Frozen during

An alternate method involved pre-machining the core detail to contour while it was stabilized in a frozen block of water or other medium. This entailed the expense and time to freeze the block and keep it frozen during machining as well as the risk of contaminating the core bond surfaces. In addition it was difficult to maintain the dimensional tolerances necessary to match the spar dimensions to the core adequately. Both spar and core details had machining tolerances and significant hand sanding of the core was often required to match the details. 

Frozen reference materials have been produced by NIST (Wise et al. 1993). These materials do not have the disadvantages of the oils or freeze-dried materials, but are more difficult to transport. Obviously they have to be kept deep-frozen during transport, which makes their use rather expensive. Since the early 1990 s a new approach in this field has been introduced. This concerned the use of wet, sterilized fish and shellfish samples. These samples, packed in glass jars or in tins, were firstly used in the QUASIMEME program as reference materials for inter-laboratory studies (de Boer 1997). Later, when it appeared that the stability was maintained for longer periods, tests for organic contaminants based on this principle were also prepared. 

Thin sections can also be obtained from frozen soil. This type of thin section is best suited to soils that are naturally frozen at least part of the time. In these cases, the soil thin section must be kept frozen during the subsequent examination. Sectioning of frozen soil is generally more difficult than sectioning of resin-impregnated solids [10],... 

The maximum conversion of thymine to photoproducts in frozen aqueous solutions is 83-90%31 in samples subjected to alternate cycles of freezing and thawing, and 48-50% in samples continuously frozen during irradiation. This difference is attributed to depletion of thymine in the thymine crystallites of the continuously frozen solutions. The existence of a maximum at less than 100% in the conversion may reflect either the equilibrium always present between monomer and dimer, or... 

Figure 7 Several manganese C IV-EPR signals from the OEC in PS II, labelled by S-state. The S0 multiline EPR signal was generated by three-flash illumination of spinach thylakoid membranes. The S, multiline EPR signal was observed by parallel mode EPR detection of dark-adapted Synechocystis PS II particles. The S2 multiline and g = 4.1 EPR signals were generated by 195 K illumination of spinach thylakoid membranes. The S2-Yz EPR signal was generated in acetate inhibited spinach thylakoid membranes frozen during illumination. For further details and references see reference 449. Reproduced with permission from reference 449.

If the gas is to act on the film surface at room temperature, the film must be annealed at a somewhat higher temperature, so that its own structure will remain frozen during the experiment. 

The aim of this work is the quantitative description of the hydrogen bonds frozen during the transition into the vitreous state. The theory is based on the general kinetical theory of vitrification proposed by us in an earlier paper [3]. Let us write the equation for the formation and dissociation of the hydrogen bonds. It is an equation for a bimolecuiar process of the form... 

The parameters which appear in these equations axe Bk, Ap, ap, Cq and 7,. The Bk values are usually chosen to be the absolute value of the corresponding core orbital energies. Ap, ap, Cq and jq are calibrated to reproduce the orbital energies and shapes of the valence orbitals as obtained from all electron calculations on the atom. The outer core orbitals are in principle included in the valence space but these orbitals axe often kept frozen during both the parameter fitting and the molecular calculations. 

If the spin conversion is frozen during the encounters ( fkptj c 1), the results are slightly different. In the extreme case of no spin conversion go = gi and the general expression (3.820) reduces to the following one ... 

To circumvent this difficulty, a general procedure was developed. After the L-BOVB step, the orbitals are initially subject to localization1 using any standard localization procedure, and then the active orbitals are split while the inactive ones are kept frozen during the optimization process. 

The second step specifies which orbitals are frozen and which ones will be optimized in the VB calculation. After the file specification (three first lines), the first line shows that there are 28 basis functions. The second line specifies that 2 MOs arising from the Hartree—Fock calculation will be frozen during the VB calculation, and that among the 28 basis functions, only 26 will be kept as the basis on which the VB orbitals will be expanded. The third and fourth lines indicate, respectively, the MOs that are frozen, and the basis functions that are kept for the variational procedure. In the present case, the MOs that are frozen correspond to the Is core, and the Is basis functions are eliminated from the VB orbitals. 

The procedures for calculating the performance are also represented on fig. II. C. 1. For the modified Bray process the flow proceeds from the chamber condition (C) and follows the equilibrium result to a point just past the throat condition to the freezing point (B). Since equilibrium prevails from (C) to (B), the process is isentropic. From (B), the flow expands to (R) and remains frozen during the process. Again this step takes place in Plane A since the flow is frozen. 

Despite lack of sequence homology, the function of the quinone reduction site (Qi site) is similar to that of the secondary quinone-binding site (Qb site) of bacterial reaction centers. Both sites have a conserved histidine residue as quinone ligand and both quinone molecules are reduced to hydroquinone in two consecutive one-electron transfer steps. The midpoint potential for the first step is pH-independent at near neutrality, whereas that for the second reduction varies by 120mV per pH unit (Robertson et al., 1984). This suggests a reaction pathway Q —> Q" QH2, with both protons added concomitantly with the second electron. A stable semi-quinone anion intermediate can be detected by EPR spectroscopy of samples frozen during turnover (Yu et al., 1980 de Vries et al., 1980) or with the redox potential adjusted near the midpoint of ubiquinone (Robertson et al., 1984 Ohnishi and Trumpower, 1980). The semiquinone signal is not observed in the presence of antimycin, which is consistent with the proposal that antimycin inhibits the reaction at the site (Mitchell, 1976 Mitchell, 1975). 

Crystallization during rewarming can be used to crystallize water that has not been frozen during quick freezing. After crystallization the product is cooled... 

The laser-induced breakdowns are caused by three consequent mechanisms [22] (i) tiie excitation of electrons in tiie conduction band by impact and multiphoton ionization (MPI), (ii) radiation-induced heating of tiie conduction-band electrons, and (iii) transfer of the plasma energy to the lattice. The key benefit of ultia-short femtosecond laser pulses lies in their ability to deposit energy in materials in a very short time interval. Heat diffusion is frozen during the interaction and the shock-like energy deposition leads to ablation for ultra-short pulses. This is because tiie pulse... 

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