ZoekresultatenZoekresultaten
Volg ons op
Volg ons op
Types
0Instelling
26Bestandstype
9Taal
5Publicatiejaar
12Thema's
14Producttype
14Publicaties met bestand / URL
2Projectstatus
3Aggregation into groups may affect performance of individuals through the balance and strength of facilitative versus competitive interactions. We studied in situ how seasonal variation in abiotic environment affects this balance for blue mussels, a semi-sessile species. We hypothesize that seasonal variation in stresses and resources affects the strength of the interaction. We expected that, in benign conditions (here: high food availability, medium temperatures, low hydrodynamic stress), performance is dominated by growth and is better at low densities, while at adverse conditions (here: low food availability, low or high temperatures, high hydrodynamic stress), performance is dominated by survival and higher at high densities. Mussels were kept in shallow subtidal exclosures at 10 different densities for a one-month period. This exact procedure was repeated seven times at the same location within a one-year period. We measured development in mussel patch shape, performance, and environmental parameters. Environmental conditions for mussels were most benign in summer and most adverse in winter. Patches developed into less complex shapes at lower densities, but also after stronger hydrodynamic disturbances. Towards summer, mussels became more active, aggregation behavior increased, and interactions became more pronounced. Towards winter, mussels became less active: aggregation behavior and growth rates declined and at the lowest temperatures survival started to decrease with mussel density. Survival and growth (by proxy of mussel condition) were both density-dependent; however, contrary to our expectations we found positive interactions between density and survival at the most benign conditions in summer and negative interactions at the most adverse conditions in winter. In between the two seasons, the strength of the interactions increased towards summer and decreased towards winter following a bell-shaped pattern. This pattern might be explained by the environmental mediated aggregation behavior of the mussels. The obvious seasonal pattern in balance and strength of density-dependent interactions demonstrates that strength and direction of intra-specific interactions are both strongly affected by environmental context.
DOCUMENT
PURPOSE: Several studies have reported seasonal variation in intake of food groups and certain nutrients. However, whether this could lead to a seasonal pattern of diet quality has not been addressed. We aimed to describe the seasonality of diet quality, and to examine the contribution of the food groups included in the dietary guidelines to this seasonality.
METHODS: Among 9701 middle-aged and elderly participants of the Rotterdam Study, a prospective population-based cohort, diet was assessed using food-frequency questionnaires (FFQ). Diet quality was measured as adherence to the Dutch dietary guidelines, and expressed in a diet quality score ranging from 0 to 14 points. The seasonality of diet quality and of the food group intake was examined using cosinor linear mixed models. Models were adjusted for sex, age, cohort, energy intake, physical activity, body mass index, comorbidities, and education.
RESULTS: Diet quality had a seasonal pattern with a winter-peak (seasonal variation = 0.10 points, December-peak) especially among participants who were men, obese and of high socio-economic level. This pattern was mostly explained by the seasonal variation in the intake of legumes (seasonal variation = 3.52 g/day, December-peak), nuts (seasonal variation = 0.78 g/day, January-peak), sugar-containing beverages (seasonal variation = 12.96 milliliters/day, June-peak), and dairy (seasonal variation = 17.52 g/day, June-peak).
CONCLUSIONS: Diet quality varies seasonally with heterogeneous seasonality of food groups counteractively contributing to the seasonal pattern in diet quality. This seasonality should be considered in future research on dietary behavior. Also, season-specific recommendations and policies are required to improve diet quality throughout the year.
DOCUMENT
Studies monitoring vitamin D status in athletes are seldom conducted for a period of 12 months or longer, thereby lacking insight into seasonal fluctuations. The objective of the cur-rent study was to identify seasonal changes in total 25-hydroxyvitamin D (25(OH)D) concen-tration throughout the year. Fifty-two, mainly Caucasian athletes with a sufficient 25(OH)D concentration (>75 nmol/L) in June were included in this study. Serum 25(OH)D concentra-tion was measured every three months (June, September, December, March, June). Addition-ally, vitamin D intake and sun exposure were assessed by questionnaires at the same time points. Highest total 25(OH)D concentrations were found at the end of summer (113±26 nmol/L), whereas lowest concentrations were observed at the end of winter (78±30 nmol/L). Although all athletes had a sufficient 25(OH)D concentration at the start of the study, nearly 20% of the athletes were deficient (<50 nmol/L) in late winter.
DOCUMENT
Renewable energy sources have an intermittent character that does not necessarily match energy demand. Such imbalances tend to increase system cost as they require mitigation measures and this is undesirable when available resources should be focused on increasing renewable energy supply. Matching supply and demand should therefore be inherent to early stages of system design, to avoid mismatch costs to the greatest extent possible and we need guidelines for that. This paper delivers such guidelines by exploring design of hybrid wind and solar energy and unusual large solar installation angles. The hybrid wind and solar energy supply and energy demand is studied with an analytical analysis of average monthly energy yields in The Netherlands, Spain and Britain, capacity factor statistics and a dynamic energy supply simulation. The analytical focus in this paper differs from that found in literature, where analyses entirely rely on simulations. Additionally, the seasonal energy yield profile of solar energy at large installation angles is studied with the web application PVGIS and an hourly simulation of the energy yield, based on the Perez model. In Europe, the energy yield of solar PV peaks during the summer months and the energy yield of wind turbines is highest during the winter months. As a consequence, three basic hybrid supply profiles, based on three different mix ratios of wind to solar PV, can be differentiated: a heating profile with high monthly energy yield during the winter months, a flat or baseload profile and a cooling profile with high monthly energy yield during the summer months. It is shown that the baseload profile in The Netherlands is achieved at a ratio of wind to solar energy yield and power of respectively Ew/Es = 1.7 and Pw/Ps = 0.6. The baseload ratio for Spain and Britain is comparable because of similar seasonal weather patterns, so that this baseload ratio is likely comparable for other European countries too. In addition to the seasonal benefits, the hybrid mix is also ideal for the short-term as wind and solar PV adds up to a total that has fewer energy supply flaws and peaks than with each energy source individually and it is shown that they are seldom (3%) both at rated power. This allows them to share one cable, allowing “cable pooling”, with curtailment to -for example-manage cable capacity. A dynamic simulation with the baseload mix supply and a flat demand reveals that a 100% and 75% yearly energy match cause a curtailment loss of respectively 6% and 1%. Curtailment losses of the baseload mix are thereby shown to be small. Tuning of the energy supply of solar panels separately is also possible. Compared to standard 40◦ slope in The Netherlands, facade panels have smaller yield during the summer months, but almost equal yield during the rest of the year, so that the total yield adds up to 72% of standard 40◦ slope panels. Additionally, an hourly energy yield simulation reveals that: façade (90◦) and 60◦ slope panels with an inverter rated at respectively 50% and 65% Wp, produce 95% of the maximum energy yield at that slope. The flatter seasonal yield profile of “large slope panels” together with decreased peak power fits Dutch demand and grid capacity more effectively.
DOCUMENT
Annual rhythms in humans have been described for a limited number of behavioral and physiological parameters. The aim of this study was to investigate time-of-year variations in late arrivals, sick leaves, dismissals from class (attendance), and grades (performance). Data were collected in Dutch high school students across 4 academic years (indicators of attendance in about 1700 students; grades in about 200 students). Absenteeism showed a seasonal variation, with a peak in winter, which was more strongly associated with photoperiod (number of hours of daylight) compared with other factors assessed (e.g., weather conditions). Grades also varied with time of year, albeit differently across the 4 years. The observed time-of-year variation in the number of sick leaves was in accordance with the literature on the seasonality of infectious diseases (e.g., influenza usually breaks out in winter). The winter peak in late arrivals was unexpected and requires more research. Our findings could be relevant for a seasonal adaptation of school schedules and working environments (e.g., later school and work hours in winter, especially at higher latitudes where seasonal differences in photoperiod are more pronounced).
DOCUMENT
Avans University of Applied Sciences is redrafting its courses and curricula in view of sustainability. For chemical engineering in particular that implies a focus on 'green' and bio-based processes, products and energy. Avans is situated in the Southwest region of the Netherlands and specifically in that region much development occurs towards 'a bio-based economy'. There is much agriculture based business, small and large companies, important chemical industry and it is situated between major industrial and chemical industry centers and leading international ports. Chemical companies see many opportunities in bio-based products and processes. Connecting the chemical and agrofood sector will lead to unexpected new innovation opportunities. Biomass has quite other characteristics than oil and gas, in composition, availability, and offers new options with respect to compounds that can be derived from it. So there is a strong need to develop and introduce novel processes, products and production routes based on biomass resources. It requires other technologies and equipment, another approach and another mindset than those chemical engineers are being taught at present. Process design, modeling, and optimization will have to be adapted to the new circumstances. Chemical engineering in its basic knowledge won't be different but in practice students will need other and extra knowledge and therefore get other cases to study in projects. That transition will be gradually but it starts now. The bio-based economy already asks for new approaches in education, in particular in chemical engineering. Already now we observe an increasing need for personnel with knowledge of biobased issues on site and for a more bio-based oriented chemical engineering curriculum. To acquire that new knowledge and to observe what is needed by industries involved in that bio-based economy Avans University of Applied Sciences is actively participating in projects with local companies, other universities and research institutes. For this paper we have taken the international (Interreg) cooperation project 'Energy Conversion Parks' (ECP) in which we partake as example how such projects can and must contribute when developing a 'bio-based chemical engineering curriculum'. Besides attention for the specific types of equipment, processes and compounds involved, it shows that crucial knowledge also concerns the complexity of energetic optimization and the need for economic synergy when using different biomass streams and conversion technologies. Aspects involved are also bio-refinery, bio-cascading (implying use of all biomass components for products with the highest possible value) and optimizing input and output for seasonal variations in availability and demand. It shows the need for special mathematical models to calculate mass and energy balances for integrated bio-based installations, as well as the economical profitability of the different possible combination of biomass inputs and conversion techniques. The cooperation with industrial partners shows which the important technologies and knowledge for the bio-based oriented chemical engineer are. Students work on cases derived from the projects. The research results increase the knowledge we can teach. Representatives of the various project partners, from industry and research institutes, contribute with lectures based on practice information. In this manner it is possible to develop curricula that are useful for industry and society as a whole and at the same time attractive for the much needed new students.
DOCUMENT
Current symptom detection methods for energy diagnosis in heating, ventilation and air conditioning (HVAC) systems are not standardised and not consistent with HVAC process and instrumentation diagrams (P&IDs) as used by engineers to design and operate these systems, leading to a very limited application of energy performance diagnosis systems in practice. This paper proposes detection methods to overcome these issues, based on the 4S3F (four types of symptom and three types of faults) framework. A set of generic symptoms divided into three categories (balance, energy performance and operational state symptoms) is discussed and related performance indicators are developed, using efficiencies, seasonal performance factors, capacities, and control and design-based operational indicators. The symptom detection method was applied successfully to the HVAC system of the building of The Hague University of Applied Sciences. Detection results on an annual, monthly and daily basis are discussed and compared. Link to the formail publication via its DOI https://doi.org/10.1016/j.autcon.2020.103344
DOCUMENT
In the literature about web survey methodology, significant eorts have been made to understand the role of time-invariant factors (e.g. gender, education and marital status) in (non-)response mechanisms. Time-invariant factors alone, however, cannot account for most variations in (non-)responses, especially fluctuations of response rates over time. This observation inspires us to investigate the counterpart of time-invariant factors, namely time-varying factors and the potential role they play in web survey (non-)response. Specifically, we study the effects of time, weather and societal trends (derived from Google Trends data) on the daily (non-)response patterns of the 2016 and 2017 Dutch Health Surveys. Using discrete-time survival analysis, we find, among others, that weekends, holidays, pleasant weather, disease outbreaks and terrorism salience are associated with fewer responses. Furthermore, we show that using these variables alone achieves satisfactory prediction accuracy of both daily and cumulative response rates when the trained model is applied to future unseen data. This approach has the further benefit of requiring only non-personal contextual information and thus involving no privacy issues. We discuss the implications of the study for survey research and data collection.
DOCUMENT
Few people I know act likea magnet in the way Laura does. If you hear her speak, see her move, enjoy her smile - you can't help but want to be a part of what makes her heart beat faster. She radiates passion for her dream topic biomimicry and before you know it you're caught in that dream. From the day I met her, I was captivated by her enthusiasm and knowledge about this topic. In fact, meeting Laura made me decide to join the university as I thought: if people like Laura work at THUAS, I want to be a part of this organization'. Over the years I have seen her finish the Msc in biomimicry at Arizona State University followed by a PhD at TUDelft. And all that next to her full time job as a teacher. It's only a miracle that she still found the time to go outdoors and be in Nature. But luckily, she did as this is what nourishes her - and that nourishment is brought into the classroom affecting generations of students. I am very proud of how she builds her tribe just like Nature does; grassroots from the bottom up, not supported but also not inhibited by formal structures. In that way she truly acts as a bridge helping others to tap into Nature's wisdom. This morning I harvested the remaining vegetables from my garden and turned them into lunch. It's the second year I grow vegetables and it feels like I am only at the beginning of learning to collaborate with Nature. In Spring and Summer, Ihave witnessed in awe how seeds become seedlings which then grow into mature plants carrying fruit. The sheer wonder of Nature never ceases to amaze me, and my garden is only an attempt to be more aware of seasonal rhythms. It's Autumn right now, a time of year that invites us to go inside, reflect and let go of old baggage that no longer serves us. We'll be approaching the stage of wintering soon in which our inner journey will benefit from the darkness of wintertime introspection, along with the space to process the old, integrate learnings, and then germinate the new. Over the course of her career, Laura has gone through these seasonal cycles - reinventing herself in the past decade as a teacher, researcher and regenerative leader. One of Laura's many qualities is that she embodies three leadership characteristics derived from Nature. First, she acknowledges the importance of interconnection. Many times, we think of Nature as being separate from us, but in reality we humans are Nature. Connection with Nature enables us to think within systems and understand that we can't direct the system, but instead we're all part of multiple systems. Second, sensing the system and our part in it builds resilience. Even if things don't go as we expected or imagined, rather than reacting, we can step back and engage with more insight. Laura's adaptability to a system's needs while spotting opportunities to crack it open, is admirable. As the system is always in evolution, so is she - remarkably receptive to change even in the final stages of her career. Third, Laura creates space for people to develop and thrive, acting as multipliers of her vision and love for the natural world. In her leadership she embodies the ideal elder while being able to perceive the world through the eyes of a child - with continuous wonder for how life unfolds. This book is a bricolage of Laura's post-doc research conducted the past two years. In it you will find an array of fascinating reads and tools that help you deepen your practice as a biomimicry professional. The book is a community effort integrating tools Laura has co-created with her ecosystem as well as more in-depth readings written by some of the talents she has nourished over time. I wish for you to enjoy this careful curation of both practical as well as more conceptual contributions. May it inspire your own thriving in bringing Nature based wisdom to the core of our daily lives.
DOCUMENT
Global climate change is resulting in a wide range of biotic responses, including changes in diel activity and seasonal phenology patterns, range shifts polewards in each hemisphere and/or to higher elevations, and altered intensity and frequency of interactions between species in ecosystems.Oak (Thaumetopoea processionea) and pine (T. pityocampa) processionary moths (hereafter OPM and PPM, respectively) are thermophilic species that are native to central and southern Europe. The larvae of both species are gregarious and produce large silken ‘nests’ that they use to congregate when not feeding. During outbreaks, processionary caterpillars are capable of stripping foliage from theirfood plants (oak and pine trees), generating considerable economic damage. Moreover, the third to last instar caterpillars of both species produce copious hairs as a means of defence against naturalenemies, including both vertebrate and invertebrate predators, and parasitoids. These hairs contain the toxin thaumetopoein that causes strong allergic reactions when it comes into contact with humanskin or other membranes. In response to a warming climate, PPM is expanding its range northwards, while OPM outbreaks are increasing in frequency and intensity, particularly in northern Germany,the Netherlands, and southern U.K., where it was either absent or rare previously. Here, we discuss how warming and escape from co-evolved natural enemies has benefitted both species, and suggest possible strategies for biological control.
DOCUMENT
