Automated Design of a Broadside-Radiating Linearly Polarized Isotropic Metasurface Antenna

We present the automated design of a broadside-radiating metasurface antenna. The design is carried out by employing a continuous isotropic Impedance Boundary Condition through an optimization procedure based on the equivalent surface current only. A modified gradient-descent optimization algorithm is applied to minimize an objective function that incorporates both realizability and far field requirements. The antenna is then implemented by a suitable arrangement of circular unit cells, selected from a database of precomputed shapes. This procedure is applied to the design of a broadside-radiating, linearly polarized circular metasurface antenna working at 23 GHz, with size ≈12λ . The obtained design is then validated with commercial software simulations

Genetic and molecular analysis of wings apart-like (wapl), a gene controlling heterochromatin organization in Drosophila melanogaster.

Mutations in the X-linked gene wings apart-like (wapl) result in late larval lethality associated with an unusual chromosome morphology. In brain cell metaphases of wapl mutants, sister chromatids of all chromosomes are aligned parallel to each other instead of assuming the typical morphology observed in wild type. This effect is due to a loosening of the adhesion between sister chromatids in the heterochromatic regions of the chromosomes. Despite this aberrant chromosome morphology, mutant brains exhibit normal mitotic parameters, suggesting that heterochromatin cohesion is not essential for proper centromere function. On the basis of these observations, we examined the role of wapl in meiotic chromosome segregation in females. wapl exhibits a clear dominant effect on achiasmate segregation, giving further support to the hypothesis that proximal heterochromatin is involved in chromosome pairing during female meiosis. We also examined whether wapl modulates position-effect variegation (PEV). Our analyses showed that wapl is a dominant suppressor of both white and Stubble variegation, while it is a weak enhancer of brown variegation. wapl maps to region 2D of the X chromosome between Pgd and pn. We identified the wapl gene within a previously conducted chromosomal walk in this region. The wapl transcriptional unit gives rise to two alternatively spliced transcripts 6.5- and 5-kb long. The protein encoded by the larger of these transcripts appears to be conserved among higher eukaryotes and contains a tract of acidic amino acids reminiscent of many chromatin-associated proteins, including two [HP1 and SU(VAR)3-7] encoded by other genes that act as suppressors of PEV

STUDY OF RECONFIGURABLE LEAKY WAVE ANTENNAS BASED ON LIQUID CRYSTALS FOR CONTINUOUS BEAM SCANNING WITH A SINGLE CONTROL

This work presents the results of a study on electronically scanning antennas based on liquid crystals. In particular, the study aims at assessing the feasibility of a leaky wave antenna providing a continuous scanning at fixed frequency with a single voltage control. The radiating part is constituted by a parallel plate waveguide partially filled by liquid crystals with gradually modulated, electrically small slots etched on the upper wall. The feeding network is realized through a pillbox network. The concept is first validated through the realization and experimental characterization of a static antenna prototype. Preliminary experimental results on a reconfigurable antenna prototype are also presented

Yeti, an essential Drosophila melanogaster gene, encodes a protein required for chromatin organization

The evolutionarily conserved family of Bucentaur (BCNT) proteins exhibits a widespread distribution in animal and plants, yet its biological role remains largely unknown. Using Drosophila melanogaster as a model organism, we investigated the in vivo role of the Drosophila BCNT member called YETI. We report that loss of YETI causes lethality before pupation and defects in higher-order chromatin organization, as evidenced by severe impairment in the association of histone H2A.V, nucleosomal histones and epigenetic marks with polytene chromosomes. We also find that YETI binds to polytene chromosomes through its conserved BCNT domain and interacts with the histone variant H2A.V, HP1a and Domino-A (DOM-A), the ATPase subunit of the DOM/Tip60 chromatin remodeling complex. Furthermore, we identify YETI as a downstream target of the Drosophila DOM-A. On the basis of these results, we propose that YETI interacts with H2A.V-exchanging machinery, as a chaperone or as a new subunit of the DOM/Tip60 remodeling complex, and acts to regulate the accumulation of H2A.V at chromatin sites. Overall, our findings suggest an unanticipated role of YETI protein in chromatin organization and provide, for the first time, mechanistic clues on how BCNT proteins control development in multicellular organisms

Wapl is an essential regulator of chromatin structure and chromosome segregation

International audienceMammalian genomes contain several billion base pairs of DNA that are packaged in chromatin fibres. At selected gene loci, cohesin complexes have been proposed to arrange these fibres into higher-order structures1, 2, 3, 4, 5, 6, 7, but how important this function is for determining overall chromosome architecture and how the process is regulated are not well understood. Using conditional mutagenesis in the mouse, here we show that depletion of the cohesin-associated protein Wapl8, 9 stably locks cohesin on DNA, leads to clustering of cohesin in axial structures, and causes chromatin condensation in interphase chromosomes. These findings reveal that the stability of cohesin-DNA interactions is an important determinant of chromatin structure, and indicate that cohesin has an architectural role in interphase chromosome territories. Furthermore, we show that regulation of cohesin-DNA interactions by Wapl is important for embryonic development, expression of genes such as c-myc (also known as Myc), and cell cycle progression. In mitosis, Wapl-mediated release of cohesin from DNA is essential for proper chromosome segregation and protects cohesin from cleavage by the protease separase, thus enabling mitotic exit in the presence of functional cohesin complexes