Nickel, iron-containing clay minerals from Niquelandia deposit, Brazil 2. Behaviour under reducing conditions

The reduction behavior of two Ni, Fe-rich dioctahedral smectite clays has been investigated by temperature-programmed reduction (TPR). For both clays, the reduction process of the transition metal elements occurs in two steps. At about 400 degrees C, Fe3+ is first reduced to Fe2+. At higher temperatures, further reduction of iron and reduction of nickel are achieved. Samples reduced at 400 degrees C and 700 degrees C have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Mossbauer spectroscopy (MS), and transmission electron microscopy (TEM). After a treatment at 700 degrees C, metallic particles deposited on the silicates has been evidenced by TEM and confirmed with the other techniques. (C) 2000 Elsevier Science B.V. All rights reserved

Nickel, iron-containing clay minerals from Niquelandia deposit, Brazil 1. Characterization

Two representative samples of Ni, Fe-containing clays from Niquelandia deposit, Colas, Brazil, have been characterized by different methods and techniques. X-ray diffraction (XRD) was used for the identification of the crystalline phases and to follow the structural modifications occurring upon thermal treatments. One of the samples (N4) is a pure smectite, while the second one (N7) is a mixture of 2:1 (smectite) and 1:1 (lizardite) phases. The thermoanalytical results [differential thermal analysis (DTA), thermogravimetric analysis (TGA)] are consistent with the XRD identification and the low nickel content of lizardite. Mossbauer spectroscopy data allow to assign most of the iron contents to two octahedral sites. From those results and the chemical analysis data, structural formulas of the smectite are proposed. Both clays are montmorillonite-type with appreciable Al for Si tetrahedral substitutions. (C) 2000 Elsevier Science B.V. All rights reserved

Surface area and microporosity of 1.8 nm pillared clays from the nitrogen adsorption isotherm

Nitrogen adsorption isotherms have been established over Al-, Ga-, and Ga-Al-pillared clays exhibiting 1.8 nm spacings and treated by the BET and Langmuir methods. It is shown that neither method yields a truly satisfying determination of the surface of pillared clays. This may be explained by the fact that multilayer adsorption required by the BET theory cannot occur within the micropores of these solids, whereas adsorption on the external surface is not ruled by the Langmuir equation. The external surfaces and micropore volumes have been determined by the t method. It is shown that the choice of the standard t function and the domain of the V-t curve considered for the linear fitting may influence the external surface and the micropore volume. A modified approach to treating the N-2 adsorption isotherm is proposed to establish the micropore volume and the external surface area of pillared clays. In this method, it is considered that (i) the BET theory is governing the adsorption on the external surface and (ii) the micropore volume is completely filled in the zone of validity of the BET method. This approach leads in the case of pillared clays to S-BET ext and C-BET ext values close to those obtained for non-pillared clays, and to micropore volumes consistent with those reported in the literature. For pillared clays with d(001) values near 1.8 nm, the micropore volume can be transformed into a microporous surface assuming that the adsorption on this surface is limited to a monolayer; the total surface area is obtained by summing up the microporous surface and S-BET ext. A comparison is made between the total surface calculated in this way and the surface obtained from the application of the BET and Langmuir methods on the experimental isotherm not corrected for the adsorption within the micropores

Words against injustices: a deep narrative analysis of energy cultures in poverty of Abuja, Mumbai and Rio de Janeiro

Slum rehabilitation housing (SRH) are critical transitional spaces in urban informality that has deep-rooted implications on poverty alleviation efforts. However, current literature reports systemic injustices in SRH on access to essential services, including energy injustices. This study investigated distributive injustices in the SRH across three cities, Abuja, Mumbai and Rio de Janeiro, developing ‘energy cultures’ narratives. It employed a computational social science methodology that used textual analysis, followed by a constructivist grounded theoretic approach to inform just policy design. The analysis was performed at two scales to identify and contrast injustices in the study areas. The result at an aggregated scale showed commonalities were around the poor design of the built environment, administrative lags of the utilities and high electricity bills. Case study-specific results showed that poverty penalties were linked with the energy cultures of each SRHs. In the Mumbai case, poverty penalties were associated with the aspirational purchase of household appliances due to move from slums to SRH. The Abuja case showed low power quality and load shedding frequently damaged appliances that increase the maintenance costs for the occupants. The Rio de Janeiro SRH case had injustices embedded through the adoption of inefficient appliances received as charity from higher-income households. Fuel stacking was also observed in the SRH that illustrated cultural identities associated with cooking energy. The conclusion was drawn to support just policy design by considering the socio-cultural context of the built environment, improving utility governance and promoting cleaner fuel mix at the household level

Assessment of chemiluminescence and PCR effectiveness in relation to conventional serological tests for the diagnosis of Chagas' disease Avaliação da eficiência da quimiluminescência e PCR em relação aos testes sorológicos convencionais para o diagnóstico da doença de Chagas

While testing 414 sera for the diagnosis of Chagas' disease, the conventional reactions of indirect hemagglutination, indirect immunofluorescence and the immunosorbent assay showed a sensitivity of 95.7%, 100% and 98.2% and a specificity of 98%, 98% and 96.4%, respectively, and an excellent association using Fisher's exact test. Chemiluminescence presented 100% sensitivity and 89.6% specificity, while PCR showed 100% specificity and 1.2% sensitivity. It is believed that the three conventional serological reactions are still adequate for diagnosing Chagas' disease.<br>No exame de 414 soros, para o diagnóstico da doença de Chagas, as reações convencionais de hemaglutinação indireta, imunofluorescência indireta e o ensaio imunoenzimático mostraram, respectivamente, uma sensibilidade de 95,7%, 100% e 98,2% e uma especificidade de 98%, 98% e 96,4% e excelente associação usando teste exato de Fisher. A quimioluminescência apresentou 100% de sensibilidade, 89,6% de especificidade e a PCR 100% de especificidade e 1,2% de sensibilidade. Acredita-se que as três reações sorológicas convencionais ainda são suficientes para o diagnóstico da doença de Chagas