S-Phase

S-phase is, by definition, the period in the cell cycle during which DNA is synthesised. It is clear, however, that DNA synthesis does not start suddenly, proceed at full speed, and then stop suddenly, and hence to define exactly the beginning and end of S-phase is virtually impossible. 

It has been shown using DNA fibre autoradiography (Cairns, 1966, 1972) that in animal cells the synthesis of DNA occurs in discrete, short stretches or replicons (Huberman and Riggs, 1968). Replicons vary in size from 15-60 /am but are mostly less than 30 /im long in tissue culture cells (but see Callan, 1972). DNA synthesis is initiated in the middle of a replicon and proceeds bidirectionally to the ends of the replicon (Hand and Tamm, 1974). Later adjacent 

If cells are synchronised at the G1 /S boundary and then released, the rate of DNA synthesis is initially slow but accelerates to reach a maximum at about 3h and then decelerates until S-phase is essentially complete in 6-7 h (Stubblefield and Mueller, 1962 Adams, 1969b). As replication occurs different numbers of replicons are active at any one time, and so it is not surprising that more careful labelling reveals bursts of tritiated thymidine incorporation throughout S-phase rather than a steady even progression (Klevecz, 1969 Lett and Sun, 1970 Klevecz et al., 1974). 

This was shown clearly by Stubblefield and Mueller (1962), who demonstrated focalised synthesis of DNA by pulse-labelling a random population of cells with tritiated thymidine and then after varied time intervals visualised autoradiographically the regions of metaphase chromosomes where incorporation has occurred. 

One of the X-chromosomes in cells of female mammals has been found to replicate later than any other DNA in the cell (e.g. Gilbert et al., 1965), and particular satellites replicate at particular times in S-phase. Thus there is a specific temporal order in which particular replicons replicate. 

Sialon S-phase was first observed by Hwang et of. [28] as a second phase in the preparation of a-sialons, with strontium as the densifying additive. The general 

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This region has been divided into two subphases, L and S. The L phase differs from the L2 phase in the direction of tilt. Molecules tilt toward their nearest neighbors in L2 and toward next nearest neighbors in L (a smectic F phase). The S phase comprises the higher-ir and lower-T part of L2. This phase is characterized by smectic H or a tilted herringbone structure and there are two molecules (of different orientation) in the unit cell. Another phase having a different tilt direction, L, can appear between the L2 and L 2 phases. A new phase has been identified in the L 2 domain. It is probably a smectic L structure of different azimuthal tilt than L2 [185]. 

S. Chains in the S phase are also oriented normal to the surface, yet the unit cell is rectangular possibly because of restricted rotation. This structure is characterized as the smectic E or herringbone phase. Schofield and Rice [204] applied a lattice density functional theory to describe the second-order rotator (LS)-heiTingbone (S) phase transition. 

The hypersurface fomied from variations in the system s coordinates and momenta at//(p, q) = /Tis the microcanonical system s phase space, which, for a Hamiltonian with 3n coordinates, has a dimension of 6n -1. The assumption that the system s states are populated statistically means that the population density over the whole surface of the phase space is unifomi. Thus, the ratio of molecules at the dividing surface to the total molecules [dA(qi, p )/A]... 

As discussed in section A3.12.2. intrinsic non-RRKM behaviour occurs when there is at least one bottleneck for transitions between the reactant molecule s vibrational states, so drat IVR is slow and a microcanonical ensemble over the reactant s phase space is not maintained during the unimolecular reaction. The above discussion of mode-specific decomposition illustrates that there are unimolecular reactions which are intrinsically non-RRKM. Many van der Waals molecules behave in this maimer [4,82]. For example, in an initial microcanonical ensemble for the ( 211 )2 van der Waals molecule both the C2H4—C2H4 intennolecular modes and C2H4 intramolecular modes are excited with equal probabilities. However, this microcanonical ensemble is not maintained as the dimer dissociates. States with energy in the intermolecular modes react more rapidly than do those with the C2H4 intramolecular modes excited [85]. 

Figure Bl.18.6. Schematic representation of Zemike s phase contrast method. The object is assumed to be a relief grating in a transparent material of constant index of refraction. Phase and amplitude are varied by the Zemike diaphragm, such that an amplitude image is obtained whose contrast is, m principle, adjustable.

The full quantum mechanical study of nuclear dynamics in molecules has received considerable attention in recent years. An important example of such developments is the work carried out on the prototypical systems H3 [1-5] and its isotopic variant HD2 [5-8], Li3 [9-12], Na3 [13,14], and HO2 [15-18], In particular, for the alkali metal trimers, the possibility of a conical intersection between the two lowest doublet potential energy surfaces introduces a complication that makes their theoretical study fairly challenging. Thus, alkali metal trimers have recently emerged as ideal systems to study molecular vibronic dynamics, especially the so-called geometric phase (GP) effect [13,19,20] (often referred to as the molecular Aharonov-Bohm effect [19] or Berry s phase effect [21]) for further discussion on this topic see [22-25], and references cited therein. The same features also turn out to be present in the case of HO2, and their exact treatment assumes even further complexity [18],... 

We follow this with a low temperature approximation to the integral over the well s phase space population. The resulting equilibrium constant is... 

Gibbsitic [14762-49-3] Gibbs-Kelvin equation Gibbs phase rule Gibbs s phase rule Gibbs s theorem Gibbs-Thomson equation... 

Several of the Al—Li alloys developed in the 1980s contain both magnesium and copper. No quaternary Al—Cu—Li—Mg phase has been found in the alloys. The S -phase in addition to 5 and provides precipitation hardening. 

SCE increases absolute colony number and surviving fraction of CEU-E, CEU-G, and CEU-GM in kradiated human BM. An increase in the fraction of CDSd cells in the radioresistant S-phase has been noted, which suggests a possible mechanism (184). A cautionary note has been sounded about attempting to predict interactions between SCE and CSEs in hemopoieticaHy deprived individuals (185). Although SCE synergizes with GM-CSE or GM-CSE and lL-3 to increase CEU-GM in vitro, no such effect has been found in vivo. 

Tellurium Sulfide. In the hquid state, teUurium is completely miscible with sulfur. The Te—S phase diagram shows a eutectic at 105—110°C when the sulfur content is 98—99 atom % (94—98 wt %). TeUurium—sulfur aUoys have semiconductor properties (see Semiconductors). Bands attributed to teUurium sulfide [16608-21 -2] TeS, molecules have been observed. 

This is Gibbs s phase rule. It specifies the number of independent intensive variables that can and must be fixed in order to estabbsh the intensive equibbrium state of a system and to render an equibbrium problem solvable. 

Product formation kinetics in mammalian cells has been studied extensively for hybridomas. Most monoclonal antibodies are produced at an enhanced rate during the Gq phase of the cell cycle (8—10). A model for antibody production based on this cell cycle dependence and traditional Monod kinetics for cell growth has been proposed (11). However, it is not clear if this cell cycle dependence carries over to recombinant CHO cells. In fact it has been reported that dihydrofolate reductase, the gene for which is co-amplified with the gene for the recombinant protein in CHO cells, synthesis is associated with the S phase of the cell cycle (12). Hence it is possible that the product formation kinetics in recombinant CHO cells is different from that of hybridomas. 

Pollution level Minimum creepage distance between phase and ground mm per kV(r.m.s.) (phase to phase)... 

Batsanov, S.S., Phase Transformations and the Synthesis of Inorganic Substances in Shock Compression, Russian J. Inorg. Chem. 28 (11), 1545-1550 (1982). 

Closed-loop peak Mp = 5.5 dB Gain margin = 13.75dB Bandwidth = 5.09 rad/s Phase margin = 30.6 ... 

For a system such as discussed here, the Gibb s Phase Rule [59] applies and establishes the degrees of freedom for control and operation of the system at equilibrium. The number of independent variables that can be defined for a system are ... 

Gibb s Phase Rule. The phase rule derived by W. J. Gibbs applies to multiphase equilibria in multicomponent systems, in the absence of chemical reactions. It is written as... 

The sulphide usually forms an interconnected network of particles within a matrix of oxide and thus provides paths for rapid diffusion of nickel to the interface with the gas. At high temperatures, when the liquid Ni-S phase is stable, a duplex scale forms with an inner region of sulphide and an outer porous NiO layer. The temperature dependence of the reaction is complex and is a function of gas pressure as indicated in Fig. 7.40 . A strong dependence on gas pressure is observed and, at the higher partial pressures, a maximum in the rate occurs at about 600°C corresponding to the point at which NiS04 becomes unstable. Further increases in temperature lead to the exclusive formation of NiO and a large decrease in the rate of the reaction, due to the fact that NijSj becomes unstable above about 806°C. 

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