Abstract: An acoustic device including: a vibrating film which has waterproofness; a support which is located alongside the vibrating film in a direction and supports the vibrating film; a waterproof which is in contact with the support; an insulating plate which is located on an opposite side of the waterproof to a side where the support is arranged, and which has a first through hole leading to the vibrating film; and a metal plate which is located on an opposite side of the insulating plate to the waterproof, which has a second through hole communicating with or containing the first through hole, and which is fixed in a state pressing the insulating plate along the direction.

Abstract: For reducing the equipment cost for monitoring dust particles and improving the operation efficiency in a clean room, a plurality of sampling tubes each having a plurality of perforations formed in the side thereof and along the extension thereof are disposed under the floor board of the clean room so as to extend in X and Y directions. The perforations are for sucking the air together with dust particles discharged from the clean room through openings formed in the regions defined in rows and columns on the floor board. The perforations are formed corresponding to each of the region. The sampling tubes are sequentially selected to be connected to laser particle counters dedicated for the X direction and Y direction, respectively, and the dust particles sent via each of the sampling tubes are counted.

Abstract: A process for purifying 7-dimenthylamino-6-demethyl-6-deoxytetracycline represented by the following formula, ##STR1## which comprises dissolving 7-dimethylamino-6-demethyl-6-deoxytetracycline or its hydrochloride having a lower purity in a mixed solvent of an alcohol and water by using hydrochloric acid and then adjusting the pH of the solution to 3.5 to 4.5 to recrystallize the hydrochloride having a higher purity.

Abstract: The present invention relates to a spherical amino acid having an average particle size of about 1 mm or below and a process for the preparation thereof.