Specifications Essential requirements

Harmonised standards are technical specifications adopted by one of the European standards organisations following a mandate issued by the European Commission on which Member States were consulted. When published by the Commission in the Official Journal of the European Communities, the hamionised standards give presumption of confomiity to the essential requirements they specify. This means that manufacturers applying these standards do not have to demonstrate the compliance of the manufactured products with the relevant requirements of the directive. 

The principles referred to so far are common to all New Approach directives. The individual directives obviously need to be specific on topics such as the scope, the essential requirements, the classification of the products and on the use of modules for conformity assessment. The pressure equipment directive includes some additional sector specific dispositions which relate to recognised third party organisations , the European approval for materials , a committee for pressure equipment and the user inspectorates . 

Copper is required for all forms of aerobic and most forms of anaerobic life. In humans, the biological function of copper is related to the enzymatic action of specific essential copper proteins (66). Lack of these copper enzymes is considered a primary factor in cerebral degeneration, depigmentation, and arterial changes. Because of the abundance of copper in most human diets, chemically significant copper deficiency is extremely rare (67). 

For an electronic wavefunction, antisymmetry is a physical requirement following from the fact that electrons are fermions. It is essentially a requirement that y agree with the results of experimental physics. More specifically, this requirement means that any valid wavefunction must satisfy the following condition ... 

Although the directives allow flexibility in the methods and solutions that a manufacturer may employ to fulfil the essential requirements, they promote the use of standards as the preferred method to establish conformity. Specifically, the directives stipulate that Member States shall presume compliance with the essential requirements in respect of devices that are in conformity with relevant harmonised standards. 

The linearity of IMS is not sufficient for accurate quantitation of analytes. However, detection of contraband essentially requires a posi-tive/negative response, so that for this purpose linearity is not critical. The method is sensitive (sub-nanogram range) and has sufficient resolution ability [15,16]. The instrument can be adjusted to provide even better resolution for specific analytes of interest (e.g. drugs vs. explosives). These features, along with the reliability of the instrument, have made it the method of choice for field operations. IMS instrumentation has undergone numerous modifications that are promising for field... 

Where the purpose is simply to make a comparison or to check against a specification the value of the results is less critically dependent on the relation of the test conditions to service. This does not mean that the test conditions are unimportant for comparison or quality checks but that their relevance to service need only be established in general terms and not proved rigorously. The essential requirement for comparison is that the test conditions are not such that they give a distorted view of relative performance. For quality control it is particularly important that the test procedures and conditions are standardised and reproducible. 

In general, nephelometric measurements essentially require an instrument with a photocell placed in position so that it may receive selectively the scattered light rather than the transmitted light. As this principle and geometry also hold good specifically to fluorimeters and, therefore, these can be employed as nephelometers by selecting proper filters. 

RIA for hydromorphone and hydrocodone are fairly sensitive in the nanogram per millilitre range but essentially require the preparation of a specific antibody. The laid-out RIA method is quite capable of estimating the above drugs within a range of 2.5-20 ng ml 1 using standard 100 pi plasma sample only. 

Host defense peptide hydrophobicity (H) is defined as the proportion of hydrophobic amino acids within a peptide. Typically, these peptides are comprised of >30% hydrophobic residues and this governs the ability of a host defense peptide to partition into the lipid bilayer, an essential requirement for antimicrobial peptide-membrane interactions. Typically, the hydrophobic and hydrophilic amino acids of natural peptides are segregated to create specific regions or domains that allow for optimal interaction with microbial membranes. This likely represents evolutionary optimization to maximize the selectivity of these defense molecules. It has been established that increasing antimicrobial peptide hydrophobicity above a specific threshold correlates... 

European Communities are presumed by Member States to comply with those aspects of the essential requirements that are covered by the standard. Harmonised standards are those adopted by the EC standards bodies pursuant to a mandate issued by the Commission, in this case the European Committee for Standardisation (CEN) and the European Committee for Electrotechnical Standardisation (CENELEC). A large number of standards are contemplated but may take time to be written and adopted. Standards may be horizontal (covering aspects common to all or a number of product types) or vertical (dealing only with a specific aspect or specific product type). Important harmonised standards exist on the following ... 

There are many engineering and biological principles which must be taken into account when designing scaffolds for cell transplantation. Some are peculiar to the specific application while others are essential requirements which must be observed for all organs. The primary role of a scaffold is to provide a temporary... 

As modified so far the polyethylenimines, in contrast to enzymes, are weak in structural specificity toward substrates. This need not be a defect, however, for these macromolecular catalysts do not have to operate in a cellular environment and hence need not be subject to constraints designed to maintain the stability of a very complex, integrated biochemical network. Nevertheless, circumstances may arise where substrate specificity may be an essential requirement. We have some ideas on how this might be achieved with these relatively elastic macromolecular frameworks. For example, preliminary experiments show that we can attach —SH groups covalently to the polymer. It should be possible thereafter to add to the polymer solution an inhibitor with a structure analogous to the potential substrate and then to expose the solution to air... 

Different classes of solid propellants DB, CMDB, and fuel rich (FR) have been developed in order to meet the requirements of various missions in terms of specific impulse (Lsp) and wide range of burn rates with low pressure index (n). High density, low temperature sensitivity and good mechanical properties constitute other essential requirements of these propellants. The salient features of such performance parameters are ... 

One substance that has been found to be an essential requirement for the biosynthesis of DNA is the cobalt-containing vitamin B12 (42). Ever since this substance was first isolated and its structure determined, there has been a widespread search for the specific reactions that it mediates. The first such reaction was discovered by Barker, Weissbach, and Smyth (5), when they examined the enzymatic isomerization of glutamic acid to /3-methylaspartic acid. They were... 

Studies of specific adsorption of a series of anions to be discussed in detail elsewhere (5), have shown that the maximum specific adsorption at any pH, r0(1)H>, is related to the pKD of the anion acid and the charge on the adsorbing species. From these studies essential requirements for specific adsorption of anions, or exchange of specifically adsorbed ions, seem to be as follows ... 

The investigations of W. H. Stein and Moore and their colleagues were first reported in 1959 157). The inactivation of RNase by iodo-acetate was studied. A maximum in the rate of activity loss was noted at pH 5.5. Reaction with a methionine residue was found at pH 2.8 at pH 8.5-10 lysine residues were modified, but at pH 5.5-6.0 only histidine appeared to be involved. The specific reaction required the structure of the native enzyme. Reaction with histidine was not observed under a variety of denaturing conditions 158). Iodoacetamide did not cause activity loss, or only very slow loss, or alkylate His 119 in the native enzyme at pH 5.5. The negative charge on the carboxyl group of the iodoacetate ion was apparently essential. 

Most of the enzymes that are absolutely essential for cloning were discussed in the previous chapter. The most important enzymes that have not been discussed yet are the restriction enzymes. Systematic cleavages of duplex DNA at specific sites requires restriction enzymes. Each species of bacteria harbors a unique restriction enzyme, and hundreds of restriction enzymes with different specificities have been isolated, giving researchers a great deal of choice as to how and where DNA is cut. Some of the most commonly used restriction enzymes and their recognition sites are indicated in table 27.1. Most of these enzymes recognize a sequence... 

The metals copper, chromium and cobalt also appear to be essential for growth for some, if not all, microorganisms.1218 Cobalt is an essential requirement for cobalamin-utilizing bacteria, but apart from being an alternative substrate for an Mg2+ transport system, there appears to be no highly specific transport system for Co2+. E. coli has a high affinity uptake system for cyanocobalamin, even though it does not require Bl2. Cobalamin may thus serve as a source of cobalt. 

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