National Institutes of Science and Technology

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National Institutes of Science and Technology

Brazil

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Silva J.,Federal University of Viçosa | Mello J.W.V.,Federal University of Viçosa | Mello J.W.V.,National Institutes of Science and Technology | Gasparon M.,University of Queensland | And 4 more authors.
Water Research | Year: 2010

The geochemical fates of Fe and As are so closely correlated that methods of As removal from contaminated water are in general based on the high affinity of this metalloid for Fe (hydr)oxides. Dissimilatory Fe reducing bacteria, however, play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments. The potential of Al-goethites in adsorbing As(V) compared with hematite, goethite, ferrihydrite, and gibbsite, and the stability of As retained by the Fe compounds under anoxic conditions were investigated in this study. The (hydr)oxides were synthesised, and adsorption isotherms and As(V) adsorption maxima at different pH were measured. Arsenic loaded samples were anaerobically incubated in the presence of Shewanella putrefaciens, and periodically sampled to evaluate the contents of soluble As and Fe. The As(V) adsorption maxima decreased in the following order: Fh > AlGt 13 > AlGt 20 > AlGt 23 > Gb > Hm > Gt. In terms of surface area, Gb, Gt, and Hm showed higher As(V) loading capacity than Fh, suggesting available reactive sites not fully occupied by arsenate on Fh. The same hypothesis can be considered for Al-goethites, as they showed even lower arsenate loading capacity per surface area. The presence of structural Al in the goethites enhanced considerably the As uptake capacity and stability under reducing conditions. Therefore, the Al-goethites showed good potential as adsorbents to remove As from water. S. putrefaciens cells were able to utilise both noncrystalline and crystalline Fe (hydr)oxides as electron acceptors, releasing As into solution. Al-goethites showed a decrease in Fe and As mobilisation as structural Al increased. © 2010 Elsevier Ltd.


Khandpekar M.M.,Material Research Labs | Pati S.P.,National Institutes of Science and Technology
Advanced Materials Research | Year: 2012

This paper presents an attempt to synthesize, categorize, and analyze LaF3: Ce3+, Pr3+, and Sm3+ doped (LCPS) nano crystals. The synthesis follows an aqueous route and uses a microwave heating technique ensuring uniform molarities of component rare earth elements. A low power range choice exercised ensures that phase formation was appropriate. The synthesis process lasted for about an hour. X ray diffraction pattern confirmed the hexagonal phase of the synthesized nano crystals. TEM analysis indicated an average particle size of 20 nm. The FTIR spectral analysis indicates blue florescence when excited with 254 nm radiation. UV-VIS spectral analysis indicates a band gap of 5. 00 eV. EDAX spectra indicated presence of rare earth elements in the synthesized nano crystals. © (2012) Trans Tech Publications, Switzerland.


Khandpekar M.M.,Material Research Labs | Pati S.P.,National Institutes of Science and Technology
Advanced Materials Research | Year: 2012

LaF3 nanocrystals doped with lanthanides like Ce3+, Pr3+ and Nd3+ have been prepared using microwave technique. These synthesized crystals have been characterized by X-ray powder diffraction. Well dispersed, elongated, nanorods of hexagonal geometry (approximately 20nm in size) have been found in TEM analysis. The average particle size estimated from XRD analysis is about 20 nm. Similar results for the average size are observed from TEM studies. Four characteristic peaks one at 3434 cm-1 (broad) and other at 2924, 2853, 1632 cm-1(sharp) have been observed in the FTIR spectra. Intense Blue colour (458 nm) emission has been recorded when crystals are excited with photons of wavelength 254 nm. Non Linear Optical (NLO) properties of the synthesized nanocrystals have been studied. It has been found that second harmonic generation (SHG) efficiency of the prepared samples containing rare earth elements is less than pure Potassium dihydrogen phosphate (KDP) crystals. © (2012) Trans Tech Publications, Switzerland.


E Silva M.,Federal University of Minas Gerais | Moreira P.,Federal University of Minas Gerais | Da Costa G.,Federal University of Viçosa | Saraiva A.,Federal University of Minas Gerais | And 9 more authors.
Oral Diseases | Year: 2013

Objective: Susceptibility to and severity of periodontal disease is influenced by gene polymorphisms related to the immune response. Co-stimulatory molecules, such as CD28 and CTLA-4, are critical in the development of such responses. Our hypothesis is that polymorphisms in genes that code for these molecules may be associated with periodontitis. The aim of the study was to investigate the association between +17 (T/C) CD28 and +49 (A/G) CTLA-4 gene polymorphisms and periodontitis in Brazilians. Materials and methods: Genomic DNA was obtained from oral swabs of 424 individuals categorized into three groups (control group, aggressive, and chronic periodontitis) considering clinical parameters such as probing depth and clinical attachment loss. The genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism. Results: There was an association between the T- genotype of the CD28 polymorphism and aggressive periodontitis (P = 0.04). Moreover, the A+ genotype for CTLA-4 was associated with greater clinical attachment loss in non-smokers with aggressive periodontitis (P = 0.006, OR = 16.25, CI = 2.25-117.11). Conclusions: These findings show that T- in CD28 + 17 (T/C) and the A+ in CTLA-4 +49 (A/G) genotypes are associated with susceptibility to aggressive periodontal disease. Thus, our study highlights these polymorphisms as potential genetic susceptibility markers of periodontitis in Brazilians. © 2012 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.


Muller K.,University of Management and Technology | Muller K.,Federal University of Minas Gerais | Muller K.,National Institutes of Science and Technology | Ciminelli V.S.T.,Federal University of Minas Gerais | And 4 more authors.
Water Research | Year: 2010

The sorption of the arsenite (AsO 3 3-) and the arsenate (AsO 4 3-) ions and their conjugate acids onto iron oxides is one of main processes controlling the distribution of arsenic in the environment. The present work intends to provide a large vibrational spectroscopic database for comparison of As(III) and As(V) speciation in aqueous solutions and at the iron oxide - solution interface. With this purpose, ferrihydrite, feroxyhyte, goethite and hematite were firstly synthesized, characterized in detail and used for adsorption experiments. Raman spectra were recorded from As(III) and As(V) aqueous solutions at various pH conditions selected in order to highlight arsenic speciation. Raman Scattering and Diffuse Reflectance Infrared Fourier Transform (DRIFT) studies were carried out to examine the respective As-bonding mechanisms. The collected data were curve-fitted and discussed according to molecular symmetry concepts. X-ray Absorption Near Edge Spectroscopy (XANES) was applied to confirm the oxidation state of the sorbed species. The comprehensive spectroscopic investigation contributes to a better understanding of arsenic complexation by iron oxides. © 2010 Elsevier Ltd.

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