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Search Results: 1 - 10 of 558973 matches for " H. J. L. van der Heide "
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The Inter- and Intraindividual Anatomical Relationship of the Femoral Anteversion and Distal Femoral Rotation. A Cadaveric Study on the Femoral Anteversion Angle, Posterior and Inferior Condylar Angle Using Computed Tomography  [PDF]
H. M. J. van der Linden-van der Zwaag, L. C. D. Konijn, T. J. van der Steenhoven, H. J. L. van der Heide, M. C. de Ruiter, R. G. H. H. Nelissen
Advances in Computed Tomography (ACT) , 2015, DOI: 10.4236/act.2015.41002
Malrotation following Total Knee Arthroplasty (TKA) is directly related to poor outcome. Knowledge of the rotational axes (torsion) and angles is therefore important. The aim of the study was to determine whether an association existed between the Femoral Anteversion Angle (FAA) Posterior Condylar Angle (PCA) and the Inferior Condylar Angle (ICA) in individuals. A CT scan of 50 (25 paired) cadaver femora was made. The FAA, PCA and ICA were measured. Statistical analysis of comparative relationships between these different angles was examined by calculating Pearson correlation coefficients and a paired t-test. The mean FAA, PCA and ICA for the whole group were respectively 11.7° (range 0 - 32, SD 8.2), 5.18° (range 0 - 12, SD 2.4) and 4.4° (range 0 - 10, SD 2.1). A correlation of 0.82 (p = 0.01) of the FAA was found between left versus right. For the overall group a correlation coefficient between the PCA of the left and right femur was r = 0.59, p = 0.01. The Pearson correlation between the FAA and PCA in the whole group was r = 0.27, p = 0.06. In females this was r = 0.54 (p = 0.03). Although the difference of the mean ICA and PCA was very small (0.7°), there was no correlation between these angles (r = 0.14, p = 0.23). In conclusion, one should be aware that, considering the weak correlation of the FAA and PCA, an individual rotational variation exists. Furthermore, no correlation was found between the PCA and ICA. Therefore, for now, this angle cannot be assumed to be helpful in TKA. A more individual approach in total knee arthroplasty seems essential for future TKA.
Electromagnetic vertex function of the pion at T > 0
J. van der heide,J. H. Koch,E. Laermann
Physics , 2005, DOI: 10.1140/epjc/s10052-006-0018-4
Abstract: The matrix element of the electromagnetic current between pion states is calculated in quenched lattice QCD at a temperature of $T = 0.93 T_c$. The nonperturbatively improved Sheikholeslami-Wohlert action is used together with the corresponding ${\cal O}(a)$ improved vector current. The electromagnetic vertex function is extracted for pion masses down to $360 {\rm MeV}$ and momentum transfers $Q^2 \le 2.7 {\rm GeV}^2$.
The pion form factor on the lattice at zero and finite temperature
J. van der Heide,J. H. Koch,E. Laermann
Physics , 2004, DOI: 10.1007/s00601-004-0087-6
Abstract: We calculate the electromagnetic form factor of the pion in quenched lattice QCD. The non-perturbatively improved Sheikoleslami-Wohlert lattice action is used together with the consistently O(a) improved current. We calculate the pion form factor for masses down to m_pi = 360 MeV, extract the charge radius, and extrapolate toward the physical pion mass. In the second part, we discuss results for the pion form factor and charge radius at 0.93 T_c and compare with zero temperature results.
Helicity Amplitudes for Single-Top Production
J. van der Heide,E. Laenen,L. Phaf,S. Weinzierl
Physics , 2000, DOI: 10.1103/PhysRevD.62.074025
Abstract: Single top quark production at hadron colliders allows a direct measurement of the top quark charged current coupling. We present the complete tree-level helicity amplitudes for four processes involving the production and semileptonic decay of a single top quark: W-gluon fusion, flavor excitation, s-channel production and W-associated production. For the first three processes we study the quality of the narrow top width approximation. We also examine momentum and angular distributions of some of the final state particles.
Eliciting Probabilities, Means, Medians, Variances and Covariances without Assuming Risk Neutrality  [PDF]
Karl H. Schlag, Jo?l J. van der Weele
Theoretical Economics Letters (TEL) , 2013, DOI: 10.4236/tel.2013.31006

We are interested in incentivizing experimental subjects to report their beliefs truthfully, without imposing assumptions on their risk preferences. We prove that if subjects are not risk neutral, it is not possible to elicit subjective probabilities or the mean of a subjective probability distribution truthfully using deterministic payments schemes, which are predominant in the literature. We present a simple randomization trick that transforms deterministic rewards into randomized rewards, such that agents with arbitrary risk preferences report as if they were risk neutral. Using this trick, we show how to elicit probabilities, means, medians, variances and covariances of the underlying distribution without assuming risk neutrality.

The pion form factor in improved lattice QCD
J. van der Heide,J. H. Koch,E. Laermann,M. Lutterot
Physics , 2003, DOI: 10.1016/S0370-2693(03)00559-8
Abstract: We calculate the electromagnetic form factor of the pion in lattice gauge theory. The non-perturbatively improved Sheikoleslami-Wohlert lattice action is used together with the O(a) improved current. The form factor is compared to results for other choices for the current and features of the structure of the pion deduced from the 'Bethe-Salpeter wave function' are discussed.
Positive Feedbacks in Seagrass Ecosystems – Evidence from Large-Scale Empirical Data
Tjisse van der Heide,Egbert H. van Nes,Marieke M. van Katwijk,Han Olff,Alfons J. P. Smolders
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016504
Abstract: Positive feedbacks cause a nonlinear response of ecosystems to environmental change and may even cause bistability. Even though the importance of feedback mechanisms has been demonstrated for many types of ecosystems, their identification and quantification is still difficult. Here, we investigated whether positive feedbacks between seagrasses and light conditions are likely in seagrass ecosystems dominated by the temperate seagrass Zostera marina. We applied a combination of multiple linear regression and structural equation modeling (SEM) on a dataset containing 83 sites scattered across Western Europe. Results confirmed that a positive feedback between sediment conditions, light conditions and seagrass density is likely to exist in seagrass ecosystems. This feedback indicated that seagrasses are able to trap and stabilize suspended sediments, which in turn improves water clarity and seagrass growth conditions. Furthermore, our analyses demonstrated that effects of eutrophication on light conditions, as indicated by surface water total nitrogen, were on average at least as important as sediment conditions. This suggests that in general, eutrophication might be the most important factor controlling seagrasses in sheltered estuaries, while the seagrass-sediment-light feedback is a dominant mechanism in more exposed areas. Our study demonstrates the potentials of SEM to identify and quantify positive feedbacks mechanisms for ecosystems and other complex systems.
Ecosystem Engineering by Seagrasses Interacts with Grazing to Shape an Intertidal Landscape
Tjisse van der Heide, Johan S. Ekl?f, Egbert H. van Nes, Els M. van der Zee, Serena Donadi, Ellen J. Weerman, Han Olff, Britas Klemens Eriksson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0042060
Abstract: Self-facilitation through ecosystem engineering (i.e., organism modification of the abiotic environment) and consumer-resource interactions are both major determinants of spatial patchiness in ecosystems. However, interactive effects of these two mechanisms on spatial complexity have not been extensively studied. We investigated the mechanisms underlying a spatial mosaic of low-tide exposed hummocks and waterlogged hollows on an intertidal mudflat in the Wadden Sea dominated by the seagrass Zostera noltii. A combination of field measurements, an experiment and a spatially explicit model indicated that the mosaic resulted from localized sediment accretion by seagrass followed by selective waterfowl grazing. Hollows were bare in winter, but were rapidly colonized by seagrass during the growth season. Colonized hollows were heavily grazed by brent geese and widgeon in autumn, converting these patches to a bare state again and disrupting sediment accretion by seagrass. In contrast, hummocks were covered by seagrass throughout the year and were rarely grazed, most likely because the waterfowl were not able to employ their preferred but water requiring feeding strategy (‘dabbling’) here. Our study exemplifies that interactions between ecosystem engineering by a foundation species (seagrass) and consumption (waterfowl grazing) can increase spatial complexity at the landscape level.
Overview of Actuated Arm Support Systems and Their Applications
B. van Ninhuijs,L.A. van der Heide,J.W. Jansen,B.L.J. Gysen,D.J. van der Pijl,E.A. Lomonova
Actuators , 2013, DOI: 10.3390/act2040086
Abstract: Arm support systems provide support throughout daily tasks, training or in an industrial environment. During the last decades a large diversity of actuated arm support systems have been developed. To analyze the actuation principles in these systems, an overview of actuated arm support systems is provided. This overview visualizes the current trends on research and development of these support systems and distinguishes three categories. These categories depend mainly on the functional status of the user environment, which defines the specifications. Therefore, the actuated arm support systems are classified according to their user environment, namely: ambulatory, rehabilitation and industrial. Furthermore, three main actuation principles and three mechanical construction principles have been identified.
Pressure during decision making of continuous sedation in end-of-life situations in Dutch general practice
Marco H Blanker, Marlies Koerhuis-Roessink, Siebe J Swart, Wouter WA Zuurmond, Agnes van der Heide, Roberto SGM Perez, Judith AC Rietjens
BMC Family Practice , 2012, DOI: 10.1186/1471-2296-13-68
Abstract: A sample of 918 Dutch GPs were invited to fill out a questionnaire about their last patient under continuous sedation. Cases in which GPs experienced pressure from the patient, relatives or other persons were compared to those without pressure.399 of 918 invite GPs (43%) returned the questionnaire and 250 provided detailed information about their most recent case of continuous sedation. Forty-one GPs (16%) indicated to have experienced pressure from the patient, relatives or colleagues. In GPs younger than 50, guideline knowledge was not related to experienced pressure, whereas in older GPs, 15% with and 36% without guideline knowledge reported pressure. GPs experienced pressure more often when patients had psychological symptoms (compared to physical symptoms only) and when patients had a longer estimated life expectancy. A euthanasia request of the patient coincided with a higher prevalence of pressure for GPs without, but not for GPs with previous experience with euthanasia. GPs who experienced pressure had consulted a palliative consultation team more often than GPs who did not experience pressure.One in six GPs felt pressure from patients or relatives to start sedation. This pressure was related to guideline knowledge, especially in older GPs, longer life expectancy and the presence of a euthanasia request, especially for GPs without previous experience of euthanasia.
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