• Despite the multiple roles played by antioxidants in rhizobia–legume symbioses, little is known... more • Despite the multiple roles played by antioxidants in rhizobia–legume symbioses, little is known about glutathione peroxidases (GPXs) in legumes. Here the characterization of six GPX genes of Lotus japonicus is reported.• Expression of GPX genes was analysed by quantitative reverse transcription–polymerase chain reaction in L. japonicus and Lotus corniculatus plants exposed to various treatments known to generate reactive oxygen and/or nitrogen species.• LjGPX1 and LjGPX3 were the most abundantly expressed genes in leaves, roots and nodules. Compared with roots, LjGPX1 and LjGPX6 were highly expressed in leaves and LjGPX3 and LjGPX6 in nodules. In roots, salinity decreased GPX4 expression, aluminium decreased expression of the six genes, and cadmium caused up-regulation of GPX3, GPX4 and GPX5 after 1 h and down-regulation of GPX1, GPX2, GPX4 and GPX6 after 3–24 h. Exposure of roots to sodium nitroprusside (a nitric oxide donor) for 1 h increased the mRNA levels of GPX4 and GPX6 by 3.3- and 30-fold, respectively. Thereafter, the GPX6 mRNA level remained consistently higher than that of the control. Immunogold labelling revealed the presence of GPX proteins in root and nodule amyloplasts and in leaf chloroplasts of L. japonicus and other legumes. Labelling was associated with starch grains.• These results underscore the differential regulation of GPX expression in response to cadmium, aluminium and nitric oxide, and strongly support a role for GPX6 and possibly other GPX genes in stress and/or metabolic signalling.Despite the multiple roles played by antioxidants in rhizobia–legume symbioses, little is known about glutathione peroxidases (GPXs) in legumes. Here the characterization of six GPX genes of Lotus japonicus is reported.Expression of GPX genes was analysed by quantitative reverse transcription–polymerase chain reaction in L. japonicus and Lotus corniculatus plants exposed to various treatments known to generate reactive oxygen and/or nitrogen species.LjGPX1 and LjGPX3 were the most abundantly expressed genes in leaves, roots and nodules. Compared with roots, LjGPX1 and LjGPX6 were highly expressed in leaves and LjGPX3 and LjGPX6 in nodules. In roots, salinity decreased GPX4 expression, aluminium decreased expression of the six genes, and cadmium caused up-regulation of GPX3, GPX4 and GPX5 after 1 h and down-regulation of GPX1, GPX2, GPX4 and GPX6 after 3–24 h. Exposure of roots to sodium nitroprusside (a nitric oxide donor) for 1 h increased the mRNA levels of GPX4 and GPX6 by 3.3- and 30-fold, respectively. Thereafter, the GPX6 mRNA level remained consistently higher than that of the control. Immunogold labelling revealed the presence of GPX proteins in root and nodule amyloplasts and in leaf chloroplasts of L. japonicus and other legumes. Labelling was associated with starch grains.These results underscore the differential regulation of GPX expression in response to cadmium, aluminium and nitric oxide, and strongly support a role for GPX6 and possibly other GPX genes in stress and/or metabolic signalling.
The composition of antioxidant enzymes, especially superoxide dismutase (SOD), was studied in one... more The composition of antioxidant enzymes, especially superoxide dismutase (SOD), was studied in one nontransgenic and three transgenic lines of nodulated alfalfa plants. Transgenic lines overproduced MnSOD in the mitochondria of nodules and leaves (line 1-10), MnSOD in the chloroplasts (line 4-6), and FeSOD in the chloroplasts (line 10-7). In nodules of line 10-7, the absence of transgene-encoded FeSOD activity was due to a lack of mRNA, whereas in nodules of line 4-6 the absence of transgene-encoded MnSOD activity was due to enzyme inactivation or degradation. Transgenic alfalfa showed a novel compensatory effect in the activities of MnSOD (mitochondrial) and FeSOD (plastidic) in the leaves, which was not caused by changes in the mRNA levels. These findings imply that SOD activity in plant tissues and organelles is regulated, at least partially, at the posttranslational level. All four lines had low CuZnSOD activities and an abundant FeSOD isozyme, especially in nodules, indicating that FeSOD performs important antioxidant functions other than the scavenging of superoxide radicals generated in photosynthesis. This was confirmed by the detection of FeSOD cDNAs and proteins in nodules of other legumes such as cowpea, pea, and soybean. The cDNA encoding alfalfa nodule FeSOD was characterized and the deduced protein found to contain a plastid transit peptide. A comparison of sequences and other properties reveals that there are two types of FeSODs in nodules.
IEEE Workshop on Statistical Signal and Array Processing, 1996
We previously presented a blind 2D RAKE receiver for (direct sequence spread spectrum) CDMA that ... more We previously presented a blind 2D RAKE receiver for (direct sequence spread spectrum) CDMA that cancels strong multi-user access interference (MAI) and optimally combines multipath. After passing the output of each antenna through a matched filter based on the spreading waveform of the desired user, one estimates the signal plus interference spatio-frequency correlation matrix during that portion of the bit interval where the fingers of the RAKE occur, and the interference alone spatio-frequency correlation matrix during that portion of the bit interval away from the fingers. A reduced complexity scheme that outperforms the previous algorithm in a MAI dominant environment is presented based on a data adaptive transformation to a beamspace of dimension equal to the effective number of spatial degrees of freedom taken up by the desired user's multipath
Asilomar Conference on Signals, Systems & Computers, 1995
A blind adoptive beamforming scheme is developed for CDMA that cancels strong multi-user access i... more A blind adoptive beamforming scheme is developed for CDMA that cancels strong multi-user access interference and optimally combines multipath based on the following observation: after passing the output of each antenna through a matched filter corresponding to the PN sequence of the desired user, one can isolate periods of time when the cochannel interference dominates. This allows one to estimate the spatio-frequency correlation matrix of the co-channel interference alone. The weight vector yielding the optimum signal to interference plus noise ratio for bit decisions is the "largest" generalised eigenvector of the signal plus interference spatio-frequency correlation matrix in the metric of the spatio frequency correlation matrix of the co-channel interference alone. Simulations are presented demonstrating the efficacy of the procedure.
We previously presented a blind 2D RAKE receiver for CDMA that cancels strong multi-user access i... more We previously presented a blind 2D RAKE receiver for CDMA that cancels strong multi-user access interference and optimally combines the desired user's multipath. After passing the output of each antenna through a matched filter based on the spreading waveform of the desired user, one estimates the signal plus interference space-frequency (space-time) correlation matrix during that portion of the bit interval where the fingers of the RAKE occur, and the interference alone space-frequency (space-time) correlation matrix during that portion of the bit interval away from the fingers. The vector of space-frequency (space-time) weights yielding the optimum signal to interference plus noise ratio for bit decisions is the “largest” generalized eigenvector of the resulting matrix pencil. A reduced complexity scheme was also previously presented based on a data adaptive transformation to a beamspace of dimension equal to the effective number of spatial degrees of freedom taken up by the desired user's multipath. A decision directed adaptation of this scheme for a commercial cellular CDMA system based on the IS-95 standard is presented herein. Only the uplink from mobile to base is considered
Space technology and applications international forum (STAIF - 97), 1997
ABSTRACT A novel wideband beamforming technique for cellular CDMA systems is presented. The propo... more ABSTRACT A novel wideband beamforming technique for cellular CDMA systems is presented. The proposed algorithm asymptotically provides the optimum combination of space-time samples for maximizing the SINR for the {ital Signal with the Desired Code} (SDC) by canceling strong {ital Multi-User Access Interference} (MUAI) and optimally combining the multipath. In contrast to previously proposed techniques, bit synchronization for the SDC is not required. The algorithm presented herein asymptotically provides the respective time of arrivals of the multipaths within a bit period, and the optimum beamformers for extracting each multipath. Subsequently space-time weights for combining the fingers across both space and time while canceling the MUAIs are found. {copyright} {ital 1997 American Institute of Physics.}
This article addresses the simultaneous estimation of the azimuth and elevation angles of multipl... more This article addresses the simultaneous estimation of the azimuth and elevation angles of multiple co-channel signals incident upon an array of antennas. A new closed-form algorithm that is applicable with filled circular arrays (FCAs) is presented. The algorithm, which is called FCA-ESPRIT, is applicable with any FCA geometry, e.g., FCAs constructed using rectangular, hexagonal, polar, or random sampling lattices. The only constraint imposed on the FCA geometry is that the spacing between adjacent sensors should be half a wavelength or less on average across the entire aperture. The algorithm provides automatically paired azimuth and elevation angle estimates by solving a set of ESPRIT-like equations wherein the unknowns have the form sin(θ i)ejφ(i) (where θi and φ i are the elevation and azimuth angles of the ith source, respectively). The algorithm provides arrival angle estimates via a closed-form procedure-it does not require computationally expensive search or optimization procedures
International Conference on Acoustics, Speech, and Signal Processing, 1995
The problem addressed is that of narrowband digital cellular communications in the presence of mu... more The problem addressed is that of narrowband digital cellular communications in the presence of multipath and co-channel interferers having the same symbol rate and same overall signal characteristics as the desired source. For a given signal source, an algorithm is presented for blindly estimating the weight vector yielding the optimum SINR at the beamformer output. The instrumental quantity, denoted Sxx(f), is the Fourier transform of the expected value of the zero-lag autocorrelation matrix for one symbol period. The proposed scheme employs the PRO-ESPRIT algorithm to exploit the relationship between the timing offset and optimum beamforming weight vector for each source and the principal generalized eigenvalues and eigenvectors of the matrix pencil {Sxx(1/T0), Sxx(O)}, where 1/T0 is the symbol rate. Simulations are presented showing the rapid convergence of the algorithm and an improvement of several dB over the subspace-constrained Phase-SCORE algorithm
International Conference on Acoustics, Speech, and Signal Processing, 1997
A novel wideband beamforming technique for cellular CDMA systems is presented. The proposed algor... more A novel wideband beamforming technique for cellular CDMA systems is presented. The proposed algorithm asymptotically provides the optimum combination of space-time samples to maximize the SINR for the signal with the desired code (SDC) by optimally combining its multipath and canceling strong multiuser access interference (MUAI). In contrast to previously proposed techniques, code synchronization for the SDC is not required. The algorithm presented asymptotically provides the exact time of arrivals of the multipaths within a bit period, and subsequently the optimum space-time weights for combining the fingers across both space and time. The instrumental property exploited in this technique is the fact that although the respective spectra of the SDC and MUAI components at the output of the matched filter are statistically equal, the respective spectra of their squared values differ
International Conference on Acoustics, Speech, and Signal Processing, 1996
We previously presented a blind 2D RAKE receiver for CDMA that cancels strong multi-user access i... more We previously presented a blind 2D RAKE receiver for CDMA that cancels strong multi-user access interference and optimally combines multipath. After passing the output of each antenna through a matched filter based on the spreading waveform of the desired user, one estimates the signal plus interference spatio-frequency correlation matrix during that portion of the bit interval where the fingers of the RAKE occur, and the interference alone spatio-frequency correlation matrix during that portion of the bit interval away from the fingers. The weight vector yielding the optimum signal to interference plus noise ratio for bit decisions is the “largest” generalized eigenvector of the resulting matrix pencil. However, even when the number of elements comprising the array is relatively small, this spatio-frequency correlation matrix pencil is of large dimension. In addition to detracting from the real-time applicability of the scheme, this slows up the time to convergence. A reduced complexity scheme is presented based on a data adaptive transformation to a beamspace of dimension equal to the effective number of spatial degrees of freedom taken up by the desired user's multipath
We discuss a new approach to self-organization that leads to novel adaptive algorithms for genera... more We discuss a new approach to self-organization that leads to novel adaptive algorithms for generalized eigen-decomposition and its variance for a single-layer linear feedforward neural network. First, we derive two novel iterative algorithms for linear discriminant analysis (LDA) and generalized eigen-decomposition by utilizing a constrained least-mean-squared classification error cost function, and the framework of a two-layer linear heteroassociative network performing a one-of-m classification. By using the concept of deflation, we are able to find sequential versions of these algorithms which extract the LDA components and generalized eigenvectors in a decreasing order of significance. Next, two new adaptive algorithms are described to compute the principal generalized eigenvectors of two matrices (as well as LDA) from two sequences of random matrices. We give a rigorous convergence analysis of our adaptive algorithms by using stochastic approximation theory, and prove that our algorithms converge with probability one.
• Despite the multiple roles played by antioxidants in rhizobia–legume symbioses, little is known... more • Despite the multiple roles played by antioxidants in rhizobia–legume symbioses, little is known about glutathione peroxidases (GPXs) in legumes. Here the characterization of six GPX genes of Lotus japonicus is reported.• Expression of GPX genes was analysed by quantitative reverse transcription–polymerase chain reaction in L. japonicus and Lotus corniculatus plants exposed to various treatments known to generate reactive oxygen and/or nitrogen species.• LjGPX1 and LjGPX3 were the most abundantly expressed genes in leaves, roots and nodules. Compared with roots, LjGPX1 and LjGPX6 were highly expressed in leaves and LjGPX3 and LjGPX6 in nodules. In roots, salinity decreased GPX4 expression, aluminium decreased expression of the six genes, and cadmium caused up-regulation of GPX3, GPX4 and GPX5 after 1 h and down-regulation of GPX1, GPX2, GPX4 and GPX6 after 3–24 h. Exposure of roots to sodium nitroprusside (a nitric oxide donor) for 1 h increased the mRNA levels of GPX4 and GPX6 by 3.3- and 30-fold, respectively. Thereafter, the GPX6 mRNA level remained consistently higher than that of the control. Immunogold labelling revealed the presence of GPX proteins in root and nodule amyloplasts and in leaf chloroplasts of L. japonicus and other legumes. Labelling was associated with starch grains.• These results underscore the differential regulation of GPX expression in response to cadmium, aluminium and nitric oxide, and strongly support a role for GPX6 and possibly other GPX genes in stress and/or metabolic signalling.Despite the multiple roles played by antioxidants in rhizobia–legume symbioses, little is known about glutathione peroxidases (GPXs) in legumes. Here the characterization of six GPX genes of Lotus japonicus is reported.Expression of GPX genes was analysed by quantitative reverse transcription–polymerase chain reaction in L. japonicus and Lotus corniculatus plants exposed to various treatments known to generate reactive oxygen and/or nitrogen species.LjGPX1 and LjGPX3 were the most abundantly expressed genes in leaves, roots and nodules. Compared with roots, LjGPX1 and LjGPX6 were highly expressed in leaves and LjGPX3 and LjGPX6 in nodules. In roots, salinity decreased GPX4 expression, aluminium decreased expression of the six genes, and cadmium caused up-regulation of GPX3, GPX4 and GPX5 after 1 h and down-regulation of GPX1, GPX2, GPX4 and GPX6 after 3–24 h. Exposure of roots to sodium nitroprusside (a nitric oxide donor) for 1 h increased the mRNA levels of GPX4 and GPX6 by 3.3- and 30-fold, respectively. Thereafter, the GPX6 mRNA level remained consistently higher than that of the control. Immunogold labelling revealed the presence of GPX proteins in root and nodule amyloplasts and in leaf chloroplasts of L. japonicus and other legumes. Labelling was associated with starch grains.These results underscore the differential regulation of GPX expression in response to cadmium, aluminium and nitric oxide, and strongly support a role for GPX6 and possibly other GPX genes in stress and/or metabolic signalling.
The composition of antioxidant enzymes, especially superoxide dismutase (SOD), was studied in one... more The composition of antioxidant enzymes, especially superoxide dismutase (SOD), was studied in one nontransgenic and three transgenic lines of nodulated alfalfa plants. Transgenic lines overproduced MnSOD in the mitochondria of nodules and leaves (line 1-10), MnSOD in the chloroplasts (line 4-6), and FeSOD in the chloroplasts (line 10-7). In nodules of line 10-7, the absence of transgene-encoded FeSOD activity was due to a lack of mRNA, whereas in nodules of line 4-6 the absence of transgene-encoded MnSOD activity was due to enzyme inactivation or degradation. Transgenic alfalfa showed a novel compensatory effect in the activities of MnSOD (mitochondrial) and FeSOD (plastidic) in the leaves, which was not caused by changes in the mRNA levels. These findings imply that SOD activity in plant tissues and organelles is regulated, at least partially, at the posttranslational level. All four lines had low CuZnSOD activities and an abundant FeSOD isozyme, especially in nodules, indicating that FeSOD performs important antioxidant functions other than the scavenging of superoxide radicals generated in photosynthesis. This was confirmed by the detection of FeSOD cDNAs and proteins in nodules of other legumes such as cowpea, pea, and soybean. The cDNA encoding alfalfa nodule FeSOD was characterized and the deduced protein found to contain a plastid transit peptide. A comparison of sequences and other properties reveals that there are two types of FeSODs in nodules.
IEEE Workshop on Statistical Signal and Array Processing, 1996
We previously presented a blind 2D RAKE receiver for (direct sequence spread spectrum) CDMA that ... more We previously presented a blind 2D RAKE receiver for (direct sequence spread spectrum) CDMA that cancels strong multi-user access interference (MAI) and optimally combines multipath. After passing the output of each antenna through a matched filter based on the spreading waveform of the desired user, one estimates the signal plus interference spatio-frequency correlation matrix during that portion of the bit interval where the fingers of the RAKE occur, and the interference alone spatio-frequency correlation matrix during that portion of the bit interval away from the fingers. A reduced complexity scheme that outperforms the previous algorithm in a MAI dominant environment is presented based on a data adaptive transformation to a beamspace of dimension equal to the effective number of spatial degrees of freedom taken up by the desired user's multipath
Asilomar Conference on Signals, Systems & Computers, 1995
A blind adoptive beamforming scheme is developed for CDMA that cancels strong multi-user access i... more A blind adoptive beamforming scheme is developed for CDMA that cancels strong multi-user access interference and optimally combines multipath based on the following observation: after passing the output of each antenna through a matched filter corresponding to the PN sequence of the desired user, one can isolate periods of time when the cochannel interference dominates. This allows one to estimate the spatio-frequency correlation matrix of the co-channel interference alone. The weight vector yielding the optimum signal to interference plus noise ratio for bit decisions is the "largest" generalised eigenvector of the signal plus interference spatio-frequency correlation matrix in the metric of the spatio frequency correlation matrix of the co-channel interference alone. Simulations are presented demonstrating the efficacy of the procedure.
We previously presented a blind 2D RAKE receiver for CDMA that cancels strong multi-user access i... more We previously presented a blind 2D RAKE receiver for CDMA that cancels strong multi-user access interference and optimally combines the desired user's multipath. After passing the output of each antenna through a matched filter based on the spreading waveform of the desired user, one estimates the signal plus interference space-frequency (space-time) correlation matrix during that portion of the bit interval where the fingers of the RAKE occur, and the interference alone space-frequency (space-time) correlation matrix during that portion of the bit interval away from the fingers. The vector of space-frequency (space-time) weights yielding the optimum signal to interference plus noise ratio for bit decisions is the “largest” generalized eigenvector of the resulting matrix pencil. A reduced complexity scheme was also previously presented based on a data adaptive transformation to a beamspace of dimension equal to the effective number of spatial degrees of freedom taken up by the desired user's multipath. A decision directed adaptation of this scheme for a commercial cellular CDMA system based on the IS-95 standard is presented herein. Only the uplink from mobile to base is considered
Space technology and applications international forum (STAIF - 97), 1997
ABSTRACT A novel wideband beamforming technique for cellular CDMA systems is presented. The propo... more ABSTRACT A novel wideband beamforming technique for cellular CDMA systems is presented. The proposed algorithm asymptotically provides the optimum combination of space-time samples for maximizing the SINR for the {ital Signal with the Desired Code} (SDC) by canceling strong {ital Multi-User Access Interference} (MUAI) and optimally combining the multipath. In contrast to previously proposed techniques, bit synchronization for the SDC is not required. The algorithm presented herein asymptotically provides the respective time of arrivals of the multipaths within a bit period, and the optimum beamformers for extracting each multipath. Subsequently space-time weights for combining the fingers across both space and time while canceling the MUAIs are found. {copyright} {ital 1997 American Institute of Physics.}
This article addresses the simultaneous estimation of the azimuth and elevation angles of multipl... more This article addresses the simultaneous estimation of the azimuth and elevation angles of multiple co-channel signals incident upon an array of antennas. A new closed-form algorithm that is applicable with filled circular arrays (FCAs) is presented. The algorithm, which is called FCA-ESPRIT, is applicable with any FCA geometry, e.g., FCAs constructed using rectangular, hexagonal, polar, or random sampling lattices. The only constraint imposed on the FCA geometry is that the spacing between adjacent sensors should be half a wavelength or less on average across the entire aperture. The algorithm provides automatically paired azimuth and elevation angle estimates by solving a set of ESPRIT-like equations wherein the unknowns have the form sin(θ i)ejφ(i) (where θi and φ i are the elevation and azimuth angles of the ith source, respectively). The algorithm provides arrival angle estimates via a closed-form procedure-it does not require computationally expensive search or optimization procedures
International Conference on Acoustics, Speech, and Signal Processing, 1995
The problem addressed is that of narrowband digital cellular communications in the presence of mu... more The problem addressed is that of narrowband digital cellular communications in the presence of multipath and co-channel interferers having the same symbol rate and same overall signal characteristics as the desired source. For a given signal source, an algorithm is presented for blindly estimating the weight vector yielding the optimum SINR at the beamformer output. The instrumental quantity, denoted Sxx(f), is the Fourier transform of the expected value of the zero-lag autocorrelation matrix for one symbol period. The proposed scheme employs the PRO-ESPRIT algorithm to exploit the relationship between the timing offset and optimum beamforming weight vector for each source and the principal generalized eigenvalues and eigenvectors of the matrix pencil {Sxx(1/T0), Sxx(O)}, where 1/T0 is the symbol rate. Simulations are presented showing the rapid convergence of the algorithm and an improvement of several dB over the subspace-constrained Phase-SCORE algorithm
International Conference on Acoustics, Speech, and Signal Processing, 1997
A novel wideband beamforming technique for cellular CDMA systems is presented. The proposed algor... more A novel wideband beamforming technique for cellular CDMA systems is presented. The proposed algorithm asymptotically provides the optimum combination of space-time samples to maximize the SINR for the signal with the desired code (SDC) by optimally combining its multipath and canceling strong multiuser access interference (MUAI). In contrast to previously proposed techniques, code synchronization for the SDC is not required. The algorithm presented asymptotically provides the exact time of arrivals of the multipaths within a bit period, and subsequently the optimum space-time weights for combining the fingers across both space and time. The instrumental property exploited in this technique is the fact that although the respective spectra of the SDC and MUAI components at the output of the matched filter are statistically equal, the respective spectra of their squared values differ
International Conference on Acoustics, Speech, and Signal Processing, 1996
We previously presented a blind 2D RAKE receiver for CDMA that cancels strong multi-user access i... more We previously presented a blind 2D RAKE receiver for CDMA that cancels strong multi-user access interference and optimally combines multipath. After passing the output of each antenna through a matched filter based on the spreading waveform of the desired user, one estimates the signal plus interference spatio-frequency correlation matrix during that portion of the bit interval where the fingers of the RAKE occur, and the interference alone spatio-frequency correlation matrix during that portion of the bit interval away from the fingers. The weight vector yielding the optimum signal to interference plus noise ratio for bit decisions is the “largest” generalized eigenvector of the resulting matrix pencil. However, even when the number of elements comprising the array is relatively small, this spatio-frequency correlation matrix pencil is of large dimension. In addition to detracting from the real-time applicability of the scheme, this slows up the time to convergence. A reduced complexity scheme is presented based on a data adaptive transformation to a beamspace of dimension equal to the effective number of spatial degrees of freedom taken up by the desired user's multipath
We discuss a new approach to self-organization that leads to novel adaptive algorithms for genera... more We discuss a new approach to self-organization that leads to novel adaptive algorithms for generalized eigen-decomposition and its variance for a single-layer linear feedforward neural network. First, we derive two novel iterative algorithms for linear discriminant analysis (LDA) and generalized eigen-decomposition by utilizing a constrained least-mean-squared classification error cost function, and the framework of a two-layer linear heteroassociative network performing a one-of-m classification. By using the concept of deflation, we are able to find sequential versions of these algorithms which extract the LDA components and generalized eigenvectors in a decreasing order of significance. Next, two new adaptive algorithms are described to compute the principal generalized eigenvectors of two matrices (as well as LDA) from two sequences of random matrices. We give a rigorous convergence analysis of our adaptive algorithms by using stochastic approximation theory, and prove that our algorithms converge with probability one.
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Papers by Javier Ramos