Production and characterization of activated carbon from wood wastes

Cedarwood (Cedrela Angustifolia) and teak (Tectona Grandis) woods are typically used for furniture manufacture because they have high durability, are light and easy to work. During these manufacturing process, large amount of these wastes is generated causing disposal environmental problems. In this paper, the residual wastes (sawdust) of Cedar (C) and Teak (T) are transformed into an activated material. The chemical composition of both biomass (C and T) was determinate by TGA (Thermogravimetric Analysis). Activated materials were characterized in surface area following the BET (Brunauer, Emmett and Teller) method, morphology using SEM (Scanning Electron Microscopy) and to know their functional groups a FTIR (Fourier Transform Infrared Spectroscopy) analysis was done. Their adsorption capacity was evaluated by removal of Methylene Blue (MB) and Congo Red (CR) from aqueous solutions. © Published under licence by IOP Publishing Ltd

Valence-electron transfer and a metal-insulator transition in a strongly correlated perovskite oxide

We present transport and thermal data for the quadruple-perovskites MCu3(Ti1-xRux)4O12 where 0 < x < 1. A metal-insulator transition (MIT) occurs for Ru concentrations x~0.75. At the same time, the Cu2+ antiferromagnetic state is destroyed and it's magnetic entropy suppressed by Ru on a 1:1 basis. This implies that each Ru transfers an electron to a Cu ion and thus the MIT correlates with filling the Cu 3d shell. The Cu spin entropy in this strongly correlated electron material provides a unique probe among MIT systems.Comment: 15 pages, 4 figures, 1 tabl

Combining Indexing Schemes to Accelerate Querying XML on Content and Structure

This paper presents the advantages of combining multiple document representation schemes for query processing of XML queries on content and structure. We show how extending the Text Region approach [2] with the main features of the Binary Relation approach developed in [8] leads to a considerable speed-up in the processing of the XPath location steps. We detail how, by using the combined scheme, we reduce the number of structural joins used to process the XPath steps, while simultaneously limiting the amount of memory usage. We discuss optimisation strategies enabled by the new `combined representation scheme'. Experiments comparing the efficiency of alternative query processing strategies on a subset of the queries used at INEX 2003 (the Initiative for the Evaluation of XML Retrieval [4]) demonstrate a favourable performance for the combined indexing scheme

XML and Context: Structural Features Relevant to Search Tasks

We describe ongoing research into the relationship between search tasks and information retrieval strategies with respect to the use of structural information. We define a classification of search tasks in structured document collections and analyse the relevance of different structural features regarding each of these tasks for the INEX collection. The results presented show important differences in relevance of different features such as size and type of the components regarding informational and resource tasks

The Kagome-staircase lattice: Magnetic ordering in Ni3V2O8 and Co3V2O8

Ni3V2O8 and Co3V2O8 have spin-1 and spin-3/2 magnetic lattices that are a new anisotropic variant of the Kagome net, wherein edge-sharing MO6 octahedra form the rises and rungs of a "Kagome staircase". The anisotropy largely relieves the geometric frustration, but results in rich magnetic behavior. Characterization of the magnetization of polycrystalline samples reveals that the compounds are ferrimagnetic in character. Heat capacity measurements show the presence of four magnetic phase transitions below 9 K for Ni3V2O8 and two below 11 K for Co3V2O8. Comparison to the low temperature heat capacity of isostructural nonmagnetic Zn3V2O8 provides an estimate of the magnetic entropy involved with the phase transitions. The results suggest that Co3V2O8 may display magnetic transitions below 2 K.Comment: 9 pages, 5 figure

Finite-Temperature Transition into a Power-Law Spin Phase with an Extensive Zero-Point Entropy

We introduce an $xy$ generalization of the frustrated Ising model on a triangular lattice. The presence of continuous degrees of freedom stabilizes a {\em finite-temperature} spin state with {\em power-law} discrete spin correlations and an extensive zero-point entropy. In this phase, the unquenched degrees of freedom can be described by a fluctuating surface with logarithmic height correlations. Finite-size Monte Carlo simulations have been used to characterize the exponents of the transition and the dynamics of the low-temperature phase

The Kagome Antiferromagnet with Defects: Satisfaction, Frustration, and Spin Folding in a Random Spin System

It is shown that site disorder induces noncoplanar states, competing with the thermal selection of coplanar states, in the nearest neighbor, classical kagome Heisenberg antiferromagnet (AFM). For weak disorder, it is found that the ground state energy is the sum of energies of separately satisfied triangles of spins. This implies that disorder does not induce conventional spin glass behavior. A transformation is presented, mapping ground state spin configurations onto a folded triangular sheet (a new kind of ``spin origami'') which has conformations similar to those of tethered membranes.Comment: REVTEX, 11 pages + 3 pictures upon reques

Order induced by dipolar interactions in a geometrically frustrated antiferromagnet

We study the classical Heisenberg model for spins on a pyrochlore lattice interacting via long range dipole-dipole forces and nearest neighbor exchange. Antiferromagnetic exchange alone is known not to induce ordering in this system. We analyze low temperature order resulting from the combined interactions, both by using a mean-field approach and by examining the energy cost of fluctuations about an ordered state. We discuss behavior as a function of the ratio of the dipolar and exchange interaction strengths and find two types of ordered phase. We relate our results to the recent experimental work and reproduce and extend the theoretical calculations on the pyrochlore compound, Gd$_2$Ti$_2$O$_7$, by Raju \textit{et al.}, Phys. Rev. B {\bf 59}, 14489 (1999).Comment: 5 pages, 5 figures, AMSLaTe

Surface features in video retrieval

This paper assesses the usefulness of surface features in a multimedia retrieval setting. Surface features describe the metadata or structure of a document rather than the content. We note that the distribution of these features varies across topics. The paper shows how these distributions can be obtained through relevance feedback and how this allows for adaptation of (content-based) search results for topic or user preference. An analysis of the distribution of surface features in the TRECVID collection indicates that they are potentially useful, and a preliminary feedback experiment confirms that exploiting surface features can improve retrieval effectiveness