Retardation variable

Cblorina.ted Pa.ra.ffins, The term chlotinated paraffins covers a variety of compositions. The prime variables are molecular weight of the starting paraffin and the chlorine content of the final product. Typical products contain from 12—24 carbons and from 40—70 wt % chlorine. Liquid chlotinated paraffins are used as plasticizers (qv) and flame retardants ia paint (qv) and PVC formulations. The soHd materials are used as additive flame retardants ia a variety of thermoplastics. In this use, they are combiaed with antimony oxide which acts as a synergist. Thermal stabilizers, such as those used ia PVC (see vinyl polymers), must be used to overcome the inherent thermal iastabiUty. 

Laboratory experiments using rodents, or the use of gas analysis, tend to be confused by the dominant variable of fuel—air ratio as well as important effects of burning configuration, heat input, equipment design, and toxicity criteria used, ie, death vs incapacitation, time to death, lethal concentration, etc (154,155). Some comparisons of polyurethane foam combustion toxicity with and without phosphoms flame retardants show no consistent positive or negative effect. Moreover, data from small-scale tests have doubtful relevance to real fine ha2ards. 

In an electrooptic material the phase retardation angle is controlled by altering birefringence, which is in turn controlled by the potential of an apphed electric field. An electrooptic device thus acts as a variable phase optical retardation plate, and can be used to modulate the wavelength or intensity of an incident beam. 

There are methods to manipulate the backbones of polymers in several areas that include control of microstructures such as crystallinity, precise control of molecular weight, copolymerization of additives (flame retardants), antioxidants, stabilizers, etc.), and direct attachment of pigments. A major development with all this type action has been to provide significant reduction in the variability of plastic performances, more processes can run at room temperature and atmospheric pressure, and 80% energy cost reductions. 

The retarding influence of the product barrier in many solid—solid interactions is a rate-controlling factor that is not usually apparent in the decompositions of single solids. However, even where diffusion control operates, this is often in addition to, and in conjunction with, geometric factors (i.e. changes in reaction interfacial area with a) and kinetic equations based on contributions from both sources are discussed in Chap. 3, Sect. 3.3. As in the decompositions of single solids, reaction rate coefficients (and the shapes of a—time curves) for solid + solid reactions are sensitive to sizes, shapes and, here, also on the relative dispositions of the components of the reactant mixture. Inevitably as the number of different crystalline components present initially is increased, the number of variables requiring specification to define the reactant completely rises the parameters concerned are mentioned in Table 17. 

It is possible to determine components in complex EPs where matrix effects can be severe. For example, zinc (as zinc borate), chlorine (as dechlorane flame retardant), antimony (as oxide) and fibre-glass have been determined in nylon using just one standard. Many users have refined the universal precalibrated programmes for standardless XRF and made them more efficient for matrix correction by using variable correction coefficients. OilQuant offers possibilities for analysing polymers [243]. Software packages usually provide ... 

Often these design criteria involve competitive requirements. What is best for meeting one criterion may be counterproductive in meeting another. For example, certain excipients such as the hydrophobic stearate lubricants are important for efficient manufacture, yet they have the potential to retard the release of drug from an immediate-release formulation. The design of a dosage form thus frequently requires the optimization of formulation and process variables in a way that best meets all design criteria. 

In the last example, the control of the lube oil temperature may initially seem easy. Apparently, the operator need only measure the lube oil temperature, compare the actual temperature to the desired (setpoint), compute the amount of error (if any), and adjust the temperature control valve to correct the error accordingly. However, processes have the characteristic of delaying and retarding changes in the values of the process variables. This characteristic greatly increases the difficulty of control. 

Figure 5.8 GALDI mass spectra of mastic with variable amounts of polymer, artificially aged for 880 h (36] (a) without polymer (b) normal mastic and (c) with added polymer. Oxidation and decomposition is enhanced with lower amounts of polymer, thus the mastic polymer retards oxidation of the triterpenoids...

Disorders of glutathione Defective synthesis of glutathione, the major intracellular antioxidant Spinocerebellar degeneration, mental retardation, cataracts, hemolysis. Severe acidosis in some cases N-acetylcysteine (variable response)... 

Multiple sulfatase deficiency (MSD). The clinical presentation of MSD includes features of MLD and the MPS, with the features that resemble MLD, such as gait disturbances, psychomotor retardation and polyneuropathy predominating. MPS-like features, such as facial coarsening, hepatosplenomegaly and joint stiffness, are present to a milder and variable extent. A reduction in the activity of all sulfatases is the key diagnostic abnormality. Von Figura and associates have demonstrated that catalytic activity of all sulfatases requires a post-translational modification in which a cysteine residue (cysteine 69 in arylsulfatase A) is oxidized to an aldehyde. It is this modification that is defective in MSD [5]. 

Data are scarce on the toxicity of PCP to mammalian wildlife, but studies with livestock and small laboratory animals show that the chemical is rapidly excreted. However, there is great variability between species in their ability to depurate PCP, as well as in their overall sensitivity. Acute oral LD50 values in laboratory animals were 27 to 300 mg/kg BW. Tissue residues were elevated at dietary levels as low as 0.05 mg/kg feed and at air levels >0.1 mg/m3. Histopathology, reproductive impairment, and retarded growth were evident at doses of 0.2 to 1.25 mg/kg BW, and when the diets fed contained >30 mg PCP/kg. 

The resin reaction rate at different sea water conditions (e.g. temperature, pH) and paint variables (e.g. retardants, additives). 

Fig. 6. Potential distribution and electron kinetic energy functions in a simple ion source using the R.P.D. method (see text) the effect of a variable retarding potential is shown schematically.

Fragile X syndrome is the leading inherited cause of mental retardation in humans. It affects about 1 out of 2000 males and about 1 out of 4000 females. The degree of mental retardation is quite variable, from a mild mental impairment to severe mental retardation. The disease is frequently more serious in males than females males have only the defective X chromosome, whereas females have one normal X chromosome to go along with the defective one. There is no specific treatment for Fragile X syndrome. 

---