The effect of fluoroacetate on the growth of the facultative methylotrophs bacterium 5H2, Pseudomonas AM1 and bacterium 5B1

The effects of levamisole administration (20 mg/kg, i.p. daily for 10 days) on various parameters of hepatic microsomal metabolism in the famale rat were examined. Levamisole pretreatment resulted in significant increases over control values in the metabolism of aminopyrine and aniline in vitro, and in microsomal content of cytochrome P-450 and cytochrome b5.     

Comments on “Theory and application of covariance matrixtapers for robust adaptive beamforming” [and reply]

For original paper see Guerci (IEEE Trans. Signal Processing, vol.47, p.977-85, 1999 April). Covariance matrix tapers and derivative constraints in the directions of jammers have been proposed for broadening the null in adaptive processing, thereby improving the algorithms' robustness. In this correspondence, the relationship between these two methods is explored. A reply is given in which Guerci makes some further points     

A computationally efficient two-step implementation of the GLRT

In this paper, the performance of a new two-step adaptive detection algorithm is analyzed. The two-step GLRT consists of an initial adaptive matched filter (AMF) test followed by a generalized likelihood ratio test (GLRT). Analytical expressions are provided for the probability of false alarm (P_FA) and the probability of detection (P_D) in unknown complex Gaussian interference. The analysis shows that the two-step GLRT significantly reduces the computational load over the GLRT while maintaining detection and sidelobe rejection performance commensurate with the GLRT. The two-step GLRT detection algorithm is also compared with another two-step detection algorithm: the adaptive sidelobe blanker (ASB). Both the two-step GLRT and the ASB are characterized in terms of the mainbeam detection performance and the rejection of sidelobe targets. We demonstrate that for a given P_FA, the two-step GLRT has a broad range of threshold pairs (one threshold for the AMF test and one for the GLRT) that provide performance identical to the GLRT. This is in contrast with the ASB, where the threshold pairs that maximize the P_D are a function of the target's signal-to-interference-plus-noise ratio (SINR). Hence, for a fixed pair of thresholds, the two-step GLRT can provide slightly better mainbeam detection performance than the ASB in the transition region from low to high detection probabilities     

Forward-backward averaging in the presence of array manifold errors

We investigate the use of forward-backward (f/b) averaging for estimating the covariance matrix used for adaptive beamforming and space-time adaptive processing (STAP). We demonstrate that the estimation loss is reduced by the use of f/b averaging and, for some STAP cases, f/b averaging can even quadruple the available sample support. We also show that unknown array manifold errors have little effect on the effectiveness of f/b averaging. The gain from f/b averaging is demonstrated on data from the mountaintop database     

Comment on “Constrained Hung-Turner adaptive beamformingalgorithm with additional robustness to wide-band and movingjammers” [and reply]

One of the major claims in the paper of Gershman et al. (see ibid., vol.44, p.361-6, 1996) is that Hung-Turner (1983) projections do not adequately suppress wide-band interference. This statement is only true if too few snapshots are used to estimate the interference subspace. For Hung-Turner projections the use of more snapshots than the rank of the interference is called “averaging over the dimension”. The authors implicitly and wrongly claim that even with “averaging over the dimension”, Hung-Turner projections perform poorly in the presence of wide-band interference. In this comment, we show theoretically and by simulation that Hung-Turner projections adequately suppress wide-band jammers if the number of snapshots is equal to or larger than the rank of the interference. Here, the same sensor array processing model and assumptions are used. Gershman et al. reply that they proposed a new modification of the Hung-Turner (HT) algorithm improving the robustness of this algorithm against wide-band and moving jammers. They also add that their approach can be applied to other adaptive array algorithms as well, and the critical comment contains a misinterpretation of their results and conclusions     

Production of adaptive array troughs by dispersion synthesis

An adaptive technique is presented that produces array pattern troughs in response to discrete interference sources. The technique applies a transform to the sample covariance matrix that synthesises dispersion, thus making the interferers appear to cover a greater angular extent