Problems to overcome

The low unsaturation requires powerful curing systems whilst the hydrocarbon nature of the polymer causes bonding problems. To overcome these problems chlorinated and brominated butyl rubbers (CIIR and BUR) have been introduced and have found use in the tyre industry. 

There will be many times in the second half of this course when you will be trying to determine which way a reaction will proceed from two possible outcomes. Many times, you will choose one outcome, because the other outcome has steric problems to overcome (the geometry of the molecules does not permit the reactive sites to get close together). In fact, you will learn to make decisions like this as soon as you learn your first reactions Sn2 versus SnI reactions. Now that we know why geometry is so important, we need to brush up on some basic concepts. 

A more difficult problem to overcome is the overestimation of carotenoid concentrations in processed foods due to the usually more efficient extraction of carotenoids in such foods as a result of the denaturation of the carotenoid-protein complexes and cell damage. In addition, weight changes due to loss or gain of water or fat, enzymatic oxidation of carotenoids in raw samples, and leaching of soluble solids during processing should be considered. 

Calorimetry. Radioactive decay produces heat and the rate of heat production can be used to calculate half-life. If the heat production from a known quantity of a pure parent, P, is measured by calorimetry, and the energy released by each decay is also known, the half-life can be calculated in a manner similar to that of the specific activity approach. Calorimetry has been widely used to assess half-lives and works particularly well for pure a-emitters (Attree et al. 1962). As with the specific activity approach, calibration of the measurement technique and purity of the nuclide are the two biggest problems to overcome. Calorimetry provides the best estimates of the half lives of several U-series nuclides including Pa, Ra, Ac, and °Po (Holden 1990). 

The problems to overcome in order to attain atomic resolution with an STM can be divided into three areas ... 

For a battery to give a reasonable power output, the ionic conductivity of the electrolyte must be substantial. Historically, this was achieved by the use of liquid electrolytes. However, over the last quarter of a century there has been increasing emphasis on the production of batteries and related devices employing solid electrolytes. These are sturdy and ideal for applications where liquid electrolytes pose problems. The primary technical problem to overcome is that of achieving high ionic conductivity across the solid. 

The scientific interest in solid surfaces whether in the context of heterogeneous catalysis, solid state electronics, or corrosion is a direct consequence of the fact that their properties are unique with relation to the corresponding properties of the bulk solid. This is not difficult to appreciate since at the surface there is a breakdown of translational symmetry, extreme gradients of chemical composition are feasible, and perturbation of both bulk structure and charge are possible. There are, therefore, formidable problems to overcome if we are to arrive at a situation where surface structure, electronic... 

Cr(salen) supported on amino-modifed silica 56 was reported by Corma at al. [82] that showed high activity and selectivity for ARO of meso epoxides with TMSN3 but suffered aeute eatalyst leaching problem. To overcome this problem, Jaeobs et al. [84] made an... 

There had been two major problems to overcome for the development of MRNi with high EDA. One was the possibility of the presence of two kinds of differentiating sites on the surface of MRNi. That is, even though the same modifying reagent was used, MRNi often produced an opposite direction of EDA when modifying conditions were varied. The other problem was the possibility of the presence of unmodified surface area on the catalyst. 

The most general method for the preparation of solid phosphides is from the elements however, there are several problems to overcome in that highly electropositive metals are often air- and moisture-sensitive, so that the educts and often the products must be handled under inert conditions (glove box or Schlenk technique). A well described example for the synthesis of the air- and moisture-sensitive phosphides Na3 7 and Na3Pii has been described. ... 

Phytotoxicity is a much more difficult problem to overcome with sys-temics, because they are brought into intimate contact with the host plant. 

We can apply different types of minimization methods (steepest descent, Newton method, etc.) to the straightforward minimization of the corresponding misfit functional /(m). However, all these solutions have many limitations and are very sensitive to small variations of the observed data due to the principal instability of the inverse problem. To overcome this difficulty, we have to apply a regularizing method. 

Tape users have an additional problem to overcome. What if you type in a program in several sittings The next day, you come to your computer, load and run the Proofreader, then try to load the partially completed program so that you can add to it. But since the Proofreader is trying to hide in the cassette buffer, it is wiped out ... 

Although DFT is now rapidly replacing the HK method, there remain a number of fundamental problems to overcome. For example, energetic heterogeneity and hysteresis phenomena are generally not taken into account in the application of DFT for pore size analysis. On the other hand, in principle DFT should be applicable to both microporous and mesoporous solids. The derived pore size distributions are shown in Figure 3. It is of interest that the results of the DFT analysis and the Os-plots are at least consistent, but further progress will depend on the application of DFT to a number of well-defined pore structures. 

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