Repairs patch

Ultimately the DNA lesion is repaired by a short patch repair mechanism, which, in linker regions of nucleosomes or open regions of chromatin (where lesions are generally concentrated) is associated with minimal nucleosome rearrangement (Jones et al, 2001). 

Tsutakawa, S. E., Jingami, H. and Morikawa, K. (1999). Recognition of a TG mismatch the crystal structine of very short patch repair endonuclease in complex with a DNA duplex. Cell 99, 615-623. 

Figure 6.46 Representation of two mechanisms of repair of DNA damage such as ultraviolet light-induced dimerization. The upper line represents cut and patch repair, the lower sister-strand exchange. Thick lines represent newly synthesized DNA. Source From Ref. 12.

Thus, DNA gaps produced in BER can be filled in with a small number of bases (short patch repair) by these enzymes (Figure 7.1). 

Fortini P, DogUotti E. Base damage and single-strand break repair mechanisms and functional significance of short- and long-patch repair subpathways. DNA Repair 2007 6 398-409. 

Caulking sealants Anticarbonation coatings Elastomeric coatings Patch-repair mortars General-purpose adhesives Crack injecting systems... 

Aliphatic amines are used principally in civil engineering applications such as in patch repair systems, adhesives, floorings, high solid coatings and grouts. 

Acrylic polymer concrete and mortars fast curing good chemical properties patch repairs... 

If conditions are severe, for example if there is widespread spalling and corrosion, patch repairs are carried out, followed by application of acrylic coating as the final part of the repair. Surface treatment with a silane... 

Structural and semistructural adhesives for steel and aluminium, crack repair adhesives for concrete and as patch-repair compounds and grouting compounds (Morton International, 1988 Rees et al., 1994). 

The crystal structure of a very short patch repair (Vsr) endonuclease complex with DNA containing a TG mismatch shows novel interactions of intercalated aromatic side chains which recognise the mismatch site. The enzyme also distorts the DNA backbone, and many protein side chain interactions stabilise the complex. Crystallographic studies of duplexes containing the mutagenic... 

Lieb, M. (1995) Very short patch repair of T G mismatches in vivo importance of context and accessory proteins. 

B. Short-Patch versus Long-Patch Repair. 19... 

Together Avith the known interactions between FEN-1 and PCNA (Wu et aL, 1996), these interactions indicate that long-patch repair is a tightly coordinated event, using interactions between enzymes and with PCNA as a scaffold. 

Protection effect. MacroceU currents can have beneficial effects on rebars that are polarized cathodically. This is indirectly evident for patch repair of chloride-contaminated structures when only the concrete in the corroding areas is replaced with alkaline and chloride-free mortar, but surrounding concrete containing chlorides is not removed. Before the repair, the corroding rebars behave as an anode with respect to those in the surrounding areas, which are polarized cathodically and thus are protected by the macrocell. After the repair, formerly anodic zones no longer provide protection, and corrosion can initiate in the areas surrounding repaired zones (these have been called incipient anodes) [3]. Consequences for repair are discussed in Chapter 18. 

Other field tests with proprietary vapour-phase inhibitors [17] in a parking garage with chloride-contaminated precast slabs did not show encouraging results. Corrosion-rate measurements showed a reduction of 60% in areas with initially intense corrosion but also an increase of corrosion rate in areas with low corrosion rates. On structures from 1960 with an admixed-chloride content higher than 1% by mass of cement, already featuring patch repairs, a three-year corrosion rate survey showed lower corrosion rates in the treated areas compared to untreated ones, but cracking and spalling increased also in the treated areas [18]. 

Conventional repair. The most utilised method consists in the removal of carbonated concrete and its replacement with alkaline mortar or concrete. This method is convenient when the corrosion attack is limited to zones of small extent (for example when the thickness of the concrete cover is reduced locally). In that case it is usually called patch repair. Conversely, it may be rather expensive when repair is required on large surfaces. In fact, concrete must be removed in all the zones where carbonation and subsequent corrosion of steel are expected to damage the structure within the design life of the repair. Even structurally sound concrete must be removed where the corrosion rate of the embedded steel is expected to... 

G. Sergi, C. L. Page, Sacrificial anodes for cathodic prevention of reinforcing steel around patch repairs applied to chlorideEuropean Federation of Corrosion, Event No. 227, Aachen, 30 August-2 September 1999, 248. 

Non-alkaline (polymer) mortars have been used for repairs however, they do not promote repassivation and they are only based on physical effects. Epoj mortors applied as patch repairs have in the past been unsuc-... 

Recently this technique has been proposed in conjunction with conventional patch repair of chloride-contaminated structures in order to avoid the initiation of incipient pitting around the repaired zones, by utihsing sacrificial anodes embedded near the periphery of the repair patches [20,21]. Cathodic prevention is now being used in several countries. ... 

G. Sergi, G. L. Page, Sacrificial anodes for cathodic prevention of reinforcing steel around patch repairs applied to chloride-contaminated... 

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