Custo de produção do maracujá-amarelo (Passiflora edulis)

Objetivou-se analisar economicamente a cultura do maracujá-amarelo (Passiflora edulis) na região de Marília-SP, safra de 2010/2011. Foram utilizadas estruturas do custo operacional efetivo e custo operacional total referente à fase de implantação e condução da lavoura por unidade de área e cinco indicadores de rentabilidade. Identificou-se um custo total de produção de R$ 37.751,67 por hectare ou R$ 1,89 por quilo da fruta. Os itens do custo operacional efetivo que mais oneraram o sistema de produção corresponderam às operações de máquinas (31,1%) e mão de obra (23,5%). Os indicadores de rentabilidade mostraram-se desfavoráveis para o sistema produtivo analisado, em decorrência, principalmente, do alto preço dos insumos e práticas para controle de doenças. Há necessidade de adequações técnicas relacionadas com o manejo fitossanitário da cultura para a redução do custo total de produção de modo a tornar a atividade rentável.

Custo de produção de goiabas para mesa produzidas com e sem ensacamento: estudo de caso

O ensacamento de goiabas para mesa tem por finalidade proteger os frutos contra o ataque de pragas, reduzir a aplicações e os níveis de resíduo de agroquímicos. O objetivo deste trabalho foi avaliar a sustentabilidade econômica da produção de goiabas, por meio da comparação do custo de produção entre os sistemas de cultivo com e sem ensacamento dos frutos. Foi realizado um estudo de caso com dados obtidos de uma propriedade comercial de goiabas para mesa no município de Valinhos - SP. O custo de produção foi calculado do Custo Total (CT), composto pelo Custo Operacional (CO) e o Custo Anual de Recuperação do Patrimônio (CARP). Para este estudo de caso, o Custo Total de produção de goiaba ensacada foi de R$ 72.208,39 ha-1, e o da goiaba não ensacada R$ 66.467,30 ha-1. Verificou-se, que para manter a Receita Líquida Total obtida pelo produtor, o preço médio de venda deveria passar de R$ 1,85 kg-1 para, no mínimo, R$ 1,96 kg -1 quando os frutos receberem ensacamento. Ambos os sistemas de produção apresentam-se sustentáveis economicamente.

A tomografia por emissão de pósitrons com 2-[18F]-fluoro-2-desoxi-D-glicose é custo-efetiva em pacientes com câncer de pulmão não pequenas células no Brasil

OBJETIVO: Comparar a acurácia e a custo-efetividade do estadiamento metabólico (EM) com o FDG-PET em relação ao estadiamento convencional (EC) no estadiamento inicial de pacientes com câncer de pulmão não pequenas células (CPNPC). MATERIAIS E MÉTODOS: Noventa e cinco pacientes com diagnóstico inicial de CPNPC foram estadiados antes do início do tratamento. Os resultados do EC e EM foram comparados quanto a definição do tratamento e incidência de toracotomia fútil em cada estratégia. RESULTADOS: O EM com FDG-PET classificou 48,4% dos pacientes como estádio mais avançado e 5,3% como menos avançado. O resultado do EM modificaria o tratamento em 41% dos pacientes. A toracotomia foi considerada fútil em 47% dos pacientes com EC e em 19% dos casos com EM. O custo das toracotomias fúteis em oito pacientes no EM foi de R$ 79.720, enquanto em 31 pacientes no EC seria de R$ 308.915. Apenas esta economia seria mais que suficiente para cobrir os custos de todos os exames de FDG-PET nos 95 pacientes (R$ 126.350) ou de FDG-PET/CT (R$ 193.515). CONCLUSÃO: O EM com FDG-PET tem maior acurácia que o EC em pacientes com CPNPC. A FDG-PET e FDG-PET/CT são custo-efetivas e sua utilização se justifica economicamente na saúde pública no Brasil.

Técnicas in situ de baixo custo em eletroquímica: a microbalança a cristal de quartzo

Among in situ techniques, the electrochemical quartz crystal microbalance (EQCM) is a powerful tool for the study of electrochemical reactions that produce mass changes in the electrode/solution interface. This review present some systems in which the EQCM combined with classical electrochemical techniques, gives relevant information for understanding the charge transport process at a molecular level. The aim of this review is to do a brief description of experimental arrangements, with emphasis on some special cares that must be considered by the users. Secondly, some chosen electrochemical systems where the technique was successfully applied are discussed. Finally, a brief analysis of electroacoustic impedance experiments was done in order to show when the Sauerbrey equation can be used.

Construção e otimização de um reator de baixo custo para a fotodegradação da matéria orgânica em águas naturais e sua aplicação no estudo da especiação do cobre por voltametria

This work describes the construction of a home-made low-cost reactor, using easily available materials, capable of destroying efficiently dissolved organic matter. Just 30 minutes of irradiation were sufficient to destroy more than 99% of the humic acids present in a solution of 4 mg C L-1. Copper speciation was evaluated in natural waters of different salinities to test the reactor's efficiency in destroying organically complexed metal species. The effect of the organic matter concentration, salinity, dissolved oxygen and temperature in the photo-oxidation process is discussed.

Métodos de baixo custo para purificação de reagentes e controle da contaminação para a determinação de metais traços em águas naturais

Probably one of the most difficult and challenging aspects of measuring trace metals in natural waters is to avoid contamination during sampling, manipulation and analysis. This work discusses how to avoid contamination using simple procedures, and considers alternative methods to purify deionised water and low grade reagents to enable accurate determination of trace metals in natural waters in a common laboratory. Measurements were performed by cathodic stripping voltammetry and copper was used as a model metal to test the procedures. It was possible to evaluate copper speciation in natural waters even when total dissolved copper concentration was as low as 1.5 nmol L-1. The methods' accuracy was confirmed by analysis of certified seawater.

Desenvolvimento de um dispositivo de baixo custo para medidas por quimiluminescência

A simple and low cost device (ca. US$ 150) that comprises two photodiodes fixed in lab-made Perspex flow cell is proposed for chemiluminescence measurements. The characteristics of the device (large observation window and reduced thickness) allow maximizing the amount of the emitted radiation detected. A sensitivity improvement of ca. 50 % was observed by employing two photodiodes for signal measurements. The performance of the device was assessed by the oxidation of luminol by hydrogen peroxide, yielding a linear response within the range of 2.50 to 500 µmol L-1 H2O2. The detection limit was estimated as 0.8 µmol L-1 hydrogen peroxide which is comparable with those obtained by using equipments based on photomultipliers.

Um banho termostático de baixo custo (temperatura ambiente até 0ºC)

Thermal baths to decrease ambient temperature are an indispensable tool for most research and teaching laboratories, especially those in tropical or equatorial regions. A simple and inexpensive thermal bath has been developed based on a scratched compressor. It has three possible setups for cooling: sample immersed into the bath, sample flowing through the bath, and cooling liquid flowing in a jacket around the sample. It has been tested for 40 months. The temperature ranges from room temperature to 0 °C, when using water. The repeatability is better than 3% and the precision varies from 0.5% to 2%.

Recuperação de sílica-gel utilizando processos oxidativos avançados: uma alternativa simples e de baixo custo

Silica gel is widely used as adsorbent for isolating and purifying natural compounds. Intensive use and high cost make this process expensive and generate solid residues contaminated with many different organic compounds. In the present work a simple method for recycling silica was investigated, by using Advanced Oxidative Processes. Silica gel was treated with H2O2/solar light and compared with a sample treated by conventional methods (high temperature and oxidation with KMnO4). High temperature treatment changes the structure of the silica and, consequently, the separation efficiency. Oxidation by using KMnO4 requires multiple steps and produces residues, including manganese and oxalic acid. The method using H2O2/solar light to recuperate silica gel does not modify its separation efficiency and is less expensive than the traditional methods. Additionally, HPLC and GC-MS analysis indicate that H2O2/solar light eliminates all residues of the silica gel.

Multímetro interfaceado de baixo custo para aquisição de dados

A digital multimeter (~U$ 240.00 on the national market) connected to a microcomputer by a RS-232 serial interface is proposed for data acquisition in equipment with analog output. Data are measured at the rate of 2 points per second and stored in text files by the software that accompanies the device, running in a Windows environment. The performance of the multimeter was verified by monitoring the transient signals generated in flow injection systems associated with fluorimetric, spectrophotometric and flame photometric detection. In addition, the performance of the proposed device was similar to that attained by employing an interface card with a 12-bit analog-to-digital converter for acquisition of the signals generated by a capillary electrophoresis equipment with oscillometric detection.

Montagem de câmara com lâmpada de ultravioleta de baixo custo

Thin layer chromatography is a quick, inexpensive and effective way of screening mixtures of non-volatile organic compounds and it is highly recommended for analytical studies. Inspection of plates under ultraviolet light for the detection of colourless compounds should be performed before any further chemical methods are applied. Construction of a low-cost UV-viewing cabinet with lamp employing parts easily found on the local market is described.

Um fotômetro multi-led microcontrolado, portátil e de baixo custo

A microcontrolled, portable and inexpensive photometer is described. It uses six light-emitting diodes (LEDs) as radiation sources and a phototransistor as detector, as well as a microcontroller (PIC - Programmable Controller of Interruption). This device provided total autonomy to the proposed photometer, which was successfully applied to determination of Fe2+ in ferrous syrups and of seven clinical biochemical parameters. As the components are cheap (~U$30.00) and easy to find, the proposed photometer is an economical alternative for routine chemical analyses in small laboratories, for research and teaching. Being portable and microcontrolled, it allows doing field chemical analyses.

Construção de amostrador passivo de baixo custo para determinação de dióxido de nitrogênio

A new passive sampling system for monitoring NO2 in air has been developed to measure gas concentrations in indoor and outdoor air. The sampler is inexpensive, and easy to construct and operate. Nitrogen dioxide forms a derivative after reaction with a filter coated with triethanolamine and ethyleneglycol. The nitrogen dioxide derivative is extracted from the filter, and the concentration is determined by colorimetry. To test the sampler for measuring ambient level nitrogen dioxide, measurements were carried out inside homes and in a range of workplace environments.

Um aparato para monitorar reações rápidas: um "stopped-flow" artesanal de baixo custo

The modern stopped-flow reaction analyzer has shown high efficiency and flexibility, which provides outstanding sample economy with a dead-time of less than 1 ms. However the cost of the equipment imposes a serious restriction to many Brazilian scientists and teachers. In this work we describe the construction of a low-cost stopped-flow system coupled to a UV-Vis spectrophotometer. The performance of the system was checked by monitoring the kinetics of two reactions: the fading of phenolphthalein in aqueous alkaline solution and the chlorophyll a demetallation in acid medium. The apparatus showed reasonable efficiency with a dead-time of 0.3 to 0.5 s. The very good results obtained in these two illustrative processes show that the system is satisfactory for determining rate constants with mean reaction times ranging from seconds to minutes.

Um espalhador de baixo custo de fase estacionária em placas para cromatografia em camada delgada

Chromatography is a means of separating mixtures into their several components. TLC, mainly a liquid/solid process, is one of the separation techniques most often used. It is indispensable in laboratories dealing with natural products, organic and analytical chemistry. Commercial chromatography plates are offered at relatively high cost. In this work the construction of a hand-operated plate coater of stationary phases of low cost and good reproducibility is described to be used in teaching laboratories and research.