Future contributions to Journal of chemical crystallograpy

Future contributions to Journal of chemical crystallograpy     

XPS study of the supported phase — SiO2 interaction in Mo/SiO2 and CoMo/SiO2 hydrodesulphurization catalysts in their oxidic precursor form

XPS results on two series of catalysts, namely Mo/SiO₂ and CoMo/SiO₂ in the oxidic form, are reported. In the first series the molybdenum oxide content deposited on SiO₂ ranges from 2.8 to 20.6 weight %. The second series was obtained by cobalt impregnation of the first series; in this case the atomic ratio Co/(Co + Mo) was fixed at 0.36.XPS binding energy and intensities measurements enable estimation of the interaction and dispersion between the oxide phase and the support to be made.In the case of molybdenum deposited alone on the support, the binding energies of the Mo and O levels both increase with MoO₃ content. When cobalt is also present on the support, the binding energies of the Mo and O levels remain constant. The relative intensities I_Mo/I_Si and I_Co/I_Si remain constant up to 12% active phase and then drastically increase for higher amounts of oxide.These results confirm the existence of a relatively strong Mo/SiO₂ interaction. This interaction is substantially weaker when Co is supported on the MoSiO₂ solid, leading to the formation of CoMoO₄ at the expense of the Mo/SiO₂ interaction. Furthermore, it is shown that at high content of oxide the active phase is deposited on the outer surface of the particle and not inside the pores.     

TiO2在Al2O3表面上分散状态的AEM研究

本文运用AEM方法考察了制备技术对TiO_2在Al_2O_3表面分散状态的影响. 发现嫁接法可使TiO_2非常均匀地分散在Al_2O_3表面上, 浸渍法也能得到较为均匀的TiO_2分布, 而沉淀法所得到的TiO_2分散度较差. TiO_3只聚集在Al_20_3表面上的局部区域。     

Large deviations for Langevin spin glass dynamics

Summary We study the asymptotic behaviour of asymmetrical spin glass dynamics in a Sherrington-Kirkpatrick model as proposed by Sompolinsky-Zippelius. We prove that the annealed law of the empirical measure on path space of these dynamics satisfy a large deviation principle in the high temperature regime. We study the rate function of this large deviation principle and prove that it achieves its minimum value at a unique probability measureQ which is not markovian. We deduce that the quenched law of the empirical measure converges to _Q . Extending then the preceeding results to replicated dynamics, we investigate the quenched behavior of a single spin. We get quenched convergence toQ in the case of a symmetric initial law and even potential for the free spin.     

Random Matrices and Complexity of Spin Glasses

We give an asymptotic evaluation of the complexity of spherical p‐spin spin glass models via random matrix theory. This study enables us to obtain detailed information about the bottom of the energy landscape, including the absolute minimum (the ground state), and the other local minima, and describe an interesting layered structure of the low critical values for the Hamiltonians of these models. We also show that our approach allows us to compute the related TAPcomplexity and extend the results known in the physics literature. As an independent tool, we prove a large deviation principle for the k^th‐largest eigenvalue of the Gaussian orthogonal ensemble, extending the results of Ben Arous, Dembo, and Guionnet. © 2012 Wiley Periodicals, Inc.     

Mössbauer emission spectroscopy of an unsupported cobalt-molybdenum hydrodesulfurization catalyst

A new internal standard method coupled with the standard addition method for PIXE analysis has been developed. In its basic principle, this method is characterized by that a suitable element present initially in the sample is used as an internal standard, and further the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample contains W_a g of trace element A to be determined together with an element B which is usable as an internal standard, and when the comparative standard is prepared by adding an exactly known amount of element A, W _a ^* g, to the duplicated sample, the absolute concentration of W_a can easily be determined by the following equation even if the above sample and comparative standard are irradiated separately by a different number of protons W_a=W _a ^* /[(R^*/R)-1] where R and R^* are ratios of net photopeak counts due to the characteristic X-rays from the element A and B in the irradiated sample and comparative standard, respectively. The usefulness of the method was examined through determination of Cu, Zn, Rb and Sr in two biological materials, such as spinach and orchard leaves. As a result, this method was demonstrated to be sensitive, highly reproducible and reasonably accurate.     

A key to progress: Identification of the state of catalysts during the catalytic reaction

We stress the importance of identifying the state in which catalysts are during the catalytic reaction. Catalysts as prepared do not correspond to the real working catalyst. Several examples will be recalled, and a new one (Mo-Te-O catalyst) will be mentioned. In a more detailed way, it will be shown that the working state of MoO₃ is Mo_xO_3x-2 with 8 ≤x≤18. The pitfalls encountered when focusing on catalysts as prepared (as opposed to catalysts “as they work”) is illustrated in the case of mixed Sb_xMo_yO_z oxides which decompose spontaneously during the reaction.     

Laplace asymptotics for reaction-diffusion equations

Summary We obtain sharp (i.e. non logarithmic) asymptotics for the solution of non homogeneous Kolmogorov-Petrovski-Piskunov equation depending on a small parameter , for points ahead of the Freidlin-KPP front.     

The arcsine law as a universal aging scheme for trap models

We give a general proof of aging for trap models using the arcsine law for stable subordinators. This proof is based on abstract conditions on the potential theory of the underlying graph and on the randomness of the trapping landscape. We apply this proof to aging for trap models on large, two‐dimensional tori and for trap dynamics of the random energy model on a broad range of time scales. © 2006 Wiley Periodicals, Inc.     

Effect of hydrolysis degree and mass molecular weight on the structure and properties of PVA films

In this work, we aim to analyze the variation of structural, thermal, and dielectric properties of polyvinyl alcohol (PVA) films by varying the molecular weight (Mw) and the hydrolysis degree (HD). The XRD study revealed the improvement of the crystallinity degree by the increase of HD or the decrease of Mw. The DSC study showed the decrease of the molecular mobility with the increase of either the hydrolysis degree or the molecular weight. The dielectric measurements showed four dielectric processes attributed to electrode/sample polarization, α _a-relaxation, α _c-relaxation, and β-relaxation. The activation energy attributed to α _a-relaxation and α _c-relaxation, increase with the increase of the molecular weight Mw, and the decrease of HD. The Ac conductivity is well fitted to the universal Jonsher law in the frequency range where the electrode/sample polarization can be neglected.