Nutrição do porta-enxerto 'Flying Dragon'

No Brasil, o uso do trifoliata 'Flying Dragon', como porta-enxerto em citros, tem crescido quando se buscam pomares com altas densidades, devido, principalmente, a induzir nanismo à maioria das variedades de copa compatíveis. No entanto, por possuir desenvolvimento lento, existe a necessidade de se estudar melhor o crescimento desse porta-enxerto. A nutrição é uma importante ferramenta que visa a acelerar o crescimento e a melhorar o vigor e a qualidade das plantas. Diante disso, foi avaliada a aplicação de nutrientes no crescimento do porta-enxerto em três experimentos. No primeiro experimento, utilizaram-se seis doses de N parceladas; no segundo, seis doses de P (aplicadas em dose total, misturadas diretamente no substrato); e no terceiro, seis doses de K parceladas. As seis doses foram constituídas por: D0 = testemunha sem adubação; D1= metade da dose-padrão; D2 = a dose-padrão (920 mg dm-3 de N, 790 mg dm-3 de K e 100 mg dm-3 de P); D3 = uma vez e meia a dose-padrão; D4 = duas vezes a dose-padrão; e D5 = duas vezes e meia a dose-padrão. Assim, coletaram-se dados biométricos da planta de diâmetro e altura, quinzenalmente, e dados de massa seca da parte aérea e da raiz, mensalmente. O delineamento utilizado foi o inteiramente casualizado, com parcela subdividida. O nitrogênio teve papel fundamental no incremento das massas secas de raiz e da parte aérea.

Estudo comparativo da qualidade da imagem e do kerma, de entrada e de saída, em simulador de tórax utilizando sistemas analógico e digitalizado CR de aquisição de imagens

OBJETIVO: O processo de migração de sistemas analógicos para digitalizados, para aplicações diagnósticas, requer cuidados específicos, a fim de manter a qualidade das imagens e minimizar a dose no paciente. Este trabalho tem como objetivo analisar e comparar a qualidade da imagem e o kerma num simulador não antropomórfico de tórax gerados por sistemas analógicos e digitalizados CR. MATERIAIS E MÉTODOS: Foram analisados a qualidade da imagem e o kerma, de entrada e saída, no simulador para dois equipamentos de raios X diferentes (Siemens e Emic), com diferentes sistemas de retificação de onda (12 pulsos e alta frequência). Ambos os sistemas (analógico e digitalizado) estavam sendo utilizados no mesmo local. Foram geradas imagens em filme e em image plates. RESULTADOS: Foi observado aumento na tensão e/ou na carga transportada pelo tubo de raios X quando houve a migração para o sistema CR, para manutenção das características diagnósticas da imagem. Isto resultou em aumento de kerma coletado. CONCLUSÃO: As maiores diferenças determinadas (aumento de dose e redução da qualidade da imagem) foram observadas no equipamento com retificação de onda de 12 pulsos e transdutor de imagem CR (image plates).

Síndrome do crânio em folha de trevo: relato de caso

O objetivo deste relato é apresentar um caso raro de malformação craniana - a síndrome do crânio em folha de trevo -, cuja característica foi percebida após o nascimento de uma criança com os sinais da anomalia. Métodos de diagnóstico por imagem, como tomografia computadorizada e radiografia convencional, foram utilizados para a caracterização da síndrome.

Classificação de Bosniak para cistos renais complexos: histórico e análise crítica

A classificação de Bosniak para cistos renais surgiu na década de 1980 para tentar padronizar a descrição e condutas em relação às lesões renais císticas complexas. Esta classificação sofreu alterações na década de 1990 e, a última, em 2005. Atualmente, são definidas cinco categorias de lesões císticas renais – I, II, II-F, III e IV –, de acordo com o grau de complexidade e maior probabilidade de malignidade. Apesar de inicialmente ter sido descrita para a tomografia computadorizada, esta classificação é utilizada, com algumas vantagens, também na ressonância magnética. O presente artigo revisa as diferentes fases desta classificação, sua eficácia diagnóstica e os aspectos mais controversos de sua utilização.

Estudo do comportamento ácido-base da 4,4'-ditiodipiridina

Despite the importance of the 4,4'-dithiodipyridine as an electrode modifier on the protein electrochemical studies and as a remarkable bridged-ligand on conducting electronic density in binuclear mixed valence complexes, there is no data available in the literature concerning acid-base behavior of this compound. Aiming to afford such information we undertook the ionization equilibrium study of this ligand. Although two acid species, DTDPH+ and DTDPH2+ have been detected in solution, only the diacid-form was possible to be isolated as a perclorate salt DTDPH2(ClO4)2. The ionization constants for the two step equilibrium processes (pKa1=2.70 and pKa2=4.80) were determined by using the spectrophotometric technique and aqueous solutions of CF3COONa, mu=0,1 mol.L-1 .

Estudo comparativo da seletividade de um método cinético-catalítico: a determinação de Cr(VI) pela oxidação da o-dianisidina pelo peróxido de hidrogênio

Selectivity studies for the determination of Cr(VI) using the catalytic oxidation of the o-dianisidine by hydrogen peroxide showed two distincts situations. In the first, when interferents were studied by a univariate procedure, Cr(III) and Cu(II) cause serious interferences even at the 2:1 proportion, relative to Cr(VI), while Fe(III) interfered at the 15:1 ratio and EDTA at the 10:1 ratio. On the other hand, when a multivariate investigation was performed, Cr(III) did not present any significant principal effects and its significant interaction effects were negative, in contrast to EDTA, that presented positive interaction effects although, like Cr(III), did not show significant interaction effects. In view of the interferent's action it become necessary to separate Cr(VI) by extraction with methylisobutylketone in a chloridric acid medium before its determination in vegetals and in wastewater from a cellulose industry samples. Using this procedure, the method precision is ±0,5% at the 10 ng/mL Cr(VI) concentration level. The detection and quantification limits, calculated by means of absorbance measurements of ten replicates of blank reagents were 1,1 and 3,2 ng/mL, respectively. The results obtained with real samples showed a relative standard deviation between 1,2% and 3,0% relative to their reference values.

Aplicação de métodos quimiométricos na especiação de Cr(VI) em solução aquosa

The equilibria, the spectra and the identities of the species of Cr(VI) that are present in aqueous solution have long been an active subject of discussion in the literature. In this paper, three different chemometric methodologies are applied to sets of UV/Visible spectra of aqueous Cr(VI) solutions, in order to solve a chemical system where there is no available information concerning the composition of the samples nor spectral information about the pure species. Imbrie Q-mode factor analysis, followed by varimax rotation and Imbrie oblique projection, were used to estimate the composition of Cr(VI) equilibrium solutions and, by combining these results with the k-matrix method, to obtain the pure spectra of the species. Evolving factor analysis and self modeling curve resolution were used to confirm the number of the species and the resolution of the system, respectively. Sets of 3.3×10-4 and 3.3×10-5 mol L-1 Cr(VI) solutions, respectively, were analyzed in the pH range from 1 to 12. Two factors were identified, which were related to the chromate ion (CrO4(2-)) and bichromate ion (HCrO4-). The pK of the equilibrium was estimated as 5.8.

Filme fino de ZrO2 enxertado sobre a superfície de sílica gel: preparação e propriedade de adsorção de Cr(VI)

The present experiment describes an easy procedure for obtaining SiO2/ZrO2 by reacting ZrOCl2 with SiO2 with the following characteristics: S BET = 500 m² g-1 and an average pore diameter of 6 nm. The material obtained presented 1.3 wt% ZrO2 content corresponding to 140 mumol g-1. The average density of ZrO2 onto SiO2/ZrO2 matrix is 2.8x10-11 mol cm-2. The adsorption isotherm for Cr(VI) showed a maximum of adsorption value (200 mumol g-1) at pH 2. The adsorption can be described by the reaction: =Zr(OH)2 + 2HCrO4- + 2H+ [(=Zr(OH2+)2) (HCrO4-)2]. Above the zero point of charge, i.e. pH > 5.5 due to the surface charge inversion, desorption of Cr(VI) occurs according to the reaction: [(=Zr(OH2+)2) (HCrO4-)2] + 6OH- (=ZrO2)2- + 6H2O + 2CrO4(2-).

Extração de Al(III), Cr(III) e Fe(III) de meio etanólico usando o xerogel anilinapropilsílica

In this study, the preparation of the xerogel anilinepropylsilica is reported. The ability of the xerogel for extracting Al(III), Cr(III) and Fe(III) from ethanol was investigated at 25 ºC. The xerogel adsorption capacities were obtained from the adsorption isotherms by using the batch method. Flame atomic absorption spectrometry (FAAS) was used to estimate the concentration of metal ions in solution. The adsorption affinity follows the series Cr(III) > Fe(III) > Al(III) and the maximum adsorption capacities of the metal ions were 0.61, 0.52 and 0.43 mmol g-1, respectively.

Adsorção de As, Cu, Pb e Cr na avaliação da capacidade de fixação de metais por resíduo de mineradoras de ferro

Two samples of residues from iron mining plants have been investigated for their retention capacity of As, Cu, Cr, and Pb. The sample with the higher content of iron oxides showed the highest capacity to retain metals. The adsorption affinity series changes from Pb>Cu>Cr~As to As>Pb>Cu>Cr or As>Cu>Cr>Pb, depending on the material and the concentration of the initial solution. In the competitive environment, the Pb adsorption decreases and the As, Cu and Cr adsorption increases. Sequential extraction procedures, carried out after adsorption batch experiments, showed that the most important adsorption process occurs in the oxide fraction and that the major part of the absorbed metal is remobilized from exchangeable and oxide fractions.

Utilização de pelos de animais silvestres para monitoramento ambiental de Cd, Cr, Cu, Fe, Mn, Pb e Zn

This study investigates the use of wild animal hair of C. brachyurus, C. thous and L. pardalis as biomonitors of trace metal at Parque Nacional das Emas, Brazil. Results reveal a strong correlation between Cd and Pb as well as Cu and Zn, which suggests a single source of emission. Most metals showed a lower or equal concentration than those obtained in previous studies. The research shows that monitoring may be performed only with Zn, Pb, Cd, and Cr because of statistical similarity and of a non-natural occurrence of large amounts of the material under analysis.

Desenvolvimento e aplicação de sistema passivo de coleta de poluentes atmosféricos para monitoramento de Cd, Cr, Pb, Cu, Fe, Mn, Zn e particulados totais

The objective of this study was to assess a new monitoring technique of particulate and trace metals in the atmosphere via the use of a passive sampler of air pollutants in the city of Goiânia. The average particulate weight and average concentrations of metals Fe, Cr, Zn, Pb, Cu, Mn, and Cd were 0.1104 g and 257.5; 23.4; 17.8; 6.7; 1.9; 0.8; 0.2 μg/m²/day, respectively. Higher Pb and Cr concentrations were obtained in areas with intense traffic. This study revealed that it is possible to monitor trace metals with passive sampling, developed at a low cost and operational facility.

Adsorção de Cr(VI) em esferas reticuladas de quitosana: novas correlações cinéticas e termodinâmicas utilizando microcalorimetria isotérmica contínua

The synthesis and characterization of crosslinked chitosan microbeads and their application in the removal of Cr(VI) are described. New kinetic and thermodynamic parameters of Cr(VI) adsorptions processes were found using continuous isothermal calorimetry. All adsorption processes are exothermic in nature. However, a multivariate statistical analysis have pointed out that adsorption enthalpies were affected by important binary interactions of the initial Cr(VI) in solution and temperature. The adsorption energetic data were well fitted to a kinetic exponential model, which have indicated fractionary adsorption kinetic orders.

Pré-concentração de Cr(III) e análise de especiação de cromo empregando montmorilonita saturada com íons potássio

The clay mineral montmorillonite-K10 (MT), treated under acidic medium and saturated with potassium ions (MTK), was employed in sorption and desorption studies aiming the preconcentration of Cr(III) and the speciation analysis of chromium. The sorption process of Cr(III) was close to 100%, suggesting that MTK was a good material for Cr(III) preconcentration, although, the maximum recovery in HNO3 solution was near 89%. On the other hand, Cr(VI) practically was not retained in MTK, suggesting this material as an appropriate mineral phase to be used in speciation analysis of chromium in aqueous medium.

Determinación simultánea de Cr, Ni y V en orina mediante et aas

A procedure for the simultaneous determination of Cr, Ni, and V in urine by electrothermal atomic absorption spectrometry (ET AAS) was optimized by factorial design, and performed at a pyrolysis and atomization temperatures of 1300 and 2500 ºC, respectively, using 15 µg de Mg(NO3)2 as chemical modifier. Characteristics mass of 14, 6 and 220 ρg and detection limits of the method of 0.07, 0.38 and 0.75 µg L-1 were obtained for Cr, Ni and V respectively. The methodology was validated using a Liphochek Urine Metals Control sample (Bio-Rad) (P=0.05). The methodology was applied to samples of voluntary Venezuelan people, not environmentally exposed to specific emissions, and results ranging from < LOD-1.1 and 1.3-3.3 µg L-1 was observed for Cr and V, respectively, and not detectable levels for Ni.