Seal resistance

Leather To 210 Good mechanical properties for sealing. Resistant to alcohol, gasobne, many oils and solvents, synthetic hydraulic fluids, water. 

The planar chips used by the PatchXpress, QPatch, and Patchliner systems incorporate a glass-based substrate that permits the formation of GQ-level seal resistances between the cells and the plate. Consequently, the noise level on these systems tends to be low and they are thus capable of distinguishing small ionic currents (<100 pA) reliably. Their planar chips contain 8, 16, or 48 wells with a single aperture in the center bottom position of each well. These systems permit parallel recordings from several individual cells on the chip. However, due to variation in the performance of randomly selected cells, only a proportion are expected to complete any given experimental protocol and so the capacity to acquire pharmacology data may not match initial expectations (Xu et al. 2003). 

When using glass in electrical engineering (in particular for glass seals), resistivity is specified by the Tk 100 value. This is the temperature at which the glass has a resistivity of 100 MO cm. The Tk 100 values for current commercial glasses are listed in Table 17. 

Acceptance criteria Initial seal resistance >1 GQ access resistance s MQ stable leakage current<100 pA at -80 mV HP voltage error (test pulse current amplitude xaccess resistance) <5 mV hERG peak tail current amplitude > prepulse current amplitude rundown of test pulse amplitude <2 % per minute. 

IonWorks HT Load the reservoir in the buffer position with 4 ml PBS and cell position with cell suspension. Pipette the test compound, vehicle control, and positive control (threefold above the final concentration, DMSO <0.33 %) in a 96-well V-bottom plate. Load the plate in plate 1 position, and clamp PatchPlate into the PatchPlate station. With the fluidics-head (F-head) add 3.5 pi PBS to each well of PatchPlate and perfuse its underside with internal solution. Prime and de-bubble the electronics head (E-head), and perform hole test by applying voltage pulse. Dispense 3.5 pi of cell suspension in each well of PatchPlate with F-head. Allow 200 s for cells to reach the hole in each well, and seal it. Determine the seal resistance in each well with E-head. Change the underside solution of PatchPlate with access solution. After 9 min (perforation time) perform pre-compound hERG current measurements with E-head. Add 3.5 pi solution from each well of compound plate to 4 wells on a PatchPlate . 

Acceptance criteria Pre- and post-scan seal resistance >60 mO, pre-scan hERG tail current amplitude >150 pA. 

It is heat seal resistant unless produced as a coextrusion or coated. A good barrier to most gases and volatiles, but only fair to moisture. It is easily metallised. Found as PETP and PETG (Kodak), Pet G contains an additional glycol molecule. 

Question by M. B. Hammond, North American Aviation Was any consideration at all given to making the outside seal resistant to aerodynamic heating Was the seal required to maintain vacuum even in high-altitude environments and provide stiffness, resistance to abrasion, and fire resistance on the ground ... 

Answer by Author The seal resistance to aerodynamic heating was not checked but is assumed to be low a guard would most likely be required. The seal did maintain its own vacuum at high altitudes. No data on the other criteria were gathered. 

Fig. 1 Schematic diagram of the patch-damp technique [5] A heat-polished glass pipette (tip diameter in the order of l jim) is pressed against a clean membrane surface. Upon slight suction a high resistance seal (> 1 GO) forms between the tip of the pipette and the membrane. This high seal resistance and the small membrane area reduce the background noise in such a way, that it becomes possible to measure currents (< IpA) passing through a single ion channel protein. The mechanical stability of the seal between pipette and membrane allows the isolation of the membrane patch encircled by the pipette The withdrawal of the pipette in the attached configuration results in an inside-out patch.

Johnson noise [11-13], which occurs on the seal, i.e., in the junction between the pipette and the membrane. The spectral density of this noise is inversely proportional to the seal resistance. Therefore, it is important to have a very tight seal, the so-called gigaseal, which should significantly improve the noise characteristics of the patch-clamp record. 

Builenweg JR, Rutten WLC, Willems WPA, Van Nieuwkasteele JW (1998) Measurement of sealing resistance of cell-electrode interfaces in neuronal cultures using impedance spectroscopy. Med Biol Eng Comput 36 630-637... 

Ruororubbers and silicones are the best materials to make seals resistant to extreme temperature conditions. Viton, a fluororubber marketed by M/S Du Pont USA, can operate at 200°C in contact with oils and lubricants. Polysulfide rubbers have low compression set, but exhibit excellent fuel resistance. For improved compression set, it is admixed with relatively cheap conventional nitrile rubbers. The fluorine-containing rubbers, such as fluororubber, possess outstanding resistance to heat, fuels and hydraulic fluids coupled with extremely good aging characteristics. The reversible physical effects with respect to the ultimate tensile strength of this rubber vulcanizate is a noteworthy phenomenon since this is not associated with the deterioration of the rubber itself. Fluororubber is resistant to most fluids used in the aircraft industiy, such as synthetic, ester type lubricants, aromatic and aliphatic hydrocarbons, and water. 

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. 

Seals are made by applying gentle suction to identified synaptic boutons visualized with Nomarski optics. Seal resistances of up to 30 G 2 form, and currents can be recorded in cell-attached, inside-out or whole-cell recording configurations (Martinez-Padron and Ferrus 1997). Records from enlarged, mutant type III boutons on muscle 12 (>2 im in diameter) showed an average input resistance of 8-10 G 2 and mean bouton capaci-... 

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