We have developed a continuously tunable, broadband terahertz attenuator with a transmission tuning range greater than 10. Attenuation tuning is achieved electrically, by simply changing the DC voltage applied to a heating wire attached to a bulk silicon wafer, which controls its temperature between room temperature and !550 K, with the corresponding free-carrier density adjusted between !10 cm...

We present a practical and inexpensive method for creating physical objects that cast different color shadow images when illuminated by prescribed lighting configurations. The input to our system is a number of lighting configurations and corresponding desired shadow images. Our approach computes attenuation masks, which are then printed on transparent materials and stacked to form a single mul...

With the aim of achieving constant insertion loss, this paper presents the design of a 24 GHz reflectivetype phase shifter (RTPS) integrated with a switched -attenuator for phased array transmitters. Three RTPS circuits with hybrid coupler and capacitive-type reflective loads are cascaded to obtain required phase-shift. Accumulation-mode MOS (AMOS) varactors are used as reflective loads for pha...

A genetically structured mathematical model of the trp attenuator in Escherichia coli based on known coupling mechanisms of the transcription of the trp leader region and translation of the trp leader peptide region is proposed. The model simulates, both qualitatively and quantitatively, the effects of tryptophan on the repression of cloned gene products. It shows that repression by attenuation...

The vertical circuitry controls the vertical axis of the display and consists of an input coupling circuit, the input attenuator, and the vertical amplifier (for dual trace oscilloscopes, there are two identical vertical circuits, one for each channel). All signals connected to the vertical input jacks are fed through at least part of the vertical circuitry before they are used by other oscillo...

UNLABELLED Attenuation of photons degrades both the accuracy and the precision of SPECT images; attenuation correction algorithms correct the bias but cannot improve precision. Increased noise due to photon attenuation is most pronounced in regions deep in solid body sections, such as the brain and abdomen. We have quantified the degradation in performance in several estimation tasks that can b...

The DNA sequence changes of 31 mutations altering the attenuation control mechanism of the histidine operon are presented. These mutations are discussed in terms of a model for operon regulation that involves a his leader peptide gene whose translation regulates formation of alternative stem-loop structures in the his leader messenger RNA. Three suppressible mutations generate nonsense codons (...

Recombinant plasmids were constructed which carry defined regions of the threonine (thr) operon regulatory region of Escherichia coli. In vitro transcription experiments utilizing plasmid or restriction fragment templates showed that two major RNA transcripts, which differ in length by one to a few bases, are transcribed from this region. The approximate length of the transcripts is 150 to 170 ...

Rifampin-resistant mutants of Escherichia coli were isolated which had altered patterns of resistance or sensitivity to the inhibitory compounds 5-methyltryptophan and 5-methylanthranilate. The levels of tryptophan (trp) operon polypeptides in different rifampin-resistant mutants were elevated or reduced, in a manner consistent with their sensitivity to the two analogs. Complementation tests es...

Optical Amplifiers are essentials components in long haul fibre optic system. An amplifier is a electronic device that can increase the power of signal. An Optical Amplifier is effectively the opposite of attenuator while Optical Amplifiers provide gain and attenuator provides loss. When a signal travels in a optical fibre medium the signal suffer from various losses such as fibre losses, atten...