Electromechanically Tunable Metasurface Transmission Waveplate at Terahertz Frequencies

Dynamic polarization control of light is essential for numerous applications ranging from enhanced imaging to materials characterization and identification. We present a reconfigurable terahertz metasurface quarter-waveplate consisting of electromechanically actuated micro-cantilever arrays. Our anisotropic metasurface enables tunable polarization conversion cantilever actuation. Specifically, voltage-based actuation provides mode selective control of the resonance frequency, enabling real-time tuning of the polarization state of the transmitted light. The polarization tunable metasurface has been fabricated using surface micromachining and characterized using terahertz time domain spectroscopy. We observe a ~230 GHz cantilever actuated frequency shift of the resonance mode, sufficient to modulate the transmitted wave from pure circular polarization to linear polarization. Our CMOS-compatible tunable quarter-waveplate enriches the library of terahertz optical components, thereby facilitating practical applications of terahertz technologies

CRL4-like Clr4 complex in Schizosaccharomyces pombe depends on an exposed surface of Dos1 for heterochromatin silencing

Repressive histone H3 lysine 9 methylation (H3K9me) and its recognition by HP1 proteins are necessary for pericentromeric heterochromatin formation. In Schizosaccharomyces pombe, H3K9me deposition depends on the RNAi pathway. Cryptic loci regulator 4 (Clr4), the only known H3K9 methyltransferase in this organism, is a subunit of the Clr4 methyltransferase complex (CLRC), whose composition is reminiscent of a CRL4 type cullin-RING ubiquitin ligase (CRL) including its cullin Cul4, the RING-box protein Pip1, the DNA damage binding protein 1 homolog Rik1, and the DCAF-like protein delocalization of Swi6 1 (Dos1). Dos2 and Stc1 have been proposed to be part of the complex but do not bear similarity to canonical ubiquitin ligase components. CLRC is an active E3 ligase in vitro, and this activity is necessary for heterochromatin assembly in vivo. The similarity between CLRC and the CRLs suggests that the WD repeat protein Dos1 will act to mediate target recognition and substrate specificity for CLRC. Here, we present a pairwise interaction screen that confirms a CRL4-like subunit arrangement and further identifies Dos2 as a central component of the complex and recruiter of Stc1. We determined the crystal structure of the Dos1 WD repeat domain, revealing an eight-bladed beta-propeller fold. Functional mapping of the putative target-binding surface of Dos1 identifies key residues required for heterochromatic silencing, consistent with Dos1's role as the specificity factor for the E3 ubiquitin ligase

Integrated Waste Management Technology with Focus on the Brazilian Amazon

This study deals with the management of the specific residues of tires, electro-electronics and batteries in a city in the Brazilian Amazon. The goal is to propose sustainable actions for the residues under study and, using SWOT analysis, to build a prognosis capable of contributing to environmental, economic and social sustainability. The specific objectives are: (1) Characterization of the hazardousness of the waste under study and the responsibility for its management; (2)identification of actions and goals in the management of specific solid waste; (3) use of the SWOT matrix to identify the positives and negatives inthe waste management under study; (4) propose actions and goals to combat the problems encountered. The choice of sample was purposely directed to the public managers directly involved in implementing the plan with a focus on the residues under study. It is an exploratory descriptive study, mixed I character and with qualitative results. The result points to problems that demand immediate and urgent solution suggestions are made for actions and aims with immediate effect. These actions would enable entrepreneurs to optimize sustainable social and economic development in the Amazon. This study may benefit business owners, governments and other institutions interested in specific waste-related issues

Effect of Spatial Locality Prefetching on Structural Locality

The purpose of this research was to analyze the effect that spatial locality prefetching in cache memory has on the structural locality of program memory referencing behavior. To examine this, a software simulator was built to model a proposed two-level cache memory subsystem. The proposed subsystem was designed to use spatial locality prefetching to exploit the structural locality contained in executing computer workloads. New memory referencing models were developed to incorporate the combined use of structural locality and spatial locality prefetching. From these models, equations were derived to predict the hit rates for both caches. Combined with the state transition probabilities of the memory referencing models, measurements from the trace-driven simulations were used to solve the hit probability equations. This research showed that performance gains through structural locality prefetching are still possible even when spatial locality prefetching is being used in the lower level cache

Terahertz third harmonic generation in c-axis La1.85_{1.85}Sr0.15_{0.15}CuO4_4

Terahertz nonlinear optics is a viable method to interrogate collective phenomena in quantum materials spanning ferroelectrics, charge-density waves, and superconductivity. In superconductors this includes the Higgs amplitude and Josephson phase modes. We have investigated the nonlinear c-axis response of optimally doped La$_{1.85}$Sr$_{0.15}$CuO$_4$ using high-field THz time domain spectroscopy (THz-TDS) at field strengths up to $\sim$80 kV/cm. With increasing field, we observe a distinct red-shift of the Josephson plasma edge and enhanced reflectivity (above the plasma edge) arising from third harmonic generation. The non-monotonic temperature dependent response is consistent with nonlinear drive of the Josephson Plasma Mode (JPM) as verified with comparison to theoretical expectations. Our results add to the understanding that, using THz light, the JPM (in addition to the Higgs mode) provides a route to interrogate and control superconducting properties

Preferentially Quantized Linker DNA Lengths in Saccharomyces cerevisiae

The exact lengths of linker DNAs connecting adjacent nucleosomes specify the intrinsic three-dimensional structures of eukaryotic chromatin fibers. Some studies suggest that linker DNA lengths preferentially occur at certain quantized values, differing one from another by integral multiples of the DNA helical repeat, ∼10 bp; however, studies in the literature are inconsistent. Here, we investigate linker DNA length distributions in the yeast Saccharomyces cerevisiae genome, using two novel methods: a Fourier analysis of genomic dinucleotide periodicities adjacent to experimentally mapped nucleosomes and a duration hidden Markov model applied to experimentally defined dinucleosomes. Both methods reveal that linker DNA lengths in yeast are preferentially periodic at the DNA helical repeat (∼10 bp), obeying the forms 10n+5 bp (integer n). This 10 bp periodicity implies an ordered superhelical intrinsic structure for the average chromatin fiber in yeast

Hypomethylation of a LINE-1 Promoter Activates an Alternate Transcript of the MET Oncogene in Bladders with Cancer

It was recently shown that a large portion of the human transcriptome can originate from within repetitive elements, leading to ectopic expression of protein-coding genes. However the mechanism of transcriptional activation of repetitive elements has not been definitively elucidated. For the first time, we directly demonstrate that hypomethylation of retrotransposons can cause altered gene expression in humans. We also reveal that active LINE-1s switch from a tetranucleosome to dinucleosome structure, acquiring H2A.Z- and nucleosome-free regions upstream of TSSs, previously shown only at active single-copy genes. Hypomethylation of a specific LINE-1 promoter was also found to induce an alternate transcript of the MET oncogene in bladder tumors and across the entire urothelium of tumor-bearing bladders. These data show that, in addition to contributing to chromosomal instability, hypomethylation of LINE-1s can alter the functional transcriptome and plays a role not only in human disease but also in disease predisposition