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The possibility of exploiting a thermally-induced solid-state reaction to obtain the formation of a fluorene and TCNQ molecular complex was proposed by some of us (Kumar et al., Cryst. Growth Des., 2009, 9(8), 3396–3404). In this paper, we generalize and rationalize the approach to other charge transfer (CT) molecular complexes with naphthalene and anthracene, changing the size of the donor moiety to propose a general approach for the preparation of this class of materials by exploiting the solid-state synthesis method. Moreover, the kinetic features of the solid state reactions were fully elucidated by Raman spectroscopy and high resolution X-ray Powder Diffraction analysis (in situ Raman/XRPD), exploiting the Avrami equation in isothermal and non-isothermal conditions; rate constants, reaction orders and activation energies were obtained. All the three tested solid-state charge transfer (SS-CT) reactions obeyed a general rule, whereby the most apt reaction temperature was predicted. Finally, a method based on principal component analysis (PCA) for a fast kinetic analysis of in situ XRD synchrotron data was successfully developed, employing a formalism suitable for the analysis of non-isothermal reaction data, thus allowing a high throughput approach for the fast screening of the kinetics of parent reactions. PCA analysis was exploited as an alternative technique to obtain kinetic information in a faster and more efficient way, which can be used for online monitoring and/or in all those cases where Rietveld analysis is not feasible. [ABSTRACT FROM AUTHOR]

Chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) are emerging CO2 capture technologies that could reduce appreciably the costs associated with the capture of CO2. In CLC and CLOU, the oxygen required to combust a hydrocarbon is provided by a solid oxygen carrier. Among the transition metal oxides typically considered for CLC and CLOU, copper oxide (CuO) stands out owing to its high oxygen carrying capacity, exothermic reduction reactions and fast reduction kinetics. However, the low Tammann (sintering) temperature of CuO is a serious drawback. In this context, it has been proposed to support CuO on high Tammann temperature and low cost alumina (Al2O3), thus, reducing the morphological changes occurring over multiple CLC or CLOU redox cycles and stabilizing, in turn, the high activity of CuO. However, in CuO–Al2O3 systems, phase stabilization and avoiding the formation of the CuAl2O4 spinel is key to obtaining a material with a high redox stability and activity. Here, we report a Na+ doping strategy to phase stabilize Al2O3-supported CuO, yielding in turn an inexpensive material with a high redox stability and CO2 capture efficiency. We also demonstrate that doping CuO–Al2O3 with Na+ improves the oxygen uncoupling characteristics and coke resistance of the oxygen carriers. Utilizing in situ and ex situ X-ray absorption spectroscopy (XAS), the local structure of Cu and the reduction pathways of CuO were determined as a function of the Na+ content and cycle number. Finally, using 4-point conductivity measurements, we confirm that doping of Al2O3-supported CuO with Na+ lowers the activation energy for charge transport explaining conclusively the improved redox characteristics of the new oxygen carriers developed. [ABSTRACT FROM AUTHOR]

The reduction of a Re promoted Co/γ-Al2O3 catalyst was monitored in situ by synchrotron X-ray powder diffraction (XRPD) under H2 environment. Whole powder pattern analysis revealed a non-linear expansion of the unit cell of γ-Al2O3 during the reduction process, suggesting the diffusion of Co cations into the structure of the support. The non-linear cell expansion coincided with the formation of a CoO phase. In addition, space resolved diffraction at the inlet and the outlet of the reactor evidenced a negative effect of the partial pressure of indigenous H2O(g) on the reduction process. [ABSTRACT FROM AUTHOR]

The commercially dominating technology for hydrogen production (i.e. steam methane reforming) emits large quantities of CO2 into the atmosphere. On the other hand, emerging thermochemical water splitting cycles allow the production of a pure stream of H2 while simultaneously capturing CO2. From a thermodynamic point of view, the Fe2O3–Fe couple is arguably the most attractive candidate for thermochemical water splitting owing to its high H2 yield and H2 equilibrium partial pressure. However, the low reactivity of Fe2O3 with methane and the high activity of Fe for methane decomposition (leading to carbon deposition and in turn COx poisoning of the H2 stream) are major drawbacks. Here, we report the development of MgAl2O4-stabilized, Cu-modified, Fe2O3-based redox materials for thermochemical water-splitting that show a high reactivity towards CH4 and low rates of carbon deposition. To elucidate the effect of Cu doping on reducing significantly the rate of carbon deposition (while not affecting negatively the high redox activity of the material) extended X-ray absorption fine structure spectroscopy and energy dispersive X-ray spectroscopy was employed. [ABSTRACT FROM AUTHOR]

New in situ Raman and synchrotron X-ray diffraction data (between 300 and 400 K) in conjunction with separate temperature-dependent Raman data (between 7 and 400 K) are presented. The low-frequency Raman spectra show good agreement with theoretical values obtained previously using periodic DFT calculations. The temperature-dependent spectra reveal the presence of significant anharmonicity of librational modes neither predicted theoretically nor noted in previous experiments. The splitting of the internal deformation mode υ2 (of E symmetry in the free ion) decreases continuously with increasing temperature, but drops abruptly at the first-order orthorhombic to hexagonal phase transition observed at 381 K. The temperature dependence of the linewidth of the internal deformation mode υ2 reveals coupling to reorientational motions of the borohydride ion in the orthorhombic phase. The thermal evolution of both crystal structure and vibration frequencies agree with the phase diagram suggested by the Landau theory. [ABSTRACT FROM AUTHOR]

Using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) we have studied the electronic properties of a novel, planar, metal semiconductor contact. For this purpose we take advantage of the unique properties of the Pt-modified Ge(001) surface, which consist of coexisting metallic and semiconducting terraces. Spatially resolved STS measurements reveal that the higher lying metallic terraces induce electronic states in the band gap region of the lower lying semiconducting terraces. [ABSTRACT FROM AUTHOR]

To evaluate senile gait patterns in octagenarians and nonagenarians, we provided a standardized questionnaire on gait disabilities to 153 elderly subjects over 88 years of age. Subjects represented a relatively healthy subgroup of noninstitu-tionalized residents who participated in a gerontological survey of all inhabitants of the city of Leiden who were 85 years of age or older. Of the 142 subjects who responded to this questionnaire, 87 persons (61 %) claimed distinct diseases as a cause of gait impairment. Forty-two of the remaining 55 persons were investigated neurologically and received a standardized assessment of gait. Twenty-five persons (18% of all responders) had a completely normal gait, whereas a wide spectrum of gait abnormalities—mainly with ataxic features—was encountered in the remaining persons. It is concluded that a surprisingly high number of very old community residents can have a completely normal gait. Gait disorders in this age group are most frequently associated with common distinct diseases. In addition, many elderly have a gait disturbance of variable clinical nature and unclear pathologic basis, which may represent the “idiopathic senile gait.”U Geriatr Psychiatry Neurol 1992;5:78–84). [ABSTRACT FROM PUBLISHER]

Discusses the thermal expansion and phase purity of commercial magnesium diboride. Comparison of peak widths of Alfa Aesar and Pfalz and Bauer samples; Influence of starting composition, impurities, microstructure and defects on the structural and superconducting properties of magnesium boride.

The article presents the response of the author to the comments given by some anthropologists regarding his article "Dogon Restudied." According to the author, the comments of the anthropologists indicate that the problem of Dogon ethnography is significant in Africanist anthropology. The author advocates the argument raised by Peter Ian Crawford that the films on Dogon culture constitute one of the high points in visual anthropology.

Hybrid perovskites form an emerging family of exceptional light harvesting compounds. However, the mechanism underpinning their photovoltaic effect is still far from understood, which is impeded by a lack of clarity on their structures. Here we show that iodide ions in the methylammonium lead iodide migrate via interstitial sites at temperatures above 280 K. This coincides with temperature dependent static distortions resulting in pseudocubic local symmetry. Based on bond distance analysis, the migrating and distorted iodines are at lengths consistent with the formation of I2 molecules, suggesting a 2I−→I2+2e− redox couple. The actual formula of this compound is thus (CH3NH3)PbI3−2x(I2)x where x∼0.007 at room temperature. A crucial feature of the tetragonal structure is that the methylammonium ions do not sit centrally in the A-site cavity, but disordered around two off-centre orientations that facilitate the interstitial ion migration via a gate opening mechanism. [ABSTRACT FROM AUTHOR]

Examines the prevalence of subjective dysphagia in community residents aged over 87 years old in Leiden, Netherlands. Implications of dysphagia for social and physical health; Increase of the prevalence of dysphagia with age; Severity of dysphagia in elderly people.