Fundamental oscillations up to 1.08 THz with the output power of 5.5 microwatts was achieved in GalnAs/AlAs resonant tunneling diodes (RTDs) at room temperature. The graded emitter, thin barriers, and high-indium-composition transit layers were introduced to reduce the tunneling and transit delays. The first two of these structures are the same as those in RTDs oscillating at 1.04 THz reported ...

We have studied intersubband absorption in strain compensated InxGa12xAs/AlAs/InyAl12yAs multiple quantum wells and superlattices grown on InP. X-ray diffraction shows that the layers are pseudomorphically strained and exhibit slight compositional grading of the interfaces. Owing to the high AlAs barriers, the intersubband absorption can be tailored to wavelengths shorter than 2 mm. In some sam...

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We have observed very large tunneling magnetoresistance (TMR) in epitaxially grown Ga1−xMnxAs/AlAs/Ga1−xMnxAs ferromagnetic semiconductor tunnel junctions. Large TMR ratios more than 70% were obtained in junctions with a very thin (5 1.6 nm) AlAs tunnel barrier when the magnetic field was applied along the [100] axis in the film plane. The TMR was found to rapidly decrease with increasing the b...

Several substances have been shown to affect hepatic heme synthesis in the rat liver. Phenobarbital and the polycyclic hydrocarbon, 3,4-benzpyrene, produce an induction of aminolevulinic acid synthetase (ALAS), the enzyme mediating the first step in heme synthesis. This is followed sequentially by increased incorporation of glycine into microsomal heme, increased microsomal protoheme, cytochrom...

The T box riboswitch regulates expression of amino acid-related genes in Gram-positive bacteria by monitoring the aminoacylation status of a specific tRNA, the binding of which affects the folding of the riboswitch into mutually exclusive terminator or antiterminator structures. Two main pairing interactions between the tRNA and the leader RNA have been demonstrated to be necessary, but not suf...