Analytical solutions for the subsidiary maxima in multiple slit interference

Optical Review - We present analytical solutions for the subsidiary maxima in multiple slit interference up to eleven slits. For the number of slits N, there exist $$N-2$$ subsidiary maxima between...     

Dual Sulfide–Disulfide Crosslinked Networks with Rapid and Room Temperature Self‐Healability

Polymer‐based crosslinked networks with intrinsic self‐repairing ability have emerged due to their built‐in ability to repair physical damages. Here, novel dual sulfide–disulfide crosslinked networks (s‐ssPxNs) are reported exhibiting rapid and room temperature self‐healability within seconds to minutes, with no extra healing agents and no change under any environmental conditions. The method to synthesize these self‐healable networks utilizes a combination of well‐known crosslinking chemistry: photoinduced thiol‐ene click‐type radical addition, generating lightly sulfide‐crosslinked polysulfide‐based networks with excess thiols, and their oxidation, creating dynamic disulfide crosslinkages to yield the dual s‐ssPxNs. The resulting s‐ssPxN networks show rapid self‐healing within 30 s to 30 min at room temperature, as well as self‐healing elasticity with reversible viscoelastic properties. These results, combined with tunable self‐healing kinetics, demonstrate the versatility of the method as a new means to synthesize smart multifunctional polymeric materials.

     

Abnormal adsorption behavior of dimethyl disulfide on gold surfaces

Adsorption of dimethyl disulfide (DMDS) on gold colloidal nanoparticle surfaces has been examined to check its binding mechanism. Differently from previous results, DMDS molecules adsorbed on the gold surface at high concentration showed the S–S stretching band at 500 cm⁻¹ in surface-enhanced Raman scattering (SERS) spectra, which indicates the presence of intact adsorption of DMDS molecules. However, it was found that the S–S bond of disulfides was easily cleaved on the gold surface at low concentration. These behaviors were not observed for diethyl disulfide (DEDS) or diphenyl disulfide (DPDS). Our results indicate that DMDS molecules with the shortest alkyl chains on the gold surface can be inserted into self-assembled monolayers (SAMs) without the S–S bond cleavage during self-assembly due to insufficient lateral van der Waals interaction and the low adsorption activity of disulfides, whereas DEDS with longer alkyl chains or DPDS with the weak disulfide bond dissociation energy would not. These unusual DMDS adsorption behaviors were examined by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). We also compared the bonding dissociation energy of the S–S bonds of various disulfides by means of a density functional theory (DFT) calculation.     

Electrode performance and X-ray absorption spectroscopy of La0.8Sr0.2Mn1−x Cu x O3 (0 ≤ x ≤ 0.2)–GDC composite cathodes for SOFCs

Electrochemical properties of composite cathodes consisting of La_0.8Sr_0.2Mn_1?x Cu _x O₃ (LSMCu, 0?≤?x?≤?0.2) and Ce_0.8Gd_0.2O_2?x (GDC) were determined by impedance spectroscopy, and conduction mechanism for the composite cathodes was investigated by a near-edge X-ray absorption fine-structure analysis (NEXAFS). LSMCu–GDC cathodes showed lower polarization resistance (R _p) than LSM–GDC up to 750 °C, whereas they exhibited better performance at higher temperature (≥800 °C). The best performance was achieved with the LSMCu10–GDC cathode: 0.27 and 0.08?Ω cm² at 800 °C and 850 °C, respectively. NEXAFS and refinement results confirmed that Cu doping caused the oxidation of Mn³⁺ to Mn⁴⁺ and lattice contraction. This additional Mn⁴⁺ can lead to the formation of oxygen vacancies when Mn⁴⁺ is converted to Mn³⁺ at relatively high temperatures (above 600 °C). This in turn contributes to improved oxygen ion transport in LSM. The LSMCu–GDC composite cathode can thus be considered a suitable potential cathode for SOFC applications.     

Blue Luminescence of Dendrimer‐Encapsulated Gold Nanoclusters

Direct evidence for the blue luminescence of gold nanoclusters encapsulated inside hydroxyl‐terminated polyamidoamine (PAMAM) dendrimers was provided by spectroscopic studies as well as by theoretical calculations. Steady‐state and time‐resolved spectroscopic studies showed that the luminescence of the gold nanoclusters consisted largely of two electronic transitions. Theoretical calculations indicate that the two transitions are attributed to the different sizes of the gold nanoclusters (Au₈ and Au₁₃). The luminescence of the gold nanoclusters was clearly distinguished from that of the dendrimers.     

CoMnO2-Decorated Polyimide-Based Carbon Fiber Electrodes for Wire-Type Asymmetric Supercapacitor Applications

In this work, we report the carbon fiber-based wire-type asymmetric supercapacitors (ASCs). The highly conductive carbon fibers were prepared by the carbonized and graphitized process using the polyimide (PI) as a carbon fiber precursor. To assemble the ASC device, the CoMnO₂-coated and Fe₂O₃-coated carbon fibers were used as the cathode and the anode materials, respectively. Herein, the nanostructured CoMnO₂ were directly deposited onto carbon fibers by a chemical oxidation route without high temperature treatment in presence of ammonium persulfate (APS) as an oxidizing agent. FE-SEM analysis confirmed that the CoMnO₂-coated carbon fiber electrode exhibited the porous hierarchical interconnected nanosheet structures, depending on the added amount of APS, and Fe₂O₃-coated carbon fiber electrode showed a uniform distribution of porous Fe₂O₃ nanorods over the surface of carbon fibers. The electrochemical properties of the CoMnO₂-coated carbon fiber with the concentration of 6 mmol APS presented the enhanced electrochemical activity, probably due to its porous morphologies and good conductivity. Further, to reduce the interfacial contact resistance as well as improve the adhesion between transition metal nanostructures and carbon fibers, the carbon fibers were pre-coated with the Ni layer as a seed layer using an electrochemical deposition method. The fabricated ASC device delivered a specific capacitance of 221 F g⁻¹ at 0.7 A g⁻¹ and good rate capability of 34.8% at 4.9 A g⁻¹. Moreover, the wire-type device displayed the superior energy density of 60.2 Wh kg⁻¹ at a power density of 490 W kg⁻¹ and excellent capacitance retention of 95% up to 3000 charge/discharge cycles.     

Spectroscopic investigation on the electronic structure of a 5d band insulator SrHfO3 in proximity to ferroelectric instability: Comparison with SrTiO3 and SrZrO3

We investigated the high-energy electronic structure of a 5d perovskite SrHfO₃ by using optical spectroscopy and O 1s x-ray absorption spectroscopy. From the combined spectra the values of electronic structure parameters are estimated properly. In particular, the crystal field splitting energy, which is closely associated with the p–d hybridization strength, is as high as ～5 eV, and the Sr 4d bands appear to be strongly mixed with the Hf 5d bands. These findings are discussed in relation to a possible ferroelectric instability in SrHfO₃, and are compared with electronic properties of similar compounds, 3d SrTiO₃ and 4d SrZrO₃.     

Observational constraints on decaying vacuum dark energy model

The decaying vacuum model (DV), treating dark energy as a varying vacuum, has been studied well recently. The vacuum energy decays linearly with the Hubble parameter in the late-times, ρ _Λ (t)∝H(t), and produces the additional matter component. We constrain the parameters of the DV model using the recent data-sets from supernovae, gamma-ray bursts, baryon acoustic oscillations, CMB, the Hubble rate and X-rays in galaxy clusters. It is found that the best fit of the matter density contrast Ω _m in the DV model is much lager than that in ΛCDM model. We give the confidence contours in the Ω _m –h plane up to 3σ confidence level. Besides, the normalized likelihoods of Ω _m and h are presented, respectively.     

Spin-orbital pattern dependent polaron absorption in manganites

We systematically investigated optical properties of Nd1-xSrxMnO3 single crystals ( x = 0.40, 0.50, 0.55, and 0.65). They are similar in their spin-orbital (SO) disordered states at room temperature. At low temperature, the crystals enter into various SO ordered states, i.e., F-, CE-, A-, and C-type orderings, and their mid-infrared absorptions become quite different. The remarkable variation can be explained by polaron dynamics which depend on the ordering patterns. This SO pattern dependent polaron model can also explain the pseudo CE-type ordering case, demonstrating that this scheme can explain the carrier dynamics in complex SO configurations.     

Complete condensation in a zero range process on scale-free networks

We study a zero range process on scale-free networks in order to investigate how network structure influences particle dynamics. The zero range process is defined with the rate p(n) = n(delta) at which particles hop out of nodes with n particles. We show analytically that a complete condensation occurs when delta < or = delta(c) triple bond 1/(gamma-1) where gamma is the degree distribution exponent of the underlying networks. In the complete condensation, those nodes whose degree is higher than a threshold are occupied by macroscopic numbers of particles, while the other nodes are occupied by negligible numbers of particles. We also show numerically that the relaxation time follows a power-law scaling tau approximately L(z) with the network size L and a dynamic exponent z in the condensed phase.