University of Amsterdam

About: University of Amsterdam is a education organization based out in Amsterdam, Noord-Holland, Netherlands. It is known for research contribution in the topics: Population & Context (language use). The organization has 59309 authors who have published 140894 publications receiving 5984137 citations. The organization is also known as: UvA & Universiteit van Amsterdam.

Summer heatwaves promote blooms of harmful cyanobacteria

Abstract: Dense surface blooms of toxic cyanobacteria in eutrophic lakes may lead to mass mortalities of fish and birds, and provide a serious health threat for cattle, pets, and humans. It has been argued that global warming may increase the incidence of harmful algal blooms. Here, we report on a lake experiment where intermittent artificial mixing failed to control blooms of the harmful cyanobacterium Microcystis during the summer of 2003, one of the hottest summers ever recorded in Europe. To understand this failure, we develop a coupled biological-physical model investigating how competition for light between buoyant cyanobacteria, diatoms and green algae in eutrophic lakes is affected by the meteorological conditions of this extreme summer heatwave. The model consists of a phytoplankton competition model coupled to a one-dimensional hydrodynamic model, driven by meteorological data. The model predicts that high temperatures favour cyanobacteria directly, through increased growth rates. Moreover, high temperatures also increase the stability of the water column, thereby reducing vertical turbulent mixing, which shifts the competitive balance in favour of buoyant cyanobacteria. Through these direct and indirect temperature effects, in combination with reduced wind speed and reduced cloudiness, summer heatwaves boost the development of harmful cyanobacterial blooms. These findings warn that climate change is likely to yield an increased threat of harmful cyanobacteria in eutrophic freshwater ecosystems.

Measuring innovative work behaviour

Abstract: Both scientists and practitioners emphasize the importance of innovative work behaviour (IWB) of individual employees for organizational success, but the measurement of IWB is still at an evolutionary stage. This article is concerned with developed a measure of IWB with four potential dimensions: the exploration, generation, championing and implementation of ideas. From a pilot survey among 81 research professionals and their supervisors, we derived an initial version of ten items. Next, analysis of validity drew on survey data from 703 matched dyads of knowledge workers and their supervisors in 94 knowledge intensive services firms. It included confirmatory factor analyses and hierarchical multilevel regressions to test hypothesized relationships of IWB with related constructs, including participative leadership, external work contacts and innovative output. These analyses demonstrated sufficient reliability and criterion validity. Evidence for the distinctiveness of the four dimensions was, however, weak, suggesting that IWB is one-dimensional. We conclude that further research on this issue is merited.

Myocardial infarction accelerates atherosclerosis

Abstract: During progression of atherosclerosis, myeloid cells destabilize lipid-rich plaques in the arterial wall and cause their rupture, thus triggering myocardial infarction and stroke. Survivors of acute coronary syndromes have a high risk of recurrent events for unknown reasons. Here we show that the systemic response to ischaemic injury aggravates chronic atherosclerosis. After myocardial infarction or stroke, Apoe-/- mice developed larger atherosclerotic lesions with a more advanced morphology. This disease acceleration persisted over many weeks and was associated with markedly increased monocyte recruitment. Seeking the source of surplus monocytes in plaques, we found that myocardial infarction liberated haematopoietic stem and progenitor cells from bone marrow niches via sympathetic nervous system signalling. The progenitors then seeded the spleen, yielding a sustained boost in monocyte production. These observations provide new mechanistic insight into atherogenesis and provide a novel therapeutic opportunity to mitigate disease progression.

What is the value of entrepreneurship? A review of recent research

Abstract: This article examines to what extent recent empirical evidence can collectively and systematically substantiate the claim that entrepreneurship has important economic value. Hence, a systematic review is provided that answers the question: What is the contribution of entrepreneurs to the economy in comparison to non-entrepreneurs? We study the relative contribution of entrepreneurs to the economy based on four measures that have most widely been studied empirically. Hence, we answer the question: What is the contribution of entrepreneurs to (i) employment generation and dynamics, (ii) innovation, and (iii) productivity and growth, relative to the contributions of the entrepreneurs’ counterparts, i.e., the ‘control group’? A fourth type of contribution studied is the role of entrepreneurship in increasing individuals’ utility levels. Based on 57 recent studies of high quality that contain 87 relevant separate analyses, we conclude that entrepreneurs have a very important—but specific—function in the economy. They engender relatively much employment creation, productivity growth and produce and commercialize high-quality innovations. They are more satisfied than employees. More importantly, recent studies show that entrepreneurial firms produce important spillovers that affect regional employment growth rates of all companies in the region in the long run. However, the counterparts cannot be missed either as they account for a relatively high value of GDP, a less volatile and more secure labor market, higher paid jobs and a greater number of innovations and they have a more active role in the adoption of innovations.

Fifteen years experience with finger arterial pressure monitoring: assessment of the technology

Abstract: We review the Finapres technology, embodied in several TNO-prototypes and in the Ohmeda 2300 and 2300e Finapres NIBP. Finapres is an acronym for FINger Arterial PRESsure, the device delivers a continuous finger arterial pressure waveform. Many papers report on the accuracy of the device in comparison with intra-arterial or with noninvasive but intermittent blood pressure measurements. We compiled the results of 43 such papers and found systolic, diastolic and mean accuracies, in this order, ranging from -48 to 30 mmHg, from -20 to 18 mmHg, and from -13 to 25 mmHg. Weighted for the number of subjects included pooled accuracies were -0.8 (SD 11.9), -1.6 (8.3) and -1.6 (7.6) mmHg respectively. Subdividing the pooled group according to criteria such as reference blood pressure, place of application, and prototype or commercial device we found no significant differences in mean differences or SD. Measurement at the finger allows uninterrupted recordings of long duration. The transmission of the pressure pulse along the arm arteries, however, causes distortion of the pulse waveform and depression of the mean blood pressure level. These effects can be reduced by appropriate filtering, and upper arm 'return-to-flow' calibration to bring accuracy and precision within AAMI limits. For the assessment of beat-to-beat changes in blood pressure and assessment of blood pressure variability Finapres proved a reliable alternative for invasive measurements when mean and diastolic pressures are concerned. Differences in systolic pressure are larger and reach statistical significance but are not of clinical relevance. Finger arteries are affected by contraction and dilatation in relation to psychological and physical (heat, cold, blood loss, orthostasis) stress. Effects of these phenomena are reduced by the built-in Physiocal algorithm. However, full smooth muscle contraction should be avoided in the awake patient by comforting the patient, and coveting the hand. Arterial state can be monitored by observing the behaviour of the Physiocal algorithm. We conclude that Finapres accuracy and precision usually suffice for reliable tracking of changes in blood pressure. Diagnostic accuracy may be achieved with future application of corrective measures.