A new adamantanecarboxylate coordination polymer: poly[[(μ3‐adamantane‐1,3‐dicarboxylato)aquadioxidouranium(VI)] monohydrate]

The title compound, {[U(C₁₂H₁₄O₄)O₂(H₂O)]·H₂O}_n, is the first actinide complex featuring adamantanecarboxylate ligands. The metal ion possesses a pentagonal–bipyramidal UO₇ coordination involving two axial oxide ligands [U—O = 1.732 (5) and 1.764 (5) Å] and five equatorial O atoms [U—O = 2.259 (5)–2.494 (4) Å] of aqua and carboxylate ligands. The latter display pseudo‐chelating and bridging coordination modes of the carboxylate groups that are responsible for the generation of the centrosymmetric discrete uranium–carboxylate [UO₂(μ‐RCOO)₂UO₂] dimers [U...U = 5.5130 (5) Å] and their connection into one‐dimensional chains. Hydrogen bonding involving two coordinated and two solvent water molecules [O...O = 2.719 (7)–2.872 (7) Å] yields centrosymmetric (H₂O)₄ ensembles and provides noncovalent linkage between the coordination chains to generate a three‐dimensional network structure.     

Hydrogen Production by Water Dissociation in Surface‐Modified BaCoxFeyZr1−x−yO3−δ Hollow‐Fiber Membrane Reactor with Improved Oxygen Permeation

A porous perovskite BaCo_xFe_yZr_0.9?x?yPd_0.1O_3?δ (BCFZ‐Pd) coating was deposited onto the outer surface of a BaCo_xFe_yZr_1?x?yO_3?δ (BCFZ) perovskite hollow‐fiber membrane. The surface morphology of the modified BCFZ fiber was characterized by scanning electron microscopy (SEM), indicating the formation of a BCFZ‐Pd porous layer on the outer surface of a dense BCFZ hollow‐fiber membrane. The oxygen permeation flux of the BCFZ membrane with a BCFZ‐Pd porous layer increased 3.5 times more than that of the blank BCFZ membrane when feeding reactive CH₄ onto the permeation side of the membrane. The blank BCFZ membrane and surface‐modified BCFZ membrane were used as reactors to shift the equilibrium of thermal water dissociation for hydrogen production because they allow the selective removal of the produced oxygen from the water dissociation system. It was found that the hydrogen production rate increased from 0.7 to 2.1 mL H₂ min^?1 cm^?2 at 950 °C after depositing a BCFZ‐Pd porous layer onto the BCFZ membrane.     

Two Distinct Mechanisms of Alkyne Insertion into the Metal–Sulfur Bond: Combined Experimental and Theoretical Study and Application in Catalysis

The present study reports the evidence for the multiple carbon–carbon bond insertion into the metal–heteroatom bond via a five‐coordinate metal complex. Detailed analysis of the model catalytic reaction of the carbon–sulfur (C? S) bond formation unveiled the mechanism of metal‐mediated alkyne insertion: a new pathway of C? S bond formation without preliminary ligand dissociation was revealed based on experimental and theoretical investigations. According to this pathway alkyne insertion into the metal–sulfur bond led to the formation of intermediate metal complex capable of direct C? S reductive elimination. In contrast, an intermediate metal complex formed through alkyne insertion through the traditional pathway involving preliminary ligand dissociation suffered from “improper” geometry configuration, which may block the whole catalytic cycle. A new catalytic system was developed to solve the problem of stereoselective S? S bond addition to internal alkynes and a cost‐efficient Ni‐catalyzed synthetic procedure is reported to furnish formation of target vinyl sulfides with high yields (up to 99 %) and excellent Z/E selectivity (>99:1).     

C m -Approximation by Polyanalytic Polynomials on Compact Subsets of the Complex Plane

Several necessary and sufficient conditions on C ^m -approximability of functions on compact subsets of the complex plane by polyanalytic polynomials are obtained. The resulting conditions for approximation are of the topological nature.     

AgGaS2- and Al-doped GaSe Crystals for IR Applications

We report a systematic study of AgGaS₂- and Al-doped GaSe crystals in comparison with pure GaSe and S-doped GaSe crystals. AgGaS₂-doped GaSe (GaSe:AgGaS₂) crystal was grown by Bridgman technique from the melt of GaSe:AgGaS₂ (10.6 wt.%). Its real composition was identified as GaSe:S (2 wt.%). Al-doped GaSe (GaSe:Al) crystals were grown from the melt of GaSe and 0.01, 0.05, 0.1, 0.5, 1, 2 mass % of aluminium. Al content in the grown crystals is too small to be measured. The hardness of GaSe:S (2 wt.%) crystal grown from the melt of GaSe:AgGaS₂ is 25% higher than that of GaSe:S (2 wt.%) crystal grown by a conventional S-doping technique and 1.5- to 1.9-times higher than that of pure GaSe. GaSe:Al crystals are characterized by 2.5- to 3-times higher hardness than that of pure GaSe and by extremely low conductivity of ≤ 10^− 7 Om^− 1 cm^− 1. A comparative experiment on SHG in AgGaS₂-, Al-, S-doped GaSe and pure GaSe is carried out under the pumps of 2.12-2.9 μm fs OPA and 9.2−10.8 μm ns CO₂ laser. It was found that GaSe:S crystals possess the best physical properties for mid-IR applications among these doped GaSe crystals. GaSe:Al crystals have relatively low conductivity which have strong potential for THz application.     

General method for determining the masses of semi-invisibly decaying particles at hadron colliders

We present a general solution to the long-standing problem of determining the masses of pair-produced, semi-invisibly decaying particles at hadron colliders. We define two new transverse kinematic variables M(CT)(⊥) and M(CT)(∥), which are suitable one-dimensional projections of the contransverse mass M(CT). We derive analytical formulas for the boundaries of the kinematically allowed regions in the (M(CT)(⊥),M(CT)(∥)) and (M(CT)(⊥),M(CT)) parameter planes and introduce suitable variables D(CT)(∥) and D(CT) to measure the distance to those boundaries on an event per event basis. We show that the masses can be reliably extracted from the end-point measurements of M(CT)(⊥)(max) and D(CT)(min) (or D(CT)(∥)(min)). We illustrate our method with dilepton tt events at the LHC.     

A wet chemical preparation of transparent conducting thin films of Al-doped ZnO nanoparticles

A wet chemical deposition method for preparing transparent conductive thin films on the base of Al-doped ZnO (AZO) nanoparticles has been demonstrated. AZO nanoparticles with a size of 7 nm have been synthesised by a simple precipitation method in refluxed conditions in ethanol using zinc acetate and Al-isopropylate. The presence of Al in ZnO was revealed by the EDX elemental analysis (1.8 at.%) and UV–Vis spectroscopy (a blue shift due to Burstein–Moss effect). The obtained colloid solution with the AZO nanoparticles was used for preparing by spin-coating thin films on glass substrates. The film demonstrated excellent homogeneity and transparency (T > 90%) in the visible spectrum after heating at 400 °C. Its resistivity turned to be excessively high (ρ = 2.6 Ω cm) that we ascribe to a poor charge percolation due to a high film porosity revealed by SEM observations. To improve the percolation via reducing the porosity, a sol–gel solution was deposited “layer-by-layer” in alternation with layers derived from the AZO colloid followed by heating. As it was shown by optical spectroscopy measurements, the density of thus prepared film was increased more than twice leading to a significant decrease in resistivity to 1.3 × 10⁻² Ω cm.     

Experimental study of resistive bistability in metal oxide junctions

We have studied resistive bistability (memory) effects in junctions based on metal oxides, with a focus on sample-to-sample reproducibility, which is necessary for the use of such junctions as crosspoint devices of hybrid CMOS/nanoelectronic circuits. Few-nm-thick layers of NbO _x , CuO _x and TiO _x have been formed by thermal and plasma oxidation, at various deposition and oxidation conditions, both with and without rapid thermal post-annealing. The resistive bistability effect has been observed for all these materials, with particularly high endurance (over 10³ switching cycles) obtained for single-layer TiO₂ junctions, and the best reproducibility reached for multi-layer junctions of the same material. Fabrication optimization has allowed us to improve the OFF/ON resistance ratio to about 10³, but the sample-to-sample reproducibility is so far lower than that required for large-scale integration.     

Signal beating elimination using single-mode fiber to multimode fiber coupling

We experimentally demonstrate an all-passive fiber-based approach to prevent undesired beating during signal merging and detection. Beating occurs when optical signals of very close or the same wavelength are combined at a coupler and detected using a photodetector. Our approach is based on signal coupling from several single-mode fibers to a single piece of multimode fiber without interference, such that different signals propagate in different modes with different spatial positions inside the multimode fiber. We have investigated signal beating when the signals are coherent, partially coherent, or incoherent with each other. The measured results for single-mode to multimode coupling show signal beating is substantially reduced, resulting in widely opened eye diagrams and error-free bit error rate performance.     

Ionization penalty in nonlinear Raman neuroimaging

Light-assisted ionization accompanying coherent anti-Stokes Raman scattering (CARS) of ultrashort laser pulses in brain tissue is shown to manifest itself in a detectable blueshift of the anti-Stokes signal. This blueshift can serve as an indicator of ionization processes in CARS-based neuroimaging.