Reversion, resistance

The first commercial boards usiag electroless plating for connection between the sides were made by Motorola ia 1953 (41). An unclad plastic board was coated with electroless silver, a reverse resist appHed, and copper electroplated to the required circuit thickness. The resist and excess silver were removed. This semi-additive process is stiU used, with copper replacing the silver. 

SemiadditiveMethod. The semiadditive method was developed to reduce copper waste. Thin 5.0 lm (4.5 mg/cm ) copper foil laminates are used, or the whole surface may be plated with a thin layer of electroless copper. Hole forming, catalysis, and electroless copper plating are done as for subtractive circuitry. A strippable reverse—resist coating is then appHed. Copper is electroplated to 35 p.m or more, followed by tin or tin—lead plating to serve as an etch resist. The resist is removed, and the whole board is etched. The original thin copper layer is quickly removed to leave the desired circuit. This method wastes less than 10% of the copper. 

Logothetis [62] describes the use of triazine accelerators in the vulcanization of nitrile and fluoro elastomers. The triazine is more effective than the thiazole accelerators and produces highly reversion-resistant vulcanizates. 

NR can be cross-linked by a blocked diphenyl methanes diisocyanate to produce urethane crosslinks. The cross-linking agent dissociates into two quinonedioxime molecules and one diphenyl methane diisocyanate. The quinone reacts with the rubber via a nitroso group and forms cross-links via diisocyanato group. The performance of this system in NR is characterized by excellent age resistance and outstanding reversion resistance. 

Further variation of the structure of nitroso compound and diisocyanate yielded NOVOR 924. An NR vulcanizate containing NOVOR 924 is more reversion-resistant than any EV system [63]. 

In order to improve reversion resistance, the use of PerkaUnk 900 is recommended. The highlights of performance enhancement are document by Datta and Hondeveld [86]. 

Compared to the previous example, the engine mount formulation contains a cure package tending to an SEV system this will provide a greater degree of reversion resistance compared to a CV cure system. Nonetheless, the antireversion agent is still able to provide significant, additional benefit. 

Reversion characteristics of NR are of great concern. Lot of novel chemicals have been introduced to increase the reversion resistance of NR. Examples of these are zinc soap activator (Structol-A73), silane couphng agent (Si-69), anti-reversion agent (Perkalink 900), and post-vulcanization stabilizer (Durahnk HTS and Vulcuren KA 9188 Figure 32.7). These materials will enhance the life of the tire, enable the users for more retreading, and thereby reduce the material demand. " ... 

The effect of palm oil fatty acid additive (POEA) on curing characteristics and vulcanizate properties of sdica-filled NR compounds was studied by Ismail [30]. The incorporation of POEA improved the cure rate and state of cure of the compounds. Compared to the control, the incorporation of POEA not only enhanced the vulcanizate properties but also improved the reversion resistance of the silica-filled NR compounds. 

Mono- or di-sulphenamides of pentachlorothiophenol are claimed to provide reversion resistance. 

Dithiophosphates such as zinc dibutyl dithiophosphate used with a sulphenamide can give improved reversion resistance. 

Fig. 4.3. SEM micrograph of image-reversal resist stripes of a test pattern after photolithography. The resist shows an rmdercut profile as desired for the lift-off process...

Andersson DI, Hughes D (2010) Antibiotic resistance and its cost is it possible to reverse resistance Nat Rev Microbiol 8(4) 260-271... 

It has been shown that many cancer cell lines that are resistant to cis-Pt have elevated levels of gluthathione (Table I) (92-101) on the other hand, depletion of GSH with buthionine sulfoxime reverses resistance only for the A2780 ovarian carcinoma cell line (93). Resistant cancer cell lines, which have no elevated levels of GSH, could also not be sensitized by depletion of GSH (75, 91, 102). These results are rather controversial and therefore the precise role of GSH in mediating cis-Pt resistance is still unclear at present. More research is necessary to explain the rather low increased levels of GSH with respect to the sometimes significant increase in resistance. 

These two rubbers are prepared by halogenation of the butyl. Halogenation gives increased cure reactivity. As a result, improvement occurs in vulcanization rates resulting in improved properties over butyl. The state of cure and reversion resistance and covulcanization with other diene rubbers can also be suitably monitored. CIIR and BIIR vulcanizates have lower gas permeability,... 

Weinberg OK, Marquez-Garban DC, Pietras RJ. New approaches to reverse resistance to hormonal therapy in human breast cancer. Drug Resist Update. 2005 8 219-233. 

Bebawy et al. [186] demonstrated that CPZ (9) and vinblastine inhibited each other s transport in a human lymphoblastic leukemia cell line (CCRF-CEM/VLBioo). CPZ (9) reversed resistance to vinblastine but not to fluores-cently labeled colchicine and it increased resistance to colchicine. Colchicine was supposed to be transported from the inner leaflet of the membrane and vinblastine from the outer leaflet. CPZ (9) was assumed to be located in the inner membrane leaflet where it interacts with anionic groups of phospholipids and it may inhibit vinblastine transport via allosteric interactions. The authors concluded that transport of P-gp substrates and its modulation by CPZ (9) (or verapamil (79)) are dependent on substrate localization inside the membrane. Contrary to CPZ (9) location in the inner leaflet of the membrane, other modulators and substrates of P-gp were proved to be rather localized within the interface region of the membrane. The location of seven P-gp substrates and two modulators within neutral phospholipid bilayers was examined by NMR spectroscopy by Siarheyeva et al. [129]. The substrates and the modulators of P-gp were found in the highest concentrations within the membrane interface region. The role of drug-lipid membrane interactions in MDR and its reversal was reviewed in detail elsewhere [53,187]. 

Houghton PJ, Germain GS, Harwood FC, Schuetz JD, Stewart CF, Buchdunger E, Traxler P (2004) Imatinib mesylate is a potent inhibitor of the ABCG2 (BCRP) transporter and reverses resistance to topotecan and SN-38 in vitro. Cancer Res 64, 2333— 2337. 

Bolger, J. C., New One Part Epoxies Are Flexible and Reversion Resistant, Insulation, October 1969, pp. 38-44. 

Ohsumi K, Sekiyama T, Nakagawa R, Tsuji T, Morinaga Y, Ohishi K (1994) 1,4-dihydropyridine compounds useful as reverse resistance agents. US Patent 5 292 757... 

Concentration polarization caused by macromolecules, which may induce a reversible osmotic pressure that disappears after the filtration pressure is released, and the adsorption on the membrane pores of solid materials or inside the membrane pores of solid materials, which are rid of by rinsing the membrane after the filtration process, are occurrences that both contribute to the reversible resistance to permeation, 7 rev On the other hand, the solids that are deposited on the membrane surface or inside the pores, which are removed only by chemical cleaning of the membrane, constitute the irreversible fouling, Rmev-... 

These considerations provide a strong argument and rationale for discovery and development of inhibitors of RND transporters from Gram-negative bacteria that could be used in conjunction vdth antibiotics. Such inhibitors would increase antibacterial potency, expand the spectrum of antibacterial activity, reverse resistance... 

Additional studies carried out in animal models of temporal lobe epilepsy (TLE) further support the use of selective ABCBl inhibitors to reverse drug resistance in RE. Thus, tariquidar potentiates the effect of phenytoin and countervails resistance to phenobarbital in a rat model of TLE. Furthermore, cyclosporin A helps reverse resistance to phenytoin in a rat model of AED-resistant status epilepticus. Finally, verapamil counteracts resistance to oxacarbazepine in rats with pilocarpine-induced seizures [42]. 

Importantly, in a recent study, overexpression of SKI is linked to the upregulation of Bcr-Abl, leading to alterations of the balance between pro-apoptotic Ci8-ceramide and pro-survival SIP, leading to resistance to imatinib mesylate in K562 human CML cells (Baran et al., 2007). Importantly, down-regulation of SKI significantly reversed resistance to drug-induced apoptosis in these cells (Baran et al., 2007). 

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