The effect of ozone on photosynthesis and respiration of Scenedesmus obtusiusculus Chod., with a general discussion of effects of air pollutants in plants

In the present study the mode of action of the air pollutant ozone was investigated by studying its effects on photosynthesis, respiration and some biochemical and structural properties of the unicellular alga, Scenedesmus obtusiusculus CHOD.In chapter 1, an effort was made to review the extensive literature on the effects of the most important air pollutant gases SO 2 , HF, NO 2 , PAN and O 3 on the processes of photosynthesis and respiration, while possible modes of action of each of these gases are discussed.In chapter 2, section 2.1., the procedure for ozone exposure is extensively described; a lot of time was required to obtain a reliable experimental design.In chapter 3, section 3.1., it is shown that photosynthesis and dark respiration are inhibited by previous exposure of the cell suspensions to ozone; the inhibition is increased with the duration of exposure and with temperature during exposure. The effect of an ozone treatment is increased by light during the exposure, and, consequently, photosynthesis appears more inhibited in as much as the light- intensity during the preceding exposure to ozone was higher. Photosynthesis is most inhibited in the light saturated part of the light intensity curve, which indicates that the inhibition of dark reactions of photosynthesis is more pronounced than that of the primary photoreactions. The degree of inhibition of photosynthesis is practically independent of cell density during a preceding exposure to ozone in the dark. The inhibition of photosynthesis, induced by an ozone exposure in the light, can be somewhat recovered by an after-treatment with pure air; however, the recovery effect was not alway very clear.In chapter 3, section 3.2., it is shown that the chlorophyll content decreases by exposure to ozone; the decrease is more pronounced after exposure in the light than after exposure in the dark. Preferentially, chlorophyll a is destroyed, which implies that the ratio chlorophyll a/b decreases.In chapter 3, section 3.3., it appeared in a preliminary study that there is a substantial loss of lipid in ozone-exposed algae, and there are indications that this is mainly due to oxidation of the unsaturated fatty acid, linolenic acid. Malondialdehyde production, often accompanying lipid peroxidation, was not detected in the ozone exposed algae.In chapter 3, section 3.4., it is shown in a preliminary study that there is a very small loss of protein content in ozone-exposed algae, which may be ascribed mainly to oxidation of the acid component serine, and of an unidentified alkaline compound.In chapter 3, section 3.5., in a preliminary study, it is described that, in ozone exposed algae, ultrastructural changes are observed, e.g., a disruption of the plasmalemma and the chloroplast envelope, a widening of the chloroplast membrane system, and the formation of electron-thin ring systems around starch granules

A putative mechanism for bog patterning

The surface of bogs commonly shows various spatial vegetation patterning. Typical are ¿string patterns¿ consisting of regular densely vegetated bands oriented perpendicular to the slope. Here, we report on regular ¿maze patterns¿ on flat ground, consisting of bands densely vegetated by vascular plants in a more sparsely vegetated matrix of nonvascular plant communities. We present a model reproducing these maze and string patterns, describing how nutrient-limited vascular plants are controlled by, and in turn control, both hydrology and solute transport. We propose that the patterns are self-organized and originate from a nutrient accumulation mechanism. In the model, this is caused by the convective transport of nutrients in the groundwater toward areas with higher vascular plant biomass, driven by differences in transpiration rate. In a numerical bifurcation analysis we show how the maze patterns originate from the spatially homogeneous equilibrium and how this is affected by changes in rainfall, nutrient input, and plant properties. Our results confirm earlier model results, showing that redistribution of a limiting resource may lead to fine-scale facilitative and coarse-scale competitive plant interactions in different ecosystems. Self-organization in ecosystems may be a more general phenomenon than previously thought, which can be mechanistically linked to scale-dependent facilitation and competition

Treatment decision for transcatheter aortic valve implantation: the role of the heart team: Position statement paper of the Dutch Working Group of Transcatheter Heart Interventions

The current paper presents a position statement of the Dutch Working Group of Transcatheter Heart Valve Interventions that describes which patients with aortic stenosis should be considered for transcatheter aortic valve implantation and how this treatment proposal/decision should be made. Given the complexity of the disease and the assessment of its severity, in particular in combination with the continuous emergence of new clinical insights and evidence from physiological and randomised clinical studies plus the introduction of novel innovative treatment modalities, the gatekeeper of the treatment proposal/decision and, thus, of qualification for cost reimbursement is the heart team, which consists of dedicated professionals working in specialised centres

Methods of data collection and definitions of cardiac outcomes in the Rotterdam Study

The prevalence of cardiovascular diseases is rising. Therefore, adequate risk prediction and identification of its determinants is increasingly important. The Rotterdam Study is a prospective population-based cohort study ongoing since 1990 in the city of Rotterdam, The Netherlands. One of the main targets of the Rotterdam Study is to identify the determinants and prognosis of cardiovascular diseases. Case finding in epidemiological studies is strongly depending on various sources of followup and clear outcome definitions. The sources used for collection of data in the Rotterdam Study are diverse and the definitions of outcomes in the Rotterdam Study have changed due to the introduction of novel diagnostics and therapeutic interventions. This article gives the methods for data collection and the up-to-date definitions of the cardiac outcomes based on international guidelines, including the recently adopted cardiovascular disease mortality definitions. In all, detailed description of cardiac outcome definitions enhances the possibility to make comparisons with other studies in the field of cardiovascular research and may increase the strength of collaborations

Protocol of the Healthy Brain Study: An accessible resource for understanding the human brain and how it dynamically and individually operates in its bio-social context

The endeavor to understand the human brain has seen more progress in the last few decades than in the previous two millennia. Still, our understanding of how the human brain relates to behavior in the real world and how this link is modulated by biological, social, and environmental factors is limited. To address this, we designed the Healthy Brain Study (HBS), an interdisciplinary, longitudinal, cohort study based on multidimensional, dynamic assessments in both the laboratory and the real world. Here, we describe the rationale and design of the currently ongoing HBS. The HBS is examining a population-based sample of 1,000 healthy participants (age 30-39) who are thoroughly studied across an entire year. Data are collected through cognitive, affective, behavioral, and physiological testing, neuroimaging, bio-sampling, questionnaires, ecological momentary assessment, and real-world assessments using wearable devices. These data will become an accessible resource for the scientific community enabling the next step in understanding the human brain and how it dynamically and individually operates in its bio-social context. An access procedure to the collected data and bio-samples is in place and published on https://www.healthybrainstudy.nl/en/data-and-methods. https://www.trialregister.nl/trial/795

Protocol of the Healthy Brain Study: An accessible resource for understanding the human brain and how it dynamically and individually operates in its bio-social context

The endeavor to understand the human brain has seen more progress in the last few decades than in the previous two millennia. Still, our understanding of how the human brain relates to behavior in the real world and how this link is modulated by biological, social, and environmental factors is limited. To address this, we designed the Healthy Brain Study (HBS), an interdisciplinary, longitudinal, cohort study based on multidimensional, dynamic assessments in both the laboratory and the real world. Here, we describe the rationale and design of the currently ongoing HBS. The HBS is examining a population-based sample of 1,000 healthy participants (age 30-39) who are thoroughly studied across an entire year. Data are collected through cognitive, affective, behavioral, and physiological testing, neuroimaging, bio-sampling, questionnaires, ecological momentary assessment, and real-world assessments using wearable devices. These data will become an accessible resource for the scientific community enabling the next step in understanding the human brain and how it dynamically and individually operates in its bio-social context. An access procedure to the collected data and bio-samples is in place and published on https://www.healthybrainstudy.nl/en/data-and-methods/access. Trail registration: https://www.trialregister.nl/trial/7955

Finding a balance in dimensions of blended learning

This article is a formative evaluation of a course in which a blended learning environment was created and a good balance in dimensions of blended learning was sought. Blended learning is defined as the total mix of pedagogical methods, using a combination of different learning strategies, both with and without the use of technology. The evaluation is based on a model of blended learning that has four dimensions: structured/unstructured, individual/group, face-to-face/at-a-distance, and self/teacher directed. These dimensions are used for the evaluation of a module entitled Society and Technology that is taught at Delft University of Technology. We describe how the module evolved in terms of these four dimensions of blended learning. We then use this case as the basis for a discussion about an effective balance in blended learning and further research in this field

Angiosarcoma of the Descending Aorta, Diagnostic Difficulties

: Introduction: Primary angiosarcomas of the aorta are rare and because of their non-specific presentation, the initial diagnosis is often very difficult. Report: A 66 year old woman, initially suffering from night sweats and general malaise, is presented. A computerized tomography (CT) scan was performed which showed a filling defect of the descending aorta. This defect later caused embolic occlusion of the celiac vessels. The patient underwent surgical resection of the filling defect of the descending aorta and an embolectomy of the celiac vessels. The defect was histopathologically diagnosed as an angiosarcoma. The clinical presentation, diagnostic pitfalls, histopathological diagnosis, and the therapeutic management are discussed. Discussion: In this case report, the importance of carefully diagnosing an angiosarcoma is highlighted as the consequences could be rapid metastasization or embolization. Keywords: Angiosarcoma, Descending aorta, Malignancy, Primary aortic tumo