mariana Rivas - Academia.edu (original) (raw)
Papers by mariana Rivas
Journal of Chemical Education, 2019
Over the past several decades, green chemistry has gained prominence in chemistry education. Howe... more Over the past several decades, green chemistry has gained prominence in chemistry education. However, the development of green chemistry curricula has not reached all levels of education equally, focusing mainly on elective and upper division courses. We deliberately focused our green chemistry curriculum redesign on a high enrollment introductory general chemistry laboratory course at the University of California, Berkeley. We developed over 30 new experiments that introduced students to green chemistry concepts and applications, while maintaining canonical general chemistry learning goals. The context of the curriculum and required course assignments encouraged students to use green chemistry principles to explore and solve real-world problems. After completing this redesigned course, we hypothesized that students would value green chemistry and feel more confident in their green chemistry knowledge. We developed new methods to measure students' attitudes toward and understanding of green chemistry as a system instead of isolated reactions or processes. These assessments allowed us to better understand both the progression and limitations in student green chemistry and systems-thinking. Since over 2000 students complete the laboratory course each year, we used a combination of fixed response items and free response items from online surveys and in-class assignments and exams. This approach allowed efficient assessment of thousands of students, while still gaining valuable and nuanced views of student understanding and attitudes. These assessments indicated that the new general chemistry laboratory curriculum succeeded in providing an environment in which students learned green chemistry concepts and realized that chemistry has connections to their future courses and professions.
Revista Argentina de microbiología
Culture media, reagents, and commercial kits were compared on artificially contaminated food samp... more Culture media, reagents, and commercial kits were compared on artificially contaminated food samples. The objective was to find an isolation method for Escherichia coli O157:H7 sensitive, specific and accessible in terms of cost, requirements of equipments and qualification of the analyst. The adopted scheme consisted in a selective enrichment at 42 degrees C during 18 to 24 h, using an appropriate medium, in accordance with the nature of the sample, followed by a step of immunomagnetic separation and simultaneous isolation on a chromogenic agar and MacConkey sorbitol agar with potassium tellurite and cefixime, during 18-24 h at 37 degrees C. The presumptive colonies were confirmed as E. coli O157 by serological and biochemical tests. Secondly, this methodology was applied to food samples, water, bovine gastric content and manure. A total of 410 samples were studied: 279 from meat, 54 milk and dairy products, 6 from vegetables, 27 water samples and 44 bovine gastric content and manu...
Acta Scientiarum. Health Science, 2005
A food-frequency questionnaire (FFQ) was designed to assess the average consumption frequency of ... more A food-frequency questionnaire (FFQ) was designed to assess the average consumption frequency of food items and to characterize the food pattern among workers. A list of consumed food and usual serving sizes was compiled from previous local survey, using single 24 hours dietary recalls and frequency questionnaires. The list was composed of 127 items and the nutrient composition was calculated by the computer program DietPro version 3.0. The FFQ was administered to each subject twice in a period of six months. To characterize food pattern consumption, the most frequently mentioned foods were identified. One hundred and four (104) workers were studied, randomly selected. Items consumed at least once a day by 50% of the workers were: white bread, margarine, black coffee, white sugar, red beans and white rice. Variety of daily consumed foods was small. The top 30 foods on a daily basis ranged from less than 1.5 to 92%. This FFQ is easy to administer when studying the dietary intake of low-income populations.
Stroke after cannabis consumption
Journal of Chemical Education, 2019
Over the past several decades, green chemistry has gained prominence in chemistry education. Howe... more Over the past several decades, green chemistry has gained prominence in chemistry education. However, the development of green chemistry curricula has not reached all levels of education equally, focusing mainly on elective and upper division courses. We deliberately focused our green chemistry curriculum redesign on a high enrollment introductory general chemistry laboratory course at the University of California, Berkeley. We developed over 30 new experiments that introduced students to green chemistry concepts and applications, while maintaining canonical general chemistry learning goals. The context of the curriculum and required course assignments encouraged students to use green chemistry principles to explore and solve real-world problems. After completing this redesigned course, we hypothesized that students would value green chemistry and feel more confident in their green chemistry knowledge. We developed new methods to measure students' attitudes toward and understanding of green chemistry as a system instead of isolated reactions or processes. These assessments allowed us to better understand both the progression and limitations in student green chemistry and systems-thinking. Since over 2000 students complete the laboratory course each year, we used a combination of fixed response items and free response items from online surveys and in-class assignments and exams. This approach allowed efficient assessment of thousands of students, while still gaining valuable and nuanced views of student understanding and attitudes. These assessments indicated that the new general chemistry laboratory curriculum succeeded in providing an environment in which students learned green chemistry concepts and realized that chemistry has connections to their future courses and professions.
Revista Argentina de microbiología
Culture media, reagents, and commercial kits were compared on artificially contaminated food samp... more Culture media, reagents, and commercial kits were compared on artificially contaminated food samples. The objective was to find an isolation method for Escherichia coli O157:H7 sensitive, specific and accessible in terms of cost, requirements of equipments and qualification of the analyst. The adopted scheme consisted in a selective enrichment at 42 degrees C during 18 to 24 h, using an appropriate medium, in accordance with the nature of the sample, followed by a step of immunomagnetic separation and simultaneous isolation on a chromogenic agar and MacConkey sorbitol agar with potassium tellurite and cefixime, during 18-24 h at 37 degrees C. The presumptive colonies were confirmed as E. coli O157 by serological and biochemical tests. Secondly, this methodology was applied to food samples, water, bovine gastric content and manure. A total of 410 samples were studied: 279 from meat, 54 milk and dairy products, 6 from vegetables, 27 water samples and 44 bovine gastric content and manu...
Acta Scientiarum. Health Science, 2005
A food-frequency questionnaire (FFQ) was designed to assess the average consumption frequency of ... more A food-frequency questionnaire (FFQ) was designed to assess the average consumption frequency of food items and to characterize the food pattern among workers. A list of consumed food and usual serving sizes was compiled from previous local survey, using single 24 hours dietary recalls and frequency questionnaires. The list was composed of 127 items and the nutrient composition was calculated by the computer program DietPro version 3.0. The FFQ was administered to each subject twice in a period of six months. To characterize food pattern consumption, the most frequently mentioned foods were identified. One hundred and four (104) workers were studied, randomly selected. Items consumed at least once a day by 50% of the workers were: white bread, margarine, black coffee, white sugar, red beans and white rice. Variety of daily consumed foods was small. The top 30 foods on a daily basis ranged from less than 1.5 to 92%. This FFQ is easy to administer when studying the dietary intake of low-income populations.
Stroke after cannabis consumption