Synthetic phases

During the S phase, mammahan cells contain greater quantities of DNA polymerase than during the nonsynthetic phases of the cell cycle. Furthermore, those eiKymes responsible for formation of the substrates for DNA synthesis—ie, deoxyribonucleoside triphosphates—are also increased in activity, and their activity will diminish following the synthetic phase until the reappearance of the signal for renewed DNA... 

As illustrated above, analytical reasoning dominates current clinical pharmacology in that many efforts are directed at isolating and understanding the various factors that influence clinical effects. This is indeed the analytical phase outlined above, the indispensable phase of data gathering. But the objective is the prediction of clinical effects from results obtained with experimental model systems, and to this end a synthetic phase is necessary. 

Figure 3.13. Halfwidths of the V] and L Raman modes vs. composition for synthetic (squares) and biogenic (circles) phases. Calcite is represented by the triangle. Least squares line drawn through synthetic phases for reference. (After Bischoff et al., 1985.)...

Bischoff W.D., Bishop F.C. and Mackenzie F.T. (1983) Biogenically produced magnesian calcite Inhomogeneities in chemical and physical properties comparison with synthetic phases. Amer. Mineral. 68, 1183-1188. 

There are three Ti02 polymorphs, namely, rutile, anatase, and brookite an additional synthetic phase called Ti02 (B) and some high-pressure polymorphs have been also reported [45,46], Both the rutile and anatase polymorphs have photocatalytic properties however, these properties are more developed in the anatase polymorph [46],... 

The wide range of structural units exhibited by the natural and synthetic phases suggests that many new open frameworks with ion-exchange and sorption properties can be obtained. Exploratory synthesis of novel microporons solids is currently an active research area. 

Therefore the development of synthetic phases that can offer similar recognition properties seems desirable. One promising way to introduce selectivity in chemical analysis is the use of molecularly imprinted polymers (MIPs) [14-16]. These can in favourable cases recognise small molecules with affinities and selectivites exceeding that of antibody-antigen and have, due to their robustness, capacity and reproducibility, potential as reusable adsorbents in assays or sample pretreatment. 

Nowakowski RS, Lewin SB, Miller MW (1989) Bromodeoxyuri-dine immunohistochemical determination of the lengths of the cell cycle and the DNA-synthetic phase for a anatomically defined population. J Neurocy tol 18 311—318. 

DX-906Sa Propanoic acid derivative Synthetic Phase n dimeal trials... 

Bums et al. [2] developed a detailed stmctural hierarchy for inorganic uranyl compounds, and included both minerals and synthetic phases. At that time, 180 stmctures were available for inclusion. Bums [22] expanded the stmctural hierarchy and updated it in the case of minerals only. Bums [3] further developed the entire hierarchy and included coverage of 368 mineral and S5mthetic phases. The stmctural hierarchy is based upon the linkages of those polyhedra that contain higher-valence cations. In every case this includes polyhedra with U , and often it includes one or more other t5q>es of cation polyhedra. For the purposes of the hierarchy, bonds to low-valence cations and H bonds are ignored (although these bonds are important for the stability of the entire stmcture). 

Based on the leaching data [40,69,83] as well as data on radiation resistance of fast neutron irradiated [84-85] and actinide-doped Synrocs [86-88], as well as individual synthetic phases and their natural analogues study [14-18,89-91] zirconolite- and pyrochlore-based ceramics have been proposed for immobilization of excess plutonium and the other actinides. Moreover, additional phases, which were not part of the Synroc formulation, have been considered because of their chemical durability and radiation resistance (e.g., murataite, zircon, garnet, monazite, britholite). Of particular interest are the zirconate pyrochlores, many of which are extremely radiation resistant [8,92]. Zirconolite-based ceramics. Zirconolite, ideally CaZrTi207, is a major actinide host phase in the Synroc-type ceramics. Study of natural and synthetic samples... 

Figure 1 Phases of the cell cycle. Go, resting phase (nonproliferation of cells) Gi, pre-DNA synthetic phase (12h to a few days). S, DNA synthesis (usually 2-4 h) Ga, post-DNA synthesis (2-4h cells are tetraphoid in this stage) M, mitosis (1-2 h).

As discussed above, PAHs tend to exert their adverse effects on rapidly proliferating tissues, such as the bone marrow blood forming elements. It is likely that PAH-induced toxicity in this tissue is due to a specific attack on DNA of cells in the S or synthetic phase of mitosis (EPA 1988a). 

Silica, the main component of silicates, is widely used as mentioned earlier. In its crystalline and noncrystalline polymorphs, silica is used industrially as a raw material for glasses, ceramics, foundry molds, in the production of silicon, and more recently in technical applications such as quartz oscillators and optical waveguides for longdistance telecommunications. Of the crystalline forms, only a-quartz is commonly used as sand or as natural and synthetic single crystals. Cristobalite is often utilized as the synthetic phase in glass-ceramics. 

A synthetic phase, zeolite Linde W, with the MER structure exhibited cation preferences as K>NH4 Na -Ca>Mg (Sherman [42])... 

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