Reaction of a model siderophore with Ni(II), Co(II) and Zn(II) in aqueous solution: Kinetics and spectroscopy

A spectroscopic study was performed showing that the [Fe(III)(L(2-))(2)](1-) (L(2-) = dopacatecholate) complex reacts with Ni(II), Co(II) and Zn(II) in an aqueous solution containing S(2)O(3)(2-) resulting in the soluble [M(L(1-))(3)](1-) (L(1-) = dopasemiquinone; M = Ni(II), Co(II) or Zn(II) complex species. The Raman and IR spectra of the [CTA][M(L(1-))(3)] complexes, CTA hexadecyltrimethylammonium cation, in the solid state were obtained. The kinetic constants for the metal substitution reactions were determined at four different temperatures, providing values for Delta W(not equal) Delta S(not equal) and Delta G(not equal). The reactions were slow (k = 10(-1)1 M s(-1)) and endothermic. The system investigated can be considered as a simplified model to explain some aspects of siderophore chemistry. (c) 2007 Elsevier Inc. All rights reserved.

Adsorption of 4-aminopyridine on Co and Ag electrodes probed by SERS

The adsorption of 4-aminopyridine (4-AP) on Co and Ag electrodes in acid or alkaline solutions of KCl and KI electrolyte salts were monitored by the Surface-enhanced Raman Spectroscopy (SERS) technique. The SERS intensity for the Ag electrode was in 2 orders of magnitude higher than for the Co electrode, due to the enhancement of the Raman cross-section on Ag by the surface-plasmon excitation. In acidic chloride medium (pH 4), the SERS results for Ag electrodes indicate that the protonated form of 4-AP (4-APH(+)) adsorbs in the potential range of -0.1 to -0.6 V (Ag broken vertical bar AgCl broken vertical bar KCl sat) through hydrogen-bonding between 4-APH(+) and Cl(-) adsorbed on the electrode surface: at more negative potentials the neutral form 4-AP is the predominant adsorbed species. For Co electrode in the same medium, only bands due to neutral 4-AP were observed in the spectra at -0.8 and -0.9 V. For more negative potentials bands assigned to both 4-AP and 4-AP surface complex are observed, with the lasts being enhanced, as the potentials are turned more negative. In alkaline chloride medium (pH 13), for less negative potentials the bands assigned to free 4-AP were observed in the spectra of both Ag and Co surfaces. For more negative potentials, only bands assigned to the 4-AP surface complex were observed. For 0.1 mol L(-1) KI acidic or alkaline solutions, bands assigned to 4-AP and 4-APH(+) were observed in a wider potential range than in chloride solutions. An adsorption scheme of 4-AP on Ag and Co is proposed for acidic and alkaline solutions. (C) 2010 Elsevier B.V. All rights reserved.

��xidos do tipo perovskita para rea����o de redu����o de no com CO

In this work, the perovskite-type oxides LaNiO3, LaMnO3, La0,7Sr0,3NiO3 and La0,7Sr0,3MnO3 were prepared by co-precipitation and tested in the NO reduction with CO at 400 and 500 ��C for 10 h. The catalysts were characterized by X-ray diffraction, temperature programmed reduction with hydrogen, nitrogen adsorption and chemical analysis. The nonstoichiometric oxygen was quantified by temperature programmed reduction, and the catalytic tests showed that the La0,7Sr0,3MnO3 catalyst presented the higher performance for the reduction reaction of NO with CO. The partial substitution of lanthanum by strontium increased the NO conversion and the N2 yield.

Co-eletrodeposi����o oscilat��ria de cobre e estanho

It is investigated in the present contribution the oscillatory co-electrodeposition of CuSn on a polycrystalline gold surface in the presence of Triton X-100 surfactant and citric acid as additive, in acidic media. The experiments were conducted under potentiostatic control and the system dynamics characterized in terms of the morphology and stability of the current oscillations. Besides modulations in the frequency and amplitude of the current oscillations, several patterned states were observed, including relaxation-like and mixed mode oscillations. The oscillations were found to be very robust and some time series presented regular motions up to about two hours.

��reas de vulnerabilidade para co-infec����o HIV-aids/TB em Ribeir��o Preto, SP

OBJETIVO: Identificar ��reas de vulnerabilidade para os casos novos de co-infec����o HIV/tuberculose (TB). M��TODOS: Estudo descritivo ecol��gico realizado por meio do georreferenciamento dos casos novos de HIV/TB notificados em Ribeir��o Preto, SP, em 2006. Os dados foram obtidos do sistema de informa����o estadual paulista de notifica����o de TB. Os casos novos de co-infec����o HIV/TB foram analisados conforme caracter��sticas sociodemogr��ficas e cl��nicas e, posteriormente, georreferenciados na base cartogr��fica do munic��pio segundo endere��o residencial. Os setores do munic��pio foram categorizados em tr��s n��veis socioecon��micos: inferior, intermedi��rio e superior, com base na an��lise de componentes principais das vari��veis do censo demogr��fico de 2000 (renda, instru����o e percentagem de domic��lios com cinco ou mais moradores). Foi calculada a incid��ncia da co-infec����o HIV/TB para cada n��vel socioecon��mico. RESULTADOS: A co-infec����o HIV/TB acometeu mais adultos do sexo masculino em idade economicamente ativa e a forma pulmonar da TB foi a mais comum. A distribui����o espacial mostrou que as incid��ncias nas ��reas com n��veis socioecon��micos intermedi��rios e inferiores (8,3 e 11,5 casos por 100 mil habitantes, respectivamente) foram superiores ��quela (4,8 casos por 100 mil habitantes) de n��vel socioecon��mico superior. CONCLUS��ES: A taxa de incid��ncia de co-infec����o HIV/TB analisada por n��veis socioecon��micos mostrou padra��o espacial de distribui��a��o n��o homog��neo e apresentou valores mais altos em ��reas de maior vulnerabilidade social. O estudo diagnosticou a��reas geogra��ficas priorita��rias para o controle da co-infec����o e a tecnologia do sistema de informa����o geogr��fica pode ser empregada no planejamento das a����es em sa��de pelos gestores municipais.

Pr��tese total articulada de joelho utilizada no tratamento de osteossarcoma apendicular em c��o

O objetivo do trabalho foi reportar o planejamento cir��rgico, a t��cnica operat��ria, a instrumenta����o e os resultados da substitui����o completa do ter��o m��dio distal do f��mur, do plat�� tibial e da articula����o do joelho por pr��tese em um c��o acometido por osteossarcoma no f��mur esquerdo. A pr��tese foi confeccionada em a��o, apresentando tr��s componentes articulados, mantendo o movimento semelhante �� articula����o do joelho. As por����es femorais e tibiais da pr��tese foram cimentadas aos respectivos ossos, ap��s ostectomia do f��mur e do plat�� tibial. O animal foi submetido a seis sess��es de quimioterapia, com doxorrubicina e carboplatina, intercaladas mensalmente, objetivando inibir o crescimento de poss��veis met��stases pulmonares. Durante os seis primeiros dias, o animal apresentou neuropraxia e impot��ncia funcional do membro. Aos 10 dias, o c��o iniciou leve apoio e aos 30 dias j�� utilizava o membro p��lvico de forma mais efetiva, por��m, o ��ngulo de extens��o da articula����o foi reduzido de 150° a 100° devido �� contratura muscular e �� fibrose na regi��o da fossa popl��tea. Ap��s um ano de observa����o, n��o houve melhora do ��ngulo de extens��o do joelho, por��m, o animal fazia uso do membro com claudica����o. Aos 425 dias de p��s-operat��rio, o animal veio a ��bito por insufici��ncia renal. Nesse tempo n��o ocorreram met��stases pulmonares ou locais vis��veis radiograficamente, mas o propriet��rio n��o permitiu a realiza����o da necropsia do paciente, sendo imposs��vel confirmar outros dados que pudessem esclarecer melhor a causa morte. Conclui-se que a substitui����o total do joelho de c��o �� uma cirurgia fact��vel, que permite a preserva����o e a utiliza����o do membro ap��s ressec����o da neoplasia, embora outras pesquisas devam ser conduzidas para obten����o de melhores resultados p��s-cir��rgicos.

Meningoencefalite necrotizante de c��o Malt��s

A Meningoencefalite Necrotizante (MEN) �� uma encefalopatia causada por uma disfun����o inflamat��ria de caracter��stica necrotizante. O objetivo deste relato �� descrever os aspectos cl��nicos e anatomopatol��gicos da Meningoencefalite Necrotizante (MEN) em um c��o Malt��s. A doen��a tem um car��ter necr��tico ��nico e est�� relacionada intimamente �� Encefalite do C��o Pug (ECP) devido a suas semelhan��as, bem como �� Leucoencefalite Necrotizante (LEN). Embora o primeiro relato de caso de ECP tenha mais de 15 anos e o primeiro relato de caso de MEN em Malt��s tenha 11 anos, h�� muito a ser revelado sobre a etiologia e os mecanismos imunopatol��gicos da doen��a. Neste trabalho, relata-se o caso de um c��o Malt��s com sinais que foram compat��veis com a MEN. Foram detectadas nas imagens macrosc��picas, cavita����o cerebral, e na microscopia, perda de c��lulas do par��nquima em certas regi��es do c��rtex cerebral. A partir dessas descobertas descreve-se o primeiro caso de MEN em c��o Malt��s no Brasil.

Microstructural Evidence of beta Co(2)Si- phase Stability in the Co-Si System

The aim of this work was to verify the stability of the beta Co(2)Si phase in the Co-Si system. The samples were produced via arc-melting and characterized through Scanning Electron Microscopy (SEM) and Differential Thermal Analysis (DTA). The results have confirmed the stability of the beta Co(2)Si phase, however, a modification of the shape of beta CoSi phase field is proposed in order to fully explain the results.

Polyelectrolyte-protein complexation driven by charge regulation

The interplay between the biocolloidal characteristics (especially size and charge), pH, salt concentration and the thermal energy results in a unique collection of mesoscopic forces of importance to the molecular organization and function in biological systems. By means of Monte Carlo simulations and semi-quantitative analysis in terms of perturbation theory, we describe a general electrostatic mechanism that gives attraction at low electrolyte concentrations. This charge regulation mechanism due to titrating amino acid residues is discussed in a purely electrostatic framework. The complexation data reported here for interaction between a polyelectrolyte chain and the proteins albumin, goat and bovine alpha-lactalbumin, beta-lactoglobulin, insulin, k-casein, lysozyme and pectin methylesterase illustrate the importance of the charge regulation mechanism. Special attention is given to pH congruent to pI where ion-dipole and charge regulation interactions could overcome the repulsive ion-ion interaction. By means of protein mutations, we confirm the importance of the charge regulation mechanism, and quantify when the complexation is dominated either by charge regulation or by the ion-dipole term.

High levels of T lymphocyte activation in Leishmania-HIV-1 co-infected individuals despite low HIV viral load

Background: Concomitant infections may influence HIV progression by causing chronic activation leading to decline in T-cell function. In the Americas, visceral (AVL) and tegumentary leishmaniasis (ATL) have emerged as important opportunistic infections in HIV-AIDS patients and both of those diseases have been implicated as potentially important co-factors in disease progression. We investigated whether leishmaniasis increases lymphocyte activation in HIV-1 co-infected patients. This might contribute to impaired cellular immune function. Methods: To address this issue we analyzed CD4(+) T absolute counts and the proportion of CD8(+) T cells expressing CD38 in Leishmania/HIV co-infected patients that recovered after anti-leishmanial therapy. Results: We found that, despite clinical remission of leishmaniasis, AVL co-infected patients presented a more severe immunossupression as suggested by CD4(+) T cell counts under 200 cells/mm(3), differing from ATL/HIV-AIDS cases that tends to show higher lymphocytes levels (over 350 cells/mm(3)). Furthermore, five out of nine, AVL/HIV-AIDS presented low CD4(+) T cell counts in spite of low or undetectable viral load. Expression of CD38 on CD8(+) T lymphocytes was significantly higher in AVL or ATL/HIV-AIDS cases compared to HIV/AIDS patients without leishmaniasis or healthy subjects. Conclusions: Leishmania infection can increase the degree of immune system activation in individuals concomitantly infected with HIV. In addition, AVL/HIV-AIDS patients can present low CD4(+) T cell counts and higher proportion of activated T lymphocytes even when HIV viral load is suppressed under HAART. This fact can cause a misinterpretation of these laboratorial markers in co-infected patients.

Ultra-Structural Changes at the Apical Stop Irradiated with CO(2) Laser

Objective: This study evaluated ultra-structural dentine changes at the apical stop after CO(2) laser irradiation used during biomechanical preparation. Background: Most studies evaluating the sealing efficiency of CO(2) lasers have been carried out after apical root canal resections and retro-filling procedures. Methods: Sixty human canines were prepared with #1 to #6 Largo burs. The apical stops were established at 1 mm (n = 30) and 2 mm (n = 30) from the apex. Final irrigation was performed with 1% NaOCl and 15% EDTA followed by 20 ml of distilled and deionized water. Specimens were subdivided into three subgroups (n = 10 for each stop distance): GI-no radiation (n = 20); GII-3W potency (n = 20), GIII-5W potency (n = 20). After preparation, specimens were evaluated by scanning electron microscopy, with ultra-structural changes classified according to a scoring system based on six qualitatively different outcomes. Results: Statistical analysis using the Mann-Whitney test confirmed more intense results for the specimens irradiated at 5 W potency than at 3 W (p<0.0001). The Kruskal-Wallis test indicated that when using the same potencies (3 or 5 W) at 1 and 2 mm from the apex, there were no statistically significant differences in ultra-structural changes. Conclusions: Our results showed that ultra-structural changes ranged from smear layer removal to dentine fusion. As laser potency was increased from 3 to 5 W, ultra-structural changes included extensive fused lava-like areas sealing the apical foramen.

Mycoflora and Co-Occurrence of Fumonisins and Aflatoxins in Freshly Harvested Corn in Different Regions of Brazil

Natural mycoflora and co-occurrence of fumonisins (FB(1), FB(2)) and aflatoxins (AFB(1), AFB(2), AFG(1) and AFG(2)) in freshly harvested corn grain samples from four regions of Brazil were investigated. Fusarium verticillioides was predominant in all samples. Analysis of fumonisins showed that 98% of the samples were contaminated with FB(1) and 74.5% with FB(1) + FB(2), with toxin levels ranging from 0.015 to 9.67 mu g/g for FB(1) and from 0.015 to 3.16 mu g/g for FB(2). Twenty-one (10.5%) samples were contaminated with AFB(1), seven (3.5%) with AFB(2) and only one (0.5%) with AFG(1) and AFG(2). Co-contamination with aflatoxins and fumonisins was observed in 7% of the samples. The highest contamination of fumonisins and aflatoxins was observed in Nova Odessa (SP) and Varzea Grande (MT), respectively. The lowest contamination of these mycotoxins was found in Varzea Grande and Nova Odessa, respectively.

Piezomagnetic behavior of Co-doped ZnO nanoribbons

Using ab initio total energy calculations, we show that bilayer systems of ZnO nanoribbons, (ZnO)(2)NR, doped with Co atoms exhibit a piezomagnetic behavior. We find the formation of energetically stable zigzag chains of Co atoms along the edge sites of (ZnO)(2)NR's, Co(Zn(chain))-(ZnO)(2)NR. At the ground state, the antiferromagnetic and the ferromagnetic states are very close in energy, whereas upon longitudinal stretch, parallel to the nanoribbon growth direction, it becomes ferromagnetic. Further electronic structure calculations indicate that not only the magnetic state but also the electronic structure of CoZn(chain)-(ZnO)(2)NR can be tuned by the mechanical stretch. In this case, we find that stretched NR's exhibit dispersive unpaired electronic states within the (ZnO)(2)NR band gap.

Absence of ferromagnetic order in high quality bulk Co-doped ZnO samples

Bulk Zn(1-x)Co(x)O samples were synthesized via standard solid-state reaction route with different Co molar concentrations up to 21%. A detailed microstructural analysis was carried out to investigate alternative sources of ferromagnetism, such as secondary phases and nanocrystals embedded in the bulk material. Conjugating different techniques we confirmed the Zn replacement by Co ions in the wurtzite ZnO structure, which retains, however, a high crystalline quality. No segregated secondary phases neither Co-rich nanocrystals were detected. Superconducting quantum interference device magnetometry demonstrates a paramagnetic Curie-Weiss behavior with antiferromagnetic interactions. We discuss the observed room temperature paramagnetism of our samples considering the current models for the magnetic properties of diluted magnetic semiconductors. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3459885]

Ferromagnetic coupling in a Co-doped graphenelike ZnO sheet

Using first-principles calculations it is demonstrated that Co doped graphenelike ZnO sheet presents ferromagnetic coupling. The Co atoms are energetically barrierless absorbed in the Zn sites, suffering a Jahn-Teller distortion. The results reveal that the origin of the ferromagnetic coupling, different from the bulk 3D ZnO stacking, is mainly guided by a direct exchange interaction without any additional defect. This ferromagnetic coupling is due to the system topology, namely, it is a direct consequence of the two-dimensional character of the ZnO monolayer within graphenelike structure. Increasing the number of ZnO layers the ferromagnetic coupling vanishes.