Analytical models to determine room requirements in outpatient clinics

Outpatient clinics traditionally organize processes such that the doctor remains in a consultation room while patients visit for consultation, we call this the Patient-to-Doctor policy (PtD-policy). A different approach is the Doctor-to-Patient policy (DtP-policy), whereby the doctor travels between multiple consultation rooms, in which patients prepare for their consultation. In the latter approach, the doctor saves time by consulting fully prepared patients. We use a queueing theoretic and a discrete-event simulation approach to provide generic models that enable performance evaluations of the two policies for different parameter settings. These models can be used by managers of outpatient clinics to compare the two policies and choose a particular policy when redesigning the patient process.We use the models to analytically show that the DtP-policy is superior to the PtD-policy under the condition that the doctor’s travel time between rooms is lower than the patient’s preparation time. In addition, to calculate the required number of consultation rooms in the DtP-policy, we provide an expression for the fraction of consultations that are in immediate succession; or, in other words, the fraction of time the next patient is prepared and ready, immediately after a doctor finishes a consultation. We apply our methods for a range of distributions and parameters and to a case study in a medium-sized general hospital that inspired this research

Bijenhotel symbool van chemievrij beheer golfbaan

Bijen op de golfbaan, personen die dak- en thuisloos dreigen te worden en zich inzetten voor de bij: het zijn geen alledaagse combinaties, maar succes hadden deze Brabantse projecten wel. De provincie Noord-Brabant investeert flink in de bij. In de periode 2014–2015 werd € 300.000 besteed aan bijenprojecten, van 2015 tot 2018 wordt daar nog eens € 750.000 aan uitgegeven. De Brabantse Milieufederatie voerde twee van de bijenprojecten uit. Dit artikel gaat over het eerste project: bijenhotels op golfbanen en recreatieterreinen

Dak- en thuislozen zetten zich in voor bijen

In Breda vindt een initiatief plaats om dak- en thuislozen weer in de maatschappij te integreren door ze te betrekken bij de bijenhouderij. Dat gaat in de praktijk niet zonder vallen en opstaan, zoals blijkt. Marian Hulshof van de Brabantse Milieufederatie bericht over successen en uitdagingen in dit project waarin verschillende instanties samenwerken

Random walk on the high-dimensional IIC

We study the asymptotic behavior the exit times of random walk from Euclidean balls around the origin of the incipient infinite cluster in a manner inspired by [26]. We do this by obtaining bounds on the effective resistance between the origin and the boundary of these Euclidean balls. We show that the geometric properties of long-range percolation clusters are significantly different from those of finite-range clusters. We also study the behavior of random walk on the backbone of the IIC and we prove that the Alexander-Orbach conjecture holds for the incipient infinite cluster in high dimensions, both for long-range percolation and for finite-range percolation

High-dimensional incipient infinite clusters revisited

The incipient infinite cluster (IIC) measure is the percolation measure at criticality conditioned on the cluster of the origin to be infinite. Using the lace expansion, we construct the IIC measure for high-dimensional percolation models in three different ways, extending previous work by the second author and Jarai. We show that each construction yields the same measure, indicating that the IIC is a robust object. Furthermore, our constructions apply to spread-out versions of both finite-range and long-range percolation models. We also obtain estimates on structural properties of the IIC, such as the volume of the intersection between the IIC and Euclidean balls

Large Sample Size Fallacy in Trials About Antipsychotics for Neuropsychiatric Symptoms in Dementia

Background: A typical antipsychotics for neuropsychiatric symptoms in dementia have been tested in much larger trials than the older conventional drugs. The advantage of larger sample sizes is that negative findings become less likely and the effect estimates more precise. However, as sample sizes increase, the trials also get more expensive and time consuming while exposing more patients to drugs with unknown safety profiles. Moreover, a large sample size might yield a statistically significant effect that is not necessarily clinically relevant. Objective: To assess (1) the variation in sample size and sample size calculations of antipsychotic trials in dementia, (2) the size of reported treatment effects and related statistical significance, and (3) general study characteristics that might be related to sample size. Study Design and Setting: We performed a meta-epidemiological study of randomized trials that tested antipsychotics for neuropsychiatric symptoms in dementia. The trials compared conventional or atypical antipsychotics with placebo or another antipsychotic. Two reviewers independently extracted sample size, sample size calculations, reported treatment effects with p-values, and general study characteristics (drug type, trial duration, type of funding). We calculated a reference sample size of 83 and 433 per study group for the placebo-controlled and head-to-head trials respectively. Results: We identified 33 placebo-controlled trials, and 18 head-to-head trials. Only 14 (42%) and 2 (11%), respectively, reported a sample size calculation. The average sample size per arm was 34 (range 6-179) in placebo-controlled trials testing conventional drugs, 107 (8-237) in such trials testing atypical drugs, and 104 (95-115) in such trials testing both drug types; it was 31 (10-88) in head-to-head trials. Thirteen out of 18 trials with sample sizes larger than required (72%) reported a statistically significant treatment effect, of which two (15%) were clinically relevant. None of the head-to-head trials reported a statistically significant treatment effect, even though some suggested non-inferiority. In placebo-controlled trials of atypical drugs, longer trial duration (>6 weeks) and commercial funding were associated with higher sample size. Conclusion: Sample size calculations were poorly reported in antipsychotic trials for dementia. Placebo-controlled trials of atypical antipsychotics showed large sample size fallacy while head-to-head trials were massively underpowered

Thermal dosimetry for bladder hyperthermia treatment. An overview.

The urinary bladder is a fluid-filled organ. This makes, on the one hand, the internal surface of the bladder wall relatively easy to heat and ensures in most cases a relatively homogeneous temperature distribution; on the other hand the variable volume, organ motion, and moving fluid cause artefacts for most non-invasive thermometry methods, and require additional efforts in planning accurate thermal treatment of bladder cancer. We give an overview of the thermometry methods currently used and investigated for hyperthermia treatments of bladder cancer, and discuss their advantages and disadvantages within the context of the specific disease (muscle-invasive or non-muscle-invasive bladder cancer) and the heating technique used. The role of treatment simulation to determine the thermal dose delivered is also discussed. Generally speaking, invasive measurement methods are more accurate than non-invasive methods, but provide more limited spatial information; therefore, a combination of both is desirable, preferably supplemented by simulations. Current efforts at research and clinical centres continue to improve non-invasive thermometry methods and the reliability of treatment planning and control software. Due to the challenges in measuring temperature across the non-stationary bladder wall and surrounding tissues, more research is needed to increase our knowledge about the penetration depth and typical heating pattern of the various hyperthermia devices, in order to further improve treatments. The ability to better determine the delivered thermal dose will enable clinicians to investigate the optimal treatment parameters, and consequentially, to give better controlled, thus even more reliable and effective, thermal treatments

The impact of school size reduction on the development of academic skills in rural primary schools

Basisscholen aan de ‘randen’ van Nederland krimpen al geruime tijd in leerlingenaantallen. Doordat basisscholen kleiner worden, de onderwijscontext ongunstiger wordt en hoog opgeleide ouders wegtrekken staat de onderwijskwaliteit onder druk en zouden de leerprestaties kunnen dalen. Met dit surveyonderzoek is de ontwikkeling van leerprestaties in een krimpgebied onderzocht en nagegaan of de ernst van de krimp en sociaaleconomische achtergrond van leerlingen hier invloed op hebben. De data zijn afkomstig van schooladministratie- en leerlingvolgsystemen van bijna 1600 leerlingen op 24 reguliere basisscholen in Oost-Groningen. Gevonden is dat de gemiddelde vaardigheidsscores voor rekenen-wiskunde, begrijpend en technisch lezen licht fluctueren rondom de landelijke norm in de midden- en bovenbouw. Meerniveau groeicurve-analyses tonen de veerkracht van de basisscholen. Bij een minder goede leerlingencohort wordt de aanvankelijke achterstand weggewerkt totdat er in groep 8 geen noemenswaardige verschillen meer zijn met de andere leerlingcohorten. Ook de relatief ongunstige sociaaleconomische achtergrond van leerlingen en de mate van krimp vormen geen belemmering voor de ontwikkeling van de leerprestaties. Aanvankelijke lagere leerprestaties worden te niet gedaan, ongeacht de ernst van de krimp waarmee de school geconfronteerd wordt. Basisscholen in het krimpgebied Oost-Groningen weten voldoende te anticiperen op de ernstige gevolgen van krimp.Because of school size reduction, less favorable educational context and migration of high educated parents it is assumed that student achievement levels are gradually decreasing in rural areas. We studied the development of mathematics, reading comprehension and language decoding skills and whether this is influenced by the severity of school size reduction. Longitudinal data of 1600 pupils of 24 Dutch rural primary schools are used. Their average achievement level in grade one (6-7 year-olds), three-four, and six fluctuated slightly around thenational average. Multilevel polynomial growth models show that in case of an underachieving cohort at grade one the lag of development is gradually eliminated, regardless of the severity the school size reduction. In grade six all pupil cohorts attain a similar level. Dutch primary schools in a rural area are able to react effectively to the severe consequences of the reducing school size