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

An investigation of thermodynamics, microscopic structure, depolarized Rayleigh scattering, and collision dynamics in Xe-N-2 supercritical mixtures

We would like to dedicate this work to the late Professor W. A. Steele (W.A.S.), Penn State University, USA. NATO Research-Project SA 5-2-05(CRG 950087) JARC (97) 288 is acknowledged for project funding to J.S., H.V. and W.A.S. The Greek State Scholarships Foundation (IKY) is acknowledged for an award based on performance to S. M. This work was supported by computational time granted from the Greek Research & Technology Network (GRNET) in the National HPC facility ARIS. The CPU time of the Computing Centre of the University of Athens (Greece) is gratefully acknowledged. This research utilized Queen Mary’s Mid-Plus computational facilities, supported by QMUL Research-IT and funded by EPSRC grant EP/K000128/1. J.K. acknowledges financial support from the NSF Grant No. CHE-1565872 to Millard Alexander

Nontrivial dependence of dielectric stiffness and SHG on dc bias in relaxors and dipole glasses

Dielectric permittivity and Second Harmonic Generation (SHG) studies in the field-cooled mode show a linear dependence of dielectric stiffness (inverse dielectric permittivity) on dc bias in PMN-PT crystals and SHG intensity in KTaO$_{3}$:Li at small Li concentrations. We explain this unusual result in the framework of a theory of transverse, hydrodynamic-type, instability of local polarization.Comment: 5 figure

The boron-oxygen core of borinate esters is responsible for the store-operated calcium entry potentiation ability

International audienceBACKGROUND: Store-Operated Calcium Entry (SOCE) is the major Ca2+ ion entry pathway in lymphocytes and is responsible of a severe combined immunodeficiency (SCID) when deficient. It has recently been observed or highlighted in other cell types such as myoblasts and neurons, suggesting a wider physiological role of this pathway. Whereas Orai1 protein is considered to be the channel allowing the SOCE in T cells, it is hypothesized that other proteins like TRPC could associate with Orai1 to form SOCE with different pharmacology and kinetics in other cell types. Unraveling SOCE cell functions requires specific effectors to be identified, just as dihydropyridines were crucial for the study of Ca2+ voltage-gated channels, or spider/snake toxins for other ion channel classes. To identify novel SOCE effectors, we analyzed the effects of 2-aminoethyl diphenylborinate (2-APB) and its analogues. 2-APB is a molecule known to both potentiate and inhibit T cell SOCE, but it is also an effector of TRP channels and endoplasmic reticulum Ca2+-ATPase. RESULTS: A structure-function analysis allowed to discover that the boron-oxygen core present in 2-APB and in the borinate ester analogues is absolutely required for the dual effects on SOCE. Indeed, a 2-APB analogue where the boron-oxygen core is replaced by a carbon-phosphorus core is devoid of potentiating capacity (while retaining inhibition capacity), highlighting the key role of the boron-oxygen core present in borinate esters for the potentiation function. However, dimesityl borinate ester, a 2-APB analogue with a terminal B-OH group showed an efficient inhibitory ability, without any potentiating capacity. The removal or addition of phenyl groups respectively decrease or increase the efficiency of the borinate esters to potentiate and inhibit the SOCE. mRNA expression revealed that Jurkat T cells mainly expressed Orai1, and were the more sensitive to 2-APB modulation of SOCE. CONCLUSIONS: This study allows the discovery of new boron-oxygen core containing compounds with the same ability as 2-APB to both potentiate and inhibit the SOCE of different leukocyte cell lines. These compounds could represent new tools to characterize the different types of SOCE and the first step in the development of new immunomodulators

Laser induced ultrafast combustion synthesis of solution-based AlOx for thin film transistors

Solution processing of amorphous metal oxides using excimer laser annealing (ELA) has been lately used as a viable option to implement large-area electronics, offering high quality materials at a reduced associated cost and process time. However, the research has been focused on semiconductor and transparent conductive oxide layers rather than on the insulator layer. In this work we present amorphous aluminum oxide (AlOx) thin films produced at low temperature (≤150 °C) via combustion synthesis triggered by ELA, for oxide thin film transistors (TFTs) suitable for manufacturing flexible electronics. The study showed that combining ELA and combustion synthesis leads to an improvement in the dielectric thin film's densification in a shorter time (≤15 min). Optimized dielectric layers were obtained combining a short drying cycle at 150 °C followed by ELA treatment. High breakdown voltage (4 MV cm−1) and optimal dielectric constant (9) was attained. In general, TFT devices comprising the AlOx fabricated with a drying cycle of 15 min followed by ELA presented great TFT properties, a high saturation mobility (20.4 ± 0.9 cm2 V−1 s−1), a small subthreshold slope (0.10 ± 0.01 V dec−1) and a turn-on voltage ∼0 V. ELA is shown to provide excellent quality solution-based high-κ AlOx dielectric, that surpass other methods, like hot plate annealing and deep ultraviolet (DUV) curing. The results achieved are promising and expected to be of high value to the printed electronic industry due to the ultra-fast film densification and the surface/area selective nature of ELA

Double-Stranded RNA Attenuates the Barrier Function of Human Pulmonary Artery Endothelial Cells

Circulating RNA may result from excessive cell damage or acute viral infection and can interact with vascular endothelial cells. Despite the obvious clinical implications associated with the presence of circulating RNA, its pathological effects on endothelial cells and the governing molecular mechanisms are still not fully elucidated. We analyzed the effects of double stranded RNA on primary human pulmonary artery endothelial cells (hPAECs). The effect of natural and synthetic double-stranded RNA (dsRNA) on hPAECs was investigated using trans-endothelial electric resistance, molecule trafficking, calcium (Ca2+) homeostasis, gene expression and proliferation studies. Furthermore, the morphology and mechanical changes of the cells caused by synthetic dsRNA was followed by in-situ atomic force microscopy, by vascular-endothelial cadherin and F-actin staining. Our results indicated that exposure of hPAECs to synthetic dsRNA led to functional deficits. This was reflected by morphological and mechanical changes and an increase in the permeability of the endothelial monolayer. hPAECs treated with synthetic dsRNA accumulated in the G1 phase of the cell cycle. Additionally, the proliferation rate of the cells in the presence of synthetic dsRNA was significantly decreased. Furthermore, we found that natural and synthetic dsRNA modulated Ca2+ signaling in hPAECs by inhibiting the sarco-endoplasmic Ca2+-ATPase (SERCA) which is involved in the regulation of the intracellular Ca2+ homeostasis and thus cell growth. Even upon synthetic dsRNA stimulation silencing of SERCA3 preserved the endothelial monolayer integrity. Our data identify novel mechanisms by which dsRNA can disrupt endothelial barrier function and these may be relevant in inflammatory processes

Phase stability of Fe-5at%Cr and Fe-10at%Cr films under Fe+ ion irradiation

This work is within the objective of understanding the effects caused to Fe–Cr alloys by fast Fe ion irradiation. As the penetration length of Fe ion is of the order of hundreds of nanometers, 70 nm Fe-5at%C and Fe-10at%Cr films were irradiated at room temperature with 490 keV Fe+ ions at increasing fluence corresponding to a maximum damage of 50 displacements per atom (dpa). In Fe-5at%Cr alloy the Cr solute concentration remains unaltered even after a damage of 50 dpa. In the 10at%Cr the Cr solute concentration is reduced, with the increase of damage, asymptotically to a value of 7.2 at%

Vaccinia Virus G8R Protein: A Structural Ortholog of Proliferating Cell Nuclear Antigen (PCNA)

BACKGROUND: Eukaryotic DNA replication involves the synthesis of both a DNA leading and lagging strand, the latter requiring several additional proteins including flap endonuclease (FEN-1) and proliferating cell nuclear antigen (PCNA) in order to remove RNA primers used in the synthesis of Okazaki fragments. Poxviruses are complex viruses (dsDNA genomes) that infect eukaryotes, but surprisingly little is known about the process of DNA replication. Given our previous results that the vaccinia virus (VACV) G5R protein may be structurally similar to a FEN-1-like protein and a recent finding that poxviruses encode a primase function, we undertook a series of in silico analyses to identify whether VACV also encodes a PCNA-like protein. RESULTS: An InterProScan of all VACV proteins using the JIPS software package was used to identify any PCNA-like proteins. The VACV G8R protein was identified as the only vaccinia protein that contained a PCNA-like sliding clamp motif. The VACV G8R protein plays a role in poxvirus late transcription and is known to interact with several other poxvirus proteins including itself. The secondary and tertiary structure of the VACV G8R protein was predicted and compared to the secondary and tertiary structure of both human and yeast PCNA proteins, and a high degree of similarity between all three proteins was noted. CONCLUSIONS: The structure of the VACV G8R protein is predicted to closely resemble the eukaryotic PCNA protein; it possesses several other features including a conserved ubiquitylation and SUMOylation site that suggest that, like its counterpart in T4 bacteriophage (gp45), it may function as a sliding clamp ushering transcription factors to RNA polymerase during late transcription

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