Effects of External Environment

Whilst some pipe users take pressure containment as their primary design criterion, others, notably the installers of large diameter pipes intended for low pressure drainage and sewerage, are far more concerned with design against failure by collapse or buckling 

Reproduced with permission from T. Stafford, Plastics in Pressure Pipes, Rapra, Review Report, 1998, 9, 6. 1998, Rapra Technology Limited. 

The effect of ground loads on pipes can be described by equations that involve the primary geometric and material property variables. Various analytical approaches have been adopted and there has been some disagreement between different national codes. The analyses are usually based on techniques first described by Spangler to calculate deflection of highway culverts. In the UK equations devised by the Transport and Road Research Laboratory (TRRL) [4] have been used. The German and Scandinavian codes have become widely used in Europe but in future it is likely that computer-interpreted 

By way of example the equation below is that attributed to Spangler who developed it in the late 1940s to aid highway culvert design and it has been the basis of most subsequent expressions. This equation has the form  

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That is why we consider the safety of a new pistol and its ammunition to be the most important characteristics (Jankovych Majtanik 2008). We require the pistol and its ammunition to resist a wide range of effects of external environment without getting dangerous or useless for real user. The safety precautions must be kept during common manipulation, transportation, storing and also during operation (shooting) when pistol and its ammimition must fulfil all required functions. Furthermore, the ammunition must stay safe not only in the period of use, but also in the period of retirement when it is either irreversibly adjusted or physically liquidated (disposal). 

The conformation of proteins integrated into a membrane depends not only on the type and sequence of the amino adds but also on the lipid environment, i.e. the composition of the membrane. The effect of lipid environments and external factors such... 

One point of particular relevance in the photodynamics that has not been addressed is the effect of the environment (external fields, solvents, solid surfaces, and protein cavities). Environmental effects can change the relative position of the electronic states, the position, and the topology of the conical intersections [62], It is still early to say whether it is possible to establish principles to make general predictions about the environmental effects on the photodynamics or it will be always necessary to make a particular analysis for each system. In... 

Many new physical methods were developed in response to needs of spin chemists. In particular, the time-resolved EPR (TREPR) ° and time-resolved NMR (CIDNP) techniques were found to be of unparalleled utility in terms of mechanistic understanding of radical chemistry. Theoretical work to explain CIDNP and CIDEP phenomena was able to link, for the first time, the spin physics of radical pairs to their diffusion, molecular tumbling, confinement (solvent cages versus supramo-lecular environments ), and the effects of externally applied magnetic fields. ... 

The main topics to be covered build upon our knowledge of the mechanical and rheological properties of membranes and their response to perturbations. In the remaining parts of this introductory section, some of these properties are briefly described to set the basis for a discussion of the behavior and response of membranes to external forces. The following sections consider in detail the morphological changes and poration electric fields can induce in vesicles made of membranes in different phases, and the effects of media environment and various molecular inclusions in the lipid bilayer, that is, the specific membrane composition. Finally, some application aspects of the work are discussed. 

Zhu, Y. G. (2001). Effect of external potassium (K) supply on the uptake of by spring wheat (Triticum aestivum cv. Tonic) a large scale hydroponic study. J. Environ. Radioact.55, 303-314. 

The external effects of the environment on polymer blends are chemical in nature, and normally lead to degradation of the polymers. Chain scission, depolymerization and reactions on the side-chain substituents all contribute to overall deterioration of blend properties. These are described for blends containing polyvinyl chloride, polystyrene, acrylics and polyolefins mixed with a variety of other polymers. The general feamres of radiation damage and the detrimental effects of processing are reviewed. 

The central nervous system (CNS) appropriately excites the muscle, and the generated tension is transferred to the skeletal system by the tendon to cause motion, stabilize the joint, and resist the effect of external forces on the body. Hence the functional evaluation of muscles cannot be performed without the characterization of the interfaced mechanical environment. 

The external causes of aging, on the other hand, originate with chemical and physical effects of the environment on the material ... 

The temperature distribution is changing due to change of external environment, and by comparing the relationship between ambient temperature variations and box-girder temperature variations, the effects of environment on box-girder temperature variations was analyzed. 

A) For the isolated systems, the effect of its environment is encapsulated by the external potential (potential energy) of the particle, V (xs pso AEk), where x i and ps denote the system s degrees of freedom and their conjugate momenta, respectively, while asj and Am represent the system s and the environment s parameters (such as the mass, electric charge, etc.), respectively. Needless to say, V is the one-particle observable changing the states of the open system, not yet of the environment. 

The last severe environment on our list is external stress. External stresses (14,33) especially affect the water uptake or saltwater penetration of adhesive bonds. However, some adhesives may appear insensitive to stresses. Presumably, the critical stress level (34) is so high that no environmental attacks can take place below that level. Thus, it is difficult to discuss the effect of external stresses without considering the fracture mechanics of adhesive joints. In general, external stresses accelerate bond degradation when the joint is exposed to severe environments. 

Kaezorek E. Effect of external addition of rhamnolipids biosurfactant on the modification of gram positive and gram negative bacteria cell surfaces during biodegradation of hydrocarbon fuel contamination. Pol J Environ Stud 2012 21 901. 

Biological systems can be treated at various different levels within a Car-Parrinello approach. One possibility is to use intelligently designed cluster models of the active site. Currently, systems of typically a few himdred atoms can be treated at the full quantum level. In addition, a static external field that captures the electrostatic field of the surrounding protein can be introduced. A common procedure is to parameterize the external electrostatic field in terms of point charges from empirical protein force fields. The most comprehensive approach for the treatment of biological systems within a Car-Parrinello framework are mixed quantum/classical QM/MM simulations. In these hybrid simulations, the reactive part of the system is treated within a standard Car-Parrinello scheme, whereas the surroimding protein is described with an empirically derived force field. In this way, electrostatic as well as steric and mechanic effects of the environment can be taken explicitly into account. 

Lanthanides in solids showing optical activity in the near and far IR, visible and near uv regions of the electromagnetic spectrum are invariably in the divalent and trivalent states. To arrive at these states of ionization the outer 6s and 5d shell and some of the 4f electrons are removed and the observed electronic transitions may be ascribed to the partially filled 4f shells. The closed shell 5s and 5p electrons remain in trivalent and divalent rare earths and serve to shield the active electrons from external perturbations, thus weakening the effects of the environs on the ions. The net result is that the energy levels of ions responsible for the... 

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