Spontaneous drawbacks

False. Continuous cultures operate for lengthy periods. Spontaneous mutations will arise and if they can compete successfully with the parent organism (by virtue of higher growth rate) they can predominate in the culture. Batch cultures have short growth times and so do not suffer such drawbacks. 

In this chapter, we describe some of the more widely used and successful kinetic techniques involving controlled hydrodynamics. We briefly discuss the nature of mass transport associated with each method, and assess the attributes and drawbacks. While the application of hydrodynamic methods to liquid liquid interfaces has largely involved the study of spontaneous processes, several of these methods can be used to investigate electrochemical processes at polarized ITIES we consider these applications when appropriate. We aim to provide an historical overview of the field, but since some of the older techniques have been reviewed extensively [2,3,13], we emphasize the most recent developments and applications. 

An alternative way to preform a channeled plasma consists in exploiting the nanosecond precursor that usually precedes a short femtosecond pulse in the output of a multi-terawatt laser system. In fact, the amplified spontaneous emission (ASE) pedestal has typically an intensity 106-1010 times lower than the main pulse, which, however, can be sufficient to ionize a gas-jet or a solid target. This drawback can be turned into a benefit assuming that this long precursor can prepare the plasma channel for the short pulse propagation. 

One of the first synthetic applications of organoboranes in radical chemistry is the conjugate addition to enones (Scheme 23, Eq. 23a) and enals reported by Brown [58-61]. Addition to -substituted enones and enals are not spontaneous and initiation with the oxygen [62], diacetyl peroxide [63], or under irradiation [63] is necessary (Eq. 23b). A serious drawback of this strategy is that only one of the three alkyl groups is efficiently transferred, so the method is restricted to trialkylboranes derived from the hydroboration of easily available and cheap alkenes. To overcome this limitation B-alkylboracyclanes have been used but this approach was not successful for the generation of tertiary alkyl radicals [64,65]. 

Despite many advantages fluoridation may also have some drawbacks. One of the most important is increased formation of dental calculi. As fluoridation considerably reduces the solubility of apatites, the supersaturation of saliva with respect to apatite is appreciably increased and may favour the spontaneous precipitation of fluoridated apatites and the formation of dental calculi. This phenomenon would occur especially in the case of fluoridated toothpaste, and most of them... 

Nuclear track detectors are very simple and very efficient detectors of rare events that produce highly ionizing radiation. Carefully prepared and scanned track detectors have been used to identify individual rare decays. The detectors are integrating in that the damage caused by a track is not spontaneously repaired. The drawback to track detectors is that the tracks are small and can only be observed with a microscope. In the past, scanning by eye was extremely labor intensive and prone to error. Modern computer-controlled scanning has improved the speed and reliability of the analysis. Plastic track detectors that are sensitive to a particles are used extensively in commercial radon detectors. 

Another example is the injection moulding of a pail, where the injection takes place at the bottom. The most removed part, the brim of the pail, will solidify first, thus impeding the shrinkage of the remaining part, in particular of the bottom. The bottom is, therefore, heavily stressed and may spontaneously break in shock loading. A better construction of the mould can prevent this drawback, namely by making the bottom not flat but somewhat hollow, so that the stresses easily disappear by a minor deformation of the bottom. 

Changes in the number or structure of chromosomes account for nearly half the spontaneous abortions and for many of the congenital defects in livebom children. One in 200 newborn persons has a detectable chromosomal abnormality.188 188 An increase in this incidence could be detected in a moderate sample if it were carefully chosen. A drawback is the very long time—40 yr or more--that could elapse between parental e qposure and the birth of affected offspring. 

Recently, much attention has been paid to metal hydrides as a promising way for storing hydrogen. However, the drawback of this material is that it reacts spontaneously in air and moisture-rich environments. 

A somewhat different note has been sounded from the Committee on Occupational Medical Practice of the American College of Occupational and Environmental Medicine. The committee pointed out that risks to laboratory workers resulting from spontaneous infection are presumably similar to those involved in vaccination. The positive aspect of immunization is that it renders possible control over the time and initial site of entry of the virus. In the Committee s opinion, it is important for scientists and technicians to understand the US Public Health Service recommendations and to have the opportunity to receive Vaccinia immunization. They should also understand the possible drawbacks and have the opportunity to refuse vaccination (17). These different recommendations in the USA are also reflected in different national recommendations in other countries. 

Tt is impossible to distinguish shrinkage or expansion caused by parallel physical and chemical processes taking place spontaneously in the given refractory. This drawback can be eliminated by using torsion tests. 

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