Ether‐Soluble Cu53 Nanoclusters as an Effective Precursor of High‐Quality CuI Films for Optoelectronic Applications

An effective strategy is developed to synthesize high‐nuclearity Cu clusters, [Cu₅₃(RCOO)₁₀(C≡CtBu)₂₀Cl₂H₁₈]⁺ ( Cu₅₃ ), which is the largest Cu^I/Cu⁰ cluster reported to date. Cu powder and Ph₂SiH₂ are employed as the reducing agents in the synthesis. As revealed by single‐crystal diffraction, Cu₅₃ is arranged as a four‐concentric‐shell Cu₃@Cu₁₀Cl₂@Cu₂₀@Cu₂₀ structure, possessing an atomic arrangement of concentric M₁₂ icosahedral and M₂₀ dodecahedral shells which popularly occurs in Au/Ag nanoclusters. Surprisingly, Cu₅₃ can be dissolved in diethyl ether and spin coated to form uniform nanoclusters film on organolead halide perovskite. The cluster film can subsequently be converted into high‐quality CuI film via in situ iodination at room temperature. The as‐fabricated CuI film is an excellent hole‐transport layer for fabricating highly stable CuI‐based perovskite solar cells (PSCs) with 14.3 % of efficiency.     

A rapid technique to determine the internal area function of finite-length ducts using maximum length sequence analysis

This paper describes a rapid technique for reconstruction of the internal area function of a duct using blockage-induced eigenvalue shifts determined from eigenfrequencies measured under two sets of duct termination boundary conditions. A single broad band maximum length sequence (MLS) measurement of short duration is utilized to obtain the transfer function of the duct, which in turn can be utilized to determine its eigenvalue shifts and subsequently its internal area function using an inverse perturbation technique. The reconstruction results display the same order of accuracy as those obtained previously using swept sine measurements of extended duration. An expression for the determination of the area function is presented utilizing resonant frequency information alone, thus rendering duct length determination unnecessary. A computational routine further simplifies the process such that the accuracy of the technique could be ascertained for a range of configurations including longer ducts and ducts that initially have nonuniform internal cross section over their length. Development of a relationship between obstacle length and wavelength of the lowest eigenfrequency required for successful reconstruction is also described. This is an important result for longer ducts where measurement of lower eigenfrequencies may present problems using standard measurement equipment.     

Measuring gravitational effect of superintense laser by spin-squeezed Bose—Einstein condensates interferometer

We consider an extremely intense laser, enclosed by an atom interferometer. The gravitational potential generated from the high-intensity laser is solved from the Einstein field equation under the Newtonian limit. We compute the strength of the gravitational force and study the feasibility of measuring the force by the atom interferometer. The intense laser field from the laser pulse can induce a phase change in the interferometer with Bose-Einstein condensates. We push up the sensitivity limit of the interferometer with Bose-Einstein condensates by spin-squeezing effect and determine the sensitivity gap for measuring the gravitational effect from intense laser by atom interferometer.     

Distribution of animal population fluctuations

We show that the fluctuations of a variety of animal (insect, mammal and fish) populations are well-modeled by stable (Lévy) distributions, a family of distributions which includes the Gaussian. Our findings together with the finding [A.P. Allen, B.-L. Li, E.L. Charnov, Ecol. Lett. 4 (2001) 1-3] that bird population fluctuations are well-modeled by Gaussian distributions suggest the hypothesis that, in general, animal population fluctuations are well-modeled by stable distributions. If the hypothesis is confirmed, the stable law for the distribution of animal population fluctuations would be useful for animal population modeling, prediction and management.     

Observation of green emission from Ce-doped gadolinium oxide nanoparticles

Green emission at around 500 nm is observed in Gd₂O₃:Ce³⁺ nanoparticles and the intensity is highly dependent on the concentration of Ce³⁺ in the nanoparticles. The luminescence of this emission displays both picosecond (ps) and millisecond (ms) lifetimes. The ms lifetime is over four orders of magnitude longer than typical luminescence lifetimes (10-40 ns) of Ce³⁺ in traditional Ce³⁺ doped phosphors and therefore likely originates from defect states. The picosecond lifetime is shorter than the typical Ce³⁺ value and is also likely due to defect or surface states. When the samples are annealed at 700 °C, this emission disappears possibly due to changes in the defect moieties or concentration. In addition, a blue emission at around 430 nm is observed in freshly prepared Gd₂O₃ undoped nanoparticles, which is attributed to the stabilizer, polyethylene glycol biscarboxymethyl ether. On aging, the undoped particles show similar emission to the doped particles with similar luminescence lifetimes. When Eu³⁺ ions are co-doped in Gd₂O₃:Ce nanoparticles, both the green emission and the emission at 612 nm from Eu³⁺ are observed.     

Dynamic response in a poro-elastic ground induced by a moving air pressure

A steady-state theory is worked out for the dynamic response of a saturated poro-elastic ground to pressure distribution travelling along the ground surface. A boundary layer approximation is applied to Biot's equations for two phases. Sample result for supersonic, transonic and subsonic loads are presented.     

Cluster of clusters: Structural rules for vertex-sharing icosahedral supraclusters

Structural rules for supraclusters based on vertex-sharing icosahedra are developed. These simple rules are useful in elucidating the structural relationships of these clusters of clusters.     

Propagation-Dispersion Equation

A propagation-dispersion equation is derived for the first passage distribution function of a particle moving on a substrate with time delays. The equation is obtained as the hydrodynamic limit of the first visit equation, an exact microscopic finite difference equation describing the motion of a particle on a lattice whose sites operate as time-delayers. The propagation-dispersion equation should be contrasted with the advection-diffusion equation (or the classical Fokker–Planck equation) as it describes a dispersion process in time (instead of diffusion in space) with a drift expressed by a propagation speed with non-zero bounded values. The temporal dispersion coefficient is shown to exhibit a form analogous to Taylor's dispersivity. Physical systems where the propagation-dispersion equation applies are discussed.