Patching and sealing

They are used extensively to react with epoxy or phenoHc resins, yielding adhesives that are useful in casting and laminating, in stmctural work, for patching and sealing compounds, and for protective coatings. The amount used in epoxy appHcations far exceeds the use with phenoHc resins. 

If a combination of patching and sealing is required for a carbonated structure, the patch repairs must remove all carbonated concrete around the steel. In some cases this will only require exposure of the front face but in more extreme conditions it may need concrete removal behind the steel to restore the passive alkaline environment. Much has been published about anticarbonation coatings and their effectiveness but it is not easy to find independent information about specific products. Careful comparison of product information may be required. This may include the requirement for independent testing. The principle of anticarbonation coatings are that they are porous enough to let water vapour move in and out of the concrete but... 

Concrete is one of the most durable materials and is commonly used for constructions in civil engineering. Thus, bonding, patching, and sealing of concrete is of large interest. 

A 1-in square of Webril is saturated with liquid, or up to 0.5 g of viscous substances, and applied to the surface of the pad to be applied to the skin. The patch is applied to the upper back and sealed in place with occlusive tape. The patch is removed after 24 h, the area is evaluated and a fresh patch applied. The procedure is repeated daily for up to 21 days. Lanman et al. (1968) increased the sensitivity of the assay by increasing the number of test subjects from 10 to 24. 

The final pharmaceutical dosage forms commonly packaged in unit-dose form are transdermal patches and sublingual films. These drugs are often very sensitive to light and moisture, so they are frequently sealed in foil wrappers or other impervious media. 

Chem. Desap. Carbor lated styrene-butadiene emulsion Uses Modifier for concrete applies., underiayment, patch, thin-set mortars, grouL marine decking, and seal coatings cement additive (imparts water and chem. resist., adhesion to metal, cement)... 

Fig. 5 Assembly of the patch clamp device, (a) Aligning and sealing the processed silicon chip (gray wafer) between upper and lower chambers (yellow and blue) electrically isolates one side of the chip from the other (except through the pore in the silicon) and enables independent experimental manipulation of each side. The top and bottom chambers are composed of cured PDMS (yellow) coupled to machined polycarbonate (light blue) supports. The bottom polycarbonate support interfaces the lower PDMS vertical channel to a syringe which is used to...

The temporary treatment, until such time that corner cracking is permanently repaired, consists of cleaning and sealing the crack. Permanent repair consists of full-depth concrete or asphalt patching. 

Black rubber can sensitize hydraulic engineers. Assembly workers build the frame and both rivet and seal. Set-up men, riveters, retouching specialists, and engine fitter-mechanics may come into contact with sealants that may contain phenol-formaldehyde resin (Beck 1989), epoxy base (Handley and Burrows 1994), hexavalent chromate in hardeners for epoxy-based sealants (Handley and Burrows 1994) and polysulfides in two-part sealant bases (Wilkinson and Beck 1993 Bruze et al. 1996). Thiocol, a synthetic rubber based on polysulfide polymers, is used by aircraft fitters to dip screws and rivets into before use, and a fingertip dermatitis localized to the thumb and first two fingers of the dominant hand was seen in five of six fitters with positive patch-test reactions to the polysulfide-polymer-containing system (Wilkinson and Beck 1993). 

Where a definitive identification of the contents of the munition is required, it will normally be necessary to breach the munition case and take and analyse a sample of the chemical fill. This is a difficult and hazardous task, and will normally be attempted only in the field, in exceptional circumstances. Techniques for safely penetrating a munition in the field have, however, been developed. One system, developed by the United Kingdom, is based on the use of a commercial nail gun to penetrate the case of thin walled munitions. A special rubber patch is first placed on the wall of the munition and the nail gun, fitted with a specially designed hardened steel pin, is clamped to the wall of the munition. The gun is set up so that it can be fired remotely, and when this is done the steel pin is driven through the rubber patch and penetrates the wall of the munition. The rubber patch reduces the risk of leakage due to any over-pressure present within the munition. Once the pin has been safely inserted, the munition is transferred to a sealed glovebox. The pin can then be carefully removed and a sample of the fill extracted via the resulting hole in the munition wall for chemical analysis. 

Allene (propadiene) is condensed under high vacuum into a 2-litre round-bottomed flask and, after several freeze-and-pump cycles to remove residual oxygen and volatile impurities, the reaction vessel is sealed (internal pressure at room temperature approximately 1000 mb). After 20 hours at 460° C (a high-temperature drying oven) the inner surface of the flask is covered completely by a deep-black, shiny film which can be removed in patches and whose electrical conductivity is 10 S cm. When this film is doped by treating if for 30 minutes with a saturated solution of iodine in carbon tetrachloride its appearance changes to a shiny gold. After solvent removal, the conductivity is found to have increased by a factor of 10. Several other alkynes were polymerized under above conditions and the results of these experiments are summarized in Table 3.7. 

Focal recording electrodes are pulled from glass capillary tubes (e.g., 75 il, 1.5-mm outer diameter) and then fire polished and shaped on a microforge to allow perpendicular approach to the muscle for obtaining better seal resistance. The loose-patch electrodes are made with an inner diameter of 5-10 pm. When filled with the appropriate bath solution, they have resistances of 0.5-2 M 2. Seals around the boutons are made by applying mild suction and usually increase the resistance two to six times (seal factor Rivosecchi et al. 1994). Recordings are made with a loose patch-clamp amplifier and contain a calibration pulse to measure electrode series and seal resistances. These measurements are used to correct for attenuated current amplitudes at the electrode tip. 

The patch-clamp technique is based on the formation of a high resistance seal (109-10lon) between the tip of a glass micropipette and the cell membrane it touches (gigaohm-seal). This technique allows recordings of ionic currents through single ion channels in the intact cell membrane and in isolated membrane patches at a... 

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