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چکیده
One way to rtidiate m impulse-like waveform is to employ a TEM-fed paraboloidal reflector mtenna. Various performance features of this antenna, such as prcpulse, impulse amplitude, impulse width etc., h:~vcbeen an;dyzcd in the past ( 1 to 8]. It hos been obscrveci that the low frequency or Iatc-time pcrforrmmce of this fotm of an IRA is governed by the elecrnc and magnetic dipole morncnts. A knowledge of these dipole moments helps in designing an optimal matching network ‘to be inserted at the junction of the feed horn and the reflector. Ev:duation of the electric dipole rnomcnt is addressed in this note find the magnetic dipole moment will bc consicicrcd in a future note.
منابع مشابه
A ribosome profiling study of mRNA cleavage by the endonuclease RelE
Implicated in persistence and stress response pathways in bacteria, RelE shuts down protein synthesis by cleaving mRNA within the ribosomal A site. Structural and biochemical studies have shown that RelE cuts with some sequence specificity, which we further characterize here, and that it shows no activity outside the context of the ribosome. We obtained a global view of the effect of RelE on tr...
متن کاملInhibitory mechanism of Escherichia coli RelE-RelB toxin-antitoxin module involves a helix displacement near an mRNA interferase active site.
In Escherichia coli, RelE toxin participates in growth arrest and cell death by inducing mRNA degradation at the ribosomal A-site under stress conditions. The NMR structures of a mutant of E. coli RelE toxin, RelE(R81A/R83A), with reduced toxicity and its complex with an inhibitory peptide from RelB antitoxin, RelB(C) (Lys(47)-Leu(79)), have been determined. In the free RelE(R81A/R83A) structur...
متن کاملPurification of the RelB and RelE proteins of Escherichia coli: RelE binds to RelB and to ribosomes.
The direct interaction of the Escherichia coli cytotoxin RelE with its specific antidote, RelB, was demonstrated in two ways: (i) copurification of the two proteins and (ii) a positive yeast two-hybrid assay involving the relB and relE genes. In addition, the purified RelE protein exhibited ribosome-binding activity in an in vitro assay, supporting previous observations suggesting that it is an...
متن کاملRelE-mediated dormancy is enhanced at high cell density in Escherichia coli.
Bacteria show remarkable adaptability under several stressful conditions by shifting themselves into a dormant state. Less is known, however, about the mechanism underlying the cell transition to dormancy. Here, we report that the transition to dormant states is mediated by one of the major toxin-antitoxin systems, RelEB, in a cell density-dependent manner in Escherichia coli K-12 MG1655. We co...
متن کاملThe Structural Basis for mRNA Recognition and Cleavage by the Ribosome-Dependent Endonuclease RelE
Translational control is widely used to adjust gene expression levels. During the stringent response in bacteria, mRNA is degraded on the ribosome by the ribosome-dependent endonuclease, RelE. The molecular basis for recognition of the ribosome and mRNA by RelE and the mechanism of cleavage are unknown. Here, we present crystal structures of E. coli RelE in isolation (2.5 A) and bound to progra...
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