Oxygen non-stoichiometry of Nd1.85Ce0.15Cu1+δOy as a function of δ and its relation with the superconducting properties

Thermogravimetric measurements of the equilibrium oxygen partial pressure ( $P_{O_2 } $ ) as a function of the oxygen contenty were performed on Nd_1.85Ce_0.15Cu_1+δO_y samples with controlled Cu contents (1+δ=1.00, 1.01 and 1.02) at 1173 and 1237 K. The data obtained showed a dependence of the oxygen non-stoichiometry on the nominal Cu content. These measurements are discussed in terms of the presence of Cu defects in the T′ structure. The superconducting response of this material in samples with controlled oxygen and Cu contents was also studied. The superconducting response was found to be very sensitive to the presence of small amounts of cationic and anionic defects.     

Dynamics of moving agents with memory

The problem of emergence of collective behavior in a system of two dimensional interacting moving agents is considered. The individual agent architecture is hybrid in the sense that the response is reactive but the agent is capable to choose between two different rules in a probabilistic way: one rule depends on the information from the environment and the other depends on the information imprinted in the agents memory. The dynamics of the system is studied through the characterization of the equilibrium state and the non-equilibrium properties of the system.     

Mikrochemische Untersuchung von Lebensmitteln

Ohne Zusammenfassung     

Single-point imaging of vulcanized boundary in rubber

A single-point imaging-based method for broad-line analysis is presented. The technique is used for obtaining spectroscopic information of a two-component covulcanized rubber sample. A new noninvasive procedure allows for the discrimination of natural rubber and poly(styrene-cobutadiene) rubber components, resulting in chemical and mechanical characterization of the sample interface. On the basis of the space-resolved chemical shift weighted measurements a sharp interface of thickness less than 200 um was found. Spin-spin relaxation weighted profiles show a wider interface, with a gradual cross-link density change extended to about 500 μm over the natural-rubber component.     

Stability properties for solution operators

We study stability properties of certain evolution equations including the fractional Cauchy problem. Under some spectral assumptions these equations are governed either by a resolvent or a regularized resolvent or a k-convoluted semigroup. We investigate the long time behavior for bounded solutions by a direct application of the ergodic theorems for regularized resolvents of Lizama and Prado (J. Approx. Theory 122:42–61, 2003), Prado (Semigroup Forum 73:243–252, 2006). We apply our results to the qualitative study of the fractional diffusion-wave equation on L ^p (ℝ). The author is partially supported under FONDECYT Grant n^o 1070127.     

Scatter search for the fleet size and mix vehicle routing problem with time windows

This work proposes a scatter search (SS) approach to solve the fleet size and mix vehicle routing problem with time windows (FSMVRPTW). In the FSMVRPTW the customers need to be serviced in their time windows at minimal costs by a heterogeneous fleet. Computational results on 168 benchmark problems are reported. Computational testing revealed that our algorithm presented better results compared to other methods published in the literature.     

21α‐Fluoro‐7‐norvouacapane‐17β,21α‐lactone

The crystal structure of 21α‐fluoro‐7‐norvouacapane‐17β,21α‐lactone, C₂₀H₂₅FO₃, a new synthetic derivative of the diterpenoid 6α,7β‐di­hydroxy­vouacapan‐17β‐oic acid isolated from Pterodon polygalaeflorus Benth fruits, is described.     

氢原子在过渡金属修饰的Mg(0001)面扩散的第一性原理研究

基于密度泛函理论(DFY)的第一性原理计算方法,对氢原子在过渡金属(Sc、Ti、Cr、Mn、Fe、Co、Ni、Cu、V、Zn)修饰的Mg(0001)表面扩散性能进行了研究.研究发现过渡金属元素Sc、Ti、V、Cr、Mn、Fe、Co、Ni和Cu选择替代在镁表面第二层稳定,而Zn则选择替代在第一层稳定.当镁表面掺杂Zn和Cu时,氢原子选择停留在表面稳定;当掺杂Sc、Ti、V、Cr、Mn、Fe、Co和Ni时,氢原子选择进入镁块体内部.值得一提的是氢原子通过从过渡金属顶部通道扩散进入镁块体内部的势垒大大降低,笔者用差分电荷密度分析后发现氢原子与过渡金属原子成键使扩散势垒降低.当氢原子进入镁块体内部后靠近Sc、Ti、V、Cu和Zn原子时,将与这些过渡金属原子成键,从而阻碍了氢原子继续向内部扩散;而氢原子靠近Cr、Mn、Fe、Co、Ni原子时,选择离开过渡金属从而促进了氢原子向块体内扩散,可以大幅改善镁基储氢材料的吸氢动力性能.     

The increased termal stability associated with humic acid anchored onto silica gel

Commercial humic acid (HA) was anchored onto silica gel (SiAPTS) previously modified with 3-aminopropyltrimethoxysilane (APTS). HA was anchored onto SiAPTS through two routes: adsorption and covalent chemical immobilization onto the surface. The adsorption occurred by adding SiAPTS to HA in an aqueous solution, producing SiHA1, while chemical immobilization was performed by reacting HA suspended in N,N-dimethylformamide with SiAPTS, to yield SiHA2. The infrared spectra confirm HA immobilization using both procedures and the termogravimetric results showed that the anchored compounds have significantly thermal stability increased. While natural HA presents a thermal stability up to 200°C, the anchored compound presents a thermal stability near to 750°C. This revised version was published online in July 2006 with corrections to the Cover Date.