Search results for "Methodology"
showing 10 items of 852 documents
Una propuesta sobre enseñanza de la relatividad en el bachillerato como motivación para el aprendizaje de la física
2007
Relativity is a very important part of modern physics. In this paper we analyze the teaching and learning of the theory of relativity in secondary education and we show some reasoned arguments against traditional methods to teach it. Finally, a didactic proposal for the teaching of relativity is presented; it comes as a conclusion that it is possible a suitable teaching of the principles of relative which should bring into the students a change in attitude, concepts and methodology.
Assessment of Postharvest Dehydration Kinetics and Skin Mechanical Properties of “Muscat of Alexandria” Grapes by Response Surface Methodology
2016
The dipping of berries in a dilute solution of sodium hydroxide during a short time was evaluated as pretreatment undertaken prior to convective dehydration of wine grapes. The impact of the sodium hydroxide content and dipping time on weight loss (WL) at different dehydration times was thoroughly assessed using central composite design (CCD) and response surface methodology (RSM). Furthermore, the effects of these two variables were also investigated on the skin mechanical properties of dehydrated grapes. The effect of these two pretreatment factors on the dehydration kinetics and skin hardness was satisfactorily fitted to regression models. The berry pretreatment with low sodium hydroxide…
Effects of temperature, pH and sugar concentration on the growth parameters of Saccharomyces cerevisiae, S. kudriavzevii and their interspecific hybr…
2008
The effects of temperature, pH and sugar concentration (50% glucose + 50% fructose) on the growth parameters of Saccharomyces cerevisiae T73, S. kudriavzevii IFO 1802T and the hybrid strain S. cerevisiae × S. kudriavzevii W27 were studied by means of response surface methodology based in a central composite circumscribed design. Lag phase could not be properly modelled in the wine model system, where yeasts started the fermentation in few hours after inoculation. In the case of the maximum specific growth rate (μ max), the temperature was the most important variable for three yeasts, although the effects of sugar concentration (in T73 and W27) and pH (W27 and 1802) were also significan…
Comparison of simultaneous saccharification and fermentation and separate hydrolysis and fermentation processes for butanol production from rice straw
2020
Abstract Rice straw (RS) is one of the lignocellulosic wastes with the highest global production. The main objective of this study was to maximise the butanol production by Clostridium beijerinckii DSM 6422 from RS pretreated by microwave-assisted hydrothermolysis. Two different fermentation strategies were compared: separate hydrolysis and fermentation (SHF, two-step process) and simultaneous saccharification and fermentation (SSF, one-step process). In parallel, the variables that significantly affected the butanol production were screened by using fractional factorial designs. Butanol concentration and productivity at 48 h were, respectively, 8% and 173% higher in SSF than in SHF. A one-…
Negative-pressure cavitation coupled with aqueous two-phase extraction and enrichment of flavonoids and stilbenes from the pigeon pea leaves and the …
2015
Abstract An efficient extraction method, negative-pressure cavitation coupled with aqueous two-phase extraction (NPC-ATPE), was developed to simultaneously extract and enrich flavonoids and stilbenes from pigeon pea leaves. The main bioactive compounds, cajaninstilbene acid (CSA), longistyline C (LLC), pinostrobin (PI) and pinostrobin chalcone (PIC) were chosen as target compounds. The extraction conditions were optimized using central composite design combined with response surface methodology. The optimized conditions were: concentration of (NH 4 ) 2 SO 4 21% (w/w), concentration of ethanol 23% (w/w) and temperature 30 °C, negative pressure −0.06 MPa, extraction time 30 min and the liquid…
Indoor Air Quality including Respiratory Viruses
2021
The detection of SARS-CoV-2 in indoor environments is a cause of increasing concern. In this study, three sampling methodologies have been used in order to collect SARS-CoV-2 and 17 other respiratory viruses in indoor air, combined with a new analytical process to analyze respiratory viruses. Different areas of an ophthalmological hospital were investigated for the presence of these airborne viruses. Moreover, indoor air quality (IAQ) parameters (carbon dioxide, CO2; carbon monoxide, CO; nitrogen dioxide, NO2; volatile organic compounds, VOCs; formaldehyde, HCHO; and particulate matter, PM) have been examined to study the relationship between IAQ and airborne viruses. All indoor air and sur…
Negative pressure cavitation-microwave assisted preparation of extract of Pyrola incarnata Fisch. rich in hyperin, 2'-O-galloylhyperin and chimaphili…
2013
Abstract A novel and effective extraction method, namely negative pressure cavitation-microwave assisted extraction technique (NMAE), was developed for the preparation of extracts of Pyrola incarnata Fisch., which are rich in the main constituents hyperin, 2′-O-galloylhyperin and chimaphilin. Single factor experiments and Box–Behnken design (BBD) were combined with a response surface methodology to examine factors affecting extraction. Maximum extraction yields of hyperin, 2′-O-galloylhyperin and chimaphilin (1.339 ± 0.029, 4.831 ± 0.117 and 0.329 ± 0.011 mg/g, respectively) were achieved under the following optimised conditions: 700 W microwave power, 50 °C extraction temperature, 30:1 mL/…
Negative pressure cavitation accelerated processing for extraction of main bioactive flavonoids from Radix Scutellariae
2011
Abstract To enhance the extraction efficiency and reduce the energy consumption, an emerging technology named negative pressure cavitation extraction (NPCE) has been shown to be a feasible option for the extraction of bioactive compounds in agricultural crops and medicinal plants. Meanwhile, it can be applied at the pilot scale as a manufacturing process for edible and medicinal plants. Currently, NPCE was proposed for extraction of baicalin, wogonoside, baicalein and wogonin from Radix Scutellariae on the basis of a central composite design (CCD) and response surface methodology (RSM). With proper optimization (80 mesh of particle size, 40 mL/g of liquid/solid ratio, 75% aqueous ethanol as…
Negative pressure cavitation extraction and antioxidant activity of genistein and genistin from the roots of pigeon pea [Cajanus cajan (L.) Millsp.]
2010
Abstract A new method—negative pressure cavitation extraction (NPCE) was proposed and investigated for the extraction of the main isoflavonoids, namely genistein and genistin from pigeon pea roots. The effects of extraction time and particle size on the extraction yields were firstly optimized, then a central composite design (CCD) combined with response surface methodology (RSM) was used to study the effects of negative pressure, ethanol concentration and liquid/solid ratio on the extraction yields. The maximum extraction yields of genistein and genistin reached 0.418 and 0.398 mg/g, respectively, under the optimal conditions: extraction time 45 min, particle size 50 mesh, negative pressur…
Romanian Folk Literature in Our Classes: A Proposal for the Development of Intercultural Competence
2015
Abstract The present research highlights the ways in which folk literature, this valuable tool that contributes to students’ formation from both a human and literary perspective, can promote intercultural competence in class and foster a better integration within the community, while consolidating favorable attitudes towards interculturality. We share Rodriguez Almodovar's view (2009), according to which the folk story makes the geographic space expand; it channels affectivity, while guiding the learning process towards the acceptance of social values that are representative for each culture. The objectives of our study are focused, on the one hand, on improving intercultural competence amo…