Polarization-sensitive detectors at 120–500 GHz are required for the observation of the cosmic microwave background radiation. In this paper, superconducting thin films based on Ti/TiN bilayers are ...developed to be integrated as electromagnetic wave absorbers in suspended cooled silicon bolometers. The critical temperature (
T
c
) is tuned in the range of 600–800 mK through the superconductivity proximity effect between Ti and TiN to optimize the absorption of the incident power while minimizing the heat capacity of the system at low temperature. Ti/TiN bilayer samples are fabricated on silicon with two different thicknesses (100/5 and 300/5 nm). Electrical characterizations at low temperature have been performed and revealed the effect of thermal annealing (20–250 °C) on residual stress,
T
c
, critical magnetic field (
H
c
) and resistance above
T
c
. A physical characterization by X-ray photoelectron spectroscopy provides evidences of oxidized states which may explain these effects.
Wedelolactone and nine coumestan analogues were synthesized and a structure–activity relationship performed for their effect as inhibitors of kidney Na+,K+-ATPase and ligands for the central ...benzodiazepine receptor.
Coumestans 2a–i, bearing different patterns of substitution in A- and D-rings, were synthesized and evaluated as inhibitors of kidney Na+,K+-ATPase and ligands for the central benzodiazepine (BZP) receptor. The presence of a hydroxyl group in position 2 favours the effect on Na+,K+-ATPase but decreases the affinity for the BZP receptor, allowing the design of more selective molecules than the natural wedelolactone. On the other hand, the presence of a catechol in ring D is important for the effect on both molecular targets.
The molecular mechanism involved in Na
+,K
+-ATPase inhibition by 2-methoxy-3,8,9-trihydroxy coumestan (PCALC36) was investigated. The results suggest that this compound irreversibly oxidizes ...important sulfydryl groups of the enzyme, explaining its poor selectivity toward other P-type ATPases.
The molecular mechanisms involved in Na
+,K
+-ATPase inhibition by 2-methoxy-3,8,9-trihydroxy coumestan were investigated. We show that this compound decreases the free sulfydryl groups present in the enzyme and that its inhibitory effect is prevented by dithiothreitol and other two sulfydryl containing reagents. We propose a redox cycle culminating with the irreversible oxidation of sulfydryl groups essential for the catalytic activity of this enzyme and of two other related P-type ATPases.
We report results on hexagonal-shaped microlasers formed from two-dimensional photonic crystals (PCs) using InP-based materials transferred and bonded onto SiO/sub 2// Si wafers. Two types of ...hexagonal cavities are investigated : single defect (one hole missing) cavities, so-called H1 cavities (1 /spl mu/m in diameter) and two holes missing per side H2 cavities (2 /spl mu/m in diameter). Their optical properties are analyzed using photoluminescence experiments, and plane wave method simulations have been performed for comparison. High Q modes (/spl sim/600/700) have been measured and they have been shown to enable laser effect at room temperature, under pulsed optical pumping (15% duty cycle and 25-ns pulsewidth). The study of these efficient mode characteristics gives guidance for further improvement of the operation conditions of PC lasers, such as the reduction of the threshold pumping power.
Single-mode waveguides for GRAVITY Perraut, K.; Jocou, L.; Berger, J. P. ...
Astronomy and astrophysics (Berlin),
06/2018, Volume:
614
Journal Article
Peer reviewed
Open access
Context.
Within the framework of the second-generation instrumentation of the Very Large Telescope Interferometer of the European Southern Observatory we have developed the four-telescope beam ...combiner in integrated optics.
Aims.
We optimized the performance of such beam combiners, for the first time in the near-infrared
K
band, for the GRAVITY instrument dedicated to the study of the close environment of the galactic centre black hole by precision narrow-angle astrometry and interferometric imaging.
Methods.
We optimized the design of the integrated optics chip and the manufacturing technology as well, to fulfil the very demanding throughput specification. We also designed an integrated optics assembly able to operate at 200 K in the GRAVITY cryostat to reduce thermal emission.
Results.
We manufactured about 50 beam combiners by silica-on-silicon etching technology. We glued the best combiners to single-mode fluoride fibre arrays that inject the VLTI light into the integrated optics beam combiners. The final integrated optics assemblies have been fully characterized in the laboratory and through on-site calibrations: their global throughput over the
K
band is higher than 55% and the instrumental contrast reaches more than 95% in polarized light, which is well within the GRAVITY specifications.
Conclusions.
While integrated optics technology is known to be mature enough to provide efficient and reliable beam combiners for astronomical interferometry in the
H
band, we managed to successfully extend it to the longest wavelengths of the
K
band and to manufacture the most complex integrated optics beam combiner in this specific spectral band.
Bufadienolides are structurally related to the clinically relevant cardenolides (e.g., digoxin) and are now considered as endogenous steroid hormones. Binding of ouabain to Na(+)-K(+)-ATPase has been ...associated, in kidney cells, to the activation of the Src kinase pathway and Na(+)-K(+)-ATPase internalization. Nevertheless, whether the activation of this cascade also occurs with other cardiotonic steroids and leads to diuresis and natriuresis in the isolated intact kidney is still unknown. In the present work, we perfused rat kidneys for 120 min with bufalin (1, 3, or 10 μM) and measured its vascular and tubular effects. Thereafter, we probed the effect of 10 μM 3-(4-chlorophenyl)1-(1,1-dimethylethyl)-1H-pyrazolo3,4-dpyrimidin-4amine (PP2), a Src family kinase inhibitor, and 1,4-diamino-2,3-dicyano-1,4-bis2-aminophenylthio butadiene (UO126), a highly selective inhibitor of both MEK1 and MEK2, on bufalin-induced renal alterations. Bufalin at 3 and 10 μM profoundly increased several parameters of renal function in a time- and/or concentration-dependent fashion. At a concentration that produced similar inhibition of the rat kidney Na(+)-K(+)-ATPase, ouabain had a much smaller diuretic and natriuretic effect. Although bufalin fully inhibited the rat kidney Na(+)-K(+)-ATPase in vitro, its IC(50) (33 ± 1 μM) was threefold higher than the concentration used ex vivo and all its renal effects were blunted by PP2 and UO126. Furthermore, the phosphorylated (activated) ERK1/2 expression was increased after bufalin perfusion and this effect was totally prevented after PP2 pretreatment. The present study shows for the first time the direct diuretic, natriuretic, and kaliuretic effects of bufalin in isolated rat kidney and the relevance of Na(+)-K(+)-ATPase-mediated signal transduction.
CEA has a long history of customizing optoelectronic components for space and astronomy applications. With this expertise we are undertaking a development of cooled silicon bolometers for millimeter ...(mm) wave polarization detection, typically at λ=1.5 mm, in order to address the next generation of space astronomy missions. This work presents the early results on the design and fabrication of an innovative pixel operating at very low temperature between 50 and 100 mK. This pixel is using a Ti/TiN thin film absorber and an ion-implanted silicon thermometer which exhibits a very small heat capacity and a very low 1/f noise at low temperature. This sensor is implemented on a standard SOI substrate. We performed a 2D process simulation of the silicon thermometer and an electromagnetic simulation of the pixel absorption to obtain good performances at low temperature. We present R(T) electrical characterizations of simplified silicon thermometers at low temperature showing a variable range hopping (VRH) model dominating effect. The model prediction shows a good agreement with experimental results.
The SmartCut process was first developed to obtain Si-on-insulator (SOI) materials. Now an industrial process, the main Unibond SOI-structure trends are reported. Many material combinations can be ...achieved by this process, because it appears to enable the generic development of new structures. Several of the new structures combining different materials and different bonding layers are described. These include SiGe and strained-Si films onto an oxidized Si wafer, Si-on-insulating multilayer (SOIM) structures, and InP or 4H-SiC film transfers onto low-cost substrates via metallic or even refractory conductive-film bonding layers. More recently, an original bonding process based on mark patterning, wafer bonding, and layer transfer has been proposed to obtain structures in which the relative crystalline-axis orientations of both the film and the substrate can be controlled accurately. In this case, a SmartCut process that includes a mark-patterning step appears well suited for precise control of axis orientations. A procedure is described to obtain an ultra-thin Si film bonded onto a Si wafer. An example of a pure screw dislocation network achieved by the mark patterning, bonding, and layer transfer process is reported in this paper. The results have important implications for nanostructure development. 20 refs.
We report on 2D photonic crystal InP membrane micro-lasers transferred onto a silicon wafer. Two types of lasers are investigated: microcavities and defect-free structures, exploiting either ...conventional defect modes, or DFB-like modes. Room temperature low threshold laser operation has been performed for low sized devices.
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