A semi-analytical solution for viscothermal wave propagation in narrow gaps with arbitrary boundary conditions.

Previous research has shown that viscothermal wave propagation in narrow gaps can efficiently be described by means of the low reduced frequency model. For simple geometries and boundary conditions, analytical solutions are available. For example, Beltman [4] gives the acoustic pressure in the gap between an oscillating, rigid, rectangular plate and a rigid surface. Assuming a pressure release boundary condition at the circumference of the plate, excellent agreement with experiments was obtained. In many engineering applications however, the boundary conditions may vary along the circumference of the plate. For instance, the vibrating membranes in hearing aid receivers are attached to complex structures and a simple pressure release (p = 0) or zero velocity boundary condition (dp=dn = 0) is only valid at some parts of the circumference of the vibrating structure. One can use numerical methods, like FEM or BEM, but often a large number of degrees of freedom is needed to obtain accurate results. Furthermore, a thorough understanding of the various phenomena can only be gained through a large number of calculations. In this paper a semi-analytical solution is presented for the viscothermal wave propagation in the gap between an oscillating, rigid, circular plate and a rigid surface for the boundary conditions just mentioned. The pressure in the gap is written as a series expansion of solutions satisfying the differential equations in the interior domain. Subsequently, either the pressure release or the zero velocity boundary condition is imposed on different parts of the circumference. The unknown constants in the series expansion are determined using a weak form of the boundary conditions. It is shown that only a limited number of terms is needed to accurately describe the total acoustic force on the plate. The solution is validated by means of a finite element calculation

Onderzoek crowdfunding

Eindrapport van het Honourstalent-programma van de Hanzehogeschool Groningen. Het onderzoek beschrijft de beweegredenen en risico’s van crowdfunding bij het MKB. Door meerdere oorzaken zoals Bazel III zijn bedrijven op zoek naar alternatieve financieringsvormen. Crowdfunding is hier één van. In kaart is gebracht hoe grote banken omgaan met crowdfunding, welke positie crowdfunding bij grote banken heeft en wat de beweegredenen en risico’s zijn voor geldlener en geldverschaffer

Police Leadership in Times of Transition

Large-scale police reforms in the Netherlands and Scotland were accompanied by transitions in police leadership. For the purpose of comparative research, unique interview data were collected among the Dutch and Scottish strategic police chiefs who were in charge prior to the completion of the reform process. It was found that police reform trajectories in the Netherlands and Scotland were both political projects aimed at generating more efficiency and cost-effectiveness through the centralization of police governance. Police leaders who were involved in the police reform trajectories expressed that their professional voice was largely neglected or immobilized through exclusionary practices. Moreover, it was found that deadlines prevailed over consensus and quality, impacting upon professional support for the restructuring process. The evidence-based insights help to identify critical success factors for large-scale organizational police reforms. A critical success factor is that police organizations adopt active learning and evaluation strategies before moving to a next transition

Give CRISPR a chance : the GeneSprout Initiative

Did you know that a group of early-career researchers launched an initiative enabling open dialog on new plant breeding techniques, such as genome editing? We developed a wide-ranging initiative that aims to facilitate public engagement and provide a platform for young plant scientists to encourage participation in science communication

Filtering, FDR and power

Background: In high-dimensional data analysis such as differential gene expression analysis, people often use filtering methods like fold-change or variance filters in an attempt to reduce the multiple testing penalty and improve power. However, filtering may introduce a bias on the multiple testing correction. The precise amount of bias depends on many quantities, such as fraction of probes filtered out, filter statistic and test statistic used.Results: We show that a biased multiple testing correction results if non-differentially expressed probes are not filtered out with equal probability from the entire range of p-values. We illustrate our results using both a simulation study and an experimental dataset, where the FDR is shown to be biased mostly by filters that are associated with the hypothesis being tested, such as the fold change. Filters that induce little bias on the FDR yield less additional power of detecting differentially expressed genes. Finally, we propose a statistical test that can be used in practice to determine whether any chosen filter introduces bias on the FDR estimate used, given a general experimental setup.Conclusions: Filtering out of probes must be used with care as it may bias the multiple testing correction. Researchers can use our test for FDR bias to guide their choice of filter and amount of filtering in practice

Trends in governmental expenditure on vaccination programmes in the Netherlands, a historical analysis

BACKGROUND: Health economic evaluations are often required before implementing a vaccination programme. Such evaluations rarely consider the historical context of a vaccination programme. We review the financial history of vaccination programmes in the Netherlands, and compare these to demographic and macroeconomic developments as well as avoided mortality burden. METHODS: Previously uncatalogued historical expenditures on the Dutch National Immunisation Programme (NIP) and influenza vaccination were obtained from official reports. Costs were adjusted for inflation using Consumer Price Indices and expressed in Euro of 2016. Estimates on mortality burden averted were obtained from previous research and used to calculate the ratio of expenses to averted mortality burden for vaccinations against diphtheria, tetanus, pertussis, polio, measles, mumps and rubella for birth cohorts 1953-1992. RESULTS: Developments towards a uniform government funded NIP started early 1950s with vaccinations against diphtheria, pertussis and tetanus, culminating in its official launch in 1957 together with polio vaccinations. Since the 1980s, expenditure increased nearly five-fold mostly due to the addition of new vaccines, while spending on already implemented vaccinations tended to decline. Overall, expenditure increased from € 5 million in 1957 to € 93 million in 2014. Relative to total healthcare expenditure, the NIP contributed little, ranging between 0.05% and 0.14%. Spending on influenza vaccination increased from € 37 million in 1996 to € 52 million in 2014, while relative to total healthcare expenditure it decreased from 0.069% to 0.055%. In 2014, 0.15% of healthcare expenditure and € 533 per birth was spent on vaccination programmes. Overall, for birth cohorts 1953-1992, € 5.4 thousand (95% confidence interval: 4.0-7.3) was expended per year-of-life-lost averted. CONCLUSION: The actual costs per year-of-life gained are more favorable than estimated here since averted medical costs were not included. Although expenditure on vaccination programmes increased substantially, the contribution to overall healthcare expenditure remained small

Physical and Psychosocial Correlates of Rehabilitation, Survival and Relapse in Head and Neck Cancer Patients

The number of new patients in the Netherlands each year diagnosed with head and neck cancer is about 21 00.1 This number will increase in the coming years because of progessive aging of the population and the particularly high birthrate post second world war, producing a cohort of children who are now at risk for developing head and neck cancer. Moreover, patients are currently 'in medical hands' for a longer time than before because of the introduction of treatment techniques for more advanced tumors and better palliative care. In 1995 the estimated number of patients alive with carcinoma of the most common sites of head and neck cancer was 9125.2 Traditionally, the medical treatment of head and neck tumors has been directed at irradicating the disease and aiming for a longer survival of the patient. Therefore, the main focus has been on clinical data such as localization, type and staging of the tumor and the effect of treatment, demonstrated by loco-regional control and survival. As Bailar and Gornick stated recently, the effect on mortality of new treatments, in the period 1970 through 1994, has been disappointing for most cancer sites.3 Also, the survival rate for head and neck cancer in 1994 was found largely unchanged since 1973. In the Netherlands, the 5-year overall relative survival for oral cavity cancer improved from 52 to 58%, for oropharynx cancer decreased from 38 to 30% and remained unchanged (70%) in laryngeal cancer.2 For the patients both quantity and quality of life are important. Today head and neck cancer patients and their healthcare providers are confronted with the effects of more aggressive treatment modalities introduced since the 70's. Fundamental life functions, like breathing, eating and speaking, and the bodily appearance of the patient, are often largely affected by tumor and treatment, often with severe consequences for daily life and social interaction

W3LS: Evaluation framework for World Wide Web learning

An evaluation framework for World Wide Web learning environments has been developed. The W3LS(WWW Learning Support) evaluation framework presented in this article is meant to support the evaluationof the actual use of Web learning environments. It indicates how the evaluation can be set up usingquestionnaires and interviews among other methods. The major evaluation aspects and relevant 'stakeholders' are identified. First results of cases using the W3LS evaluation framework are reported from different Higher Education institutes in the Netherlands. The usability of the framework is evaluated, and future developments in the evaluation of Web learning in Higher Education in the Netherlands are discussed