Abstract: A method for preparing and using a tetramethylammonium hydroxide etchant (180). The etchant is prepared by combining precisely known quantities of the etchant components obtained from liquid sources of tetramethylammonium hydroxide (110) and dissolved silicate (115). A precise quantity of an acidic (relative to tetramethylammonium hydroxide) oxidizer is added at intervals during a long etch as well as just before immersing a sample holder (135) and sample in the etchant (180). A precise quantity of tetramethylammonium hydroxide such as can obtained from a pipette (175) is also added during long etches to compensate for the reduction in etchant pH caused by the addition of the oxidizer.

Abstract: A method for preparing and using a tetramethylammonium hydroxide etchant (180). The etchant is prepared by combining precisely known quantities of the etchant components obtained from liquid sources of tetramethylammonium hydroxide (110) and dissolved silicate (115). A precise quantity of an acidic (relative to tetramethylammonium hydroxide) oxidizer is added at intervals during a long etch as well as just before immersing a sample holder (135) and sample in the etchant (180). A precise quantity of tetramethylammonium hydroxide such as can obtained from a pipette (175) is also added during long etches to compensate for the reduction in etchant pH caused by the addition of the oxidizer.

Abstract: Vapor-deposition polymerization films serve as vapor-sensitive dielectrics (130, 530) over surface-type capacitive electrodes (110 and 120, 510 and 520), or as protective layers (140, 142) over vapor-sensitive dielectrics (132) or flux-concentrators (150) in surface-type capacitive-electrode vapor sensors. Arrays of sensors (411-422) with different vapor-deposition polymerization films provide selectivity among different vapor species. Vapor-sensitive films (530) covering surface-type capacitive electrodes (510, 520) cointegrated with heater elements (560, 570) on thermally isolated suspended substrates (500) provide selectivity among different vapor species.

Abstract: A self-calibration circuit for sensors and transducers that produce pulse-train outputs of the type having a count-until-disabled counter (250) which counts the number of pulses corresponding to a known value of the sensed or transduced quantity in a variable frequency pulse train during the time that a known number of pulses are counted in a reference pulse train by a frequency divider (210); the count accumulated by the count-until-disabled counter being stored, after accumulation, in a settable-divisor frequency divider (220 or 240) which can provide both calibrated sensor pulse-train outputs and calibration pulse-train outputs having the same frequency as the calibrated sensor pulse-train output at known values of the sensed parameter.

Abstract: An improved user interface and related control subsystem for a recorder/player for use in flexible-practice pronunciation training is described. The interface/control subsystem lets the user activate a single switch to initiate and complete any of the following activities any number of times and in any order: select the next sample sound; listen to the currently selected sample sound; listen to the currently selected sample sound then record the user version of that sound; listen to the currently selected sample sound followed by the user version of that sound. Provision is also made for obtaining sample sounds from plug-in modules or by active recording with a means that is protected from inadvertent activation.