Estimativa por infravermelho da concentração da unidade estrutural b-O-4 em ligninas de angiospermas tropicais

Five Björkman lignins, codified as AM, LL, GG, PP and AP, were isolated from wood species of Aspidosperma macrocarpum Mart., Lophanthera lactescens Ducke, Gallesia gorazema (Vell.) Miq., Peltogyne paniculata Bth. and Aspidosperma polyneuron Muell. Arg., respectively. Analyses of the lignins were carried out by Fourier transformed infrared spectroscopy using an experimental technique, Diffusely Reflected Infrared Fourier Transformed (DRIFT), admitting in the original spectra a band at 1500 cm-1 as an internal reference. Application of a deconvolution technique made possible to estimate the percentage per mol of b-O-4 unit content around 65.5% to AM, 68.0% to LL, 71.0% to GG. 73.4% to PP and 75.0% to AP, toward AM

La efectividad de las políticas activas de mercado de trabajo para luchar contra el paro. La experiencia de Cataluña

El objetivo de este trabajo es evaluar la efectividad de las políticas activas llevadas a cabo por el Servicio de Ocupación de Cataluña (SOC) durante el año 2005. Los resultados obtenidos a partir de la aplicación de técnicas de matching muestran que la probabilidad de encontrar trabajo para un individuo que participó en alguna de las acciones del SOC analizadas es 5 puntos porcentuales superior en relación a los que no participaron. El análisis individualizado de los diferentes programas ha mostrado la eficacia de la mayor parte de las acciones realizadas. Por último, los resultados obtenidos también han puesto de manifiesto la mejora adicional que supone la combinación de algunas de las acciones.

Determinação de fósforo orgânico em águas de produção petrolífera por ICP- AES e ICP- MS após pré-concentração em coluna de sílica-C18

Results on the optimization of analytical methods for the determination of phosphorus in phosphino-polycarboxylate (PPCA), used frequently as scale inhibitor during oil production, by ICP-AES and ICP-MS are presented. Due to the complex matrix of production waters (brines) and their high concentration in inorganic phosphorus, the separation of organic phosphorus prior to its determination is necessary. In this work, minicolumns of silica immobilized C18 were used. Optimization of the separation step resulted in the following working conditions: (1) prewashing of the column with methanol (80% v/v); (2) use of a flow rate of 5 mL/min and 10 mL/min, respectively, for the preconditioning step and for percolation of the water sample; (3) final elution of organic phosphorus with 7 mL of buffer of H3BO3/NaOH (0.05 M, pH 9) with a flow rate of 1 mL/min. Sample detection limits (3s) for different combinations of nebulizers and spectrometric methods, based on 10 mL water aliquots, are: ICP-AES -Cross flow (47 mg/L) and Ultrasonic (18 mug/L); ICP-MS -Cross flow (1.2 mug/L), Cyclonic (0.7 mug/L) and Ultrasonic (0.5 mug/L). Typical recoveries of organic phosphorus are between 90 and 95% and the repeatability of the whole procedure is better than 10%. The developed methodology was applied successfully to samples from the oil-well NA 46, platform PNA 2, Campos basin, Brazil. Assessment of the PPCA inhibitor was possible at lower concentrations than achieved by current analytical methods, resulting in benefits such as reduced cost of chemicals, postponed oil production and lower environmental impacts.

Determinação de Cd, Ni e Zn por espectrometria de emissão atômica com plasma indutivamente acoplado, após separação e pré-concentração em coluna contendo p-dimetilaminobenzilidenorodanina adsorvida sobre sílica gel

A column packed with 5-(4-dimethylaminobenzylidene)rhodanine adsorbed on silica gel was used for the preconcentration of Cd, Ni and Zn at different spiked solutions prior to their determination by inductively coupled plasma atomic emission spectrometry. This column allowed recoveries over than 98% for the above elements and accurate analyses of coastal sea-water certified reference material were also achieved.

Extração e pré-concentração de compostos orgânicos voláteis por permeação em membrana para análise cromatográfica

This work discusses sample preparation processes for gas chromatography (GC) based on the technique of extraction through membrane permeation (MPE). The MPE technique may be easily coupled to GC via a relatively simple device, which is a module that holds the membrane and is directly connected to the GC column. The possibility of operational errors due to sample handling is substantially reduced in an MPE-GC system because the sample preparation and the chemical analysis are accomplished as a one-step process. The MPE technique is of relatively wide application as it can be used for aqueous samples, solid samples and gaseous samples. Depending on the type of sample the extraction is performed with the membrane in direct contact with the sample or in contact with its headspace. The MPE-GC technique is very useful in trace analysis, due to the time-dependent enrichment of the analyte. A typical application of MPE-GC is the analysis of VOCs present in water that may be accomplished with detection limits at the low ppb (mugL-1) level.

La reforma de la contratación en el mercado de trabajo: entre la flexibilidad y la seguridad

El actual debate sobre la reforma laboral pendiente en España se centra demasiado en el abaratamiento del despido o las modalidades de contratación como únicas formas de flexibilizar el mercado de trabajo. Este tipo de propuestas, además, choca con la percepción de una fuerte pérdida de seguridad de los trabajadores. En este trabajo nos planteamos cómo conciliar una mayor flexibilidad del mercado laboral sin una pérdida de la seguridad de los trabajadores. Para hacerlo revisamos qué sugiere la teoría, con qué evidencia empírica contamos y cuáles son las experiencias internacionales de las que podemos aprender para así poder hacer planteamientos serios de reformas laborales basados en evidencias y no en ocurrencias. Finalmente proponemos una línea de trabajo de la reforma del mercado de trabajo que no renuncia ni a la mejora de la flexibilidad ni a asegurar el empleo de los trabajadores.

Análisis de herramientas BI en el mercado actual

En este trabajo final de grado se pretende hacer una valoración objetiva de las herramientas disponibles en el mercado actual para la realización de proyectos de business intelligence.

Métodos de extração e/ou concentração de compostos encontrados em fluidos biológicos para posterior determinação cromatográfica

When organic compounds present in biological fluids are analysed by chromatographic methods, it is generally necessary to carry out a prior sample preparation due the high complexity of this type of sample, especially when the compounds to be determinated are found in very low concentrations. This article describes some of the principal methods for sample preparation in analyses of substances present in biological fluids. The methods include liquid-liquid extraction, solid phase extraction, supercritical fluid extraction and extraction using solid and liquid membranes. The advantages and disadvantages of these methods are discussed.

Efeito da concentração do catalisador acetilacetonato férrico na cura de poliuretano à base de polibutadieno líquido hidroxilado (PBLH) e diisocianato de isoforona (IPDI)

The reaction between hydroxy-terminated polybutadiene and isophorone diisocyanate constitutes the base of the curing process of the most composite solid propellant used in the propulsion of solid rocket propellant. In this work, differential scanning calorimetry and viscosity measurements were used to evaluate the effect of the ferric acetylacetonate catalyst concentration on the reaction between HTBR and IPDI. These analyses show one exotherm, which shifts to lower temperatures as the catalyst concentration increases. The viscosity analyses show that the increase of temperature causes, at first, a reduction in the mixture viscosity, reaching a minimum range called gelification region (increasing the crosslinking density).

Experimentos didáticos em química analítica envolvendo separação de fases e pré-concentração

The aim of this work was to propose two different didactic experiments, which can be used in practical classes of analytical chemistry courses. More flexible experiments related to the theme, giving some options to the instructor are proposed. In this way, the Experiment 1 was divided in two parts. In the first one, the visualization of two distinct phases separation is emphasized: the rich and the poor phases in surfactant. In the second part, the metal pre-concentration (Co as example) is emphasized. The Experiment 2 has three different parts. In the first one, the complex formation is pointed out, in the second one, the pH influence is shown and in the last one, the influence of the complexation time is demonstrated.

Mercado del libro y empresas editoriales entre el Centenario de Independencias y la Guerra Civil española: la editorial Sudamericana

[spa]Las estrategias comerciales de los libreros y editores españoles para desembarcar en los mercados americanos son analizadas en un contexto signado por las tendencias americanistas en el plano político y las iniciativas regeneracionistas en el económico durante el periodo que va del Centenario de las Independencias hasta la Guerra Civil española. Se abordan algunas de las políticas empresariales editoriales implementadas en Cataluña, el liderazgo ejercido por esta región como epicentro del proyecto hispano, y finalmente las condiciones que permitieron la creación de la editorial Sudamericana en Buenos Aires ante la inminencia del triunfo franquista. Los ejes de estudio son las estrategias editoriales y comerciales; el peso de las asociaciones y corporaciones patronales del libro; y los vínculos tejidos con el sector intelectual argentino en las primeras décadas del siglo XX a través de delegaciones consulares, instituciones culturales y cámaras españolas de comercio.

Pré-concentração de chumbo e cádmio em um sistema de micro extração líquido-líquido e determinação por espectrometria de absorção atômica com chama

A method for determination of lead and cadmium in aqueous samples using solvent microextraction and dithizone as complexing agent with FAAS was developed. Solvent microextraction parameters were optimized. The effect of foreign ions on the extraction yields was studied. The extraction was carried out until the aqueous to organic phase ratio achieved a 250 fold preconcentration of metals. For preconcentration times of 4 min the 3sigma detection limits, relative standard deviations (n=7) and linear calibration ranges were 1.6 mug L-1, 5.8% and 10.0 -- 80.0 mug L-1 for lead and 11.1 ng L-1, 5.9% and 0.3 -- 3.0 mug L-1 for cadmium, respectively. The solvent microextraction procedure presented here was applied to the determination of lead and cadmium in natural waters.

Determinação espectrofotométrica de alumínio em concentrados salinos utilizados em hemodiálise empregando pré-concentração em fluxo

An automatic flow injection procedure for spectrophotometric aluminium determination in purified water and solutions containing high salts concentrations used for hemodyalisis treatment was developed. The method was base on reaction of Al3+ with cianine eriochrome R (ECR) after preconcentration using the AG50W-X8 cationic-exchange resin. Elution was carried out using a 1 % (m/v) calcium chloride solution. The manifold comprised an automatic proporcional injector controlled by a computer equipped with an eletronic interface and software written in QuicBASIC 4.5 with facilities to control the injector and perform data acquisition. Samples with concentration ranging from 4.96 to 19.90 µg L-1 Al were analyzed and recoveries between 88 and 113% were obtained by using the standard addition method. Other profitable analytical characteristics such as a relative standard deviation 1.3 % (n = 10) for a typical sample 14.5 µg L-1 Al, a linear response ranging up to 60.0 µg L-1Al, and a sampling throughput of 10 determinations per hour were achieved. A detection limit of 4.2 µg L-1 Al was estimated as suggested by IUPAC.

Determinação de Mn, Cu e Zn em matrizes salinas após separação e pré-concentração usando Amberlite XAD-7 impregnada com Vermelho de Alizarina S

The aim of this work was to explore the possibility of the application of a non-ionic resin obtained by impregnation of Alizarin Red S (VAS) in Amberlite XAD-7 for manganese, copper and zinc separation and preconcentration in saline matrices. For these system, the metals were quantitatively retained, in the pH range 8.5-10.0, by using 0.50 g of solid phase, stirring time of five minutes and a total mass up to 200 mug of each cation. The sorbed elements were subsequently eluted and a fifty-fold, ten-fold and ten-fold preconcentration factor for to Zn, Cu and Mn were obtained, respectively.