The Hisparc cosmic ray experiment : data acquisition and reconstruction of shower direction

The field of cosmic ray physics is a century old and an exciting area of research. When cosmic ray particles enter our atmosphere they collide with air molecules creating new high-energy particles. These particles participate in further collisions and the entire process is known as an air shower. Much is still unknown about the origin of the high-energy particles. This thesis has been carried out as part of the HiSPARC science and outreach project. It focuses on the reconstruction of the direction of an extensive air shower using a station containing three 0.5 m^2 scintillator detectors in a 10 m triangle. This yields information on the origin of the cosmic rays. First, a method for reconstructing the shower direction is developed using a direct calculation. The method is based on the observation that a slanted air shower will arrive at separate detectors at different times. The thickness of the shower front, the geometry of the detectors, and other experimental effects result in measurement uncertainties of the arrival times. These introduce an uncertainty in the direction of the air shower. Using error propagation, equations are derived for calculating this uncertainty. The methods developed in this thesis have been verified first by simulations. Subsequently, data was analyzed from a station located inside the KASCADE air shower array in Karlsruhe, Germany. The 200 × 200 m KASCADE experiment provided us with an independent measurement of the direction of the air showers. The accuracy of the HiSPARC station has been determined to be 8.6° for proton showers arriving at an angle of 22.5°. Given the small size and low cost of a single HiSPARC station, the results are very good. Reconstructing the direction of an air shower by means of multiple stations has also been investigated. Using three stations with distances of 120 - 150 m an accuracy of only 1.5° can be accomplished. The goals of HiSPARC are two-fold. On the one hand, it is a traditional research group comprising research staff, graduate and undergraduate students. On the other hand, the experiment enables high-school students to participate in scientific research

Jacobi-Davidson type methods for generalized eigenproblems and polynomial eigenproblems : part I

In this paper we will show how the Jacobi-Davidson iterative method can be used to solve generalized eigenproblems. Similar ideas as for the standard eigenproblem are used, but the projections, that are required to reduce the given problem to a small manageable size, need more attention. We show that by proper choices for the projection operators quadratic convergence can be achieved. The advantage of our approach is that none of the involved operators needs to be inverted. It turns out that similar projections can be used for the iterative approximation of selected eigenvalues and eigenvectors of polynomial eigenvalue equations. This approach has already been used with great success for the solution of quadratic eigenproblems associated with acoustic problems

Machine Learning and Prediction in Psychological Assessment: Some Promises and Pitfalls

Multivariate analysis of psychological dat

Artificial intelligence, machine learning, and other demons

Multivariate analysis of psychological dat

Seasonal hydrogen storage decisions under constrained electricity distribution capacity

We consider a profit-maximizing renewable energy producer operating in a rural area with limited electricity distribution capacity to the grid. While maximizing profits, the energy producer is responsible for the electricity supply of a local community that aims to be self-sufficient. Energy storage is required to deal with the energy productions' uncertain and intermittent character. A promising, new solution is to use strategic hydrogen reserves. This provides a long-term storage option to deal with seasonal mismatches in energy production and the local community's demand. Using a Markov decision process, we provide a model that determines optimal daily decisions on how much energy to store as hydrogen and buy or sell from the power grid. We explicitly consider the seasonality and uncertainty of production, demand, and electricity prices. We show that ignoring seasonal demand and production patterns is suboptimal and that introducing hydrogen storage transforms loss-making operations into profitable ones. Extensive numerical experiments show that the distribution capacity should not be too small to prevent local grid congestion. A higher storage capacity increases the number of buying actions from the grid, thereby causing more congestion, which is problematic for the grid operator. We conclude that a profit-maximizing hydrogen storage operation alone is not an alternative to grid expansion to solve congestion, which is essential knowledge for policy-makers and grid operators

Seasonal hydrogen storage decisions under constrained electricity distribution capacity

The transition to renewable energy systems causes increased decentralization of the energy supply. Solar parks are built to increase renewable energy penetration and to supply local communities that become increasingly self-sufficient. These parks are generally installed in rural areas where electricity grid distribution capacity is limited. This causes the produced energy to create grid congestion. Temporary storage can be a solution. In addition to batteries, which are most suitable for intraday storage, hydrogen provides a long-term storage option and can be used to overcome seasonal mismatches in supply and demand. In this paper, we examine the operational decisions related to storing energy using hydrogen, and buying from or selling to the grid considering grid capacity limitations. We model the problem as a Markov decision process taking into account seasonal production and demand patterns, uncertain solar energy generation, and local electricity prices. We show that ignoring seasonal demand and production patterns is suboptimal. In addition, we show that the introduction of a hydrogen storage facility for a solar farm in rural areas may lead to positive profits, whereas this is loss-making without storage facilities. In a sensitivity analysis, we show that only if distribution capacity is too small, hydrogen storage does not lead to profits and reduced congestion at the cable connection. When the distribution capacity is constrained, a higher storage capacity leads to more buying-related actions from the electricity grid to prevent future shortages and to exploit price differences. This leads to more congestion at the connected cable and is an important insight for policy-makers and net-operators

Why we need systematic reviews and meta-analyses in the testing and assessment literature

Multivariate analysis of psychological dat

Increased allocation to reproduction reduces future competitive ability in a burying beetle

1. The existence of a trade-off between current and future reproduction is a fundamental prediction of life-history theory. Support for this prediction comes from brood size manipulations, showing that caring for enlarged broods often reduces the parent's future survival or fecundity. However, in many species, individuals must invest in competing for the resources required for future reproduction. Thus, a neglected aspect of this trade-off is that increased allocation to current reproduction may reduce an individual's future competitive ability. 2. We tested this prediction in the burying beetle, Nicrophorus vespilloides, a species where parents care for their offspring and where there is fierce competition for resources used for breeding. 3. We manipulated reproductive effort by providing females with either a small brood of 10 larvae or a large brood of 40 larvae and compared the ability of these females, and virgin females that had no prior access to a carcass, to compete for a second carcass against a virgin competitor. 4. We found that increased allocation to current reproduction reduced future competitive ability, as females that had cared for a small brood were more successful when competing for a second carcass against a virgin competitor than females that had cared for a large brood. In addition, the costs of reproduction were offset by the benefits of feeding from the carcass during an initial breeding attempt, as females that had cared for a small brood were better competitors than virgin females that had no prior access to a carcass, whilst females that had cared for a large brood were similar in competitive ability to virgin females. 5. Our results add to our understanding of the trade-off between current and future reproduction by showing that this trade-off can manifest through differences in future competitive ability and that direct benefits of reproduction can offset some of these costs. 16-Apr-2020Read me for "Data from RichardsonStephensSmiseth_JournalofAnimalEcology.csv" This data file consists of a comma separated values spreadsheet (.csv), which provides data for the effects of allocation to reproduction via brood size manipulation on future competitive ability in contests for a carcass. Each line in the spreadsheet represents an individual, experimental female. female_id – individual ID of the female. eclosion – date of eclosion. death – date of death. lifespan – number of days lived from eclosion to death. treatment_code – experimental treatment (control = no breeding attempt, ten = brood of ten larvae, forty = brood of forty larvae). won – outcome of the contest (Y = female won, N = female lost, NA = unclear). outcome_clear – was the outcome of the contest clear? (Y = yes, N = no). size – size of the female, measured as pronotum width (mm). competitor_size – size of the virgin female competitor measured as pronotum width (mm). size_difference – absolute difference in size between focal female and her competitor (mm). brood_size – number of larvae in the experimental brood at dispersal. dot – number and placement of identifying marks (1 or 2 = number of dots, L or R = left or right elytra). female_pre_mass – female mass prior to initial reproductive attempt (g). female_post_mass – female mass after initial reproductive attempt (g). female_mass_change – female mass change during initial reproductive attempt (g). brood_mass_pre – mass of the brood of larvae when cross fostered and given to the female (g). brood_mass_post – mass of the brood of larvae at dispersal from the carcass (g). breeding_carcass_mass – mass of the mouse carcass used for breeding (g). competition_carcass_mass – mass of the mouse carcass females competed for (g). Funding provided by: Natural Environment Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000270Award Number: NE/L002558/

Folate reference interval estimation in the Dutch general population

Background: Folate functions as an enzyme co-factor within the one-carbon metabolic pathway, providing key metabolites required for DNA synthesis and methylation. Hence, insufficient intake of folate can negatively affect health. As correct interpretation of folate status is dependent on a well-established reference interval, we set out to perform a new estimation following the restandardization of the Roche folate assay against the international folate standard. Materials and methods: The folate reference interval was estimated using samples obtained from the Dutch population-based Lifelines cohort. The reference interval was estimated using two methods: a nonparametric estimation combined with bootstrap resampling and by fitting the data to a gamma distribution. The lower reference limit was verified in a patient cohort by combined measurement of folate and homocysteine. Results: Dependent on the method used for estimation and in- or exclusion of individuals younger than 21 years of age, the lower reference limit ranged from 6.8 to 7.3 nmol/L and the upper reference limit ranged from 26 to 38.5 nmol/L. Applying a lower reference limit of 7.3 nmol/L resulted in the following percentage of folate deficiencies over a period of 12 months: general practitioner 15.5% (IQR 4.0%), general hospital 12.8% (IQR 5.3%), academic hospital 9.6% (IQR 4.3%). Conclusions: We estimated the folate reference interval in the Dutch general population which is not affected by a folic acid fortification program and verified the obtained lower reference limit by homocysteine measurements. Based on our results, we propose a folate reference interval independent of age of 7.3-38.5 nmol/