Reversibility consolidation

Parylene-C is of potential interest in conservation because of the unique application method that can result in the formation of thin, uniform, and strong films within porous or fibrous materials. However, the polymer has the disadvantages of being a non-reversible consolidant that is sensitive to ultraviolet-induced oxidation. 

The structures of sol-gel-derived inorganic polymers evolve continually as products of successive hydrolysis, condensation and restructuring (reverse of Equations 1-3) reactions. Therefore, to understand structural evolution in detail, we must understand the physical and chemical mechanisms which control the sequence and pattern of these reactions during gelation, drying, and consolidation. Although it is known that gel structure is affected by many factors including catalytic conditions, solvent composition and water to alkoxide ratio (13-141, we will show that many of the observed trends can be explained on the basis of the stability of the M-O-M condensation product in its synthesis environment. 

It is a matter of debate whether memories can be erased at all (Jacobs and Nadel 1985). However, there is some evidence from animal experiments that processes that lead to learning or LTP-induced changes in interneuronal communication can be reversed by specific opponents of the consolidation cascade, as for instance phosphatases (Genoux et al. 2002 Lin et al. 2003a,b). The decay of both LTP and memory seems to depend on NMDA receptors. However, there are conflicting data as to whether recurrent activation of NMDA receptors promotes decay or long-term consolidation processes (Shimizu et al. 2000 Villarreal et al. 2002). 

Electrochemistry has been used for more than a century in the treatment of ancient metal artifacts [281], Ideally, this technique should be able to reverse the corrosion processes that have progressively transformed the metal into an ionic compound. Depending on the conservation state of the artifact, priorities have to be attributed and the treatment will be different if consolidation, stabilization, or cleaning is privileged. 

Foley AG, Murphy KJ, Hirst WD, et al. The 5-HT6 receptor antagonist SB-271046 reverses scopolamine-disrupted consolidation of a passive avoidance task and ameliorates spatial task deficits in aged rats. Neuropsychopharmacology... 

King MV, Sleight AJ, Woolley ML, Tophan IA, Marsden CA, Fone KCF. 5-HT6 receptor antagonists reverse delay-dependent deficits in novel object discrimination by enhancing consolidation an effect sensitive to NMDA receptor antagonism. Neuropharmacology 2004 47 195-204. 

The polymers used must protect murals from moisture, must be totally inert, and must not alter the appearance of the paint layer or cause structural changes within it. Proper ventilation requirements for polymer use during conservation must also be considered. When new and better techniques become available, it must be possible to remove these polymers and the polymers used in the structural consolidation of the plasters with minimal or no damage to the tomb, in the tradition of reversible conservation treatments. 

Critical decisions are often made on the basis of subjective observations of each piece coupled with curatorial experience with similar pieces. Conservators who embark occasionally on restorative treatments such as fabric consolidation designed to reverse the symptoms of degradation have begun to address the causes and to consider the... 

Transducer output from a rotary tablet press differs in two aspects. Firstly, the lower punch plays an active role in the compression event and moves upwards as the upper punch moves downwards. The second difference is small but important. Because of the sinusoidal movement of the upper punch in an excentric press, the punch speed is only zero at the instant when it reverses direction (point E). Punches on a rotary press have a flat area on the punch head. As the punches pass under or over the pressure rolls, the flat area dictates that there is no punch movement. The period during which this occurs is called the dwell time, and though it only lasts a fraction of a second, it can have a major effect on the consolidation process. ... 

In order to sustain the benefits from fixed bed counterflow regeneration it is imperative that the resin bed remains consolidated and undisturbed at all times during loading and reverse flow regeneration. Some ways this is achieved are discussed later in Chapter 10, but it follows that conventional backwashing of a counterflow designed column is undesirable since the inevitable bed disturbance causes exhausted resin to mix with the lightly loaded resin zone at... 

Platinum remains more active than rhenimn even in the presence of CPE and CPD, which confirms that the metals play a dual role in the formation of coke dehydrogenation giving coke precursors (non operating here since CPE and CPD are already present in the reactant) and consolidation of the coke deposited on the support by continuous elimination of hydrogen via a reverse spillover phenomenon. It is clear that Pt remains more effective than Re in coke consolidation. TPO profiles on Re (Fig.4) show a small... 

The first super-deep drilling to 12.8 km in the Kola peninsula of Russia verified the effect of de-consolidation (the reverse of consolidation) in rocks at a depth >5 km (Dortman, 1992). This effect results from the increase of fracture content and porosity of rocks at depth. 

Wurtzite (wBN) can be prepared by various static and dynamic compression methods , depending on the relative amounts of hBN and rBN in the initial sample, and the T-P conditions of the consolidation. Phase stability data for wBN is available . hBN can be converted to cBN and wBN at pressures from 12 to 40 GPa and temperatures between 300 and 1200 K , also with the use of Mg as a catalyst. A mixture of hBN, H2O, and an alkaline solution (e.g., NaOH) may be subjected to a shock wave at or above 10 GPa to prepare high quality wBN . wBN is transformed to zBN by shock compression at pressure above 100 GPa , while static high pressure transforms zBN to wBN . However, the reverse transformations are also possible". Additional references on wBN are given in physics abstracts. ... 

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