Tail asymptotics for dependent subexponential differences

We study the asymptotic behavior of ?(X ? Y > u) as u → ∞, where X is subexponential, Y is positive, and the random variables X and Y may be dependent. We give criteria under which the subtraction of Y does not change the tail behavior of X. It is also studied under which conditions the comonotonic copula represents the worst-case scenario for the asymptotic behavior in the sense of minimizing the tail of X ? Y. Some explicit construction of the worst-case copula is provided in other cases.     

A novel approach for lignin modification and degradation

We report on a novel approach, the integration of the photochemical and electrochemical oxidation, for the modification and degradation of kraft lignin, where the Ta₂O₅–IrO₂ thin film was used as the electrocatalyst and the TiO₂ nanotube arrays were used as the photocatalyst. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the fabricated catalysts. A UV–Vis spectroscopy was used to monitor the processes of the photochemical and/or electrochemical degradation of lignin. The modified lignin was characterized using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy, while the intermediates produced during the photoelectrochemical process were analyzed by high-performance liquid chromatography (HPLC). Our study has demonstrated that the innovative approach described in this communication provides a promising and energy efficient, environmentally friendly method for lignin modification and degradation.     

Synthesis of silsesquioxanes based in (3-methacryloxypropyl)-trimethoxysilane using methacrylate monomers as reactive solvents

The polycondensation of (3-methacryloxypropyl)-trimethoxysilane in acidic conditions using different methacrylate monomers as reactive solvents resulted in incompletely condensed methacrylate-functionalized silsesquioxanes with a very large fraction of intramolecular cycles. UV-MALDI-TOF-MS analysis demonstrated that the species present after 2 weeks of reaction at 60 °C were: T₆(OH)₂, T₇(OH), T₈(OH)₂, T₉(OH), T₁₀(OH)₂ and T₁₁(OH). Analysis of samples after 30 months of storage at room temperature revealed the presence of T₁₂(OH)₂ and T₁₃(OH) species. The absence of higher molar mass oligomers after prolonged storage periods is attributed to dilution of the reacting medium, which discourages bimolecular reactions that lead to polymer growth. ²⁹Si NMR spectroscopy showed that the conversion in the polycondensation reaction was in the range 0.91-0.96. The methacrylate monomers are not involved in the hydrolysis-condensation reactions with MPTMS and therefore can be polymerized by thermal or photochemical means, thereby cross-linking the preformed nanosized cagelike silsesquioxanes. The formulations containing silsesquioxanes showed a markedly reduced content of extractable monomer after photopolymerization, which makes these resins very attractive for dental filling materials.     

Effect of rare fluctuations on the thermalization of isolated quantum systems

We consider the question of thermalization for isolated quantum systems after a sudden parameter change, a so-called quantum quench. In particular, we investigate the prerequisites for thermalization, focusing on the statistical properties of the time-averaged density matrix and of the expectation values of observables in the final eigenstates. We find that eigenstates, which are rare compared to the typical ones sampled by the microcanonical distribution, are responsible for the absence of thermalization of some infinite integrable models and play an important role for some nonintegrable systems of finite size, such as the Bose-Hubbard model. We stress the importance of finite size effects for the thermalization of isolated quantum systems and discuss two scenarios for thermalization.     

Sequential Surface Modification of Au Nanoparticles: From Surface‐Bound AgI Complexes to Ag0 Doping

Gold nanoparticles (Au NPs) with tailor‐made structures and properties are highly desirable for applications in catalysis and sensing. In this context, surface modifications of Au NPs are of particular relevance. Herein, we present a sequential surface modification of Au NPs with Ag^I coordination complexes, which can be converted into Ag⁰‐doped Au NPs by simple ligand‐exchange reaction. The key innovative element of this surface modification is a multifunctional bioxazoline‐based ligand that brings coordinated Ag^I into close proximity to the particle surface.