Optical Properties and Plasmonic Performance of Titanium Nitride

Titanium nitride (TiN) is one of the most well-established engineering materials nowadays. TiN can overcome most of the drawbacks of plasmonic metals due to its high electron conductivity and mobility, high melting point and due to the compatibility of its growth with Complementary Metal Oxide Semiconductor (CMOS) technology. In this work, we review the dielectric function spectra of TiN and we evaluate the plasmonic performance of TiN by calculating (i) the Surface Plasmon Polariton (SPP) dispersion relations and (ii) the Localized Surface Plasmon Resonance (LSPR) band of TiN nanoparticles, and we demonstrate a significant plasmonic performance of TiN

Towards longitudinal data analytics in Parkinson's Disease

The CloudUPDRS app has been developed as a Class I med- ical device to assess the severity of motor symptoms for Parkinson’s Disease using a fully automated data capture and signal analysis pro- cess based on the standard Unified Parkinson’s Disease Rating Scale. In this paper we report on the design and development of the signal pro- cessing and longitudinal data analytics microservices developed to carry out these assessments and to forecast the long-term development of the disease. We also report on early findings from the application of these techniques in the wild with a cohort of early adopters

Photoluminescence enhancement of ZnO via coupling with surface plasmons on Al thin films

We present that the ultra-violet emission of ZnO can be enhanced, as much as six-times its integral intensity, using an Al thin interlayer film between the Si substrate and ZnO thin film and a postfabrication laser annealing process. The laser annealing is a cold process that preserves the chemical state and integrity of the underlying aluminum layer, while it is essential for the improvement of the ZnO performance as a light emitter and leads to enhanced emission in the visible and in the ultraviolet spectral ranges. In all cases, the metal interlayer enhances the intensity of the emitted light, either through coupling of the surface plasmon that is excited at the Al/ZnO interface, in the case of light-emitting ZnO in the ultraviolet region, or by the increased back reflection from the Al layer, in the case of the visible emission. In order to evaluate the process and develop a solid understanding of the relevant physical phenomena, we investigated the effects of various metals as interlayers (Al, Ag, and Au), the metal interlayer thickness, and the incorporation of a dielectric spacer layer between Al and ZnO. Based on these experiments, Al emerged as the undisputable best choice of metal interlayers because of its compatibility with the laser annealing process, as well as due to its high optical reflectivity at 380 and 248 nm, which leads to the effective coupling with surface plasmons at the Al/ZnO interfaces at 380 nm and the secondary annealing of ZnO by the back-reflected 248 nm laser beam

Conductive nitrides: growth principles, optical and electronic properties, and their perspectives in photonics and plasmonics

The nitrides of most of the group IVb-Vb-VIb transition metals (TiN, ZrN, HfN, VN, NbN, TaN, MoN, WN) constitute the unique category of conductive ceramics. Having substantial electronic conductivity, exceptionally high melting points and covering a wide range of work function values, they were considered for a variety of electronic applications, which include diffusion barriers in metallizations of integrated circuits, Ohmic contacts on compound semiconductors, and thin film resistors, since early eighties. Among them, TiN and ZrN are recently emerging as significant candidates for plasmonic applications. So the possible plasmonic activity of the rest of transition metal nitrides (TMN) emerges as an important open question. In this work, we exhaustively review the experimental and computational (mostly ab initio) works in the literature dealing with the optical properties and electronic structure of TMN spanning over three decades of time and employing all the available growth techniques. We critically evaluate the optical properties of all TMN and we model their predicted plasmonic response. Hence, we provide a solid understanding of the intrinsic (e.g. the valence electron configuration of the constituent metal) and extrinsic (e.g. point defects and microstructure) factors that dictate the plasmonic performance. Based on the reported optical spectra, we evaluate the quality factors for surface plasmon polariton and localized surface plasmon for various TMN and critically compare them to each other. We demonstrate that, indeed TiN and ZrN along with HfN are the most well-performing plasmonic materials in the visible range, while VN and NbN may be viable alternatives for plasmonic devices in the blue, violet and near UV ranges, albeit in expense of increased electronic loss. Furthermore, we consider the alloyed ternary TMN and by critical evaluation and comparison of the reported experimental and computational works, we identify the emerging optimal tunable plasmonic conductors among the immense number of alloying combinations

Self-assembled plasmonic templates produced by microwave annealing: applications to surface-enhanced Raman scattering

Perhaps the simplest method for creating metal nanoparticles on a substrate is by driving their self-assembly with the thermal annealing of a thin metal film. By properly tuning the annealing parameters one hopes to discover a recipe that allows the pre-determined design of the NP arrangement. However, thermal treatment is known for detrimental effects and is not really the manufacturer's route of choice when it comes to large-scale applications. An alternative method is the use of microwave annealing, a method that has never been applied for metal processing, due to the high reflectance of microwave radiation at the surface of a metal. However, in this work we challenge the widely used nanostructuring methods by proving the microwave's annealing ability to produce plasmonic templates, out of extremely thin metal films, by simply using a domestic microwave oven apparatus. We show that this process is generic and independent of the deposition method used for the metal and we further quantify the suitability of these plasmonic templates for use in surface-enhanced Raman scattering applications

A polymerase III-like reinitiation mechanism is operating in regulation of histone expression in archaea

An archaeal histone gene from the hyperthermophile Pyrococcus furiosus containing four consecutive putative oligo-dT terminator sequences was used as a model system to investigate termination signals and the mechanism of termination in vitro. The archaeal RNA polymerase terminated with high efficiency at the first terminator at 90°C when it contained five to six T residues, at 80°C readthrough was significantly increased. A putative hairpin structure upstream of the first terminator had no effect on termination efficiency. Template competition experiments starting with RNA polymerase molecules engaged in ternary complexes revealed recycling of RNA polymerase from the terminator to the promoter of the same template. This facilitated reinitiation was dependent upon the presence of a terminator sequence suggest-ing that pausing at the terminator is required for recycling as in the RNA polymerase III system. Replacement of the sequences immediately down-stream of the oligo-dT terminator by an AT-rich segment improved termination efficiency. Both AT-rich and GC-rich downstream sequences seemed to impair the facilitated reinitiation pathway. Our data suggest that recycling is dependent on a subtle interplay of pausing of RNA polymerase at the ter-minator and RNA polymerase translocation beyond the oligo-dT termination signal that is dramatically affected by downstream sequences

Yeast H2A.Z, FACT complex and RSC regulate transcription of tRNA gene through differential dynamics of flanking nucleosomes

FACT complex is involved in elongation and ensures fidelity in the initiation step of transcription by RNA polymerase (pol) II. Histone variant H2A.Z is found in nucleosomes at the 5′-end of many genes. We report here H2A.Z-chaperone activity of the yeast FACT complex on the short, nucleosome-free, non-coding, pol III-transcribed yeast tRNA genes. On a prototype gene, yeast SUP4, chromatin remodeler RSC and FACT regulate its transcription through novel mechanisms, wherein the two gene-flanking nucleosomes containing H2A.Z, play different roles. Nhp6, which ensures transcription fidelity and helps load yFACT onto the gene flanking nucleosomes, has inhibitory role. RSC maintains a nucleosome abutting the gene terminator downstream, which results in reduced transcription rate in active state while H2A.Z probably helps RSC in keeping the gene nucleosome-free and serves as stress-sensor. All these factors maintain an epigenetic state which allows the gene to return quickly from repressed to active state and tones down the expression from the active SUP4 gene, required probably to maintain the balance in cellular tRNA pool

Stochasticity and traffic jams in the transcription of ribosomal RNA: Intriguing role of termination and antitermination

In fast growing bacteria, ribosomal RNA (rRNA) is required to be transcribed at very high rates to sustain the high cellular demand on ribosome synthesis. This results in dense traffic of RNA polymerases (RNAP). We developed a stochastic model, integrating results of single-molecule and quantitative in vivo studies of E. coli, to evaluate the quantitative effect of pausing, termination, and antitermination on rRNA transcription. Our calculations reveal that in dense RNAP traffic, spontaneous pausing of RNAP can lead to severe "traffic jams", as manifested in the broad distribution of inter-RNAP distances and can be a major factor limiting transcription and hence growth. Our results suggest the suppression of these pauses by the ribosomal antitermination complex to be essential at fast growth. Moreover, unsuppressed pausing by even a few non-antiterminated RNAPs can already reduce transcription drastically under dense traffic. However, the termination factor Rho can remove the non-antiterminated RNAPs and restore fast transcription. The results thus suggest an intriguing role by Rho to enhance rather than attenuate rRNA transcription.Comment: includes Supporting Informatio

Near-zero negative real permittivity in far ultraviolet: extending plasmonics and photonics with B1-MoNx

CMOS-compatible, refractory conductors are emerging as the materials that will advance novel concepts into real, practical plasmonic technologies. From the available pallet of materials, those with negative real permittivity at very short wavelengths are extremely rare; importantly, they are vulnerable to oxidation—upon exposure to far-UV radiation—and nonrefractory. Epitaxial, substoichiometric, cubic MoN (B1-MoNx) films exhibit resistivity as low as 250 μΩ cm and negative real permittivity for experimental wavelengths as short as 155 nm, accompanied with unparalleled chemical and thermal stabilities, which are reported herein. Finite-difference time domain calculations suggest that B1-MoNx operates as an active plasmonic element deeper in the UV (100–200 nm) than any other known material, apart from Al, while being by far more stable and abundant than any other UV plasmonic conductor. Unexpectedly, the unique optical performance of B1-MoNx is promoted by nitrogen vacancies, thus changing the common perception on the role of defects in plasmonic materials

Structural basis of RNA polymerase III transcription initiation.

RNA polymerase (Pol) III transcribes essential non-coding RNAs, including the entire pool of transfer RNAs, the 5S ribosomal RNA and the U6 spliceosomal RNA, and is often deregulated in cancer cells. The initiation of gene transcription by Pol III requires the activity of the transcription factor TFIIIB to form a transcriptionally active Pol III preinitiation complex (PIC). Here we present electron microscopy reconstructions of Pol III PICs at 3.4-4.0 Å and a reconstruction of unbound apo-Pol III at 3.1 Å. TFIIIB fully encircles the DNA and restructures Pol III. In particular, binding of the TFIIIB subunit Bdp1 rearranges the Pol III-specific subunits C37 and C34, thereby promoting DNA opening. The unwound DNA directly contacts both sides of the Pol III cleft. Topologically, the Pol III PIC resembles the Pol II PIC, whereas the Pol I PIC is more divergent. The structures presented unravel the molecular mechanisms underlying the first steps of Pol III transcription and also the general conserved mechanisms of gene transcription initiation