Frequency invariant MVDR beamforming without filters and implementation using MIMO radar

Frequency invariant beamforming with sensor arrays is generally achieved using filters in the form of tapped delay-lines following each sensor. However it has been recently shown that with the help of the rectangular smart antenna array, it is possible to generate frequency invariant beampattern without using filters. In this paper, this frequency invariant beamforming technique is utilized to perform MVDR beamforming in the beamspace by designing frequency invariant beams spanning the desired range of azimuthal angles and optimally combining them. However, the performance of the frequency invariant beamformer depends on the number of sensors which could be large for a rectangular array of size M × N. Making use of the virtual array concept used in MIMO radar, a novel method of producing the same frequency invariant beam, using only M transmitting and N receiving antennas, is proposed and a design example is provided to demonstrate the idea

System Identification With Sparse Coprime Sensing

Given a continuous time LTI system with impulse response h_c(t), it is shown that the uniformly spaced samples h_c(nT) can be identified for any chosen spacing by using an impulse train input with an arbitrarily small rate 1/NT and sampling the system output with an arbitrarily small rate 1/MT, provided M and N are coprime. This idea, referred to here as the sparse coprime sensing method for system identification, is closely related to well known results in multirate signal processing. It is shown that the problem can be related to the identification of a decimation filter from input-output measurements. It is also shown that the problem is equivalent to the identification of a discrete time N x M LTI system from a knowledge of the full rate input and output vector sequences

Thinned coprime arrays for DOA estimation

Sparse arrays can generate a larger aperture than traditional uniform linear arrays (ULA) and offer enhanced degrees-of-freedom (DOFs) which can be exploited in both beamforming and direction-of-arrival (DOA) estimation. One class of sparse arrays is the coprime array, composed of two uniform linear subarrays which yield an effective difference co-array with higher number of DOFs. In this work, we present a new coprime array structure termed thinned coprime array (TCA), which exploits the redundancy in the structure of the existing coprime array and achieves the same virtual aperture and DOFs as the conventional coprime array with much fewer number of sensors. An analysis of the DOFs provided by the new structure in comparison with other sparse arrays is provided and simulation results for DOA estimation using the compressive sensing based method are provided

Identification of Novel RPA-Protein Interactions Using the Yeast Two Hybrid Assay and Identification of Regions Important for Interaction Between RPA and Rad24

Replication Protein A (RPA) [Replication Factor A (RFA) in yeast] is an ssDNA binding protein composed of Rpa1, Rpa2, and Rpa3 and involved in numerous DNA processing pathways such as Replication, Recombination, and Repair. It participates in such diverse pathways by its ability to interact with numerous proteins. The goal of my project was to find novel RPA-protein interactions using the yeast two hybrid assay. Using this method, we identified several known and unknown proteins that interact with Rfa1 and showed that these interactions were dependent on the phosphorylation state of Rfa2. Next, we determine the region important for interaction between Rfa1 and Rad24. Rad24 is a checkpoint protein important for initiation of the DNA damage checkpoint signaling. By using the β- galactosidase assay, we determined the N-terminal region of Rfa1 (DBD-F) and the C-terminal region of Rad24 (460-660 aa) to be necessary for their interaction

MIMO radar with broadband waveforms: Smearing filter banks and 2D virtual arrays

In this paper MIMO radars with broadband waveforms are considered. A time domain viewpoint is taken, which allows frequency invariant beamforming with a filter bank called the smearing filter bank. Motivated by recent work on two dimensional arrays to obtain frequency invariant one dimensional beams, the generation of two dimensional virtual arrays from one dimensional ULAs is also considered. It is also argued that when the smearing filter bank is appropriately used, frequency invariant 2D beams can be generated

Effects of Content and Audience Awareness Goals for Revision on EFL Learners' Writing Performance

The process of revision and its essential role in the writing process is universally known. However, students have continuous problem in writing and especially in revising. Practitioners believe that the main problem is lack of instructional attention on revision strategies focused on content and audience awareness in classrooms, and students’ not setting any clear goals to follow while writing and revising although they are both described as goal‐directed process in cognitive model of composition writing. The purpose of this study was to figure out the effects of revising goals focused on content and audience awareness on aspects of essay writing (i.e., Task Response (TR), Cohesion and Coherence (CC), Lexical Resource (LR), and Grammar Range and Accuracy (GRA)), and overall writing performance of EFL learners. Based on their writing performance in the pretest, all 26 students were systematically assigned to two different goal conditions: a General Goal (GG, that was to improve the essay in general); and a Content plus Audience Awareness Goal (C*AG, that was to improve the essay focusing on content and organization of ideas, and communication with the intended audience). After six treatment sessions (within six weeks), they were given a writing test as the posttest. Final drafts of essays in both pretest and posttest were scored for aspects of essay writing and for overall writing performance. As a result of the treatment, students in C*AG condition managed to write essays with significantly higher quality compared to students in GG condition (t = 2.137, p = .043). Moreover, those in C*AG condition improved their essays significantly in all aspects of essay writing (t = 6.503, 5.894, 6.936, 5.744, and p = .000 for TR, CC, LR, and GRA respectively) while students’ essays in GG condition scored higher in terms of TR (t = 2.930, p = .013) and GRA (t = 2.713, p = .019) only. Based on the results, it is recommended for English writing teachers to consider revision strategies that focus on content and audience awareness in teaching writing and revising since such strategies can lead students to better performance in all aspects of essay writing

Role of Hormonal and Developmental Signaling in Plant-Cyst Nematode Interaction

Plant-parasitic cyst nematodes are one of the most destructive root parasites that cause severe yield losses in many crop plants. These obligate parasites induce a specialized multi-nucleate feeding site called syncytium. This study was conducted to explore the roles of phytohormones particularly auxin and ethylene, and miRNA-mediated crosstalk between development and defense responses in establishing the compatible interaction between Arabidopsis and Heterodera schachtii. Using yeast two-hybrid assay, a complete protein-protein interaction map between Auxin/indole-3-acetic acid (Aux/IAA) proteins and auxin response factors (ARFs) was generated. In addition, gene co-expression profiles of ARFs and Aux/IAAs were incorporated with protein-protein interaction data. Together, these analyses revealed the biological significance of the ARFs and Aux/IAA interactions in the differentiation and development of various plant tissues and organs, including H. schachtii–induced syncytium. Our analyses also provided evidence for the roles of ETHYLENE RESPONSE 1 and ETHYLENE INSENSITIVE 3/ETHYLENE INSENSITIVE LIKE 1 in regulating Arabidopsis responses to H. schachtii infection. The role of miRNAs in mediating the coordination between developmental signaling and defense response is emerging. Functional characterization of miR858 and its MYB83 target gene pointed into novel cooperative regulatory functions of this regulatory module in syncytium transcriptome reprogramming during cyst nematode parasitism of Arabidopsis. We discovered that miR858-mediated silencing of MYB83 is tightly regulated through a feedback loop that may ensure proper expression levels of more than a thousand of MYB83-regulated genes in the syncytium. Finally, the direct targets of Growth Regulating Factor 1 (GRF1) and 3, master regulators of syncytium differentiation, were identified. Specific and the shared cis-binding elements of GRF1 and GRF3 were identified, providing unprecedented understanding of the mechanism of their functional redundancy. GRF1 and GRF3 directly target genes associated with cell cycle regulation, cytoskeleton organization, phytohormone biosynthesis and signaling, and defense responses, key cellular processes that determine the outcomes of plant-cyst nematode interactions. The analysis also provided intriguing evidence for the involvement of GRF1/3 in mediating the trade-off between plant growth and stress signaling. Understanding the molecular mechanisms underlying the coordinated interactions between plant growth and defense signaling will open new avenues for enhancing plant growth and stress response simultaneously