A leitura como um processo cognitivo
Figueiredo, Olívia Maria
1999-01-01
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You search for extraction and 8,991 records were found.
The efficiency of eight different procedures used for the extraction of natural dyes was evaluated using contemporary wool samples dyed with cochineal, madder, woad, weld, brazilwood and logwood. Comparison was
made based on the LC-DAD peak areas of the natural dye’s main components which had been extracted from the wool samples. Among the tested methods, an extraction procedure
with Na2EDTA in water/DMF (1:1, v/v) proved to be the most suitable for the extraction of the studied dyes,
which presented a wide range of chemical structures. The identification of the natural dyes used in the making of an eighteenth century Arraiolos carpet was possible using the Na2EDTA/DMF extraction of the wool embroidery samples and an LC-DAD-MS methodology. The effectiveness of the Na2EDTA/DMF extraction method was particularly observed in the extractio...
The exopolymeric matrix that surrounds the biomass greatly contributes to the efficiency of activated sludge systems. To study the composition of this matrix a preliminary extraction method is required. In this work three extraction methods (vapor, sonication and combined treatment by sonication and Dowex resin) were used and compared with a new method which uses glutaraldehyde. The extraction effectiveness was estimated by measuring the total protein, the total organic carbon in the extracted solutions and by determining the monosaccharide constituents of the extracted polysaccharides. The proposed new method proved to be the most suitable because it extracted a great quantity of organic matter without disrupting the cells.
The extraction of antioxidant phenolic compounds from spent coffee grounds (SCG) was studied. Extraction experiments were carried out by the conventional solid–liquid method, using methanol as solvent at different concentrations (20–100%), solvent/solid ratios (10–40 ml/g SCG), and extraction times (30–90 min), and the influence of these operational variables on the content of total phenolic compounds and antioxidant activity of the produced extracts was evaluated. Flavonoids, chlorogenic acid, and protocatechuic acid were found in all the produced extracts and were also quantified. A strong influence (p < 0.05) of the variables on the extraction results was verified, and the conditions able to maximize each response (contents of total phenolic compounds, flavonoids, chlorogenic acid and protocatechuic acid, and antioxidant activity) w...
This work presents a methodology for the extraction of galactomannans from seeds of four different species
of Leguminosae (Adenanthera pavonina, Caesalpinia pulcherrima, Gleditsia triacanthos and Sophora
japonica) to be used e.g. in the food and biomedical industries. The galactomannans were obtained by
aqueous extraction followed by a precipitation with ethanol. This methodology is simpler and easier to
perform than other existing extraction and purification methodologies, and because it avoids the use
of organic solvents (other than ethanol), it is able to generate food grade substances and is environmentally
friendlier. The yield of extraction in different stages of the process, monosaccharide composition, as
well as physical and chemical parameters of the isolated galactomannans were determined and compared
with previously ...
The exopolymeric matrix that surrounds the biomass greatly contributes to the efficiency of activated sludge systems. To study the composition of this matrix a preliminary extraction method is required. In this work three extraction methods (vapour, sonication and combined treatment by sonication and Dowex resin) were used and compared with a new method which uses glutaraldehyde. The extraction's effectiveness was estimated by measuring the total protein content, the total organic carbon in the extracted solutions and by determining the monosaccharide constituents of the polysaccharides extracted. The new method proposed proved to be the most suitable one, as it extracts a great quantity of organic matter without disrupting the cells.
Sulfated polysaccharides (fucoidan) were recovered from brown seaweed Fucus vesiculosus by microwave-assisted extraction (MAE). Different conditions of pressure (30 to 120 psi), extraction time (1 to 31 min), and alga/water ratio (1/25 to 5/25 g ml-1) were evaluated during this process aiming to establish a condition to maximize the extraction results. The alga degradation (%), total sugar yield (%), and SO3 content (%) were also determined to each experimental condition. All the studied variables presented significant (p<0.05) influence on fucoidan yield. MAE at 120 psi, 1 min, using 1 g alga/25 ml water was the best condition for the fucoidan recovery. L-fucose was the main constituent of this polysaccharide, which also contained xylose and galactose. MAE under optimum reaction conditions was an effective method to recover fucoidan f...
Early detection of gastrointestinal (GI) can
cers is one
of most important concerns in medical field. Its detection at the
earliest stage is crucial to increase the patient survival chances.
Optical signals extraction and analysis, specifically diffuse
reflectance and intrinsic fluorescence, may impr
ove the ability to
detect GI dysplasia, once some morphological and biochemical
changes on the tissues (related with early cancer progre
ssion) can
modify these signals’
shape and intensity. The project under th
is
paper aims to develop a chip
-
sized spectros
copy microsystem for
the early detection of GI cancer. This paper presents the
characterization of silicon photodiodes (n+/p
-
epilayer type)
fabricated in a standard 0.7 μm ...
Transistor models are of utmost importance for device behaviour prediction and circuit design. Physical modelling has the advantage of the parameters being correlated based on device physics. This allows to gain insight on the device during the analysis and extraction of parameters phase. However, the extraction methods may not consider possible non-idealities of the device, which can cause modelling issues when working with novel thin film transistors (TFTs).
A simple physical DC and AC model was applied to a novel zinc tin oxide TFT annealed at low temperatures (200 ºC). The characteristic curves of four devices with different dimensions were measured and analysed, and the model parameters were extracted. The characterization and optimization of the models were implemented through the analysis of the fitting with the measured data. ...
In this paper is presented the development of a
project to extract, in real-time, information’s related with an
Electric Vehicle (EV). This project was elaborated to extract data
from an EV battery charging device developed at the University
of Minho, and from an EV prototype, the VEECO (Veículo
Eléctrico ECOlógico – Ecologic Electric Vehicle), developed in a
cooperation project of ISEL (Lisbon Superior Institute of
Engineering) and the Portuguese company VE. The main goal of
this project consists in collecting and transmitting the extracted
data to inform the EV driver about the performance and the real
behavior of the EV. Thereby, it is created an open interface to
manage, in real-time, the main data related with the EV, as the
batteries SoC (State-of-Charge), the EV speed, and internal
temperatures (like the temperature...
Water hyacinth (Eichornia crassipes) is an invasive aquatic plant that has recently been showed to have a remarkable abundance of stigmasterol in leaves and stalks. The supercritical fluid extraction (SFE) of E. crassipes parts was performed for the first time in this work, covering total yield (eta(total)), stigmasterol yield (eta(stig)), and its concentration in extracts (c(stig)). Several experiments were performed at 200 bar, two temperatures (40 and 60 degrees C), and three cosolvent amounts (0, 5, 10 wt.% ethanol). Moreover, two cumulative extraction curves were measured (200 bar and 40 or 60 degrees C). The results showed that eta(total) ranged from 0.64 to 0.73 wt.% after 6 h of extraction, eventually reaching 1.88 wt.% if the extraction time four times and ethanol is included. For eta(stig), 6 h of SFE yielded 0.20-0.22 wt.% w...
