Diffused pneumatic silencer has been widely used in pneumatic fields because of its small dimensions and high performance on noise reduction. Numerical simulation of its interior and exterior flow field is important to studying the gas flow in the silencer and the flow structure outside the silencer, understanding the mechanism of its noise reduction. Porous media model and Darcy-Forchheimer pr...

The sound attenuation of a silencer consisting lamella network made with melamine foam inserted in rectangular duct is investigated numerically and experimentally. arrangement designed so that skeleton bending elastic resonances appear at low frequency. In addition to this phenomenon, viscothermal losses the porous material ensure broadband attenuation. provides natural sub-wavelength resonator...

The control of CD4 expression is essential for proper T lymphocyte development. We have previously described a cis-acting silencer element required for repressing transcription of the CD4 gene. Here we report the cloning and characterization of a novel factor that binds to a critical functional site in the CD4 silencer. This factor, referred to as silencer-associated factor (SAF), is a member o...

Transcriptional control of the osmotically regulated proU operon of Salmonella typhimurium is mediated in part by a transcriptional silencer downstream from the promoter (D.G. Overdier and L.N. Csonka, Proc. Natl. Acad. Sci. USA 89:3140-3144, 1992). We carried out a fine-structure deletion analysis to determine the structure and the position of the silencer, which demonstrated that this regulat...

The role of the natural HMR-E silencer in modulating replication initiation and silencing by the origin recognition complex (ORC) was examined. When natural HMR-E was the only silencer controlling HMR, the silencer's ORC-binding site (ACS) was dispensable for replication initiation but essential for silencing, indicating that a non-silencer chromosomal replicator(s) existed in close proximity t...

An active silencer to attenuate internal combustion engine exhaust noise is developed. The silencer consists of an electrically controlled valve connected to a buffer volume. The pulsating flow from the engine is buffered in the volume and the valve resistance is continuously controlled such that only the mean flow passes to the atmosphere. This flow is free of fluctuations and consequently fre...

Expression of the cdc2 gene is induced steeply at the G1-S-phase boundary. The previous analysis of promoter elements that confer inducibility revealed the enhancer at positions -276 to -265. Enhancer activity is suppressed by the upstream sequence that seems to contain the silencer. The silencer element was analyzed by fusing several oligonucleotides covering the silencer region upstream of th...