Polar region

FIGURE 4 3 Adipole-dipole attractive force Two molecules of a polar sub stance associate so that the positively polarized region of one and the negatively polarized region of the other attract each other... 

Induced dipole/induced dipole forces are the only intermolecular attractive forces available to nonpolar molecules such as alkanes In addition to these forces polar molecules engage m dipole-dipole and dipole/mduced dipole attractions The dipole-dipole attractive force is easiest to visualize and is illustrated m Figure 4 3 Two molecules of a polar substance experience a mutual attraction between the positively polarized region of one molecule and the negatively polarized region of the other As its name implies the dipole/induced dipole force combines features of both the induced dipole/mduced dipole and dipole-dipole attractive forces A polar region of one mole cule alters the electron distribution m a nonpolar region of another m a direction that produces an attractive force between them... 

The most important materials among nonlinear dielectrics are ferroelectrics which can exhibit a spontaneous polarization PI in the absence of an external electric field and which can spHt into spontaneously polarized regions known as domains (5). It is evident that in the ferroelectric the domain states differ in orientation of spontaneous electric polarization, which are in equiUbrium thermodynamically, and that the ferroelectric character is estabUshed when one domain state can be transformed to another by a suitably directed external electric field (6). It is the reorientabiUty of the domain state polarizations that distinguishes ferroelectrics as a subgroup of materials from the 10-polar-point symmetry group of pyroelectric crystals (7—9). 

A range of plasticizer molecule models and a model for PVC have been generated and energy minimized to observe their most stable conformations. Such models highlight the free volume iacrease caused by the mobiHty of the plasticizer alkyl chains. More detailed models have also been produced to concentrate on the polar region of the plasticizer and its possible mode of interaction with the polymer. These show the expected repulsion between areas on the polymer and plasticizer of like charge as weU as attraction between the negative portions of the plasticizer and positive portions of the PVC. 

Fig. 6. Discharge behavior of a battery where is the open circuit voltage (a) current—potential or power curve showing M activation, ohmic, and M concentration polarization regions where the double headed arrow represents polarization loss and (b) voltage—time profile.

In the last decade, the refrigerant issue is extensively discussed due to the accepted hypothesis that the chlorine and bromine atoms from halocarbons released to the environment were using up ozone in the stratosphere, depleting it specially above the polar regions. Montreal Protocol and later agreements ban use of certain CFCs and halon compounds. It seems that all CFCs and most of the HCFCs will be out of produc tion by the time this text will be pubhshed. 

Fig. 9-16 Interference of a short (a) and a long (b) pipeline by the anode voltage cone Hill region of cathodic polarization region of anodic polarization.

Endothermic animals can achieve and sustain levels of activity even when temperatures plummet or vary widely. This can be a huge advantage over ectothermy, especially m northern latitudes, at night, or during the winter. In colder climates, an ectothermic predator such as a snake will tend to be more sluggish and less successful than an endothermic predator. There are no reptiles or insects in the polar regions. 

Adaptations to Habitats. Because of Eaith s geom-etiyf and the position of its axis, the equator receives more solar energy per unit area than the polar regions. Because Earth s axis is tilted relative to the plane of Earth s orbit around the Sun, this angle of incident radiation varies seasonally. These factors, combined with Earth s rotation, establish the major patterns of temperature, air circulation, and precipitation. 

In the mid-latitude region depicted in Fig. 7-5, the motion is characterized by large-scale eddy transport." Here the "eddies" are recognizable as ordinary high- and low-pressure weather systems, typically about 10 km in horizontal dimension. These eddies actually mix air from the polar regions with air from nearer the equator. At times, air parcels with different water content, different chemical composition and different thermodynamic characteristics are brought into contact. When cold dry air is mixed with warm moist air, clouds and precipitation occur. A frontal system is said to exist. Two such frontal systems are depicted in Fig. 7-5 (heavy lines in the midwest and southeast). 

Figure 7-7 depicts the transport of one substance - water - due to the general circulation. Here we see the overall consequence of the general circulation with its systematic pattern of vertical motions and weather systems. Water evaporates from the oceans and land surfaces at subtropical latitudes and is transported both toward the equator and the poles. Precipitation falls largely at the equator and in the mid-latitudes. Hence, the subtropics are arid, with evaporation exceeding precipitation. The polar regions likewise are arid due to water having been removed in mid-latitude weather systems prior to arrival in the Arctic... 

Fig. 17-1 The global climate system, (a) Energy fluxes, including incoming solar radiation, reflected radiation, emitted longwave radiation (from an effective altitude of ca. 6 km), and atmospheric and oceanic heat flux toward the polar regions, (b) The atmospheric circulation corresponding to part (a). Refer back to Fig. 7-4 and associated text for a discussion of the general circulation.

Tilt variations also do not affect the annual total of solar energy received by the whole Earth, but do change the annual total for polar regions (simultaneously for both hemispheres). Tilt also affects the seasonal insolation at high latitudes, with greater tilt leading to warmer summers and cooler winters in both hemispheres. 

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