Relocation Algorithms for Emergency Medical Services

Mei, R.D. van der [Promotor]Bhulai, S. [Promotor

The Minimum Expected Penalty Relocation Problem for the computation of compliance tables for ambulance vehicles

We study the ambulance relocation problem in which one tries to respond to possible future incidents quickly. For this purpose, we consider compliance table policies: a relocation strategy commonly used in practice. Each compliance table level indicates the desired waiting site locations for the available ambulances. To compute efficient compliance tables, we introduce the minimum expected penalty relocation problem (MEXPREP), which we formulate as an integer linear program. In this problem, one has the ability to control the number of waiting site relocations. Moreover, different performance measures related to response times, such as survival probabilities, can be incorporated. We show by simulation that the MEXPREP compliance tables outperform both the static policy and compliance tables obtained by the maximal expected coverage relocation problem (MECRP), which both serve as benchmarks. Besides, we perform a study on different relocation thresholds and on two different methods to assign available ambulances to desired waiting sites

Mechanisms of cancer immunotherapy combinations

Clinical responses to immunotherapy can be complete and sustained; however, compared to responses to conventional cancer therapies such as chemotherapy they are often delayed. It has become clear that when different cancer therapies are combined they can potentially synergize. Understanding how individual cancer therapeutics work enables the development of the most optimal combinations of cancer therapies. In this thesis, we have used interesting combinations of chemotherapy, cancer vaccines and immune checkpoint blockade and obtained insights in the mechanisms involved in these combinations. For example, we combined chemotherapy with vaccination and observed that none of the tested chemotherapeutics had a negative effect on vaccination, while only a few displayed synergy with vaccination in tumor eradication. We found that vaccine-induced T cells produce Tumor Necrosis Factor-α which could sensitize tumor cells for chemotherapy-induced cell death. Furthermore, we have shown that different cancer therapies modulate intratumoral myeloid cells in a unique manner which can critically affect the therapeutic efficacy of the therapy. Understanding how different therapies affect the local tumor environment will help to improve clinical responses and decrease toxicity in patients

Goal-directed visual attention drives health goal priming: an eye-tracking experiment

Objective: Several lab and field experiments have shown that goal priming interventions can be highly effective in promoting healthy food choices. Less is known, however, about the mechanisms by which goal priming affects food choice. This experiment tested the hypothesis that goal priming affects food choices through changes in visual attention. Specifically, it was hypothesized that priming with the dieting goal steers attention toward goal-relevant, low energy food products, which, in turn, increases the likelihood of choosing these products. Methods: In this eye-tracking experiment, 125 participants chose between high and low energy food products in a realistic online supermarket task while their eye movements were recorded with an eye-tracker. One group was primed with a health and dieting goal, a second group was exposed to a control prime, and a third group was exposed to no prime at all. Results: The health goal prime increased low energy food choices and decreased high energy food choices. Furthermore, the health goal prime resulted in proportionally longer total dwell times on low energy food products, and this effect mediated the goal priming effect on choices. Conclusions: The findings suggest that the effect of priming on consumer choice may originate from an increase in attention for prime-congruent items. This study supports the effectiveness of health goal priming interventions in promoting healthy eating and opens up directions for research on other behavioral interventions that steer attention toward healthy foods

Lagere nitraatconcentratie grondwater door goed mineralenmanagement

De gecorrigeerde nitraatconcentraties in het bovenste grondwater op landbouwbedrijven zijn in de jaren negentig gemiddeld teruggelopen

Longer growing seasons do not increase net carbon uptake in Northeastern Siberian tundra

With global warming, snowmelt is occurring earlier and growing seasons are becoming longer around the Arctic. It has been suggested that this would lead to more uptake of carbon due to a lengthening of the period in which plants photosynthesize. To investigate this suggestion, 8 consecutive years of eddy covariance measurements at a northeastern Siberian graminoid tundra site were investigated for patterns in net ecosystem exchange, gross primary production (GPP) and ecosystem respiration (Reco). While GPP showed no clear increase with longer growing seasons, it was significantly increased in warmer summers. Due to these warmer temperatures however, the increase in uptake was mostly offset by an increase in Reco. Therefore, overall variability in net carbon uptake was low, and no relationship with growing season length was found. Furthermore, the highest net uptake of carbon occurred with the shortest and the coldest growing season. Low uptake of carbon mostly occurred with longer or warmer growing seasons. We thus conclude that the net carbon uptake of this ecosystem is more likely to decrease rather than to increase under a warmer climate. These results contradict previous research that has showed more net carbon uptake with longer growing seasons. We hypothesize that this difference is due to site-specific differences, such as climate type and soil, and that changes in the carbon cycle with longer growing seasons will not be uniform around the Arcti