Determinação da concentração de paclobutrazol por cromatografia líquida de alta eficiência e espectroscopia

Paclobutrazol is a plant growth retardant which is used world-wide for increasing the yield of cereal crops. However, this compound remains active in the soil for several years and can severely affect the growth and development of subsequent crops, mainly by reducing vegetative vigor. The aim of this work was to develop and validate methods for the determination of paclobutrazol concentrations by both high performance liquid chromatography and spectroscopy. Both methods were satisfactory and showed appropriately low quantification limits. The determination by spectroscopy has, however, the advantage of being a method significantly less expensive than high performance liquid chromatography.

Metabólitos secundários de Esenbeckia almawillia Kaastra (Rutaceae)

The phytochemical investigation of the roots of E. almawillia is reported for the first time. Chromatographic fractionation of the methanol extract allowed the isolation of the alkaloids 3,3-diisopentenyl-N-methyl-2,4-quinoldione (1), maculine (2) and 3'-methoxygraveoline (3), (E)-N-isobutyl-3-methoxy-4,5-methylenedioxicinnamoyl amide (4), the flavones gardenine B (5) and nevadensin (6), and the sesquiterpene intermediol (7). Structure elucidation was based on the analysis of their spectrometric data (uni- and bidimensional ¹H and 13C NMR, MS and IR) and comparison with literature data. Compounds 3-7 are being reported as constituents of Esenbeckia species for the first time.

Anàlisi d'imatges estereoscòpiques utilitzant mètodes de baixa càrrega computacional

Mitjançant imatges estereoscòpiques es poden detectar la posició respecte de la càmera dels objectes que apareixen en una escena. A partir de les diferències entre les imatges captades pels dos objectius es pot determinar la profunditat dels objectes. Existeixen diversitat de tècniques de visió artificial que permeten calcular la localització dels objectes, habitualment amb l’objectiu de reconstruir l’escena en 3D. Aquestes tècniques necessiten una gran càrrega computacional, ja que utilitzen mètodes de comparació bidimensionals, i per tant, no es poden utilitzar per aplicacions en temps real. En aquest treball proposem un nou mètode d’anàlisi de les imatges estereoscòpiques que ens permeti obtenir la profunditat dels objectes d’una escena amb uns resultats acceptables. Aquest nou mètode es basa en transformar la informació bidimensional de la imatge en una informació unidimensional per tal de poder fer la comparació de les imatges amb un baix cost computacional, i dels resultats de la comparació extreure’n la profunditat dels objectes dins l’escena. Això ha de permetre, per exemple, que aquest mètode es pugui implementar en un dispositiu autònom i li permeti realitzar operacions de guiatge a través d’espais interiors i exteriors.

Extração líquido-líquido de urânio(VI) do colofanito de itataia (Santa Quitéria, Ceará) por extratantes orgânicos em presença de ácido fosfórico

This work describes the liquid-liquid extraction of uranium after digestion of colofanite (a fluoroapatite) from Itataia with sulfuric acid. The experiments were run at room temperature in one stage. Among the solutions tested the highest distribution coefficient (D > 60) was found for 40%vol. DEHPA (di(2-ethyl-hexyl)phosphoric acid) + 20% vol. TOPO (trioctylphosphine oxide) in kerosene. Thorium in the raffinate was quantitatively extracted by TOPO (0.1% vol.) in cyclohexane. Uranium stripping and separation from iron was possible using 1.5 mol L-1 ammonium or sodium carbonate (room temperature, one stage). However, pH control is essential for a good separation.

Comparação interlaboratorial para análise de dureza total e cloreto em água

Interlaboratorial comparison of the determination of hardness and chloride in water had been performed by 38 and 37 laboratories, respectively. In all cases the participating laboratories used its routine methods. Homogeneity and stability testing were performed on the samples sent to the laboratories. The codified results are graphically reported and compared to assigned value, determined by the consensus of the laboratories. Satisfactory results were obtained for 71 and 73% of the laboratories, considering hardness and chloride determination, respectively.

Modelagem da cinética de biodegradação de paclobutrazol em dois solos do semiárido do nordeste brasileiro

Mathematical models can help to prevent high levels of toxic substances in soil or fruits of plants treated with pesticides and indicate that such substances should be systematically monitored. The aim of this research was to study the kinetics of paclobutrazol biodegradation by soil native bacteria using mathematical models. Three models were used to assess the kinetics of paclobutrazol biodegradation obtained experimentally. Excellent fits were obtained using dual kinetic and logistic models. The use of glycerol as additional carbon source increased the biodegradation of PBZ and consequently decreased the time required for a given PBZ initial concentration be halved.

Biodegradação de paclobutrazol por Pseudomonas spp. em sistemas de solo saturados

Paclobutrazol is growth regulator of plants that has low mobility in soil and therefore has accumulated. The objective of this study was to investigate the paclobutrazol biodegradation in two soils from the São Francisco River Valley. The biodegradation experiments were conducted in batch using paclobutrazol and paclobutrazol added glycerol. The experiments were performed in sterile and nonsterile conditions using a mixed culture of Pseudomonas. The concentration of paclobutrazol was determined by high performance liquid chromatography. The biodegradation reached 43% in 14 days of experiments with only paclobutrazol and 70% in 28 days of experiments that contained glycerol and paclobutrazol.

Comparação estrutural entre amostras de materiais tipo hidrotalcita obtidas a partir de diferentes rotas de síntese

Three samples of hydrotalcite-like materials (HTC) were synthesized and their structural characteristics were compared with two HTCs obtained commercially. Thermal analyses, FT-IR, PXRD and textural analyses were used to investigate the structural differences between commercial and synthetic samples. Particularly, the memory effect was observed at temperature higher than 600 ºC. The Rietveld refinements were obtained with expressive accuracy and the statistical parameters of goodness of fit are quite satisfactory. In conclusion, the procedures adopted in synthesis of HTC produced crystalline materials with high surface area materials.

Desenhos de estruturas químicas correlacionam-se com propriedades biológicas: MIA-QSAR

Descriptors in multivariate image analysis applied to quantitative structure-activity relationship (MIA-QSAR) are pixels of bidimensional images of chemical structures (drawings), which were used to model the trichomonicidal activities of a series of benzimidazole derivatives. The MIA-QSAR model showed good predictive ability, with r², q² and r val. ext.² of 0.853, 0.519 and 0.778, respectively, which are comparable to the best values obtained by CoMFA e CoMSIA for the same series. A MIA-based analysis was also performed by using images of alphabetic letters with the corresponding numeric ordering as dependent variables, but no correlation was found, supporting that MIA-QSAR is not arbitrary.

Aplysfistularine: a novel dibromotyrosine derivative isolated from Aplysina fistularis

The new dibromotyrosine derivative 3,5-dibromo-4-[3'dimethylamonium]propoxyphenyl]-N,N,N-trimethylethanamonium, here referred to as aplysfistularine (1), was isolated from the marine sponge Aplysina fistularis along with 2-(3,5-dibromo-4methoxyphenyl)-N,N,N-trimethylethanamonium (2), aplysterol (3) and 24,28-didehydroaplysterol (4). Their identification was performed by mass spectrometry, infrared, ¹H and 13C NMR, and by comparison with literature data. Compound 2 and the mixture of 3 and 4 were tested in vitro (inhibitory activity) with supercoiled DNA relaxation techniques, and showed inhibitory activity on human DNA topoisomerase II-α. Compound 1 was not tested due to paucity of the material.

Constituintes químicos e atividade antioxidante de Byrsonima gardneriana (Malpighiaceae)

The phytochemical investigation of Byrsonima gardneriana led to the isolation of five triterpenes and one flavonoid: D:B-Friedoolean-5-en-3-one (1), friedoolean-14-en-3-one (2), friedelan-3-one (3), lup-20(29)-en-3-ol (4), 3β-hydroxiolean-12-ene (5) and 3,3',4',5,7-pentahydroxyflavan (6). Their structures were assigned based on spectroscopic analyses, including two-dimensional NMR techniques and comparison with published spectral data. Antioxidant activities of ethanol extract and phases were measured using the 1,2-diphenyl- 2-picryl-hydrazyl (DPPH) free radical scavenging assay, evaluation of total phenolic content and trolox equivalent antioxidant capacity (TEAC).

Produção de hidrogênio via fermentação anaeróbia - aspectos gerais e possibilidade de utilização de resíduos agroindustriais brasileiros

Biological production of hydrogen through anaerobic fermentation has received increasing attention and offers a great potential as an alternative process for clean fuel production in the future. Considering biological systems for H2 production, anaerobic fermentation stands out, primarily due to its higher production of H2 compared with other biological processes. In addition the possibility of using different agro-industrial wastes as substrates opens up infinite possibilities. The development and implementation of sustainable processes for converting renewable materials into different value-added products is essential for the full exploitation of Brazilian agro-industrial wastes.

Estudo químico e atividades antiproliferativa, tripanocida e leishmanicida de Maxillaria picta

The chemical study of the orchid Maxillaria picta resulted in the isolation of the bioactive stilbenes phoyunbene B and phoyunbene C, in addition to four phenolic acids, one xanthone, steroidal compounds and two triterpenes. Crude extract, fractions, subfractions and the isolated xanthone were evaluated for anticancer activity against human tumor cell lines and against evolutionary forms of T. cruzi and L. amazonensis. The structures of the compounds were determined by GC-MS, and ¹H NMR, 13C NMR spectral methods as well as bidimensional techniques.

Efeito da variação de parâmetros reacionais na preparação de grafeno via oxidação e redução do grafite

This work shows the influence of several reactional parameters for obtaining graphene through successive steps of oxidation and exfoliation of bulk graphite (resulting in graphene oxide), followed by chemical reduction. The results showed that changes in temperature, reaction time, reducing agent and source of primary graphite lead to different surface compositions and stability in dispersion of graphene oxide. Also, the use of different reducing agents promoted different degrees of restoration of C=C bonds in the bidimensional structure of graphene.

NOVEL SUPERABSORBENT HYDROGEL COMPOSITE BASED ON POLY(ACRYLAMIDE-CO-ACRYLATE)/NONTRONITE: CHARACTERIZATION AND SWELLING PERFORMANCE

A novel superabsorbent hydrogel (SH) composite based on a poly(acrylamide-co-acrylate) matrix filled with nontronite (NONT), a Fe(III)-rich member of the smectite group of clay minerals, is described in this manuscript. A variety of techniques, including FTIR, XRD, TGA, and SEM/EDX, were utilized to characterize this original composite. Experimental data confirmed the SH composite formation and suggested NONT was completely dispersed in the polymeric matrix. Additionally, NONT improved the water uptake capacity of the final material, which exhibited fast absorption, low sensitivity to the presence of salt, high water retention and a pH sensitive properties. These preliminary data showed that the original SH composite prepared here possesses highly attractive properties for applications in areas such as the agriculture field, particularly as a soil conditioner.