Abstract: A stable crystal (Form I crystal) of (4R,5S,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-3-({4-[(5S)-5-methyl-2,5-dihydro-1H-pyrrol-3-yl]-1,3-thiazol-2-yl}thio)-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid which has preferable properties and a process for preparation Form I crystal which is characterized of desolvating a solvated crystal of its compound.

Abstract: In a DC current detector, a current to be detected is applied to a current detecting resistor connected in series with a first diode, a voltage across the current detecting resistor is amplified by a transistor and the detected voltage is output from a collector resistor connected to the collector of the transistor. The voltage across the current detecting resistor is provided across the emitter and base of the transistor via an emitter resistor, and a second diode. A resistor the resistance value of which is selected so that the forward voltage of the second diode and the base-emitter voltage of the transistor may become equal to each other, is connected to the base of the transistor. The current detection accuracy is improved.

Abstract: A feedback type air fuel ratio controlling system for detecting and controlling an exhaust gas composition of an engine. A gas sensor provides a sensor signal related to an exhaust gas concentration. This sensor signal is coupled through an automatic gain control (AGC) DC level amplifier to a deviation detector. The deviation detector compares the signal to a reference signal V.sub.p representing a stoichiometric air fuel mixture and provides a correction signal for adjusting the engine's air fuel ratio. The AGC DC level amplifier provides automatic DC level compensation for a slowly deteriorating sensor and, working in combination with the deviation detector, an AC hysteresis response for judging rich to lean and lean to rich changes sensed by the exhaust gas sensor.