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 procedure for extraction of water-soluble mercury species from soil was studied and optimized. Aspects studied included the soil:water ratio, time of extraction, separation technique (centrifugation vs. filtration) and analytical technique used to analyze the extract (pyrolysis-atomic absorption spectrometry vs. atomic fluorescence spectrometry). Results indicated that the process of extraction is not influenced by the soil:water ratio in the range studied (1.5:100 to 20:100). The kinetic study performed showed that it takes 24. h for extraction to reach equilibrium, and that the mercury removal reaction takes place in two stages, a faster one (0 < t < 6 h), followed by a slower stage (t > 6 h). Hence, a two first-order reaction model was tested and proved to fit the experimental data. The particle size distribution seemed to have ...
Molecularly imprinted polymer (MIP) particles are here developed to target phenolic compounds present
in mixtures resulting from supercritical extraction processes. Engineered MIP particles are synthetized
considering different polymerization processes to tailor products morphology (e.g. precipitation or
inverse-suspension polymerization to obtain micro-particles [1]) and also diverse functional monomers to
explore preferential interactions with the template polyphenols (e.g. polydatin, resveratrol, etc). Moreover,
MIP particles with surface grafted functional polymer chains (e.g. using RAFT polymerization [2,3]) are
produced to assess the improvement of the selectivity of MIPs towards the target polyphenols, namely
through the tuning of the hydrophilic/hydrophobic effects (amphiphilic materials are generated). The
produced MIP...
In this work, a microwave-assisted extraction (MAE) methodology was compared with several conventional
extraction methods (Soxhlet, Bligh & Dyer, modified Bligh & Dyer, Folch, modified Folch, Hara &
Radin, Roese-Gottlieb) for quantification of total lipid content of three fish species: horse mackerel (Trachurus
trachurus), chub mackerel (Scomber japonicus), and sardine (Sardina pilchardus). The influence of
species, extraction method and frozen storage time (varying from fresh to 9 months of freezing) on total
lipid content was analysed in detail.
The efficiencies of methods MAE, Bligh & Dyer, Folch, modified Folch and Hara & Radin were the highest
and although they were not statistically different, differences existed in terms of variability, with MAE
showing the highest repeatability (CV = 0.034). Roese-Gottlieb, Soxhlet, and...
The modelling of the experimental data of the extraction of the volatile oil from six aromatic plants (coriander, fennel, savoury, winter savoury, cotton lavender and thyme) was performed using five mathematical models, based on differential mass balances. In all cases the extraction was internal diffusion controlled and the internal mass transfer coefficienty (k(s)) have been found to change with pressure, temperature and particle size. For fennel, savoury and cotton lavender, the external mass transfer and the equilibrium phase also influenced the second extraction period, since k(s) changed with the tested flow rates.
In general, the axial dispersion coefficient could be neglected for the conditions studied, since Peclet numbers were high. On the other hand, the solute-matrix interaction had to be considered in order to ensure a sa...
Microwave technologies are more and more present in food applications due
to their performance in shortening the time of treatments such as drying,
pasteurization, defrosting, or post-harvesting [1]. While solvent-free microwave
extraction has been extensively used as a green procedure for essential oil and
volatile compounds from aromatic herbs [2], its applications have been
extended to enhance extraction of phytocompounds simultaneously with drying.
In microwave drying, operational cost is lower because energy is not consumed
in heating the walls of the apparatus or the environment [3].
Microwave technologies are more and more present in food applications due to their
performance in shortening the time of treatments such as drying, pasteurization, defrosting,
or postharvesting. While solvent-free microwave extraction has been extensively used as a
green procedure for essential oil and volatile compounds from aromatic herbs [1], its
applications have been extended to enhance extraction of phytocompounds simultaneously
with drying.
In this work, microwave hydrodiffusion and gravity was performed in a laboratory microwave
oven (NEOS-GR, Milestone, Italy), in order to evaluate its efficiency in the extraction of
nonvolatile compounds such as: free sugars, f1bers, colour, and phenolic compounds. Five
different matrices were tested: broccoli by-products (90% moisture), apple pomace (80%
moisture), spent coffee gro...
Ecological, evolutionary and population genetic studies of yeasts require the processing of a
high numbers of isolates. The current molecular methods for yeast identification and
characterization require time-consuming and labor intensive DNA extraction protocols. Within
this research, we aimed to develop a high-throughput method for yeast DNA extraction.
Total yeast DNA extraction was based on a previously described standard miniprep method
(Lopez et al., 2001; Schuller et al., 2004). Several steps were simplified or skipped. Microplates
containing 30, 50, 100 or 150 μL yeast cell suspensions per well were used instead of
microtubes. All reagents volumes were reduced in proportion to the volumes of cell
suspensions.
The most suitable yeast cell suspensions were 100 and 150 μL. The quality of the obtained
DNA was not affected...
In the biotechnology field, it has been suggested that extractions in two-phase aqueous
complex-fluid systems can possibly be used instead of, or as complementary processes to,
the more typical chromatographic operations, to reduce the cost of the downstream
processing of many biological products (Lam et al., 2004; Mazzola et al., 2006). This method
offer attractive conditions to be applied in this study, thereby two-phase systems can be
exploited in separation science for the extraction/purification of desired biomolecules directly
on the culture medium (Mazzola et al., 2008). This study aimed to evaluate the aqueous two
phase system (ATPS) composed by a nonionic surfactant, Triton X-114 (TX), in presence or
absence of electrolytes, to separate two interesting biomolecules: nisin and recombinant
green fluorescent protein (GFP...
In this paper we compare different technologies that support distributed computing as a means to address complex tasks. We address the task of n-gram text extraction which is a big computational given a large amount of textual data to process. In order to deal with such complexity we have to adopt and implement parallelization patterns. Nowadays there are several patterns, platforms and even languages that can be used for the parallelization task. We implemented this task on three platforms: (1) MPJ Express, (2) Apache Hadoop, and (3) Apache Spark. The experiments were implemented using two kinds of datasets composed by: (A) a large number of small files, and (B) a small number of large files. Each experiment uses both datasets and the experiment repeats for a set of different file sizes. We compared performance and efficiency among MP...
High-pressure assisted extraction was employed to obtain fig by-product derived extracts and its impact was evaluated on antioxidant activity and total phenolic, tannin, and flavonoid. A Box-Behnken design was applied to evaluate the effects of pressure, extraction time and ethanol concentration on extractions and optimal conditions were estimated by response surface methodology. The correlation analysis of the mathematical-regression model indicated that a quadratic polynomial model could be employed to optimize the high pressure extraction of compounds. Only the models developed for total antioxidant activity by DPPH · and for total flavonoids presented coefficient determinations lower than 0.95. From response surface plots, pressure, extraction time and ethanol concentration showed independent and interactive effects. The optimal co...
