Showing papers by "Federal University of Roraima published in 2002"

Biting Indices, Host-seeking Activity and Natural Infection Rates of Anopheline Species in Boa Vista, Roraima, Brazil from 1996 to 1998

Abstract: The epidemiology of the transmission of malaria parasites varies ecologically. To observe some entomological aspects of the malaria transmission in an urban environment, a longitudinal survey of anopheline fauna was performed in Boa Vista, Roraima, Brazil. A total of 7,263 anophelines was collected in human bait at 13 de Setembro and Carana districts: Anopheles albitarsis sensu lato (82.8%), An. darlingi (10.3%), An. braziliensis (5.5%), An. peryassui (0.9%) and An. nuneztovari (0.5%). Nightly 12 h collections showed that An. albitarsis was actively biting throughout the night with peak activities at sunset and at midnight. An. darlingi bit during all night and did not demonstrate a defined biting peak. Highest biting indices, entomological inoculation rates and malaria cases were observed seasonally during the rainy season (April-November). Hourly collections showed host seek activity for all mosquitoes peaked during the first hour after sunset. An. darlingi showed the highest plasmodial malaria infection rate followed by An. albitarsis, An. braziliensis and An. nuneztovari (8.5%, 4.6%, 3% and 2.6%, respectively). An. albitarsis was the most frequently collected anopheline, presented the highest biting index and it was the second most frequently collected infected species infected with malaria parasites. An. albitarsis and An. darlingi respectively, are the primary vectors of malaria throughout Boa Vista.

Quality control of commercial tea by x-ray fluorescence

Abstract: Based on the energy-dispersive X-ray fluorescence (EDXRF) technique, the concentrations of elements (22 < Z < 30) were assessed in five kinds of commercial tea from six commercial suppliers: Matricaria chamomilla L. (camomile), Mentha piperita L. (mint), Cymbopogon citratus (DC) Stapf. (herb 'cidreira'), Malus domestica Borkh. (apple tea) and Camellia sinensis (L.) O. Kuntze (black tea). The samples were excited by an X-ray tube with an Mo anode (25 kV and 10 mA), with a Zr filter, and the characteristic X-ray were detected by an Si(Li) detector coupled to a multichannel analyzer. Using standard samples, the relationship between the detection limit and the atomic numbers of Fe, Co, Ni, Cu and Zn was determined. In some tea samples Ti was detected, but it is not an essential microelement for the plant growth. Fe, Ni and Cu were detected in all tea samples analyzed; Ti, Cr, Co and Zn were detected in Matricaria chamomilla and Malus domestica; Ti, Co and Zn in Mentha piperita and Ti, Mn, Co and Zn in Cymbopogon citratus. The inorganic constitution profile of this matrix type and the fingerprints in the production process can be evaluated by employing the EDXRF quality control of the commercial products.

Preliminary assays indicate that Antonia ovata (Loganiaceae) and Derris amazonica (Papilionaceae), ichthyotoxic plants used for fishing in Roraima, Brazil, have an insecticide effect on Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae)

Abstract: Laboratory-reared Lutzomyia longipalpis (Lutz and Neiva 1912) was tested with extracts of two ichthyotoxic plants, known as timbos, used as fishing poison in the Amazon. Phlebotomines, L. longipalpis, and plants, Antonia ovata and Derris amazonica, were collected in the Raposa-Serra do Sol Indian Reserve, a focus of visceral leishmaniasis in the State of Roraima, Brazil. Extracts were prepared from dried leaves of A. ovata and roots of D. amazonica that were percolated in water, filtered and dried out at 50°C. The solid extract obtained was diluted in water at 150, 200 and 250 mg/ml. The solution was blotted in filter paper placed at the bottom of cylindric glass tubes containing sand flies. For each plant extract and dilution, two series of triplicates with 5 male and 5 female specimens of L. longipalpis were used. Mortality was recorded every 2 h during 72 h of exposure. At 72 h the mortality was as high as 80% for extracts of A. ovata (LD50 = 233 mg/ ml), and 100% for D. amazonica (LD50 = 212 mg/ ml) whereas in the control groups maximum mortality never surpassed 13%. Preliminary assays indicated that A. ovata and D. amazonica displayed significant insecticide effect against L. longipalpis.

Thermogravimetric study about PVC-polyaniline blends

Abstract: By dissolution of PVC and polyaniline in dimethylformamide, a series of blends PVC-polyaniline were produced which were studied by scanning electron microscopy and thermogravimetry. Special attention is focused on the kinetic study of the thermal degradation steps by using non-isothermal thermogravimetric data. The results show that the thermal stability of the synthesized blend is decreased as the total amount of polyaniline is enhanced. Furthermore, the Brřnsted acid doped blend is more stable than the corresponding undoped one. PVC and the PVC-polyaniline blends exhibit two mass loss steps which activation energy values are in the range from 176 to 283 kJ mol-1 and 306 to 322 kJ mol-1, respectively.

A construção do espaço étnico roraimense, ou: os Taurepáng existem mesmo?

Abstract: Taking the publication - in 1989 and 1990 - of of two "historic-anthropological" booklets as an typically "orientalist" trial of the Diocese of Roraima to impose a "consensus" on Roraima society with relation to the "ethnic reality" of that state of Brazil, we reconstruct the history of the formation of that "consensus", starting in the 18th century, up to the decisive ethnography of Theodor Koch-Grunberg.

A calorimetric investigation into copper-arginine and copper-alanine solid state interactions

Abstract: Complexes of formula CuCl2 · 2arg and CuCl2 · 4ala (arg = arginine; ala = alanine) were prepared at room temperature by a solid state route. The metal–amino acid solid state interactions were studied by i.r. spectroscopy and solution calorimetry. For both complexes, participation of the carboxylate group as well as nitrogen in coordination are inferred, based on the i.r. data. For the copper–arginine compound, the calculated thermochemical parameters are: ΔrHm θ = −114.9 ± 1.42 and ΔfHm θ = −1608.3 ± 11.6 kJ mol−1. For copper–alanine compound, a complete set of thermochemical parameters were calculated: ΔrHm θ = −18.0 ± 0.9; ΔfHm θ = −2490.4 ± 4.3; ΔDHm θ = 597.2 ± 17.7; ΔMHm θ = 771.9 ± 18.7; ΔgHm θ = 627.1 ± 22.3 and 〈D〉 (Cu−L) = 156.8 ± 5.7 kJ mol−1. Based on ΔrHm θ and dissolution enthalpy values, a stronger intermolecular solid state interaction can be inferred for the arginine complex, than for the alanine one complex, probably due to the formation of intermolecular hydrogen bonds in the former.

Synthesis, characterization and a thermogravimetric study of copper, cobalt and tin mono- and bis-adducts with ethyleneurea, ethylenethiourea and propyleneurea

Abstract: This paper describes the synthesis, characterization and a thermogravimetric (t.g.) study of 11 adducts of general formula MCl2·nL (M = Cu, Co and Sn; n = 1 and 2 for Sn, and 2 for Cu and Co; L = ethyleneurea eu, ethylenethiourea etu, and propyleneurea pu). The i.r. results shows that the eu and pu adducts are coordinated through oxygen, whereas for etu nitrogen is the coordination site. The Δν(C=O) or Δν(C=S) trend is: Cu > Co > Sn. The t.g. curves show that the adducts release ligand molecules in a single mass loss step. As regards considering adducts with the same stoichiometry, the observed thermal stability trend is: etu > pu > eu.

A new experimental procedure to obtain titania powders as anatase phase by a sol-gel process

Abstract: Titania powders were synthesized by a sol-gel process using titanium tetrabutoxide as precursor. The syntheses were performed in water or in solutions of dimethylformamide (dmf) or dimethylsulfoxide (dmso). It is demonstrated, by X-ray diffraction patterns of the synthesized powders, that the samples obtained in dmf or dmso solutions are crystalline (anatase phase) with some minor amount of brookite phase, whereas the sample synthesized in water is amorphous. The anatase phase can be obtained independently of any previous or further treatment of the synthesized powder, such as hydrothermal or heat treatment, providing a new, simple, quick and inexpensive route to synthesize anatase powders. From the peak broadening of the anatase (101) diffraction, the crystallite sizes were calculated as 6 nm.

Scales of Basicity Based on Thermochemical Data of Adducts

Abstract: Using the values of standard molar enthalpy of reaction for dimethylethyleneurea (dmeu),dimethylformamide (dmf), dimethylacetamide (dma), tetramethylurea (tmu),hexamethylphosphoramide (hmpa) and pyridine (py) with the acids BF3, SbCl5, ZnCl2 and AsCl3, it is shown that, in terms of acid-base behaviour, ZnCl2 is closer to BF3, which differs from SbCl5. Furthermore, the equation −ΔrHm(ZnCl2) = − [1.26⋅ΔrHm(BF3)]−56.99 correlates with the standard molar enthalpy of reaction for the same set of molecules with ZnCl2 and BF3. A similar equation was obtained to estimate the enthalpy of reaction with AsCl3: −ΔrHm(AsCl3) = − [4.12⋅ΔrHm(BF3)]− 417.82. It is also shown that, for hmpa and tmu, sterical hindrance is a prominent factor that influences the coordination chemistry of the acidic centres, whose deviation from the linearity can be considered as a measure for the steric contribution to ΔrHm.

Thermogravimetric and differential scanning calorimetric investigations of manganese–glycine interactions

Abstract: Thermogravimetric (tg) and differential scanning calorimetric (dsc) data have been used to study metal–amino acid interactions in adducts of general formula MnCl2 · ngly (gly = glycine, n = 07, 20, 40 and 50) All the prepared adducts exhibit only a one step mass loss associated with the release of glycine molecules, except for the 07gly adduct, which exhibits two glycine mass loss steps From dsc data, the enthalpy values associated with the glycine mass loss can be calculated: MnCl2 · 07gly = 409 and 399 kJ mol−1, MnCl2 · 20gly = 216 kJ mol−1, MnCl2 · 40gly = 326 kJ mol−1 and MnCl2 · 50gly = 423 kJ mol−1, respectively The enthalpy associated with the ligand loss, plotted as function of the number of ligands for the n = 20, 40 and 50 adducts, gave a linear correlation, fitting the equation: ΔH (ligand loss)/kJ mol−1 = 67 × (number of ligands, n) + 76 A similar result was achieved when the enthalpy associated with the ligand loss was plotted as a function of the νa(COO−) bands associated with the coordination through the carboxylate group, 1571, 1575 and 1577 cm−1, respectively, for the n = 20, 40 and 50 adducts, giving the equation ΔH (ligand loss) /kJ mol−1 = 335 × νa(COO−) /cm−1 − 524185 This simple equation provides evidence for the enthalpy associated with the ligand loss being very closely related to the electronic density associated with the metal–amino acid bonds