Multiple representations in web-based learning of chemistry concepts

A new chemistry curriculum for secondary schools is currently under construction in the Netherlands, in which chemical knowledge will be embedded in contexts that show applications of chemistry in the society. Several research groups develop such modules and a committee appointed by the Dutch Ministry of Education advises about the chemical content and concepts.\ud A central issue in chemistry education is the relation between the real, molecular and symbolic world. Skilled chemists switch easily between these worlds, but beginning students do not. They could get better results and will be more able to solve problems if they would make better connections between the three chemical worlds. The University of Twente has developed a series of lessons about the particle model. Included in this instruction material are animations of chemical processes at the molecular level. In the lessons students are supported and stimulated to make connections between the three chemical worlds. Students are shown the importance of new chemical knowledge in society. The mental images and the knowledge schemata of the students are investigated in this research. The students were interviewed before they received instruction, and after they received about half of the instruction. At the end of the instruction they were asked to make a concept map.\ud It appeared that the links between the real, molecular and symbolic world are not strengthened after the instruction. The students make more links between the real and symbolic world, but hardly connect these world to the molecular world or vice versa. There is still a gap between the students’ mental models and scientifically accepted models as represented in animations and illustrations in the instruction. Most students liked the animations in the instruction and mentioned them as strong point. It is therefore surprising that some students could not remember the animations when they were interviewed, whilst others their representations were about the same as the animations. Clearly, the effectiveness of the animations must be enhanced and more research is needed for this

Development and validation of a risk score for chronic kidney disease in HIV infection using prospective cohort data from the D:A:D study.

Chronic kidney disease (CKD) is a major health issue for HIV-positive individuals, associated with increased morbidity and mortality. Development and implementation of a risk score model for CKD would allow comparison of the risks and benefits of adding potentially nephrotoxic antiretrovirals to a treatment regimen and would identify those at greatest risk of CKD. The aims of this study were to develop a simple, externally validated, and widely applicable long-term risk score model for CKD in HIV-positive individuals that can guide decision making in clinical practice

Efavirenz versus boosted atazanavir-containing regimens and immunologic, virologic, and clinical outcomes: A prospective study of HIV-positive individuals

OBJECTIVE: To compare regimens consisting of either ritonavir-boosted atazanavir or efavirenz and a nucleoside reverse transcriptase inhibitor (NRTI) backbone with respect to clinical, immunologic, and virologic outcomes. DESIGN: Prospective studies of human immunodeficiency virus (HIV)-infected individuals in Europe and the United States included in the HIV-CAUSAL Collaboration. METHODS: HIV-positive, antiretroviral therapy-naive, and acquired immune deficiency syndrome (AIDS)-free individuals were followed from the time they started an atazanavir or efavirenz regimen. We estimated an analog of the "intention-to-treat" effect for efavirenz versus atazanavir regimens on clinical, immunologic, and virologic outcomes with adjustment via inverse probability weighting for time-varying covariates. RESULTS: A total of 4301 individuals started an atazanavir regimen (83 deaths, 157 AIDS-defining illnesses or deaths) and 18,786 individuals started an efavirenz regimen (389 deaths, 825 AIDS-defining illnesses or deaths). During a median follow-up of 31 months, the hazard ratios (95% confidence intervals) were 0.98 (0.77, 1.24) for death and 1.09 (0.91, 1.30) for AIDS-defining illness or death comparing efavirenz with atazanavir regimens. The 5-year survival difference was 0.1% (95% confidence interval: -0.7%, 0.8%) and the AIDS-free survival difference was -0.3% (-1.2%, 0.6%). After 12 months, the mean change in CD4 cell count was 20.8 (95% confidence interval: 13.9, 27.8) cells/mm lower and the risk of virologic failure was 20% (14%, 26%) lower in the efavirenz regimens. CONCLUSION: Our estimates are consistent with a smaller 12-month increase in CD4 cell count, and a smaller risk of virologic failure at 12 months for efavirenz compared with atazanavir regimens. No overall differences could be detected with respect to 5-year survival or AIDS-free survival

The HIV continuum of care in European Union countries in 2013: data and challenges

BACKGROUND: UNAIDS has set a 90-90-90 target to curb the HIV epidemic by 2020, but methods used to assess whether countries have reached this target are not standardised, hindering comparisons. METHODS: Through a collaboration formed by the European Centre for Disease Prevention and Control (ECDC) with European HIV cohorts and surveillance agencies, we constructed a standardised, four-stage continuum of HIV care for 11 European Union (EU) countries for 2013. Stages were defined as: 1) number of people living with HIV (PLHIV) in the country by end of 2013; 2) proportion of stage 1 ever diagnosed; 3) proportion of stage 2 ever initiated ART; and 4) proportion of stage 3 who became virally-suppressed (≤200 copies/mL). Case surveillance data were used primarily to derive stages 1 (using back-calculation models) and 2, and cohort data for stages 3 and 4. RESULTS: In 2013, 674,500 people in the 11 countries were estimated to be living with HIV, ranging from 5,500 to 153,400 in each country. Overall HIV prevalence was 0.22% (range 0.09%-0.36%). Overall proportions, of each previous stage, were 84% diagnosed, 84% on ART, and 85% virally-suppressed (60% of PLHIV). Two countries achieved ≥90% for all stages, and over half had reached ≥90% for at least one stage. CONCLUSIONS: EU countries are nearing the 90-90-90 target. Reducing the proportion undiagnosed remains the greatest barrier to achieving this target, suggesting further efforts are needed to improve HIV testing rates. Standardising methods to derive comparable continuums of care remains a challenge

International Scientific Conference 18th Ružička Days “Today science, tomorrow industry”, September 16–18, 2020, Vukovar Croatia NOBEL LAUREATE RUŽIČKA AND RUŽIČKA DAYS From Vukovar to the Nobel Prize and Back

This issue of Chemical and Biochemical Engineering Quarterly (CABEQ) is dedicated to the 18th Ružička Days held September 16-18, 2020 in Vukovar. Ružička Days have been held in Vukovar since 1978, apart from the 8-year-period of the Greater Serbian aggression against Croatia, during which the city and the eastern part of Croatia were occupied. Naturally, this scientific and professional conference was named after Leopold (Lavoslav) Ružička, since he was a native of Vukovar. Therefore, a short review of his life and work will be presented in this article, as well as a brief history of Ružička Days

International Scientific Conference 18th Ružička Days “Today science, tomorrow industry”, September 16–18, 2020, Vukovar Croatia NOBEL LAUREATE RUŽIČKA AND RUŽIČKA DAYS From Vukovar to the Nobel Prize and Back

This issue of Chemical and Biochemical Engineering Quarterly (CABEQ) is dedicated to the 18th Ružička Days held September 16-18, 2020 in Vukovar. Ružička Days have been held in Vukovar since 1978, apart from the 8-year-period of the Greater Serbian aggression against Croatia, during which the city and the eastern part of Croatia were occupied. Naturally, this scientific and professional conference was named after Leopold (Lavoslav) Ružička, since he was a native of Vukovar. Therefore, a short review of his life and work will be presented in this article, as well as a brief history of Ružička Days