Ultrafast extreme ultraviolet induced isomerization of acetylene cations

Ultrafast isomerization of acetylene cations ([HC=CH](+)) in the low-lying excited A(2)Σ(g)(+) state, populated by the absorption of extreme ultraviolet (XUV) photons (38 eV), has been observed at the Free Electron Laser in Hamburg, (FLASH). Recording coincident fragments C(+) + CH2(+) as a function of time between XUV-pump and -probe pulses, generated by a split-mirror device, we find an isomerization time of 52±15 fs in a kinetic energy release (KER) window of 5.8相似文献   

Shape Selectivity in Enol Thioether Synthesis Catalyzed by Zeolites

The competitive reaction catalyzed by solid acid catalyst between two cyclohexanones (1a) and (1b) with thiophenol (2) has been studied. No selectivity was observed with the lamellar montmorillonite in contrast with microporous aluminosilicates (zeolites) where shape selectivity was observed, in particularly when the zeolites were saturated by thiophenol (2) before a competitive reaction.     

Characterization of olive mill wastewater and gamma irradiation effects on some parameters of its composition

Journal of Radioanalytical and Nuclear Chemistry - Gamma irradiation was applied to olive mill wastewater and synthetic samples prepared from Gallic acid. The effects, generated on the...     

Decay property of regularity-loss type for solutions in elastic solids with voids

In this paper, we consider the Cauchy problem for a system of elastic solids with voids. First, we show that a linear porous dissipation leads to decay rates of regularity-loss type of the solution. We show some decay estimates for initial data in H^s(R)∩L¹(R)$H^s\left(\mathbb{R}\right)\cap L^1\left(\mathbb{R}\right)$. Furthermore, we prove that by restricting the initial data to be in H^s(R)∩L^1,γ(R)$H^s\left(\mathbb{R}\right)\cap L^{1,\gamma }\left(\mathbb{R}\right)$ and γ∈[0,1]$\gamma \in [0,1]$, we can derive faster decay estimates of the solution. Second, we show that by adding a viscoelastic damping term, then we gain the regularity of the solution and obtain the optimal decay rate.     

Existence and Asymptotic Behavior of the Wave Equation with Dynamic Boundary Conditions

The goal of this work is to study a model of the strongly damped wave equation with dynamic boundary conditions and nonlinear boundary/interior sources and nonlinear boundary/interior damping. First, applying the nonlinear semigroup theory, we show the existence and uniqueness of local in time solutions. In addition, we show that in the strongly damped case solutions gain additional regularity for positive times t>0. Second, we show that under some restrictions on the initial data and if the interior source dominates the interior damping term and if the boundary source dominates the boundary damping, then the solution grows as an exponential function. Moreover, in the absence of the strong damping term, we prove that the solution ceases to exists and blows up in finite time.     

A new criterion of optimization of the simple multipole coefficients in a modified Green’s function for the elastic two-dimensional case

The question of non-uniqueness in the integral formulation of an exterior boundary value problem in the elastic two-dimensional case has been resolved using the modified Green’s function technique. In this work, a new criterion of optimality based on the minimization of the norm of the kernel of the modified integral operator is established.     

A polynuclear coordination glutarate of lanthanum(III) with an uncommon cage feature

The title compound, tri­aqua­tris­(glutarato)­dilanthanum(III) dihydrate, {[La₂(C₅H₆O₄)₃(H₂O)₃]·2H₂O}_n, is the first re­ported glutarate coordination polymer of lanthanum(III) without a protonated ligand. The noteworthy features in the structure are, firstly, the unusual binuclear lanthanum cage formed by three bridging bonds through O atoms involved in different coordination modes and, secondly, the very rare `malonate' mode exhibited by a di­carboxyl­ate ligand with an alkyl chain of five C atoms. To our knowledge, this η⁷ chelation for the glutarate ligand has not been reported and was thought to be forbidden for steric reasons. The gauche–gauche conformation of the corresponding ligand favours cage formation, but trans geometries created along the ligating O atoms prevent cluster packing. The two independent La atoms are nine‐ and tenfold coordinated, leading to distorted one‐face‐sharing LaO₇(H₂O)₂ and LaO₉(H₂O) polyhedra, respectively. In the three‐dimensional framework, these asymmetric subunits are linked in a zigzag manner via one‐edge‐sharing LaO₉(H₂O) polyhedra and are connected by the carbon backbone chains of the ligands. The structure is very compact and, unlike many other reported di­carboxyl­ate lanthanides, connectivity between the two metal atoms and the three ligands yields a crystal packing with cavities accommodating two guest water mol­ecules but without an open framework.     

Study of the miscibility and the thermal degradation of PVC/PMMA blends

The aim of this paper is to study the miscibility and the thermal degradation of PVC/PMMA blends. For that purpose, blends of variable compositions from 0 to 100 wt% were prepared with and without plasticizer. Their physico-chemical characterization was carried out by differential scanning calorimetric analysis (DSC) and Fourier transform infrared spectroscopy (FTIR). Their thermal degradation under nitrogen at 185°C was studied and the HCl evolved from PVC was measured by the pH method. Degraded samples were characterized, after purification, by FTIR and UV-visible spectroscopy. The DSC analysis showed polymer miscibility up to 60 wt% of PMMA. This miscibility is due to a specific interaction of hydrogen bonding type between carbonyl groups (C=O) of PMMA and hydrogen from (CHCl) groups of PVC as evidenced by FTIR analysis. On the other hand, it was found that PMMA exerted a stabilizing effect on the thermal degradation of PVC by reducing the zip dehydrochlorination and by leading to the formation of short polyenes.