Mirror image phenomenon

Manganese is an odd element that is underrepresented in halo stars. However, the above explanation does not seem to apply since scandium (Z = 21) and vanadium (Z = 23) do not follow the same trend, no more than does cobalt (Z = 27). It is tempting to deduce from the unusual behaviour of manganese that it is produced by SNIa events and that we are observing a mirror-image phenomenon to the one described for a elements. 

About 50 years ago, physicists were amazed to discover that the universe, which had previously been regarded as completely symmetrical, had a certain preference for left-handedness. It had been considered impossible that basic natural laws would distinguish between left and right. This assumption formed the basis for the physical law of the conservation of parity according to this, the sum of the parities before and after each physical process must be equal. In other words the mirror image of each physical phenomenon is also a real phenomenon (Ball, 1994). 

If we explore substimted methanes, we will come to a very important understanding for molecules generally and the molecules of hfe in particular the phenomenon of chirality. A molecule is said to be chiral when it and its mirror image are not superimposable in space. 

Many substances can rotate the plane of polarization of a ray of plane polarized light. These substances are said to be optically active. The first detailed analysis of this phenomenon was made by Biot, who found not only the rotation of the plane of polarization by various materials (rotatory polarization) but also the variation of the rotation with wavelength (rotatory dispersion). This work was followed up by Pasteur, Biot s student, who separated an optically inactive crystalline material (sodium ammonium tartrate) into two species which were of different crystalline form and were separately optically active. These two species rotated the plane of polarized light equally but in opposite directions and Pasteur recognized that the only difference between them was that the crystal form of one was the mirror image of the other. We know to-day, in molecular terms, that the one necessary and sufficient condition for a substance to exhibit optical activity is that its molecular structure be such that it cannot be superimposed on its image obtained by reflection in a mirror. When this condition is satisfied the molecule exists in two forms, showing equal but opposite optical properties and the two forms are called enantiomers. 

This particular example represents one class of stereoisomers known as enantiomers, which may be defined as two molecules that are mirror images but are nonetheless nonsuperimposable. Such molecules are said to possess opposite configuration. If these isomers are separated (resolved), the separate enantiomers have been found to rotate the plane of plane-polarized light. This phenomenon of optical activity has been known for well over a century. A 50-50 mixture of two enantiomers is optically inactive or racemic, since the rotation of light by one enantiomer is precisely compensated by the rotation of tight in the opposite direction by the other enantiomer. 

Abnormal Stokes Shift.—The shift of an emission band to frequencies lower than those expected from the usual mirror image relationship between absorption and fluorescence bands (i.e., lack of a common 0-0 band). The phenomenon must always indicate that the emitting state is not the one produced by absorption. A number of processes may be responsible for example, the first formed excited state may undergo a chemical transformation, such as isomerization, so that emission involves a chemical species different from that which originally absorbed the light. 

An important approach to stereochemical problems is to make use of the concept of chirality. Chirality (7), namely, the phenomenon that a chiral object and its mirror image cannot be superimposed, has been classified according to different elements of chirality. Chiral molecules may contain chiral centers, axes, and/or planes (2, 3). 

Beginning with Pasteur s work in 1860 [4] the fields of stereochemistry and biology were dominated for almost nine decades by the phenomenon now called chirality. Chiral molecules are those for which a three-dimensional model of the molecule is not superimposable on the mirror image of the model. Since the operation determining the existence of chirality is reflection in a plane mirror, this... 

Every mathematical model is a simplified mirror image of a real phenomenon. To sustain the modeling assumptions, all... 

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