The problem of generation

At the very centre of biology there are two complementary problems How does an organism produce an egg (the problem of generation), and How does an egg produce an organism (the problem of embryonic development). These questions have been debated since 

Weismann gave the name of somatic cells to those that divide only by mitosis (and are thus destined to die with the body), and called germinal cells those that can divide both by mitosis and meiosis. These are potentially immortal, because they can have descendants for an indefinite number of generations. 

The discoveries of fertilisation, meiosis and germinal cells, in conclusion, made it possible to give a precise answer to the generation problem in cellular terms the generation of a new individual starts with two meioses, when gametes are formed, and is realised at fertilisation, when a zygote is formed. 

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There is great interest in the development of methods that allow the identification of a reasonably good structure with which to start the simulation of dense atomistically detailed polymer systems. The problem of generating dense polymer systems is formidable due to the high density and the connectivity of polymer systems. For crystal structures this can be systematically achieved [33,34] for amorphous structures, however, there is no generally satisfactory method available. Two recent developments in methods for generating amorphous packing (Santos, Suter) are reviewed in Section 3. 

An overview ofthe properties ofthe materials we are studying is presented in Table 18.11. The objective of this work was to find new approaches to the problem of generating new media with low dielectric constants and high thermal stabilities for use as interlayer dielectrics in microelectronic interconnection applications. We have been partially successful in this quest but there is still much more work to be done. The materials we have been able to deposit remain to be characterized in frill detail, which includes not only elucidating their molecular structure but also measuring the panoply of physical properties necessary for practical applications. 

In view of the above, it is not surprising that significant efforts have been dedicated to the problem of generating synthetic chloride receptors. Indeed, a number of such systems are known. Unfortunately, many of them are hydrophilic polycations and, accordingly, suffer from low solubility in organic media. " " Others are metal- or metalloid-derived systems. The clinical utility of these is clouded by metal toxicity. ° The sapphyrins, being both wholly organic and... 

Inside the cell, numerous chemical processes take place at the same time. The cell solves the problem of generating a large number of different molecules at the same time with a high selectivity by the use of enzymes. The selectivity of these proteins is largely determined by their geometry. Also the selectivity of another class of proteins, the receptors, is influenced by geometrical features. Receptors and enzymes have in common that they are equipped with concave structures such as clefts or cavities [1] in which substrate molecules are bound or chemically modified. 

Algorithm I - Registration - Canonicalization of Connection Tables. A connection table for a chemical substance with n atoms can be numbered in as many as n different ways. The problem of generating a canonical form involves selecting a... 

Much has been said in the past about the problems of generating a synthetic fuels industry - an industry which may require as many as 100 major plants in the 1990 s (1 ) - not very long... 

Takano et al. have reported the first synthesis of ( )-antirhine (71) (Scheme 11),51 in which the problem of generating the desired, less stable (anti) stereochemistry at C-3 and C-15 was overcome by preparing the non-tryptamine fragment (72) from ( )-trinorcamphor (73) via a sequence of stereospecific reactions. Condensation of (72) with tryptamine, followed by cyclization and... 

Schilling and Overall (2008) recently reported a solution for the problem of generating a peptide library that contains all relevant sequences of a human proteome, without including those that are biologically irrelevant (not present in humans, such as repeating tracts of rare amino acids). These proteome-wide peptide libraries are derived from the human proteome or other species of interest. To generate this new class of peptide library, natural proteomes, for example,... 

To this point, we have considered the interaction of nonionic surfactants within the framework of the mathanatical model. The activity and character of anionics in emulsification is complicated by the ionization steps which an anionic surfactant may take when exposed to salt solutions. For instance, in a dialkyl metallic salt, there are three compounds which may exist in various concentrations, depending ipon the ionic strength of the salt solution which, in turn, would exhibit, at least, three different HLB nuiiibers. To address the problem of generating Cohesive Energy Density parameters for the anionic hydrophiles, certain standardized assunptions... 

Percolation. Application of local interactions to the problem of generating long-range order, including phase transitions and morphogenesis, to large-scale discrete models. 

Excellent reviews of electrochemical SERS, including details of instrumentation and applications, can be found in the work of Tian and the group in Xiamen [18-20]. One of the key impediments to the wider application of electrochemical SERS has been the problem of generating suitable, stable, reproducible electrode surfaces that show strong SERS signals. This is discussed below. 

In this respect, database researchers have identified two main problems (1) the first one is that of schema mapping generation, largely inspired by the seminal Clio papers [Miller et al. 2000 Popa et al. 2002] this is the problem of generating a set of mappings based on the correspondences provided as input by the user (2) the... 

Unfortunately, the approaches above are applicable only in some specific cases the above techniques benefits apply only when schemas and correspondences obey to certain structures or require the presence of key constraints to reduce the redundancy in the output. Therefore, those approaches do not represent a general solution to the problem of generating neither core nor compact universal solutions. 

While process sym basis research has not yet produced the so In lion to the problem of generation of die best flowsheet, a number of heuristic rules have been stated by various process synthesis researchers which can be of considerable aid in guiding the selection of the near optimum or base case and Tor systematically choosing those alternate sequences to be investigated. Some of the heuristic roles developed will be compering and in some cases even contradictory, but nevertheless they do serve to reduce the enormous amount of work (hat would be involvnd in evaluating all possible separation sequences. 

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