library and its catalog and other bibliographical tools. This chapter describes some of the most important and useful research tools, both online and traditional. 

The study of carbocations has now passed its centenary since the observation and assignment of the triphenylmethyl cation. Their existence as reactive intermediates in a number of important organic and biological reactions is well established. In some respects, the field is quite mature. Exhaustive studies of solvolysis and electrophilic addition and substitution reactions have been performed, and the role of carbocations, where they are intermediates, is delineated. The stable ion observations have provided important information about their structure, and the rapid rates of their intramolecular rearrangements. Modem computational methods, often in combination with stable ion experiments, provide details of the stmcture of the cations with reasonable precision. The controversial issue of nonclassical ions has more or less been resolved. A significant amount of reactivity data also now exists, in particular reactivity data for carbocations obtained using time-resolved methods under conditions where the cation is normally found as a reactive intermediate. Having said this, there is still an enormous amount of activity in the field. 

This is profoundly different from what occurs in most other processes designed to produce scientific consensus, which usually present the mean position plus some reasonable variation concerning a controversial issue. Moreover, the selection of models that predict the greatest changes appears to have ignored the in-... 

Unfortunately, these issues have not been often considered and have led to some controversy in the anion complexation data involving calixpyrroles. The following sections will discuss 1H NMR, conductometric and thermodynamics studies involving calixpyrrole, its derivatives and their interactions with the fluoride anion in different media. 

Holism is a controversial issue. Some holists maintain that the smallest unit which can be understood in itself is a comprehensive theory or the whole language. Some of their adversaries allege that all concepts can be understood on their own. My position is in between. And it is not part of it which party is more right than the other one. 

Today, I try to remind myself to never make a hasty judgment about any controversial issue without doing some research. Forming an opinion about something I personally know nothing of is foolhardy. Too often, I suspect later I might have to eat those words. 

There is some controversy over this issue. There is, of course, none over the S 2 reaction on these allylic compounds—inversion occurs as in all S 2 reactions. It used to be supposed than S 2 reactions went with retention3—that is, the nucleophile attacked the same face of the allylic system (we shall call this syn attack). The attractive rationalization was that the 7t bond attacked the C-Br bond from the back and then was itself attacked from the back by the nucleophile. This results in an anti reaction of the 7t bond and overall syn attack of the nucleophile with respect to the leaving group. 

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