Realism spatial

In contrast to the aforementioned toxicity tests, in situ toxicity tests involve exposing organisms to contaminants on-site. This provides for more environmental realism, but there is also less control over confounding variables that may affect toxicity (spatial or temporal variation in temperature, sunlight, nutrients, pH, etc.), or other factors that may disturb or disrupt the test (animals, winds, floods, vandalism, etc.). For these tests, animals may be placed in mesh cages or corralled by impermeable barriers, such as wood, metal, or plastic sheets, at various locations throughout the contaminated zone. Plants may be planted in plots of contaminated soils. Toxicity endpoints may include survival, sublethal effects, or accumulation of contaminants in body tissues. For these tests, organisms are also placed in less contaminated sites for comparison. 

Chirality has been an area of enormous interest and significance for chemists. The identification of an enantiomeric excess in some amino acids found in a meteorite (Science 1997, pp. 275, 951) has generated a lot of excitement among chemists because chirality even figures in discussions of the origin of life. Robin Le Poidevin, in the chapter "Space and the Chiral Molecule," provides an instance of a reciprocally beneficial relationship between chemistry and philosophy. He examines some implications of the phenomenon of chirality in chemistry—optical isomerism in particular—for standard philosophical positions about space. At the same time, he shows how an understanding of "spatial realism" allows us to better appreciate the often subtle differences between different kinds of isomerism. 

Another class of QKD protocols is based on entangled quantum systems [162]. Both Alice and Bob receive one member of a pair of particles obtained from the parametric downconversion process [161]. These particles feature nonclassical properties results of suitably chosen measurements on the particles exhibit, even when spatially separated, correlations that cannot be explained by any classical theory consistent with local realism. When Alice and Bob decide to establish a key, they perform independent measurements in randomly chosen bases (from a given nonorthogonal set), and using a public channel they arrive at a secret shared key in a way similar to BB84. Later developments showed a way to improve the security of this protocol by means of the so-called entanglement purification techniques [163]. 

If the particle is an electron, then ipif/ is proportional to the average electric density at x, y, z. if/if/, being independent of time, can be represented in space as a continuous cloud of electrification varying from point to point in a manner shown by the solution of the wave equation which has yielded if/. Although this cloud is fictitious and corresponds to a probability or to a time-average, it is very convenient to visualize its spatial symmetry, and even to look upon the electrical distribution as a real one. This in one sense illustrates the reluctance with which naive realism is forsaken. 

Examination of the two-photon state vector in Eq. (10) or (12) shows that it implies nonlocality and lack of realism. It implies nonlocality since a measurement causes a collapse of, say, )+, Eq. (12a), to either x)i x)2 or ll )il> )2, each possibility occurring with probability one half. Thus, detection of photon 1 to the left with polarization in the x direction ensures that photon 2 to the right behaves as a photon polarized in the x direction also. But, as we have already seen, the choice of x direction is quite arbitrary, so the polarization state measured for photon 2 is, in fact, determined by the measurement we choose to make on photon 1 at a position that may be spatially separated, in the relativistic sense, from the position at which the measurement on photon 2 is carried out. Lack of realism also follows from this argument, since it then is impossible to think of the individual photons possessing properties, in this case polarization, which exist independently of any measurements which may be made on them. 

The engravings of Giovanni Battista Piranesi (1720-1778) displayed a new spatial sensibility, a step beyond Renaissance perspective.They showed the deeper structure of things as well as their superficial appearance but without implying a veiled depth. This realism included meticulous studies of ancient construction methods, with the careful depiction of details, tools and techniques becoming the starting point for a sensuous exploration of classical construction. The artist didn t just want to catalogue Roman methods for contemporary use but wished to step into Vitruvius very shoes. 

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