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Molecule/molecular unit

Figure C2.3.3. Molecular packing of SDS monohydrate viewed as projected on the ac plane. This polymoriDh crystallizes in a triclinic cell with unit cell constants a, b and c of 10.423 A, 5.662 A and 28.913 A, respectively, and with a = 86.70°, (3 = 93.44°, y = 89.55°. There are four molecules per unit cell. Adapted from figure 2 of [18]. Figure C2.3.3. Molecular packing of SDS monohydrate viewed as projected on the ac plane. This polymoriDh crystallizes in a triclinic cell with unit cell constants a, b and c of 10.423 A, 5.662 A and 28.913 A, respectively, and with a = 86.70°, (3 = 93.44°, y = 89.55°. There are four molecules per unit cell. Adapted from figure 2 of [18].
In order to demonstrate the NDCPA a model of a system of excitons strongly coupled to phonons in a crystal with one molecule per unit cell is chosen. This model is called here the molecular crystal model. The Hamiltonian of... [Pg.444]

The types of molecules synthesized by biotechnological techniques are restricted to those biomolecules whose stmctures can be encoded in the DNA of organisms capable of translating them into functional nanomaterials. Other types of molecules and nanomaterials can be synthesized by chemical synthetic approaches, such as covalent syntheses and molecular self-assembly of molecular units. [Pg.206]

Synthetic large molecules are made by joining together thousands of small molecular units known as monomers. The process of joining the molecules is called polymerisation and the number of these units in the long molecule is known as the degree of polymerisation. The names of many polymers consist of the name of the monomer with the suffix poly-. For example, the polymers polypropylene and polystryene are produced from propylene and styrene respectively. Names, and symbols for common polymers are given in Appendix F. [Pg.2]

The turnover number of an enzyme, is a measure of its maximal catalytic activity, is defined as the number of substrate molecules converted into product per enzyme molecule per unit time when the enzyme is saturated with substrate. The turnover number is also referred to as the molecular activity of the enzyme. For the simple Michaelis-Menten reaction (14.9) under conditions of initial velocity measurements, Provided the concentration of... [Pg.438]

Figure 17.17 The structure of I2O5 showing the dimensions and conformation of a single molecular unit. Note that the molecule has no mirror plane of symmetiy so is not C2V... Figure 17.17 The structure of I2O5 showing the dimensions and conformation of a single molecular unit. Note that the molecule has no mirror plane of symmetiy so is not C2V...
A polymer is made up of a large number of small molecular units, called monomers, combined together chemically. A typical polymer molecule contains a chain of monomers several thousand units long. The monomer units of which a given polymer is composed may be the same or different. [Pg.611]

The remaining four elements form molecular solids. The atoms of white phosphorus, sulfur, and chlorine are strongly bonded into small molecules (formulas, P4, S8, and Cl2, respectively) but only weak attractions exist between the molecules. The properties are all appropriate to this description. Of course there is no simple trend in the properties since the molecular units are so different. [Pg.102]

Due to the steric requirement of these substituents the formation of a columnar structure with infinite M M interactions is inhibited, and only the association of pairs of molecular units is allowed. The Ni Ni distance is 3.21 A [164]. If the same compound is crystallized in the presence of benzimidazole, the [Ni(dmg-BF2)2]2 dimer units are sandwiched between sheets of benzimidazole molecules due to n-n interactions resulting in an increased Ni Ni separation of 3.358 A [165]. With anthracene the n-n interactions seem to be stronger, because in this case the parent dimer molecule is cleaved. Each monomer now has a conformation of type B (Fig. 32) and is sandwiched by anthracene molecules [166]. Compound 121 has the same configuration [163d]. [Pg.34]

The small molecules used as the basic building blocks for these large molecules are known as monomers. For example the commercially important material poly(vinyl chloride) is made from the monomer vinyl chloride. The repeat unit in the polymer usually corresponds to the monomer from which the polymer was made. There are exceptions to this, though. Poly(vinyl alcohol) is formally considered to be made up of vinyl alcohol (CH2CHOH) repeat units but there is, in fact, no such monomer as vinyl alcohol. The appropriate molecular unit exists in the alternative tautomeric form, ethanal CH3CHO. To make this polymer, it is necessary first to prepare poly(vinyl ethanoate) from the monomer vinyl ethanoate, and then to hydrolyse the product to yield the polymeric alcohol. [Pg.1]

When a stress is applied to the bulk polymer melt, the mass flows in the direction that relieves the stress. At the molecular level, the probability of a molecular jump becomes higher in the direction of the stress than in any other direction and hence these stress-relieving motions predominate, leading to the observed pattern of flow. There is evidence that the molecular unit of flow is not the complete macromolecule but rather a segment of the molecule containing up to 50 carbon atoms. Viscous flow takes place by successive jumps of such segments until the entire macromolecule has shifted. [Pg.78]

Since plane waves are delocalised and of infinite spatial extent, it is natural to perform these calculations in a periodic environment and periodic boundary conditions can be used to enforce this periodicity. Periodic boundary conditions for an isolated molecule are shown schematically in Fig. 8. The molecular problem then becomes formally equivalent to an electronic structure calculation for a periodic solid consisting of one molecule per unit cell. In the limit of large separation between molecules, the molecular electronic structure of the isolated gas phase molecule is obtained accurately. [Pg.23]

Monosaccharides, the molecular units of the saccharides, are carbohydrate molecules containing between three and six carbon atoms. Oligosaccharides contain small chains of two to ten monosaccharide units, and polysaccharides contain long-chain polymers of monosaccharides. [Pg.920]

T ike metals minerals also exhibit typical crystalline structures. As an example, the structure of molybdenite is shown in Figure 1.17. It is hexagonal with six-pole symmetry and contains two molecules per unit cell. Each sulfur atom is equidistant from three molybdenum atoms and each molybdenum atom is surrounded by six sulfur atoms located at the comers of a trigonal prism. There are two types of bonds that can be established between the atoms which constitute the molybdenite crystal stmcture. They are the covalent bonds between sulfur and molybdenum atoms and the Van der Waals bonds between sulfur-sulfur atoms. The Van der Waals bond is considerably weaker than the covalent sulfur-molybdenum bond. This causes the bonds of sulfur-sulfur to cleave easily, imparting to molybdenite the property of being a dry lubricant. Molybdenite adheres to metallic surfaces with the development of a molecular bond and the friction between metallic surfaces is replaced by easy friction between two layers of sulfur atoms. [Pg.53]

The chance of a collision will obviously depend upon the number of gas molecules per unit volume or, alternatively, upon the pressure. The chance of a collision will also depend upon the size of the gas molecules. For example, the chance of two basketballs thrown toward one another undergoing a collision is much greater than the chance of having a similar collision between two golf balls. An expression for the mean free path in terms of pressure and molecular diameter may be derived from kinetic theory. We give only the result, which may be expressed as... [Pg.649]

The experimental determination of D and E for a dilute single crystal is not trivial, even when the crystal axes are known. Durene, for example, has two molecules per unit cell with different orientations of the molecular plane. Thus for any orientation there are four resonances, two from each type of site. Sorting out the data is a challenging exercise.2... [Pg.122]


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See also in sourсe #XX -- [ Pg.579 , Pg.581 , Pg.592 ]




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Molecular units

Molecule/molecular unit structure

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