Search results for "quantitative analysis"
showing 10 items of 304 documents
Quantitative and qualitative analysis of the mental models deployed by undergraduate students in explaining thermally activated phenomena
2017
In this contribution we describe a research aimed at pointing out the quality of mental models undergraduate engineering students deploy when asked to create explanations for phenomena/processes and/or use a given model in the same context. Student responses to a specially designed written questionnaire are initially analyzed using researcher-generated categories of reasoning, based on the Physics Education Research literature on student understanding of the relevant physics content. The inferred students’ mental models about the analyzed phenomena are categorized as practical, descriptive, or explanatory, based on an analysis of student responses to the questionnaire. A qualitative analysi…
High-performance micellar liquid chromatography determination of sulphonamides in pharmaceuticals after azodye precolumn derivatization
1995
Abstract A chromatographic procedure with precolumn derivatization to form the N-(1-naphthyl)ethylenediamine dihydrochloride azodyes is proposed for the analysis of several sulphonamides (sodium sulphacetamide, sulphadiazine, sulphaguanidine, sulphamerazine, sulphamethizole, sulphamethoxazole, sulphanilamide and sulphathiazole) in pharmaceutical preparations (tablets, pills, capsules, suspensions and drops). The separation is performed with a 0.05 M sodium dodecyl sulphate/2.4% pentanol eluent at pH 7. The precolumn derivatization improved the resolution in the chromatograms and increased the selectivity in the determination of mixtures of sulphonamides and in preparations where other drugs…
An unsupervised quantitative method to analyse students' answering strategies to a questionnaire
2018
Questionnaires are perhaps the most widely used instruments to assess conceptual learning in physics as well as in mathematics. In the field of physics and mathematics education research it is surely interesting to be able to use a questionnaire as a “diagnostic instrument,” i.e., to know details about relationships among student answers to the different questions. In recent years several research works focused on this goal by using different quantitative methodologies, like Factor, Model and Cluster Analyses. However, very few research works deepened the theoretical aspects of the Cluster Analysis. In this contribution, we discuss two Cluster Analysis methods with respect to this issue. By…
Quantitative Analysis, InfraredUpdate based on the original article by Frederic Cadet,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & …
2012
O zadawaniu pytań na lekcji języka polskiego. Studium przypadku
2020
The article presents the results of qualitative and quantitative analysis of questions asked during a single Polish language lesson. It consists of two main parts. The first presents and comments on the results of the teacher’s questions analysis, the second ‒ questions asked by students. The concept of Bogusław Skowronek was used, who distinguished four types of questions in his classification: 1) reassuring-instrumental; 2) substantive; 3) about the meta-didactic function; 4) not related to the classroom situation. The first two categories were specified in more detail by Elizabeth Perrott’s proposition, which distinguishes between guiding questions and questions for clarification among r…
Detection of lactobacillic acid in low erucic rapeseed oil--A note of caution when quantifying cyclic fatty acid monomers in vegetable oils.
2010
International audience; The purpose of this work was to identify an unknown component which has been detected during the analysis of cyclic fatty acid monomers (CFAMs) in low erucic acid rapeseed oils (LEAR). A sample of crude LEAR was transformed into fatty acid methyl esters (FAMEs) and hydrogenated using PtO2. The hydrogenated sample was fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC) and the fraction containing the CFAMs transformed into picolinyl esters. Analysing these picolinyl derivatives by gas-liquid chromatography coupled to mass spectrometry (GC-MS) showed that the unknown product observed in LEAR is the 11,12-methylene-octadecanoic acid. This cyc…
Efficient flow injection and sequential injection methods for spectrophotometric determination of oxybenzone in sunscreens based on reaction with Ni(…
2001
Spectrophotometric determination of a widely used UV-filter, such as oxybenzone, is proposed. The method is based on the complexation reaction between oxybenzone and Ni(II) in ammoniacal medium. The stoichiometry of the reaction, established by the Job method, was 1:1. Reaction conditions were studied and the experimental parameters were optimized, for both flow injection (FI) and sequential injection (SI) determinations, with comparative purposes. Sunscreen formulations containing oxybenzone were analyzed by the proposed methods and results compared with those obtained by HPLC. Data show that both FI and SI procedures provide accurate and precise results. The ruggedness, sensitivity and LO…
O pytaniach podczas rozmowy maturalnej z języka polskiego
2019
“Now, let us move to our conversation — please name characteristics of a parable”. On questions students are asked during their high school oral leaving exam in PolishIn the article I present the results of a qualitative and quantitative analysis of 149 questions asked by teachers during 30 high school oral leaving exams in Polish. In this I use the classification formulated by Elizabeth Perrott, who, taking into account Benjamin Bloom’s “taxonomy of educational objectives”, has proposed a division of the questions by the type of thinking process launched during answering, distinguishing lower-level questions recall, understanding, application and higher-level questions analysis, synthesis …
Determination of acetazolamide in human urine samples by reversed-phase high-performance liquid chromatography in the presence of xanthines.
1992
A simple, rapid and selective high-performance liquid chromatographic assay for the determination of acetazolamide in urine samples is described. After extraction with ethyl acetate, the drug is chromatographed on an HP-Hypersil ODS-C18 column with a mobile phase of acetonitrile-phosphate buffer (pH 3) and ultraviolet detection at 275 nm. The efficiency of the extraction, the linearity and the reproducibility of the method permit the evaluation of acetazolamide urinary excretion a long time after its administration.
Quantitative Multispectral Imaging Differentiates Melanoma from Seborrheic Keratosis.
2021
Melanoma is a melanocytic tumor that is responsible for the most skin cancer-related deaths. By contrast, seborrheic keratosis (SK) is a very common benign lesion with a clinical picture that may resemble melanoma. We used a multispectral imaging device to distinguish these two entities, with the use of autofluorescence imaging with 405 nm and diffuse reflectance imaging with 525 and 660 narrow-band LED illumination. We analyzed intensity descriptors of the acquired images. These included ratios of intensity values of different channels, standard deviation and minimum/maximum values of intensity of the lesions. The pattern of the lesions was also assessed with the use of particle analysis. …